The Supplement
Starter Guide
The 5 most evidence-backed supplements — and how to actually buy them.
Most supplements on the market have thin evidence behind them. A few have been tested to exhaustion. This guide focuses on the small group that hold up across hundreds of peer-reviewed studies, plus what to look for when buying so you don’t waste money on underdosed or poorly formulated versions.
Our scoring methodology uses two tiers. Tier 1 grades the ingredient itself against published research (PubMed, clinical trials). Tier 2 grades the specific brand product on dose accuracy, purity testing, and cost per clinically effective dose. The supplements below all score high on Tier 1. Brand picks and cost-per-dose rankings live on the site.
The 5 supplements at a glance
- Creatine monohydrate — 3–5g/day for strength, lean mass, and cognition.
- Vitamin D3 — 1,000–4,000 IU/day; pair with K2 (MK-7).
- Omega-3 (EPA + DHA) — 1,000–2,000mg combined, rTG form.
- Magnesium glycinate or citrate — 200–400mg elemental.
- Protein — 20–40g/serving, whey isolate or pea+rice.
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Creatine Monohydrate
Creatine is the most studied supplement in sports nutrition, with 500+ peer-reviewed studies. Demonstrated benefits include improved strength output, lean muscle mass gains with training, and growing evidence for cognitive support in older adults and vegetarians.
3–5g daily. Loading phases (20g/day for a week) are optional and not required.
Creatine monohydrate, unflavored powder. Ignore “advanced” forms (HCL, ethyl ester, buffered) which cost 3–5× more with no clinical advantage.
Proprietary blends that bury the creatine dose. Flavored versions that add unnecessary sweeteners and gums.
Any brand claiming creatine requires “cycling” or needs to be paired with specific carb ratios. The science doesn’t support this.
Vitamin D3 (Cholecalciferol)
An estimated 35–40% of US adults are deficient or insufficient, particularly those in northern latitudes, darker skin tones, older adults, and people who work indoors. Supplementation improves bone density, immune function, and mood in deficient populations.
1,000–4,000 IU daily for most adults. Higher doses (5,000+ IU) should be based on blood work showing deficiency. Request a 25-hydroxyvitamin D test from your doctor before going above 4,000 IU.
D3 (cholecalciferol), not D2 (ergocalciferol). D3 raises blood levels more effectively. Pair with K2 (MK-7 form) for better calcium utilization and arterial health, especially at higher doses.
Gummy versions that often underdose. Vitamin D sprays and “sublingual” products with unclear absorption data.
Any supplement claiming to “fix” a deficiency without a blood test baseline.
Omega-3 (EPA + DHA)
EPA and DHA (the active forms in fish oil) have strong evidence for cardiovascular support, triglyceride reduction, and cognitive health. The evidence for ALA (plant-based omega-3 from flax) is much weaker because conversion to EPA/DHA is inefficient in humans.
1,000–2,000mg combined EPA + DHA per day. Note: this is the EPA+DHA total, not total fish oil. A 1,200mg fish oil capsule typically contains only 180mg EPA and 120mg DHA.
Triglyceride or re-esterified triglyceride (rTG) form. These absorb better than ethyl ester (EE) forms, which are cheaper and more common. Algae-based EPA/DHA is a legitimate option for vegans.
“Fish oil” products that don’t list EPA and DHA amounts separately. Low-dose gummies marketed as omega-3 when they’re mostly ALA.
Rancidity. Crack open a capsule and smell it. Fresh fish oil smells faintly of the ocean. Rancid oil smells strong, bitter, or metallic.
Magnesium (Glycinate or Citrate)
Approximately half of US adults fall short of the recommended daily intake. Supplementation has clinical evidence for sleep quality, muscle cramps, blood pressure regulation, and migraine prevention at appropriate doses.
200–400mg of elemental magnesium daily, taken with food. Start lower and increase if tolerated. This is the elemental amount, not the total compound weight (a 500mg magnesium glycinate capsule contains only ~50mg elemental magnesium).
Magnesium glycinate (best for sleep and calm, gentle on digestion) or magnesium citrate (good absorption, mild laxative effect at higher doses). Magnesium L-threonate has emerging evidence for cognitive effects but costs significantly more.
Magnesium oxide. It’s cheap, commonly used in low-end products, and has poor absorption (around 4% bioavailability).
Products that don’t specify the elemental magnesium amount. “Magnesium complex” blends that underdose each form.
Protein (Whey Isolate or Plant Blend)
Adequate protein intake supports muscle synthesis, recovery, satiety, and body composition. Most adults benefit from 0.7–1.0g per pound of body weight when strength training. Supplementation is convenient but not required if whole-food intake is sufficient.
20–40g per serving, 1–3 servings daily as needed to hit protein targets. Leucine content matters more than total protein grams for triggering muscle protein synthesis (aim for 2–3g leucine per serving).
Whey isolate if lactose is an issue (contains less than 1% lactose). Whey concentrate is fine otherwise and costs less. For plant-based: pea + rice blends have a complete amino acid profile. Soy isolate is also a legitimate option.
“Mass gainers” loaded with sugar and maltodextrin. Proprietary protein blends (often called “amino spiked”) that list multiple protein sources without specifying grams of each.
Protein content that seems too high for the serving size. Products that don’t disclose third-party testing for heavy metals.
What to look for on any supplement label
Five checks that apply across every category — not just the five above.
- Third-party testingUSP, NSF, Informed Sport, ConsumerLab, or Labdoor. The FDA does not verify supplements before sale.
- Clear dosingEach active ingredient listed with its specific amount. No proprietary blends.
- Reasonable cost per effective doseA “budget” supplement dosed below clinical levels is more expensive than a properly dosed premium product.
- Published Certificate of Analysis (COA)Serious brands post batch-specific lab results.
- No disease claimsIf the label claims to “cure,” “treat,” or “prevent” any condition, it’s operating outside FDA guidelines.