Research Summaries
Plain-language summaries of the most important clinical research on dietary supplements. Each summary includes key findings, study quality assessment, and practical takeaways.
We summarize 40 key clinical trials, meta-analyses, and systematic reviews on supplement efficacy.
We summarize 40 key clinical trials, meta-analyses, and systematic reviews on supplement efficacy. Each summary covers study design, participant counts, effect sizes, and practical takeaways — translating complex research into actionable guidance.
Supplement Industry Statistics 2026
50+ data points on market size, demographics, safety, efficacy, and trends — with one-click citations.
Akkermansia muciniphila for Metabolic Health: Landmark RCT
A landmark RCT of 40 overweight/obese participants found that pasteurized Akkermansia muciniphila supplementation for 3 months improved insulin sensitivity by 28% and reduced plasma LPS levels, a marker of gut barrier dysfunction, compared to placebo.
Alpha-Lipoic Acid for Diabetic Neuropathy: Meta-Analysis of 15 RCTs
A meta-analysis of 15 RCTs (n=1,058) found that alpha-lipoic acid at 600mg/day significantly reduced Total Symptom Score (TSS) for diabetic neuropathy by 2.45 points compared to placebo (p < 0.001), with meaningful improvements in pain, burning, and numbness within 3-5 weeks.
Ashwagandha and Cortisol Reduction: 2022 Meta-Analysis of 12 RCTs
A 2022 meta-analysis of 12 RCTs (n=1,002) found that ashwagandha supplementation significantly reduced serum cortisol levels by a weighted mean of 11.3% compared to placebo (p < 0.001). Effects were strongest with KSM-66 extract at 600mg/day for 8+ weeks.
Ashwagandha and Testosterone: Meta-Analysis of Clinical Trials
A meta-analysis of 4 RCTs (n=234) found that ashwagandha supplementation significantly increased testosterone levels by a weighted mean of 14.7% compared to placebo (p = 0.004), with effects most pronounced in physically active men and those with suboptimal baseline levels.
B Vitamins and Cognitive Decline in Elderly: 2022 Systematic Review
A systematic review of multiple RCTs found that B vitamin supplementation (B6, B12, folate) significantly reduced homocysteine levels by 25-30% and slowed brain atrophy by 30% in elderly adults with elevated homocysteine. The VITACOG trial showed a 53% reduction in brain atrophy rate in participants with homocysteine >13 umol/L.
Beetroot Supplementation and Blood Pressure: 2023 Meta-Analysis of 22 RCTs
A meta-analysis of 22 RCTs (n=1,551) found that beetroot supplementation significantly reduced systolic blood pressure by 3.55 mmHg and diastolic blood pressure by 1.32 mmHg. Effects were mediated through dietary nitrate conversion to nitric oxide, which promotes vasodilation. Benefits were dose-dependent and more pronounced with supplementation lasting 2+ weeks.
Berberine and Blood Sugar Control: 2019 Meta-Analysis
A 2019 meta-analysis (n=2,569) found that berberine significantly reduced fasting blood glucose by 0.87 mmol/L, HbA1c by 0.72%, and improved insulin sensitivity. These effects were comparable to metformin in head-to-head trials. Berberine also provided additional lipid-lowering benefits not seen with metformin alone. Note: These findings do not justify replacing prescribed diabetes medication without medical supervision.
Black Seed Oil (Nigella sativa) for Metabolic Health: Systematic Review
A systematic review of 23 clinical trials found that black seed oil (1-3g/day) significantly reduced fasting blood glucose by 17.8 mg/dL, total cholesterol by 15.6 mg/dL, and triglycerides by 20.6 mg/dL compared to placebo in adults with metabolic risk factors.
Boswellia Serrata for Osteoarthritis: RCT on Pain and Inflammation
An RCT of 60 knee osteoarthritis patients found that Boswellia serrata extract (100mg Aflapin daily) reduced WOMAC pain scores by 48.8% and improved physical function scores by 49.4% at 30 days, significantly outperforming placebo (p < 0.001).
Oral Collagen for Skin: 2021 Meta-Analysis of 19 RCTs
A 2021 meta-analysis of 19 RCTs (n=1,125) found that oral collagen peptide supplementation significantly improved skin hydration, elasticity, and reduced wrinkles compared to placebo. Skin hydration increased by a standardized mean difference of 0.53 and elasticity by 0.49 after 8-12 weeks of supplementation.
CoQ10 for Heart Failure: 2017 Meta-Analysis of 14 RCTs
A 2017 meta-analysis of 14 RCTs (n=2,149) found that CoQ10 supplementation (100-300mg/day) significantly improved left ventricular ejection fraction by 3.67% and reduced mortality in heart failure patients. The landmark Q-SYMBIO trial showed a 43% reduction in cardiovascular mortality with 300mg/day CoQ10.
Creatine and Cognitive Performance: 2023 RCT in Healthy Adults
A 2023 RCT (n=281) found that 5g/day of creatine monohydrate for 6 weeks significantly improved working memory scores by 8.5% and reduced cognitive fatigue under sleep deprivation conditions. Effects were most pronounced in vegetarians and during mentally demanding tasks.
Curcumin for Joint Pain and Arthritis: 2021 Systematic Review of 16 RCTs
A 2021 systematic review of 16 RCTs (n=1,810) found that curcumin supplementation significantly reduced joint pain scores (SMD = -0.93, p < 0.001), improved physical function (SMD = -0.85), and reduced inflammatory markers. Curcumin performed comparably to NSAIDs like ibuprofen and diclofenac for knee osteoarthritis pain with fewer GI side effects.
Elderberry Extract for Cold and Flu: RCT on Duration and Severity
An RCT of 312 air travelers found that elderberry extract (600mg/day) reduced cold duration by an average of 2 days and significantly lowered symptom severity scores compared to placebo (p < 0.01).
Fenugreek Extract for Testosterone and Libido: RCT Results
An RCT of 120 healthy men aged 43-70 found that 600mg/day of fenugreek extract (Testofen) significantly increased free testosterone by 46% and total testosterone by 6.57% after 12 weeks, with concurrent improvements in libido and sexual function scores (p < 0.01).
Glucosamine for Knee OA: 2018 Meta-Analysis of 25 RCTs
A 2018 meta-analysis of 25 RCTs (n=4,963) found that crystalline glucosamine sulfate (1,500mg/day) significantly reduced knee osteoarthritis pain (SMD = -0.47, p < 0.001) and improved physical function over 3-6 months. Glucosamine sulfate also slowed joint space narrowing compared to placebo.
L-Glutamine and Gut Permeability: Systematic Review of Clinical Evidence
A systematic review of 19 studies found that L-glutamine supplementation (0.3-0.5g/kg/day) significantly reduced markers of intestinal permeability and improved gut barrier integrity, with the strongest evidence in critically ill patients and those with IBS-D.
Green Tea EGCG and Fat Oxidation: Meta-Analysis of 15 RCTs
A meta-analysis of 15 RCTs (n=1,945) found that green tea catechins containing EGCG significantly increased fat oxidation by 16% and 24-hour energy expenditure by ~100 kcal/day compared to placebo, with the greatest effects during exercise.
Iron Supplementation for Anemia: 2019 Systematic Review
A systematic review found that alternate-day iron supplementation (40-80mg elemental iron every other day) achieved comparable hemoglobin recovery to daily dosing while reducing GI side effects by 36%. Fractional iron absorption was 40% higher on alternate days, making it a more efficient strategy.
L-Theanine for Anxiety: RCT on Alpha Brain Wave Activity
An RCT of 46 participants found that 200mg L-theanine daily for 8 weeks significantly increased alpha brain wave activity and reduced subjective anxiety scores by 21% compared to placebo (p = 0.019).
Lion's Mane and Nerve Growth Factor: 2023 Systematic Review
A systematic review of clinical trials (n=897) found that lion's mane supplementation significantly improved cognitive function in adults with mild cognitive impairment, stimulated NGF synthesis via hericenones and erinacines, and demonstrated a favorable safety profile. Effects required 8-16 weeks of daily supplementation to manifest.
Maca Root for Sexual Desire: Randomized Controlled Trial
An RCT of 57 men found that 1,500-3,000mg/day of maca root for 12 weeks significantly improved sexual desire scores compared to placebo (p < 0.01), without altering testosterone or estradiol levels.
Magnesium for Anxiety: 2017 Randomized Controlled Trial
An RCT (n=264) found that magnesium supplementation (248mg elemental magnesium/day as magnesium lactate) significantly reduced subjective anxiety scores on the GAD-7 scale compared to placebo over 6 weeks. A companion systematic review confirmed a positive trend across studies.
Magnesium and Sleep: 2023 Meta-Analysis of 8 RCTs
A 2023 meta-analysis of 8 RCTs (n=2,132) found that magnesium supplementation significantly reduced sleep onset latency by an average of 17 minutes and improved subjective sleep quality scores. Effects were strongest with magnesium glycinate at doses of 200-400mg.
Melatonin and Sleep Onset Latency: 2013 Meta-Analysis of 19 RCTs
A 2013 meta-analysis of 19 RCTs (n=1,683) found that melatonin significantly reduced sleep onset latency by 7.06 minutes (p < 0.001), increased total sleep time by 8.25 minutes (p = 0.013), and improved overall sleep quality. Effects were consistent across studies with no evidence of tolerance development over weeks of use.
Milk Thistle (Silymarin) for Liver Protection: Systematic Review
A systematic review of 17 clinical trials found that silymarin (420-840mg/day) significantly reduced ALT by 14.1 U/L and AST by 9.4 U/L in patients with NAFLD, and showed histological improvement in liver steatosis and fibrosis scores across multiple trials.
NMN Supplementation: RCT on NAD+ Levels and Aging Biomarkers
An RCT of 30 participants found that 250mg NMN daily for 12 weeks significantly increased blood NAD+ levels by 38% and improved aerobic capacity, while reducing biological age markers compared to placebo.
Omega-3 and Cardiovascular Events: 2019 Meta-Analysis of 13 RCTs
A 2019 meta-analysis of 13 RCTs (n=127,477) found that marine omega-3 supplementation reduced the risk of major cardiovascular events by 8% (RR 0.92, 95% CI: 0.87-0.98). Higher-dose EPA regimens (>1g/day) showed stronger reductions of up to 17% in cardiac mortality.
Probiotics for IBS: 2023 Meta-Analysis of 53 RCTs
Yes, probiotics actually work — a 2023 meta-analysis of 53 RCTs (n=5,545) found that probiotics significantly improved global IBS symptoms, with 21% more patients reporting relief vs placebo (NNT = 7). Multi-strain formulations and Bifidobacterium-containing products showed the strongest effects, also reducing abdominal pain, bloating, and flatulence scores.
Psyllium Husk for LDL Cholesterol: Meta-Analysis of 28 Trials
A meta-analysis of 28 RCTs (n=1,924) found that psyllium husk supplementation (7-15g/day) reduced LDL cholesterol by an average of 7% (0.33 mmol/L), with consistent effects across diverse populations and no significant adverse events.
Resveratrol for Cardiovascular Health: Systematic Review
A systematic review of 24 clinical trials found that resveratrol supplementation (150-500mg/day) significantly reduced systolic blood pressure by 3.5 mmHg and improved flow-mediated dilation by 1.5%, with the strongest effects in participants with existing metabolic dysfunction.
Rhodiola Rosea for Stress-Related Fatigue: Multicenter RCT
A multicenter RCT (n=161) found that Rhodiola rosea extract (370mg/day SHR-5) significantly reduced stress-related fatigue by 20% on the fatigue index and improved cognitive function including short-term memory and associative thinking during stressful conditions, compared to placebo.
Saw Palmetto for BPH: Meta-Analysis of IPSS and Urinary Flow
A meta-analysis of 27 RCTs (n=4,957) found that saw palmetto extract (320mg/day) reduced International Prostate Symptom Scores (IPSS) by 1.8 points and improved peak urinary flow by 1.02 mL/s compared to placebo, with effects comparable to low-dose tamsulosin.
Spirulina for Cholesterol and Triglycerides: Meta-Analysis of 12 RCTs
A meta-analysis of 12 RCTs (n=807) found that spirulina supplementation (1-8g/day) significantly reduced LDL cholesterol by 33 mg/dL (p < 0.001), triglycerides by 44 mg/dL (p = 0.001), and total cholesterol by 47 mg/dL (p < 0.001) while raising HDL by 6 mg/dL.
Tributyrin for Gut Barrier Integrity: RCT on Butyrate Delivery
An RCT of 37 adults with metabolic syndrome found that tributyrin supplementation (600mg/day for 12 weeks) significantly reduced intestinal permeability markers and plasma LPS-binding protein levels, indicating improved gut barrier function compared to placebo.
Valerian Root for Sleep Quality: Meta-Analysis of 16 RCTs
A meta-analysis of 16 RCTs (n=1,093) found that valerian root improved subjective sleep quality by 37% on average, though effects on objective sleep measures (polysomnography) were modest and not always statistically significant.
Vitamin C for Common Cold Duration: Cochrane Meta-Analysis
The Cochrane meta-analysis of 29 RCTs (n=11,306) found that regular vitamin C supplementation (≥200mg/day) did not prevent colds in the general population but reduced cold duration by 8% in adults and 14% in children, and decreased cold severity.
Vitamin D and Depression: 2022 Meta-Analysis of 41 RCTs
A 2022 meta-analysis of 41 RCTs (n=53,235) found that vitamin D supplementation significantly reduced depressive symptoms compared to placebo (ES = -0.317, 95% CI: -0.405 to -0.230, p < 0.001). Effects were strongest in those with baseline vitamin D deficiency and diagnosed depressive disorders.
Vitamin D and Immune Function: 2024 Systematic Review
A 2024 systematic review of 25 trials found that vitamin D supplementation (1,000-4,000 IU/day) reduced the risk of acute respiratory infections by 12% overall, with a 42% reduction in participants who were vitamin D deficient at baseline (serum 25(OH)D < 25 nmol/L).
Zinc and Immune Function: 2017 Systematic Review
A systematic review of clinical trials found that zinc supplementation (75mg+/day as lozenges) reduced common cold duration by an average of 33% when started within 24 hours of symptom onset. Zinc also plays essential roles in innate and adaptive immune cell function.