The supplement glossary.

Supplements, A to Z

A

Allulose Human trials

A rare sugar that tastes like sugar and carries almost none of the calories. It is not a supplement in the strict sense, but it behaves like one: taken just before a carbohydrate-heavy meal it takes the edge off the glucose rise that follows, and a twelve-week human trial found body fat and abdominal fat came down on it, an early result the researchers themselves want to see repeated.

How it works: It competes with ordinary carbohydrate for the same enzymes and transporters in the gut, so the starch and sugar in the meal are digested and absorbed more slowly. It also nudges up GLP-1, the same hormone the injectable weight loss drugs imitate.

Best used: a few grams in water, or in your coffee, ten minutes before the meal you know is carb-heavy. It sweetens like sugar, so it also replaces some of the sugar you would have eaten.

What the science says Body fat percentage and body fat mass were significantly decreased following d-allulose supplementation. Han Y et al. Nutrients, 2018. Read it on PubMed↗
On the glucose rise: Braunstein CR et al. Clin Nutr, 2020. Read it on PubMed↗

Apigenin Human trials

A flavonoid found in chamomile, parsley and celery, and the compound behind chamomile tea being a bedtime drink. The human trials are on chamomile extract, and they find better sleep quality, most clearly in older people. In animal and cell work it also raises the body's own antioxidant enzymes after exercise, dampens myostatin, the protein that caps muscle growth, and increases the number of mitochondria in muscle. Nobody has run that trial in people yet.

How it works: It binds gently to the same brain receptors that benzodiazepine sleeping tablets act on, which is why the effect is a nudge toward sleep rather than a knockout.

Best used: as the mildest possible step toward sleep. A strong chamomile tea in the evening is the honest way to take it, and the cheapest.

What the science says The use of chamomile extract can significantly improve sleep quality among elderly people. Thus, it can be used as a safe modality for promoting elderly people's sleep. Adib-Hajbaghery M, Mousavi SN. Complement Ther Med, 2017. Read it on PubMed↗

Apple cider vinegar (ACV) Human trials

The acetic acid in vinegar flattens the glucose rise after a carbohydrate-heavy meal, and pooled trials now show a small drop in weight, BMI and waist on top of that. It costs almost nothing, which is more than most of this page can say. Raw, unfiltered vinegar also carries the live culture that made it, and the acetic acid itself is a short-chain fatty acid, the same family the gut bacteria produce when they ferment fibre. In animal work it shifts the gut bacteria toward a healthier mix; that trial has not been run in people yet.

How it works: Acetic acid slows how fast the stomach empties and dampens the enzymes that break starch into sugar, so the same meal reaches the blood more slowly.

Best used: a tablespoon in a glass of water before a meal you already know is carb-heavy. Diluted, because neat vinegar is hard on tooth enamel, and upright rather than lying down before bed.

What the science says daily ACV intake significantly reduced body weight [SMD: -0.39; 95% CI: -0.63, -0.15; P = 0.001], BMI [SMD: -0.65; 95% CI: -1.05, -0.26; P = 0.001], and WC [SMD: -0.34; 95% CI: -0.67, -0.02; P = 0.04] Castagna A et al. Nutrients, 2025. Read it on PubMed↗

Ashwagandha Human trials

An adaptogenic herb with a run of human trials behind it: lower perceived stress, lower cortisol, better sleep. In a deficit that is worth having, because poor sleep and high stress are what make hunger unmanageable, and unmanageable hunger is what ends most diets. In men who lift there is also a trial showing a larger rise in testosterone than placebo, alongside more strength and muscle.

How it works: It calms the stress axis that runs from the brain to the adrenal glands, so less cortisol is released under pressure. The testosterone effect is thought to come from the same calming, since cortisol and testosterone pull against each other.

Best used: when stress and sleep are the thing going wrong, rather than the food itself. The trials used a standardised root extract such as KSM-66 for six to eight weeks.

What the science says The serum cortisol levels were substantially reduced (P=0.0006) in the Ashwagandha group, relative to the placebo group. Chandrasekhar K et al. Indian J Psychol Med, 2012. Read it on PubMed↗
On testosterone and strength in trained men: Wankhede S et al. J Int Soc Sports Nutr, 2015. Read it on PubMed↗

Astaxanthin Human trials

A red carotenoid from algae and one of the most powerful antioxidants you can buy. Taken with regular training it enhances recovery, improves muscle endurance and shifts the body toward burning fat for fuel during exercise. The older human work on skin protection from UV still stands too.

How it works: It is fat-soluble, so it sits inside the mitochondrial membrane and shields it from the oxidative stress and inflammation that hard, high-intensity training produces. That protection extends to CPT1, the enzyme that carries fatty acids into the mitochondria to be burned, which is why fat oxidation goes up.

Best used: alongside a training block, four to twelve milligrams a day with a meal that contains some fat, since it absorbs with fat. It builds up in tissue over a few weeks, so give it time.

What the science says astaxanthin supplementation combined with regular training could enhance the fat oxidation (SMD: 2.56; 95% CI: 1.24-3.89), and significantly improve the physical performance (SMD: .62; 95% CI: .17-1.06) Liu C et al. Biol Res Nurs, 2024. Read it on PubMed↗

B

BCAAs Human trials

Branched-chain amino acids: leucine, isoleucine, valine. Three of the nine essential amino acids, sold on their own. Taken during a session they reduce the soreness and muscle damage that follow hard training, which is the most consistent finding in the research. They are usually recommended for advanced lifters, endurance athletes, and people who train on a lot of carbohydrate as fuel, since a long session or a high-carb, lower-protein day is when the muscle runs short of them.

How it works: Muscle burns BCAAs directly rather than sending them to the liver first, so sipping them intra-workout keeps the supply up while the muscle is under load, which limits protein breakdown and dampens the fatigue signal to the brain.

Best used: intra-workout, in water, during long or heavy sessions. If you are already eating plenty of complete protein, whey or EAAs carry the same three plus the six others, so start there and add BCAAs when the training volume calls for it.

What the science says The cumulative results of 37 effects gathered from 8 studies published between 2007 and 2017 indicated that BCAA supplementation reduced DOMS following exercise training (ES = 0.7286, 95% CI: 0.5017 to 0.9555, p < 0.001). Fedewa MV et al. Int J Vitam Nutr Res, 2019. Read it on PubMed↗

Berberine Human trials

A plant compound with solid evidence for improving fasting glucose and HbA1c in people whose blood sugar control is already impaired, and for lowering inflammatory markers. The weight effect is real and small, about a kilogram; the blood sugar effect is the reason to take it.

How it works: It switches on AMPK, the enzyme that tells liver and muscle cells to take up glucose and burn fuel, which is the same pathway metformin works through.

Best used: with a meal, since it absorbs poorly on its own, and a formulation that addresses absorption is worth the extra. It works on the same pathway as metformin, so if you take a blood sugar medication the two add up.

What the science says The finding of our umbrella showed that the supplementation of BBR could be effective in improving glycemic parameters and inflammatory marker in adults. Nazari A et al. Clin Ther, 2023. Read it on PubMed↗

Betaine (TMG) Human trials

Trimethylglycine, a methyl donor. Its most reliable effect is lowering homocysteine, a cardiovascular marker. In trained men, six weeks of it also improved body composition, arm size and bench press work capacity.

How it works: It hands a methyl group to homocysteine, turning it back into methionine. In muscle it also acts as an osmolyte, drawing water into the cell, which supports the protein-building machinery in the same way creatine does.

Best used: at about two and a half grams a day, split across two doses, through a training block. On the label it is trimethylglycine: not glycerine, and not the same thing as glycine.

What the science says Six-weeks of betaine supplementation improved body composition, arm size, bench press work capacity, attenuated the rise in urinary HCTL, and tended to improve power (p = .07) but not strength. Cholewa JM et al. J Int Soc Sports Nutr, 2013. Read it on PubMed↗

goBHB & exogenous ketones Human trials

Beta-hydroxybutyrate taken as a drink. Raising blood ketones suppresses ghrelin and genuinely lowers hunger for a few hours: a randomised finding, not a marketing claim. goBHB is the patented form the better products use, and the one I would look for on the label. Useful as an appetite tool, and for getting through the first rough days of a low-carb switch.

How it works: It lifts blood ketones to the level you would reach after a long fast or a strict low-carb week, and that level of ketosis directly quiets the hunger hormone ghrelin, independent of what your blood sugar is doing.

Best used: as a drink when hunger is the problem and a meal is still hours away. It is sold as a salt bound to sodium, magnesium, calcium or potassium, so it doubles as an electrolyte dose; if you watch sodium or have kidney or blood pressure concerns, read the label for how much of each it carries.

What the science says Increased blood ketone levels may directly suppress appetite, as KE drinks lowered plasma ghrelin levels, perceived hunger, and desire to eat. Stubbs BJ et al. Obesity (Silver Spring), 2018. Read it on PubMed↗
On the mechanism: Deemer SE, Martins C. Nutr Res, 2020. Read it on PubMed↗

Black seed oil Human trials

Nigella sativa, active compound thymoquinone. Pooled trials point to modest improvements in weight, waist, blood sugar and lipids, and they keep showing up across dozens of studies, which is more than most of this page can say.

How it works: Thymoquinone is an antioxidant that also improves how cells respond to insulin, which is the likely route to the small drops in fasting glucose, HbA1c and weight.

Best used: as a daily oil or capsule with food. It adds to the effect of blood thinners and blood pressure medication, which is worth knowing if you take either.

What the science says Nigella sativa (MD: -2.09 kg, 95%CI: -2.92, -1.26) could result in a small improvement in body weight. Shahinfar H et al. Pharmacol Res, 2023. Read it on PubMed↗

Boron Human trials

A trace mineral. In men, ten milligrams a day for a week raised free testosterone, lowered estradiol and the protein that binds testosterone up, and brought down three inflammatory markers. It was a small early study, and the mineral is cheap, so it is an easy one to try for yourself.

How it works: It reduces sex hormone binding globulin, the protein that holds testosterone in a form the body cannot use, so more of the testosterone you already make is free to act.

Best used: at around ten milligrams a day, the dose the trial used. It is a trace mineral, so more is not better.

What the science says After one week (in samples taken at 8.00 A.M, only), the mean plasma free testosterone increased and the mean plasma estradiol decreased significantly. Naghii MR et al. J Trace Elem Med Biol, 2011. Read it on PubMed↗

C

Caffeine Human trials

The most reliably effective legal performance supplement there is, and alongside creatine one of the most studied compounds in sports science, with decades of trials behind it. It is also cheap. It increases training output, blunts appetite slightly, and gives a small bump in energy expenditure. Better training in a deficit means you hold more muscle, which is the entire point.

How it works: It blocks adenosine, the brain chemical that builds up through the day and makes effort feel harder, so the same session feels easier and you do more of it. It also frees fatty acids into the blood to be burned.

Best used: deliberately rather than all day, because tolerance builds fast. One to three milligrams per kilo of bodyweight before training is the range the trials used. The half life is roughly five hours, so an afternoon coffee is still working at bedtime.

What the science says This is the first meta-analysis specifically focused on aerobic time-trial performance to suggest that pre-exercise ingestion of low caffeine doses (1.3-3 mg·kg) may enhance endurance performance by reducing time-trial completion time. Martins GL et al. Nutrients, 2026. Read it on PubMed↗

Capsaicin Human trials

The compound that makes chilli hot, and capsiate, its non-pungent cousin from sweet peppers. Both raise energy expenditure and fat oxidation for a few hours after a dose and take the edge off appetite. The effects are real and they are small, which is why it sits alongside a plan rather than in place of one.

How it works: It binds TRPV1, the heat-sensing receptor in the gut and in fat tissue, which nudges the sympathetic nervous system to burn a little more and dampens the hunger signal. Capsiate works the same receptor without the burn.

Best used: as capsiate capsules if you do not want the heat, or as chilli in the food if you do, with meals. Higher doses do more and irritate more, so build up.

What the science says Evidence indicates that capsaicin and capsiate both augment energy expenditure and enhance fat oxidation, especially at high doses. Furthermore, the balance of the literature suggests that capsaicin and capsiate suppress orexigenic sensations. Ludy MJ, Moore GE, Mattes RD. Chem Senses, 2011. Read it on PubMed↗

Casein Human trials

The slow-digesting protein in milk. Thirty to forty grams before bed feeds muscle repair overnight and raises overnight metabolic rate, without slowing fat breakdown while you sleep.

How it works: It clots in the stomach and releases amino acids over several hours, which is why one serving before bed carries muscle protein synthesis through the night.

Best used: as the last thing before bed when you train hard, or when evening hunger is the thing that breaks the diet. Otherwise it is just protein, and any protein will do.

What the science says Pre-sleep casein protein intake (30-40 g) provides increases in overnight MPS and metabolic rate without influencing lipolysis. Jäger R et al. J Int Soc Sports Nutr, 2017. Read it on PubMed↗

Chromium picolinate Mixed trials

Chromium plays a part in how insulin works, which is why it has been sold for decades as a blood sugar and craving supplement. The strongest human result is on cravings: in overweight women who craved carbohydrates, eight weeks of it cut food intake, hunger and fat cravings against placebo. The blood sugar trials are less consistent.

How it works: It is thought to make the insulin receptor more responsive, so the sugar swing after a meal is smaller and the craving that follows the crash is quieter.

Best used: when carbohydrate cravings are the specific problem, at the one milligram a day the trial used. Fibre and protein at the same meal do the same job from the other direction, so pair it with them.

What the science says Study 1 demonstrated that CrPic, as compared to placebo, reduced food intake (P<0.0001), hunger levels (P<0.05), and fat cravings (P<0.0001) and tended to decrease body weight (P=0.08). Anton SD et al. Diabetes Technol Ther, 2008. Read it on PubMed↗

Cinnamon Human trials

The bark of the cinnamon tree, and an insulin mimetic: its compounds act on the insulin receptor and copy what insulin does, so cells take up glucose with less of it. Across 28 trials in people with type 2 diabetes it improved fasting glucose, the lipid profile and BMI, at a dose of two grams a day or less. It may also help with cortisol, indirectly: a blood sugar crash is one of the triggers that makes the adrenal glands release it, so steadier glucose means fewer of those spikes. The direct cortisol-lowering result is in animals so far, not people.

How it works: Cinnamaldehyde and the polyphenols in the bark slow the enzymes that break carbohydrate down in the gut and make cells more responsive to insulin, so glucose leaves the blood faster after a meal and the crash that follows a spike is smaller. In rodents cinnamon extract also settled an overactive stress axis; that trial has not been run in people.

Best used: a teaspoon on food or a capsule of up to two grams a day. Choose Ceylon cinnamon for daily use; the common cassia kind carries coumarin, which the liver does not like in sustained high doses.

What the science says The data suggest that cinnamon improves the glycemic and lipid profile and reduces the BMI, particularly in DM2 patients who receive cinnamon supplementation in capsule form and at a dose of ≤2 g/day. de Moura SL et al. Nutr Rev, 2025. Read it on PubMed↗

CLA Human trials

Conjugated linoleic acid, a fatty acid found naturally in beef, lamb and dairy, and taken as a capsule. Grass-fed meat and dairy are the best natural source: the animals make it in the rumen from the grass, so the grass-fed versions carry several times more of it than grain-fed. Pooled human trials show a modest loss of body fat at around three grams a day, with a small gain in fat-free mass, and it does its best work alongside training and a deficit. The dramatic results are in animals; in people it is a nudge in the right direction.

How it works: Its active form acts on the PPAR switches inside fat cells, turning fat storage down and fat breakdown up, and it moderately reduces how much fat the fat cells take in.

Best used: grass-fed beef, lamb and dairy first, then three grams a day in capsules with meals through a training block, for months rather than weeks. The effect is measured in a few hundred grams a month, so let the training and the deficit do the heavy lifting.

What the science says Given at a dose of 3.2 g/d, CLA produces a modest loss in body fat in humans. Whigham LD, Watras AC, Schoeller DA. Am J Clin Nutr, 2007. Read it on PubMed↗
On fat-free mass: Schoeller DA, Watras AC, Whigham LD. Appl Physiol Nutr Metab, 2009. Read it on PubMed↗

CoQ10 Human trials

Ubiquinone, part of how mitochondria produce energy. The evidence worth citing is in the heart: in heart failure patients, two years of it cut major cardiac events to a third of the placebo rate. It is also the supplement people on statins reach for when their legs ache, with mixed results.

How it works: It carries electrons along the chain that turns food into ATP. Statins block the body from making it along with cholesterol, which is the logic behind replacing it.

Best used: if you are on a statin and your muscles ache, or your doctor is treating your heart. Take the ubiquinol form with a meal that contains fat.

What the science says The primary long-term endpoint of MACE was reached by significantly fewer patients in the CoQ10 group (n = 10, 9%) compared to the placebo group (n = 33, 27%, p = 0.001). Mortensen AL et al. Cardiol J, 2019. Read it on PubMed↗

Creatine monohydrate Human trials

The most studied supplement in sports nutrition, by a wide margin: more published trials than anything else on this page, over more than thirty years. It improves strength and work capacity, and in a deficit that translates into holding onto muscle you would otherwise lose. Safe over years, at doses far above what anyone needs.

How it works: It tops up the phosphocreatine store in muscle, which regenerates ATP during short, hard efforts. More reps per set, session after session, is what builds and keeps the muscle.

Best used: three to five grams a day of plain monohydrate; the expensive forms have never outperformed it. No loading phase needed. It pulls water into the muscle, so expect the scale to jump two to four pounds in the first week. That is not fat.

What the science says Studies have consistently shown that creatine supplementation increases intramuscular creatine concentrations which may help explain the observed improvements in high intensity exercise performance leading to greater training adaptations. Kreider RB et al. J Int Soc Sports Nutr, 2017. Read it on PubMed↗

D

D3 & K2 (vitamin D) Human trials

Vitamin D is made in skin from sunlight, which most people do not get enough of indoors or through a northern winter, and low vitamin D is one of the most common nutrient shortfalls there is: around a billion people worldwide are short of it. Correcting a genuine deficiency helps mood, bone, immune function and muscle. In overweight men who were low in both, a year of D3 raised testosterone. K2 is the reason the two are sold together: it directs calcium into bone rather than artery walls, and a 2026 trial found the pair slowed the build-up of calcium in the coronary arteries.

How it works: D3 governs calcium absorption and switches genes on and off in immune and muscle cells. K2 activates the proteins that lock calcium into bone and keep it out of the arteries.

Best used: after a blood test rather than a guess. It is a cheap test and it turns a guess into a dose, which for most people is two to four thousand IU of D3 a day with a meal, alongside K2.

What the science says Among patients with severe CAC, supplementation with vitamin K2 and vitamin D3 reduced progression of CAC over 24 months. The reduction in calcification progression was not associated with an increase in noncalcified plaque volume. Hasific S et al. Circulation, 2026. Read it on PubMed↗
On how common deficiency is: Dumbre D, Upendra S, Zacharias BS. Public Health Nurs, 2025. Read it on PubMed↗
On testosterone: Pilz S et al. Horm Metab Res, 2011. Read it on PubMed↗

DIM Mixed trials

Diindolylmethane, formed when you digest broccoli and other brassicas. It shifts how the body metabolises estrogen toward the gentler pathway, which is the basis for it being sold for stubborn fat and estrogen dominance. A small trial showed the shift; a larger one did not, but found a drop in body fat instead.

How it works: It induces the liver enzyme that breaks estrogen down along the 2-hydroxy route rather than the 16-alpha route, a ratio some researchers associate with a healthier estrogen profile.

Best used: with the vegetables that contain it. A capsule is a concentrated version of what a serving of broccoli does; eat the broccoli first.

What the science says DIM-treated subjects, relative to placebo, showed a significant increase in levels of 2-OHE1 (P=0.020), DIM (P=0.045), and cortisol (P=0.039). Dalessandri KM et al. Nutr Cancer, 2004. Read it on PubMed↗

E

EGCG & green tea extract Human trials

Epigallocatechin gallate is the main catechin in green tea. Paired with the caffeine already in the leaf it raises daily energy expenditure by around five percent and nudges fat oxidation up. The effect is real and it is small, and it shows up most in people who are not habitual caffeine users.

How it works: Catechins slow the breakdown of norepinephrine, so its fat-burning signal lasts longer; caffeine adds its own push, and the two together do more than either alone.

Best used: as the tea. Three or four cups a day gets you the catechins and the caffeine in the ratio the trials used. The concentrated high-dose extract capsules are the form the liver injury reports attach to, so the tea is the better route.

What the science says The catechin-caffeine mixtures and caffeine-only supplementation increased energy expenditure significantly over 24 h (428.0 kJ (4.7%); P < 0.001 and 429.1 kJ (4.8%); P < 0.001, respectively). Hursel R et al. Obes Rev, 2011. Read it on PubMed↗

Electrolytes Human trials

Sodium, potassium and magnesium. The most overlooked item on this list. When you cut calories you cut sodium with them, and when you cut carbs your kidneys start dumping it. The headaches, cramps, dizziness and flatness people get in the first two weeks of a diet are usually this.

How it works: Lower carbohydrate means lower insulin, and insulin is what tells the kidneys to hold onto sodium. With it down, the kidneys let sodium and water go, and the symptoms follow until you put it back.

Best used: when you have just changed how you eat and feel terrible. Salt your food, or use an electrolyte powder without sugar. It is not a detox reaction. It is very often salt.

What the science says The most frequently reported adverse effects range from transient "keto flu" symptoms (fatigue, headache, nausea) to gastrointestinal disturbances, polyuria, and hypoglycaemia. Dyńka D et al. Ann Med, 2026. Read it on PubMed↗

Essential amino acids (EAAs) Human trials

They complete a protein that is not complete on its own. They are called essential amino acids for a reason: your body cannot produce them, and they are only found in food. They raise muscle protein synthesis and help you hold onto muscle in a deficit, which matters more with age. Whey, eggs and meat already carry all nine. Plant proteins are the ones that need completing: rice runs low on lysine, peas on methionine, and EAAs fix that.

How it works: Leucine in particular switches on mTOR, the signal that tells muscle to build. In a deficit the body leans toward breaking protein down; a high enough EAA dose tips the balance back toward keeping it.

Best used: alongside a plant-based protein, or on training days in a deep deficit. Picture Wheel of Fortune: a plant protein is a board with letters missing, and EAAs are the missing letters. Not to be confused with BCAAs, which are three of the nine.

What the science says These data demonstrate that high compared to standard EAA ingestion enhances whole-body protein status during underfeeding. Gwin JA et al. Clin Nutr, 2020. Read it on PubMed↗
On completing plant protein: Lim C et al. Curr Dev Nutr, 2024. Read it on PubMed↗

F

Fenugreek Human trials

A clover-like herb whose seeds carry soluble fibre, steroidal saponins and an unusual amino acid, 4-hydroxyisoleucine. A pooling of four trials found the seed extract raises total testosterone in men, and the trial that added resistance training found more strength and less body fat alongside it. The fibre slows carbohydrate out of the gut, which is behind its long use for blood sugar.

How it works: The saponins are thought to strengthen the luteinising hormone signal to the testes and to slow the enzymes that turn testosterone into estrogen and DHT. The galactomannan fibre forms a gel that slows sugar absorption, and 4-hydroxyisoleucine prompts the pancreas to release insulin only when glucose is already high.

Best used: as a standardised seed extract, five to six hundred milligrams a day, alongside training. The whole seed at food doses is the traditional route for blood sugar and for milk supply when breastfeeding; high supplemental doses are best left alone in pregnancy.

What the science says Fenugreek extract has a significant effect on total serum testosterone. Mansoori A et al. Phytother Res, 2020. Read it on PubMed↗
With resistance training: Wilborn C et al. Int J Sport Nutr Exerc Metab, 2010. Read it on PubMed↗

Fiber (psyllium husk) Human trials

Soluble fiber absorbs water and slows gastric emptying, which means it makes food sit longer and keeps blood sugar steadier after a meal. Pooled trials put the weight loss at around two kilograms over a few months. It is the cheapest appetite tool available, and most people eating in a deficit are well short on fiber. It also feeds the gut: the part of it that reaches the large intestine is fermented by the bacteria there, which favours the species that make butyrate, the short-chain fatty acid the gut lining runs on.

How it works: It forms a gel in the gut that is not digested, so food and sugar are absorbed more slowly, you stay full longer, and cholesterol is bound on the way through.

Best used: just before meals, which is how the trials dosed it, around ten grams a day. Ramp up slowly and drink water with it. Whole food fiber first; this is for closing the gap.

What the science says The meta-analysis showed that psyllium, dosed just before meals (mean dose 10.8 g/day, mean duration 4.8 months), was effective for decreasing body weight (MD = -2.1 kg [95% CI: -2.6 to -1.6]; p < .001). Gibb RD, Sloan KJ, McRorie JW. J Am Assoc Nurse Pract, 2023. Read it on PubMed↗
On the gut bacteria: Jalanka J et al. Int J Mol Sci, 2019. Read it on PubMed↗

Fish oil (EPA & DHA) Human trials

Omega-3 fatty acids. The evidence for lowering triglycerides is solid, the anti-inflammatory and recovery case is reasonable, and in older adults it makes muscle more responsive to protein. Worth taking if you rarely eat oily fish.

How it works: EPA and DHA are built into cell membranes and shift the signalling molecules the body makes toward less inflammatory ones. In muscle they sharpen the response to the protein-building signal that a meal sends.

Best used: as a health supplement, two grams a day or more with food, for the triglyceride and cardiovascular case rather than as a fat loss one. Two portions of oily fish a week does the same job.

What the science says omega-3 supplementation significantly reduced triglycerides (mean difference [MD] = -0.27 mmol/L, 95% CI: -0.35 to -0.20, p < 0.00001) Zhang L et al. FASEB J, 2026. Read it on PubMed↗
On muscle: Smith GI et al. Am J Clin Nutr, 2011. Read it on PubMed↗

G

Garcinia cambogia Mixed trials

Sold for years as an appetite suppressant and fat blocker. Pooling the randomised trials gives a small, statistically significant loss against placebo, just under a kilogram, which the authors themselves describe as of uncertain clinical relevance.

How it works: Hydroxycitric acid blocks an enzyme involved in turning carbohydrate into fat, and may raise serotonin, which is the proposed route to eating less.

Best used: if you have tried it and it takes the edge off your appetite, since that is a real response in some people. A pound or two over three months is the honest expectation, so let food, sleep and training do the heavy lifting.

What the science says The meta-analysis revealed a small, statistically significant difference in weight loss favouring HCA over placebo (MD: -0.88 kg; 95% CI: -1.75, -0.00). Onakpoya I et al. J Obes, 2011. Read it on PubMed↗

Ginger Human trials

Gingerols and shogaols. The anti-nausea evidence is strong and long established. Pooled weight trials show small reductions in body weight, BMI and waist circumference: real, consistent, and far smaller than the marketing.

How it works: Its compounds act on the serotonin receptors in the gut that drive nausea, and separately raise thermogenesis and satiety signalling a little.

Best used: when nausea is the problem, fresh or as a tea. As a fat loss agent it is a rounding error, but a rounding error in the right direction that also settles the stomach.

What the science says The meta-analysis showed a significant association between ginger supplementation and a reduction in body weight (WMD, -1.52 kg; 95%CI, -2.37, -0.66; P < 0.001), BMI (WMD, -0.58 kg/m2; 95%CI, -0.87, -0.30; P < 0.001), WC (WMD, -1.04 cm; 95%CI: -1.93, -0.15; P = 0.021) Rafieipour N et al. Nutr Rev, 2024. Read it on PubMed↗

Glutamine Human trials

An amino acid with genuine uses in clinical settings, such as burns and gut injury, and one human trial where it cut muscle soreness after damaging exercise at 24, 48 and 72 hours. If you eat enough protein you already get plenty of it.

How it works: It is the main fuel for the cells lining the gut and for immune cells, and blood levels drop during heavy training. Topping it up is thought to protect the gut lining and blunt the muscle damage signal.

Best used: around a hard training block when soreness is slowing the next session, or when your doctor is using it for the gut. Day to day, the protein you are already eating covers it.

What the science says L-glutamine resulted in lower soreness ratings at 24 (2.8 ± 1.2 vs. 3.4 ± 1.2), 48 (2.6 ± 1.4 vs. 3.9 ± 1.2), and 72 (1.7 ± 1.2 vs. 2.9 ± 1.3) hr postexercise (p < .01). Legault Z, Bagnall N, Kimmerly DS. Int J Sport Nutr Exerc Metab, 2015. Read it on PubMed↗

Glycine Human trials

An amino acid. Three grams before bed improved sleep quality and next-day alertness in small trials, and cut the fatigue that follows a short night. It is also the most abundant building block of collagen.

How it works: It lowers core body temperature slightly, which is one of the signals the body uses to fall asleep, and it acts as a calming neurotransmitter in the part of the brain that keeps time.

Best used: three grams before bed, which is the dose the sleep trials used. Cheap, low risk, and it tastes sweet, so it goes in a warm drink.

What the science says Recently, we found that a non-essential amino acid, glycine subjectively and objectively improves sleep quality in humans who have difficulty sleeping. Bannai M et al. Front Neurol, 2012. Read it on PubMed↗

I

Inositol Human trials

A sugar alcohol involved in insulin signalling. The evidence worth taking seriously is in women with PCOS, where myo-inositol improves insulin sensitivity and cycle regularity, and lowers the excess androgens, about as well as metformin.

How it works: It is a building block of the messenger molecules insulin uses inside the cell, so more of it makes cells more responsive to the insulin that is already there.

Best used: when insulin resistance is the actual problem and a doctor has said so, at the two to four grams a day the trials used. Outside that group the case thins out quickly.

What the science says A statistically significant reduction in the area under the curve (AUC) of insulin values during the oral glucose tolerance test (OGTT) was recorded in both examined groups after the applied therapy with MI and MET. Gudović A et al. Biomedicines, 2024. Read it on PubMed↗

Iodine Human trials

The raw material of thyroid hormone. T4 is four iodine atoms on a protein backbone and T3 is three, and without enough iodine the gland cannot make either. A severe shortage causes goitre and an underactive thyroid; a mild one makes the gland work harder to keep up. In older adults with moderate deficiency, three months of a modest dose restored their iodine status and brought down thyroglobulin, the marker of a gland straining.

How it works: The thyroid pulls iodine out of the blood, bolts it onto a scaffold protein called thyroglobulin, and cuts the finished hormone off that scaffold. When iodine runs short the pituitary raises TSH to drive the gland harder, which keeps hormone levels normal for a while, at the cost of a swelling, overworked gland.

Best used: through food first: seafood, dairy, eggs, and iodised salt if you salt at all. Sea salt and most of the fancy salts carry almost none. If you eat none of those, 150 micrograms a day, the adult requirement, is the dose. Kelp tablets are the trap: one can carry ten times that, and in a five-year study across three regions of China the people with the highest intake had the most new cases of underactive thyroid, not the fewest.

What the science says Iodine supplementation alleviated the moderate iodine deficiency and reduced elevated thyroglobulin concentrations. Thomson CD et al. Am J Clin Nutr, 2009. Read it on PubMed↗
On deficiency and mortality: Maldonado-Araque C et al. Thyroid, 2021. Read it on PubMed↗

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L-carnitine Human trials

Carnitine shuttles fatty acids into the mitochondria to be burned. Pooled trials show a small drop in weight and fat mass, and at high doses over months it reduces muscle soreness and the damage markers after training. Taken before exercise it mobilises fatty acids and shuttles them into the mitochondria, but they still have to be burned off there, so the session is what turns that into fat loss. The trick most people miss is that oral carnitine barely gets into muscle unless you take it with carbohydrate.

How it works: Muscle takes carnitine up through an insulin-dependent transporter. Taken with carbohydrate, which raises insulin, muscle carnitine rises by about a fifth over months and the muscle burns more fat during exercise.

Best used: two ways at once. Two grams a day with a carbohydrate-containing meal, for months, is what loaded the muscle in the trial. On training days a dose on its own before the session, since in a small trial the acute dose raised fat burning only when it was not taken with carbs. Oral carnitine has low bioavailability, so depending on the individual it can take a higher dose, up to 3,500 milligrams a day, to get the effect. Advanced users also have it as an injectable, which skips the gut altogether. And without the training the fat it moves has nowhere to go.

What the science says l-carnitine supplementation significantly decreased body weight [Weighted mean difference (WMD) = -1.21 kg, 95% confidence interval (CI): -1.73, -0.68; P < 0.001], body mass index (BMI)... and fat mass (WMD = -2.08 kg, 95% CI: -3.44, -0.72; P = 0.003). Talenezhad N et al. Clin Nutr ESPEN, 2020. Read it on PubMed↗
On getting it into muscle: Wall BT et al. J Physiol, 2011. Read it on PubMed↗
On a single dose before exercise: Odo S et al. J Nutr Sci Vitaminol, 2020. Read it on PubMed↗

M

Magnesium Human trials

Involved in more than three hundred essential enzyme reactions, which is to say almost everything your cells do. Intake below the recommended amount is common. Correcting a shortfall helps sleep quality, mood and daytime energy, and eases cramps. In a small Turkish trial, four weeks of it raised free and total testosterone in sedentary men and athletes alike.

How it works: It acts as the nervous system's brake, steadying the receptors that keep nerves and muscles excitable, which is why it settles both sleep and cramps. The testosterone effect is thought to run through the same route boron uses, freeing testosterone from its binding protein.

Best used: as glycinate or L-threonate at night. Citrate is absorbed well and also loosens things up. Oxide is cheap because it is barely absorbed.

What the science says This showed MgT improved sleep quality, especially deep/REM sleep stages, improved mood, energy, alertness, and daily activity and productivity. Hausenblas HA et al. Sleep Med X, 2024. Read it on PubMed↗
On testosterone: Cinar V et al. Biol Trace Elem Res, 2011. Read it on PubMed↗

Melatonin Human trials

A timing signal, not a sedative. It tells your body the night has started; it does not knock you out. Across nineteen trials it shortened the time to fall asleep, lengthened sleep and improved its quality, modestly, and the effect did not fade with continued use. Sleep is a real fat loss lever, because short sleep raises ghrelin and blunts leptin, so you wake up hungrier.

How it works: It is the hormone the pineal gland releases in darkness to set the body clock. Taken as a supplement it reinforces that signal rather than sedating the brain, which is why timing matters more than dose.

Best used: half a milligram to one milligram, taken well before bed rather than at it. More is not better here, and next-morning grogginess is usually the dose rather than the supplement.

What the science says This meta-analysis demonstrates that melatonin decreases sleep onset latency, increases total sleep time and improves overall sleep quality. Ferracioli-Oda E, Qawasmi A, Bloch MH. PLoS One, 2013. Read it on PubMed↗

Multivitamin Human trials

Insurance, not a strategy. In a long deficit your food volume drops and micronutrient gaps get easier to open up, so a basic one is reasonable cover. The large trials that exist are in older adults, where a daily multivitamin improved memory over three years.

How it works: It puts a floor under the vitamins and minerals that get harder to hit from food alone once calories come down, and the benefits seen in trials come from closing small, widespread shortfalls rather than from any one ingredient.

Best used: when a long deficit has cut your food volume down, or past sixty. If you are eating a varied diet at maintenance, the upside is small.

What the science says Daily multivitamin supplementation, compared with placebo, improves memory in older adults. Yeung LK et al. Am J Clin Nutr, 2023. Read it on PubMed↗

N

NAC Human trials

N-acetylcysteine, a precursor to glutathione. It is a genuine hospital drug, the antidote for paracetamol overdose and a mucolytic for clearing airways. By replenishing glutathione it gives broad cellular defence, supports the liver's own detox pathways and dampens inflammation across the body. Its best human evidence as a supplement is in women with PCOS, where it improved the response to fertility treatment and raised pregnancy rates.

How it works: It supplies cysteine, the amino acid that limits how fast the body can make glutathione, its main internal antioxidant, so the body can buffer more oxidative stress.

Best used: when a doctor is using it for PCOS, the airways or the liver. Its regulatory status as a supplement has been contested in the United States, so availability comes and goes.

What the science says compared to women in the control group, women receiving NAC had significantly lower average uFSH dosage and duration (p < 0.005) and significantly greater clinical pregnancy rates per OI cycle and cumulative clinical pregnancy rates per patient (p < 0.005). Fang C et al. J Ovarian Res, 2024. Read it on PubMed↗

NAD+ precursors (NR, NMN) Human trials

Nicotinamide adenine dinucleotide, the coenzyme every cell uses to turn food into ATP and to run its repair enzymes, the sirtuins. Levels fall by roughly half between early adulthood and middle age. NAD+ itself does not survive the gut, but the precursors nicotinamide riboside and NMN reliably raise blood NAD+ in people, and in older adults with poor circulation NR improved how far they could walk.

How it works: The cell converts NR and NMN into NAD+, which carries electrons through the mitochondria and switches on the sirtuins and the PARP enzymes that repair DNA and manage cellular ageing.

Best used: at 250 to 500 milligrams a day, past forty, when energy and recovery are what you are chasing. Blood NAD+ rising is proven; the blood pressure and insulin effects are still being tested, so treat those as a hope rather than a reason.

What the science says Blood NAD concentrations were statistically significantly increased among all NMN-treated groups at day 30 and day 60 when compared to both placebo and baseline (all p ≤ 0.001). Yi L et al. GeroScience, 2022. Read it on PubMed↗
On walking distance in older adults: McDermott MM et al. Nat Commun, 2024. Read it on PubMed↗

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Oil of oregano Mixed trials

Carvacrol and thymol, both of which kill microbes convincingly in a petri dish. The one human trial is small and old: six weeks of emulsified oregano oil cleared several gut parasites in most of the people who had them.

How it works: The two phenols break open microbial cell membranes, which is what gives the oil its antibacterial, antifungal and antiparasitic action in the lab.

Best used: as a short course when a stool test has found something. A gut problem deserves a proper diagnosis before any capsule.

What the science says After 6 weeks of supplementation with 600 mg emulsified oil of oregano daily, there was complete disappearance of Entamoeba hartmanni (four cases), Endolimax nana (one case), and Blastocystis hominis in eight cases. Force M, Sparks WS, Ronzio RA. Phytother Res, 2000. Read it on PubMed↗

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PQQ Human trials

Pyrroloquinoline quinone, a vitamin-like compound that works on the mitochondria. In middle-aged and older Japanese adults it improved memory, attention and judgement against placebo, and paired with exercise it raises PGC-1α, the signal that tells cells to build new mitochondria.

How it works: It is a redox cofactor that can cycle through oxidation and reduction thousands of times without breaking down, so one molecule keeps neutralising free radicals, and it switches on PGC-1α, the master regulator of mitochondrial growth.

Best used: twenty milligrams a day, often paired with CoQ10, for brain energy and focus. The inflammation and sleep claims come from smaller or open-label work, so expect the cognition effect first.

What the science says Study demonstrates that supplementation of PQQ disodium salt is useful in improving memory, attention, judgment, and cognitive function, in middle-aged to elderly population, who feel they have become more forgetful because of aging. Shiojima Y et al. J Am Nutr Assoc, 2021. Read it on PubMed↗
On PGC-1α with exercise: Hwang PS et al. J Am Coll Nutr, 2020. Read it on PubMed↗

Protein powder Human trials

The highest leverage item on this page, and it is barely a supplement: it is food in a convenient form. Protein is the most filling macronutrient and the one that protects muscle in a deficit, and it is the one almost everybody undershoots when calories come down.

How it works: Whey is fast-digesting and rich in leucine, so it switches on muscle protein synthesis quickly, and it triggers the fullness hormones PYY and GLP-1, so you eat less later.

Best used: to close the gap between what you eat and the protein target, combined with resistance training and a modest deficit, which is where the trials found the biggest change in body composition. Whey, casein and blended plant proteins all work. Pick on taste and price, because you will only take it consistently if you like it.

What the science says The benefits of WP on BC are expected to be greatest when combined with resistance training and a reduction in overall calorie consumption. Sepandi M et al. Clin Nutr ESPEN, 2022. Read it on PubMed↗

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Resveratrol Human trials

A polyphenol from the skin of red grapes, blueberries and peanuts, and the compound behind the French paradox. Across 40 trials it lowered insulin resistance, total and LDL cholesterol, triglycerides, blood pressure and three inflammatory markers. It does its clearest work in people whose metabolism is already out of balance; weight and body fat did not move.

How it works: It behaves like an energy sensor, switching on AMPK and the sirtuins in the same way a calorie deficit does, and it dampens NF-κB, the master switch for inflammation. It also raises nitric oxide in the lining of blood vessels, which is the blood pressure effect.

Best used: at 150 to 500 milligrams a day with a meal that contains fat, since it absorbs poorly on its own and is cleared fast. Trans-resveratrol is the active form to look for on the label. The metabolic markers move; the scale does not, so take it for the blood work rather than the waistline.

What the science says Resveratrol significantly reduced the homeostatic model assessment of insulin resistance (HOMA-IR), total cholesterol (TC), triglycerides (TG), low density lipoprotein (LDL) cholesterol, systolic blood pressure (SBP) and diastolic blood pressure (DBP), high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6). Shen CY et al. In Vivo, 2026. Read it on PubMed↗

S

Sea buckthorn Mixed trials

The richest source you can buy of omega-7, and specifically palmitoleic acid, a fatty acid that acts as a signalling molecule between fat tissue, liver and muscle. One small, early eight-week human study on the juice found body weight, body fat and visceral fat all fell, alongside better cholesterol and lower inflammation.

How it works: Palmitoleic acid is a lipokine: fat tissue releases it to tell the liver and muscle to handle fat and sugar better. Most of that story comes from animal work; the human trials are few.

Best used: as the juice if you are after the body composition result, since that is what the study used. The omega-7 is concentrated in the oil, so pick the form that matches what you want from it.

What the science says We observed significant decrease of body weight, body mass index (P<0.05), body fat and visceral fat (P<0.001) after 8 weeks of consumption of 100% sea buckthorn juice. Kopčeková J et al. Rocz Panstw Zakl Hig, 2023. Read it on PubMed↗

Selenium Human trials

A trace mineral the thyroid cannot work without. The enzymes that turn the storage hormone T4 into the active hormone T3 are built on it, and so are the ones that protect the gland while it works. In people with Hashimoto's it lowers the antibodies attacking the thyroid, and in one small trial of overweight adults on a modest deficit, adding it meant more fat lost, lean mass kept and leptin down compared with the diet alone.

How it works: It is built into around twenty-five selenoproteins. The deiodinase enzymes among them strip an iodine atom off T4 to make T3, the hormone that sets metabolic rate in every cell, and the glutathione peroxidases mop up the hydrogen peroxide the thyroid makes while it builds hormone.

Best used: when you know your intake is low. Two Brazil nuts a day cover it, or 100 to 200 micrograms of selenomethionine, the form the trials used. The effect is U-shaped: people who already have enough gain nothing, and in one seven-year trial 200 micrograms a day in people who were already replete raised the rate of type 2 diabetes. Not one to stack on top of a multivitamin that has it.

What the science says Unlike the placebo group, the group given Se had a significant increase in lean body and muscle mass and a significant decrease in leptin levels after 3 months on diet. Cavedon E et al. Int J Endocrinol, 2020. Read it on PubMed↗
On Hashimoto's: Huwiler VV et al. Thyroid, 2024. Read it on PubMed↗

Shilajit Human trials

A mineral-rich resin that seeps from Himalayan rock, used in Ayurvedic medicine for centuries as a restorative. In healthy men aged 45 to 55, 250 milligrams of purified shilajit twice a day for 90 days raised total testosterone, free testosterone and DHEA against placebo, with LH and FSH unchanged, which suggests it is not pushing the pituitary around to do it.

How it works: Its fulvic acid and dibenzo-α-pyrones help carry electrons through the mitochondrial chain, and are thought to support the enzymes that turn cholesterol into testosterone and DHEA. The connective tissue and fatigue claims are mechanistic so far.

Best used: purified shilajit, 250 milligrams twice a day for at least three months, which is the protocol the trial used. Purity matters with a resin dug out of rock: look for a standardised, third-party tested product.

What the science says Treatment with Shilajit for consecutive 90 days revealed that it has significantly (P < 0.05) increased total testosterone, free testosterone and dehydroepiandrosterone (DHEAS) compared with placebo. Pandit S et al. Andrologia, 2016. Read it on PubMed↗

Spirulina Human trials

A blue-green algae and one of the most nutrient-dense foods there is: sixty to seventy percent complete protein by dry weight, with iron, B vitamins and the blue pigment phycocyanin. A 2025 pooling of 35 trials found it lowers LDL, triglycerides, blood pressure and body weight, and calms inflammation. The B12 on the label is mostly a form the body cannot use.

How it works: Phycocyanin blocks the NF-κB and NADPH oxidase pathways that drive inflammation, and the algae interferes with cholesterol absorption and triglyceride production in the liver.

Best used: one to three grams a day, as powder in a shake or as tablets, for the lipid and blood pressure case. Its protein density makes it a useful top-up on plant-based days, not a replacement for a protein target.

What the science says This study demonstrates that spirulina supplementation effectively reduces the risk of CVD in adults by improving glucose homeostasis, dyslipidemia, blood pressure, anthropometric indexes, and inflammation. Shiri H et al. Complement Ther Med, 2025. Read it on PubMed↗
On allergies: Cingi C et al. Eur Arch Otorhinolaryngol, 2008. Read it on PubMed↗

T

Tart cherry Human trials

Anthocyanins, plus a small amount of naturally occurring melatonin. The strongest evidence is for muscle soreness and recovery after hard training, with a smaller signal for sleep, where a crossover trial found more total sleep and better sleep efficiency.

How it works: The anthocyanins are antioxidant and anti-inflammatory, which blunts the muscle damage from a hard session. The melatonin content shows up in the urine after a week of the juice.

Best used: around a training block when recovery is the bottleneck, or in the evening for sleep. The juice concentrate carries the sugar; the extract does not.

What the science says Tart cherry supplementation had a small beneficial effect in reducing muscle soreness (effect size [ES] = -0.44, 95% confidence interval [CI] [-0.87, -0.02]). Hill JA et al. Int J Sport Nutr Exerc Metab, 2021. Read it on PubMed↗
On sleep: Howatson G et al. Eur J Nutr, 2012. Read it on PubMed↗

Taurine Human trials

An amino sulfonic acid, and the reason energy drinks list it on the can. Meta-analysed exercise trials show a modest improvement in endurance, and a separate pooling of twenty-five trials found it lowers blood pressure by a few points. Its cardiovascular research is more interesting than its gym research.

How it works: It supports how muscle cells handle calcium and how their mitochondria work, and it relaxes blood vessels, which explains both the endurance and the blood pressure result.

Best used: one to three grams before endurance work, which is the range the trials used. The buzz in the energy drink is the caffeine sitting next to it.

What the science says Taurine ingestion improved overall endurance performance (Hedges' g = 0.40, 95% CI 0.12-0.67, P = 0.004), which was similar in TTE trials (Hedges' g = 0.43, 95% CI 0.12-0.75, P = 0.007). Waldron M et al. Sports Med, 2018. Read it on PubMed↗
On blood pressure: Tzang CC et al. Nutr Diabetes, 2024. Read it on PubMed↗

Turmeric Human trials

Curcumin is the active compound. Pooled trials show real improvements in joint pain, stiffness and mobility, enough that people in the trials cut their painkiller use, and modest drops in inflammatory markers.

How it works: It dampens the signalling pathways that drive inflammation. On its own it is very poorly absorbed; black pepper extract, piperine, blocks its breakdown and raised absorption twenty-fold in the classic trial.

Best used: paired with piperine, or as a formulated version that addresses absorption, with a meal that contains fat. Plain turmeric powder in a capsule mostly passes straight through.

What the science says The results strongly support curcuminoid supplementation in relieving pain, improving joint mobility and stiffness, and shortening medication usage of OA patients. Bideshki MV et al. Phytother Res, 2024. Read it on PubMed↗
On absorption with piperine: Shoba G et al. Planta Med, 1998. Read it on PubMed↗

Y

Yohimbine & rauwolscine Human trials

Alpha-2 adrenergic receptors put the brakes on fat release, and they are densest in exactly the areas people call stubborn: hips, thighs, lower back. Yohimbine blocks them. In one trial, twenty lean soccer players went from 9.3% to 7.1% body fat over three weeks with no loss of muscle. It works fasted, food blunts it, caffeine stacks with it. Rauwolscine, sold as alpha-yohimbine, is the more potent form of the same molecule.

How it works: Blocking the alpha-2 receptor takes the brake off, so norepinephrine can drive fat breakdown in the cells that were resisting it, particularly during fasted exercise.

Best used: fasted, before morning cardio, starting at a low dose to see how you respond. It raises heart rate and blood pressure, so it suits people with a healthy heart, no anxiety disorder and no antidepressant, particularly an MAOI. If any of those apply, this is one to leave.

What the science says Percentage of body fat significantly decreased in the yohimbine group after the supplementation protocol (9.3 +/- 1.1 vs. 7.1 +/- 2.2%; p < 0.05). Ostojic SM. Res Sports Med, 2006. Read it on PubMed↗

Z

Zinc Human trials

Involved in immune function and hormone production. Correcting a deficiency restores testosterone: in older men who were marginally short of it, six months of zinc roughly doubled serum testosterone. Supplementing when you are not deficient does not push it higher.

How it works: Zinc is a required cofactor for the enzymes that make testosterone and for the cells that run the immune response, so a shortfall shows up in both and a top-up fixes both.

Best used: at a modest daily dose, fifteen to thirty milligrams, with copper alongside it if you take it for months, since sustained high doses of zinc block copper absorption. Not one to megadose indefinitely.

What the science says Zinc supplementation of marginally zinc-deficient normal elderly men for six months resulted in an increase in serum testosterone from 8.3 +/- 6.3 to 16.0 +/- 4.4 nmol/L (p = 0.02). Prasad AS et al. Nutrition, 1996. Read it on PubMed↗

Nothing here is a shortcut. Each one does its best work on top of food, sleep and training, which is where the result actually comes from. Every quote above links to the study it came from, so read the whole thing before you spend the money.

The usual line, said once rather than under every entry: supplements are not medication, but they can add to it or get in its way. If you take anything prescribed, or you are pregnant, run the list past your doctor before adding to it.