Medical Disclaimer: This post is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare professional before starting any supplement or health regimen. Individual results vary.

Complete Guide to Supplements: What Works and What Doesn’t

I spent three years buying supplements based on Instagram ads and gym floor advice. Most of them sit unfinished in a cabinet. A few genuinely changed how I feel. After reading through meta-analyses and tracking my own blood markers, here is an honest guide to what the evidence actually supports.

Part of our Sleep Optimization Blueprint guide.

The global supplement industry reached $177 billion in 2023 (Grand View Research). Marketing budgets are enormous. Peer-reviewed evidence is thinner. The gap between the two is where most people lose money.

Tier 1: Strong Evidence

Creatine monohydrate is the most studied sports supplement in existence. A 2022 meta-analysis in the Journal of the International Society of Sports Nutrition (JISSN) covering 22 randomized trials found consistent improvements in strength output and lean mass. Dose: 3–5g daily. No loading required. Cost: under $1/day for a quality brand.

Vitamin D3 deficiency affects an estimated 42% of American adults (Nutritional Research, 2011). A 2023 Cochrane review found supplementation reduced respiratory infection risk in deficient individuals. Get a blood test first. Target 40–60 ng/mL. Standard dose: 2,000–4,000 IU with a fatty meal.

Omega-3 (EPA/DHA) from fish oil has the most evidence for cardiovascular and cognitive support. A 2019 NEJM trial (REDUCE-IT, n=8,179) found 4g/day of EPA reduced major cardiac events by 25% in high-risk patients. For general health, 1–2g EPA+DHA daily is a reasonable starting point.

Magnesium glycinate supports sleep quality and muscle recovery. Many people are subclinically deficient due to poor soil quality in modern food systems. A 2021 review in Nutrients found magnesium supplementation improved sleep efficiency in older adults. 200–400mg before bed is well-tolerated.

Tier 2: Conditional Evidence

Ashwagandha has growing evidence for stress and cortisol reduction. A 2019 double-blind trial (Medicine, n=60) found 240mg/day reduced cortisol by 23% versus placebo. Quality varies enormously by brand. Look for KSM-66 or Sensoril extracts standardized to withanolide content.

Caffeine is the most widely used performance supplement in the world and one of the most evidence-backed. It improves endurance, reaction time, and focus across dozens of trials. Tolerance builds quickly. Cycling off for 10 days every 6–8 weeks preserves effectiveness.

Tier 3: Weak or Overhyped

BCAAs are largely unnecessary if you eat enough protein. A 2017 meta-analysis in the Journal of the International Society of Sports Nutrition found no significant benefit over whole protein sources. Save the money.

Collagen peptides for joint health show mixed results. Small studies show promise; larger trials are lacking. For skin elasticity, a 2019 double-blind trial in Skin Pharmacology showed modest benefit after 12 weeks — but effect sizes were small.

Most proprietary blends hide individual doses behind “proprietary formula” labels. Without knowing exact amounts, you cannot verify you are getting therapeutic doses of any ingredient.

What I Actually Take

My current stack: Vitamin D3 (3,000 IU), magnesium glycinate (300mg at night), omega-3 (2g EPA+DHA), creatine (5g post-workout). Total cost: about $40/month. I dropped everything else after reviewing the evidence.

How to Evaluate Any Supplement

Three questions before buying: Is there a randomized controlled trial in humans? What was the dose and duration? Was the study funded by the manufacturer? Use Examine.com for unbiased summaries. Check ClinicalTrials.gov for ongoing research. PubMed for primary sources.

Bottom Line

A handful of supplements have genuine evidence. Most do not. Start with blood work to find actual deficiencies. Prioritize the Tier 1 list. Ignore anything sold primarily through influencer channels. Your baseline habits — sleep, protein intake, exercise — outperform any supplement stack.

Sources: Grand View Research (2023), JISSN meta-analysis (2022), Cochrane Review on Vitamin D (2023), REDUCE-IT trial NEJM (2019), Nutrients magnesium review (2021), Medicine ashwagandha trial (2019).