Supplement Research Database
What does peer-reviewed science actually say about popular supplement ingredients? Search below for honest, sourced evidence summaries. No marketing spin.
Creatine Monohydrate
Strong EvidenceCommon Marketing Claims
- Increases muscle strength and power
- Improves athletic performance
- Supports brain function
- Aids muscle recovery
What Research Actually Says
Creatine is one of the most extensively studied supplements in existence, with over 500 peer-reviewed papers. Research consistently shows it increases phosphocreatine stores, improving high-intensity exercise performance by 10-20%. Emerging evidence also supports cognitive benefits, particularly under stress or sleep deprivation.
Key Studies
ISSN position stand: creatine supplementation is effective, safe for all ages.
Creatine supplementation may improve short-term memory and reasoning.
Significant improvement in maximal-effort performance (+8% strength, +14% repetitions).
Bottom Line
One of the few supplements with genuinely strong evidence. Safe, cheap, effective for exercise performance. Cognitive benefits are promising but need more research.
Omega-3 Fish Oil (EPA/DHA)
Strong EvidenceCommon Marketing Claims
- Reduces heart disease risk
- Lowers triglycerides
- Supports brain health
- Reduces inflammation
What Research Actually Says
EPA and DHA omega-3 fatty acids have robust evidence for reducing triglyceride levels (25-30% reduction at 2-4g/day). Heart disease mortality reduction is more nuanced -- the VITAL trial showed no overall cardiovascular benefit at 1g/day, but the REDUCE-IT trial showed significant benefit with 4g EPA (icosapent ethyl). Anti-inflammatory effects are well-documented.
Key Studies
4g icosapent ethyl reduced cardiovascular events by 25% in high-risk patients.
1g/day omega-3 did not significantly reduce major cardiovascular events overall.
Omega-3 supplementation significantly reduces triglycerides in a dose-dependent manner.
Bottom Line
Strong evidence for triglyceride reduction and high-dose EPA for cardiovascular risk. General 'heart health' benefits at lower doses are less clear. Quality and dose matter significantly.
Ashwagandha (KSM-66)
Moderate EvidenceCommon Marketing Claims
- Reduces stress and anxiety
- Boosts testosterone
- Improves sleep quality
- Increases muscle strength
What Research Actually Says
KSM-66 ashwagandha has moderate to good evidence for cortisol and stress reduction. A systematic review found significant reductions in anxiety scores vs. placebo. Testosterone effects are modest (about 15-17% increase in some studies in men). Sleep quality improvements seen in insomniac populations.
Key Studies
600mg root extract significantly reduced cortisol levels (27.9%) and stress-related scores.
Five RCTs support ashwagandha for anxiety reduction, but study quality varies.
300mg KSM-66 2x daily improved muscle strength, recovery, and testosterone in men.
Bottom Line
One of the better-studied adaptogens. Stress reduction benefits are the best supported. Testosterone and muscle claims have some support but are often overhyped in marketing.
Probiotics
Moderate EvidenceCommon Marketing Claims
- Improves gut health
- Boosts immune function
- Aids digestion
- Helps with weight loss
What Research Actually Says
Probiotic research is highly strain-specific -- 'probiotics' as a category is too broad. Lactobacillus rhamnosus GG has strong evidence for antibiotic-associated diarrhea. Saccharomyces boulardii for C. diff prevention. VSL#3 for IBS symptoms. Generic 'probiotic blends' with random strains have much weaker evidence. Weight loss claims are largely unsupported.
Key Studies
Probiotics associated with 42% reduction in antibiotic-associated diarrhea.
Probiotics modestly improve overall IBS symptoms. Strain selection matters significantly.
Probiotic supplementation had minimal effect on body weight and BMI.
Bottom Line
Not all probiotics are created equal. Strain specificity is everything. For targeted conditions (AAD, IBS), specific strains work. Generic 'gut health' blends are mostly marketing.
Vitamin D
Strong EvidenceCommon Marketing Claims
- Strengthens bones
- Boosts immune function
- Prevents cancer
- Improves mood
What Research Actually Says
Vitamin D is essential for calcium absorption and bone health -- this is well-established. Immune function benefits are supported by observational data and some RCTs showing reduced respiratory infection risk. Cancer prevention claims are mixed: VITAL trial showed no overall reduction, but subgroup analysis suggested possible benefit with longer supplementation. Depression benefits are modest.
Key Studies
Vitamin D supplementation reduced acute respiratory infections, especially in deficient individuals.
Vitamin D supplementation did not reduce fractures by >15% in most populations.
2,000 IU/day did not significantly reduce cancer or cardiovascular events overall.
Bottom Line
Essential for deficient individuals (and many people are deficient). Bone health benefits are real. Immune benefits exist but are strongest in those who are deficient. Mega-dosing provides no extra benefit.
Turmeric / Curcumin
Moderate EvidenceCommon Marketing Claims
- Powerful anti-inflammatory
- Reduces joint pain
- Prevents cancer
- Protects the brain
What Research Actually Says
Curcumin has demonstrated anti-inflammatory properties in lab studies and some human trials. For joint pain (osteoarthritis), several RCTs show modest benefit comparable to NSAIDs. The biggest issue is bioavailability -- standard curcumin has ~1% absorption. Enhanced forms (phytosomes, with piperine) are required for meaningful blood levels. Cancer and Alzheimer prevention claims are extrapolated from cell studies and not supported by human trials.
Key Studies
Curcumin significantly reduced arthritis symptoms, comparable to ibuprofen.
Curcumin has extremely poor bioavailability; most oral intake is not absorbed.
Curcumin (500mg 3x daily) comparable to diclofenac for knee OA, with fewer GI side effects.
Bottom Line
Legitimate anti-inflammatory with real joint pain benefits IF you use an enhanced bioavailable form at adequate doses. Plain turmeric powder in cooking quantities will not provide therapeutic effects.
Collagen Peptides
Moderate EvidenceCommon Marketing Claims
- Improves skin elasticity
- Reduces wrinkles
- Supports joint health
- Strengthens hair and nails
What Research Actually Says
Hydrolyzed collagen peptides have surprisingly good evidence for skin improvements. Multiple RCTs show improved skin elasticity and hydration after 8-12 weeks. Joint pain benefits are also supported, particularly with specific collagen types. Hair and nail claims have weaker evidence. The mechanism is debated -- skeptics note collagen is just broken down to amino acids, but research suggests specific peptides may stimulate collagen synthesis.
Key Studies
2.5g collagen peptides improved skin elasticity significantly after 8 weeks.
10g collagen hydrolysate reduced joint pain in athletes over 24 weeks.
Oral collagen supplements improved skin hydration, elasticity, and reduced wrinkles.
Bottom Line
Better evidence than many skeptics assume, particularly for skin. Joint benefits are real but modest. Quality varies -- look for hydrolyzed peptides from reputable sources.
Berberine
Strong EvidenceCommon Marketing Claims
- Lowers blood sugar naturally
- Works like metformin
- Promotes weight loss
- Reduces cholesterol
What Research Actually Says
Berberine has genuinely impressive evidence for blood sugar regulation. Multiple RCTs show it reduces fasting blood glucose, HbA1c, and post-meal glucose spikes. Head-to-head comparisons with metformin show comparable effects on blood sugar, though study quality varies. Lipid-lowering effects are also documented. Weight loss effects are modest (1-2kg over 12 weeks in most studies).
Key Studies
Berberine lowered HbA1c from 7.5% to 6.6% -- comparable to metformin.
Berberine significantly reduced fasting blood glucose, HbA1c, and triglycerides.
Berberine reduced body weight and improved insulin sensitivity in metabolic syndrome.
Bottom Line
One of the most evidence-backed natural blood sugar compounds. Not a replacement for medication without medical supervision, but genuine effects. Metformin comparison is somewhat valid but oversimplified in marketing.
Melatonin
Moderate EvidenceCommon Marketing Claims
- Helps you fall asleep faster
- Improves sleep quality
- Cures insomnia
- Safe for nightly use
What Research Actually Says
Melatonin modestly reduces sleep onset latency (time to fall asleep) by an average of 7-12 minutes. It is most effective for jet lag and circadian rhythm disorders. For chronic insomnia, benefits are small. Importantly, research shows that 0.3-1mg is often as effective as 5-10mg, and most commercial products are massively overdosed. Quality control is poor -- independent testing found actual melatonin content varied from -83% to +478% of labeled amounts.
Key Studies
Melatonin reduced sleep onset latency by 7.06 minutes on average.
71% of melatonin supplements did not meet label claims. Some contained serotonin.
Melatonin has modest effects on sleep quality in primary insomnia populations.
Bottom Line
Real but modest sleep benefits. Most people take way too much. Start with 0.3-1mg. Product quality is a serious concern -- buy third-party tested brands only.
Garcinia Cambogia (HCA)
Weak EvidenceCommon Marketing Claims
- Burns fat naturally
- Suppresses appetite
- Blocks fat production
- Miracle weight loss ingredient
What Research Actually Says
Despite being one of the most marketed weight loss supplements, evidence for garcinia cambogia is extremely disappointing. A Cochrane meta-analysis found a very small, statistically significant but clinically meaningless difference in weight loss compared to placebo (about 0.9 kg or 2 lbs). Some studies showed no difference at all. The 'fat blocking' mechanism demonstrated in animal studies does not reliably translate to humans.
Key Studies
HCA generated small, short-term weight loss. Effect size was clinically insignificant.
1,500mg HCA daily failed to produce significant weight loss vs. placebo.
Bottom Line
One of the biggest supplement marketing scams. Evidence does not support meaningful weight loss. Save your money. The Dr. Oz hype was never backed by science.
Green Tea Extract (EGCG)
Moderate EvidenceCommon Marketing Claims
- Boosts metabolism
- Burns belly fat
- Powerful antioxidant
- Promotes longevity
What Research Actually Says
EGCG (the active catechin in green tea) has modest evidence for increasing metabolic rate and fat oxidation. Meta-analyses show green tea catechins can increase energy expenditure by about 80-100 calories per day and promote modest fat loss (1-2 kg over 12 weeks). Antioxidant properties are well-documented. However, concentrated green tea extract supplements have been linked to rare cases of liver damage.
Key Studies
Catechin-caffeine mixtures increased energy expenditure by ~100 kcal/day and fat oxidation.
Green tea preparations induced small, non-significant weight loss in overweight adults.
Multiple case reports of liver injury associated with concentrated green tea extract supplements.
Bottom Line
Real but very modest metabolic effects. Drinking green tea is healthier and safer than concentrated extract capsules. Will not produce noticeable weight loss alone.
Magnesium
Strong EvidenceCommon Marketing Claims
- Improves sleep
- Reduces muscle cramps
- Supports nerve function
- Reduces anxiety
What Research Actually Says
Magnesium is involved in over 300 enzymatic reactions. Deficiency is common (estimated 50% of Americans get less than recommended daily amount). Evidence supports supplementation for deficient individuals: improved sleep quality, reduced muscle cramps, and possibly reduced anxiety and depression symptoms. Form matters greatly -- oxide is poorly absorbed, while glycinate, threonate, and citrate are preferred.
Key Studies
500mg magnesium improved sleep quality, sleep time, and melatonin levels in elderly.
Suggestive evidence for magnesium in anxiety, but study quality limits conclusions.
Unclear whether magnesium supplements help with muscle cramps in the general population.
Bottom Line
One of the few supplements many people actually need due to widespread dietary insufficiency. Focus on absorbable forms. Benefits are real but primarily for those who are deficient.
Raspberry Ketones
No Credible EvidenceCommon Marketing Claims
- Melts body fat
- Boosts metabolism
- Natural fat burner
- Revolutionary weight loss compound
What Research Actually Says
There are zero published human clinical trials on raspberry ketones for weight loss. The entire marketing premise is based on a single in-vitro (test tube) study and one mouse study using doses that would be equivalent to 100+ capsules per day in humans. The compound is chemically similar to synephrine, but this does not mean it has similar effects. It is a textbook case of misleading extrapolation from preclinical research.
Key Studies
Raspberry ketones altered lipid metabolism in fat cells (in vitro only). No human data.
No human clinical trials. All evidence from animal or cell studies using impractical doses.
Bottom Line
No human evidence whatsoever. A pure marketing creation. This is one of the clearest examples of a supplement with zero scientific support being sold to millions.
CoQ10 (Ubiquinol/Ubiquinone)
Moderate EvidenceCommon Marketing Claims
- Supports heart health
- Increases cellular energy
- Reduces statin side effects
- Anti-aging antioxidant
What Research Actually Says
CoQ10 is a mitochondrial enzyme involved in energy production. For heart failure, the Q-SYMBIO trial showed significant benefits (reduced hospitalizations and cardiac mortality). For statin-induced myalgia (muscle pain), results are mixed -- some studies show benefit, others do not. Natural CoQ10 levels decline with age and statin use. Ubiquinol form is 2-3x more bioavailable than ubiquinone.
Key Studies
300mg CoQ10 reduced major adverse cardiovascular events by 43% in heart failure patients.
CoQ10 supplementation did not significantly improve statin-associated muscle symptoms.
CoQ10 deficiency increases with age. Supplementation restores mitochondrial function in deficient individuals.
Bottom Line
Good evidence for heart failure (adjunct therapy). Mixed for statin side effects. May benefit older adults or those on statins. Take ubiquinol form with food.
Lion's Mane Mushroom
Weak EvidenceCommon Marketing Claims
- Improves memory and focus
- Stimulates nerve growth
- Prevents cognitive decline
- Natural nootropic
What Research Actually Says
Lion's mane contains compounds (hericenones, erinacines) that stimulate Nerve Growth Factor (NGF) production in lab studies. One small RCT in elderly Japanese adults with mild cognitive impairment showed improved cognitive function over 16 weeks, which reversed after stopping supplementation. However, human studies are limited and small. Most evidence comes from animal and cell studies.
Key Studies
1,000mg 3x daily improved cognitive function in mild cognitive impairment over 16 weeks.
Hericenones and erinacines induce NGF synthesis in vitro. Human translation unclear.
Bottom Line
Promising but premature. Only one small human cognitive study. The NGF mechanism is interesting but most evidence is preclinical. Product quality is a major issue -- mycelium-on-grain products may contain mostly starch.
Turkesterone
No Credible EvidenceCommon Marketing Claims
- Natural anabolic compound
- Builds muscle like steroids
- Increases testosterone
- No side effects of steroids
What Research Actually Says
Turkesterone is an ecdysteroid (insect molting hormone) found in the Ajuga turkestanica plant. It went viral on social media as a 'natural steroid.' However, there are zero published human RCTs on turkesterone specifically. One 2019 study on ecdysterone (a related compound) showed no significant anabolic effect beyond placebo over 10 weeks. The 'steroid-like' claims are based entirely on Soviet-era research with questionable methodology and in-vitro studies.
Key Studies
12mg/day ecdysterone did not significantly increase muscle mass or strength vs. placebo.
Ecdysteroids have physiological effects in insects but bioavailability in mammals is very low.
Bottom Line
Social media hype with zero human clinical evidence. The compound has poor oral bioavailability in humans. Marketing compares it to anabolic steroids based on insect biology. Save your money.
Tongkat Ali (Eurycoma longifolia)
Moderate EvidenceCommon Marketing Claims
- Increases testosterone naturally
- Improves libido and sexual function
- Reduces cortisol
- Enhances athletic performance
What Research Actually Says
Tongkat Ali has a moderate body of human research, mostly from Malaysian studies. A meta-analysis found it significantly improved total testosterone levels (though effect sizes varied). Some studies show improved semen parameters and sexual function. The quality of evidence is moderate -- many studies are industry-funded, have small sample sizes, or use non-standardized extracts.
Key Studies
Tongkat ali significantly improved total testosterone in combined analysis of 9 studies.
200mg daily improved stress hormones (cortisol -16%, testosterone +37%) over 4 weeks.
Bottom Line
More human evidence than most testosterone supplements. Effects are real but modest. Not a replacement for TRT in clinically low testosterone. Extract quality varies enormously.
Apple Cider Vinegar
Weak EvidenceCommon Marketing Claims
- Aids weight loss
- Lowers blood sugar
- Improves digestion
- Cures nearly everything
What Research Actually Says
The best evidence for ACV is a modest reduction in post-meal blood glucose when consumed before carb-heavy meals (about 20-30% reduction in glucose spike). One 12-week RCT showed modest weight loss (1-2 kg) with daily ACV consumption. However, most studies are small and short-term. Claims about 'detoxifying' or curing diseases have no scientific basis. Capsule/gummy forms have not been studied and often contain little actual acetic acid.
Key Studies
Vinegar improved postprandial insulin sensitivity by 34% in insulin-resistant subjects.
15-30mL daily ACV reduced body weight by 1.2-1.7 kg over 12 weeks.
Bottom Line
May modestly help with post-meal blood sugar spikes. Weight loss effects are tiny. Not harmful in diluted form but vastly overhyped. Skip the expensive capsules.
L-Theanine
Moderate EvidenceCommon Marketing Claims
- Promotes calm focus
- Reduces anxiety
- Improves sleep quality
- Enhances caffeine benefits
What Research Actually Says
L-theanine (found naturally in green tea) increases alpha brain wave activity associated with relaxed alertness. Multiple small RCTs show it reduces physiological stress markers and subjective anxiety. The combination with caffeine has consistent evidence for improving attention and reducing caffeine jitteriness. Sleep improvements seen at higher doses (200-400mg).
Key Studies
50mg L-theanine increased alpha brain wave activity within 40 minutes.
L-theanine + caffeine improved accuracy and reduced susceptibility to distraction.
200mg L-theanine improved sleep quality and reduced stress in adults.
Bottom Line
One of the better-studied relaxation compounds. Solid evidence for calm focus, especially when combined with caffeine. Safe and well-tolerated. A good choice for stress management.
Glucosamine & Chondroitin
Moderate EvidenceCommon Marketing Claims
- Rebuilds cartilage
- Relieves joint pain
- Treats osteoarthritis
- Prevents joint degeneration
What Research Actually Says
Evidence is divided. European studies (using pharmaceutical-grade glucosamine sulfate) show meaningful benefits for knee osteoarthritis. The large US NIH-funded GAIT trial found no significant benefit over placebo for glucosamine HCl + chondroitin. The discrepancy may be due to different glucosamine forms (sulfate vs HCl), supplement quality, and study populations. Does not 'rebuild' cartilage.
Key Studies
Glucosamine HCl + chondroitin was not significantly better than placebo for OA pain.
1,500mg glucosamine sulfate reduced joint space narrowing and improved symptoms over 3 years.
Neither glucosamine nor chondroitin alone or in combination had clinically relevant effects.
Bottom Line
Form matters: glucosamine sulfate (European pharmaceutical grade) has better evidence than HCl. May help some OA patients modestly. Does not rebuild cartilage. Worth trying for 3 months to assess personal response.
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