The supplement industry is worth over $170 billion globally. Most of it is marketing. Some of it is science. The challenge is telling the difference.
This guide sorts the most popular supplements into three categories based on the quality and consistency of peer-reviewed research: strong evidence, moderate evidence, and weak or insufficient evidence. We update it quarterly as new systematic reviews and meta-analyses are published.
This is not medical advice. It’s a research summary. If you’re considering adding or changing supplements, talk to a qualified healthcare provider — especially if you take medication or have existing conditions.
How we rank evidence
We prioritize systematic reviews and meta-analyses (which aggregate multiple studies) over individual trials. We look at:
- Study quality: Was it randomized, controlled, and adequately powered?
- Consistency: Do multiple studies agree?
- Effect size: Is the benefit meaningful, or statistically significant but practically irrelevant?
- Population: Was it studied in healthy adults, or only in deficient/clinical populations?
A supplement can have “strong evidence” for one purpose and “weak evidence” for another. We specify.
Strong evidence
These supplements have consistent support from multiple high-quality systematic reviews in healthy adult populations.
Creatine monohydrate
What it does: Improves strength, power output, and muscle recovery. Emerging evidence for cognitive benefits.
The research: A 2024 systematic review of 49 RCTs with 1,863 participants found that creatine supplementation significantly increased one-rep max strength (average +2.5 kg) and fat-free muscle mass (+0.3 kg) during training programs of 6+ weeks. A separate 2024 review of 8 RCTs found improvements in working memory and processing speed in healthy adults.
Dosing: 3-5g daily. No loading phase necessary. Take consistently — timing doesn’t matter.
Who benefits most: Anyone who trains regularly. The evidence is strongest for resistance training but applies to endurance and team sports as well.
Verdict: The most well-researched supplement in existence. Safe, cheap, effective.
Vitamin D
What it does: Supports bone health, immune function, and may affect mood, cardiovascular health, and cellular aging.
The research: The VITAL trial — one of the largest randomized trials ever conducted on supplements (25,871 participants) — found that vitamin D supplementation helps maintain telomere length, a biomarker of cellular aging. Deficiency (below 20 ng/mL) is linked to increased risks of bone fractures, infections, and depression across multiple meta-analyses.
Dosing: 1,000-4,000 IU daily, depending on baseline levels. Get tested first if possible — dosing should be based on your actual blood levels, not a guess.
Who benefits most: People who live in northern latitudes, have darker skin, spend limited time outdoors, or test below 30 ng/mL. If you’re outdoors regularly in a sunny climate, you may not need it.
Verdict: Strong evidence, especially if you’re deficient. Get tested. Supplement accordingly.
Omega-3 fatty acids (EPA/DHA)
What it does: Reduces inflammation, supports cardiovascular health, and may benefit cognitive function and mood.
The research: Multiple systematic reviews support EPA and DHA supplementation for cardiovascular risk reduction. The VITAL trial showed omega-3s reduced heart attack risk by 28% and cardiovascular death risk by 50% in participants who ate less than 1.5 servings of fish per week. Benefits are most pronounced in people with low dietary fish intake.
Dosing: 1-2g combined EPA/DHA daily. Fish oil or algae-based (for vegetarians).
Who benefits most: People who eat less than 2 servings of fatty fish per week. If you eat salmon, sardines, or mackerel regularly, supplementation may be redundant.
Verdict: Strong evidence for cardiovascular health, particularly if your diet is low in fish.
Moderate evidence
These supplements show promise in multiple studies, but the evidence is less consistent, limited to specific populations, or from smaller trials.
Magnesium
What it does: Involved in 300+ enzymatic processes. May improve sleep quality, reduce muscle cramps, and support mood.
The research: A 2024 review in Nutritional Supplements for Healthy Aging highlighted magnesium as beneficial across multiple health domains. For sleep specifically, magnesium glycinate has shown improvements in sleep quality in limited studies, particularly in older adults and people with low dietary intake. However, large-scale RCTs in healthy young adults are still lacking.
Dosing: 200-400mg daily (glycinate or bisglycinate forms are best absorbed and least likely to cause digestive issues).
Who benefits most: People with poor sleep, muscle cramps, high stress, or low dietary intake (most processed-food-heavy diets are low in magnesium).
Verdict: Likely helpful, especially if your diet is lacking. Low risk, low cost. Worth trying for 30 days and seeing if you notice a difference.
Protein supplements (whey, casein, plant-based)
What it does: Helps meet daily protein targets, supports muscle recovery and growth.
The research: Protein supplementation consistently improves muscle protein synthesis when combined with resistance training. The effect is most significant when total daily protein intake would otherwise be below 1.6g/kg body weight.
Dosing: Enough to hit 1.6-2.2g protein per kg body weight daily (from all sources combined). A protein shake is a food, not a magic supplement.
Who benefits most: People who struggle to hit protein targets through whole foods. If your diet already provides enough protein, adding a shake won’t provide additional benefit.
Verdict: Not really a “supplement” — it’s food in powder form. Useful for convenience, not necessary if your diet is sufficient.
Weak or insufficient evidence
These supplements are widely marketed but lack consistent, high-quality evidence in healthy adult populations.
Collagen peptides
Marketed for: Skin elasticity, joint health, gut health.
The reality: Most collagen studies are small, short-term, and industry-funded. Your body breaks collagen down into amino acids during digestion — it doesn’t reassemble as collagen in your skin. Some studies show modest improvements in skin hydration, but the effect sizes are small and the research quality is low.
BCAAs (branched-chain amino acids)
Marketed for: Muscle recovery, reduced soreness.
The reality: If you eat adequate protein (1.6g/kg+), BCAAs provide no additional benefit. They’re a subset of the amino acids already in your food. The money spent on BCAAs would be better spent on a meal with complete protein.
Multivitamins
Marketed for: “Insurance” against nutritional gaps.
The reality: Multiple large-scale reviews have found no consistent benefit of multivitamin supplementation for all-cause mortality, cardiovascular health, or cancer prevention in well-nourished populations. The Physicians’ Health Study II of 14,641 men found no cardiovascular benefit over 11 years of daily multivitamin use. Targeted supplementation of specific deficiencies is more effective than a broad multivitamin.
”Greens” powders
Marketed for: Replacing vegetables, “detoxification,” energy.
The reality: No systematic review supports greens powders as a substitute for whole vegetables. They contain some micronutrients, but lack the fiber, water content, and phytochemical complexity of actual produce. Eat vegetables. If you can’t eat enough, a greens powder is better than nothing — but it’s not what the marketing claims.
The practical takeaway
If you’re going to take supplements, start with the ones that have the strongest evidence and the clearest relevance to your situation:
- Creatine (if you train) — 3-5g daily
- Vitamin D (if you’re deficient or at risk) — get tested first, then dose accordingly
- Omega-3 (if you don’t eat fish regularly) — 1-2g EPA/DHA daily
- Magnesium (if your sleep or stress is poor) — 200-400mg glycinate
- Protein (if you can’t hit targets through food) — enough to reach 1.6g/kg
Everything else? Optional at best. Save your money for better food and a better mattress.
The bottom line
Most supplements are solutions looking for problems. The four with strong evidence — creatine, vitamin D, omega-3, and magnesium — are cheap, safe, and well-researched. Everything else requires a specific reason and a healthy skepticism of marketing claims. When in doubt, food first.