We test nothing. We track everyone who does.

Among the most robustly supported supplements for muscle strength and lean mass across age groups. Cognition, mood, and post-menopausal muscle/bone are promising but younger and mixed; each use is graded on its own.

Omega-3 fatty acids (EPA and DHA) have strong, consistent evidence for lowering fasting triglycerides, an effect recognized by the FDA through prescription-drug approvals for fish oil at 4 g/day. The cardiovascular picture is more complicated: pharmaceutical-grade pure EPA at 4 g/day in high-risk statin-treated patients reduced major cardiac events by 25% in the REDUCE-IT trial (PMID 30415628), but standard-dose supplementation (1 g/day) did not reduce cardiovascular events in the large VITAL primary-prevention trial (PMID 30415637), and the difference in dose, formulation, and patient population matters enormously. Cognition claims are not supported by randomized trial evidence in cognitively healthy adults (Cochrane review, PMID 22696350), while DHA is a structural requirement for fetal brain development with limited but suggestive evidence supporting supplementation during pregnancy.

The evidence that protein supplementation supports muscle gain with resistance training is among the most robust in nutrition science: a 2018 meta-analysis of 49 trials (PMID 28698222) confirmed the benefit with a ceiling at roughly 1.6 g/kg/day. Heavy-metal contamination in protein powders is a legitimate concern documented across multiple independent investigations, with plant-based proteins consistently showing higher levels than whey; the widely cited 'nearly half exceed safety thresholds' headline is based on California Prop 65 limits (a threshold approximately 25x stricter than the FDA adult reference level) and the Clean Label Project methodology has been formally disputed by CRN and NPA as non-peer-reviewed and without full transparency. Consumers who prioritize both efficacy and safety are best served by NSF Certified for Sport or Informed Protein-certified products.

Magnesium evidence quality varies sharply by use case and by form. For blood pressure reduction, multiple meta-analyses of RCTs (including a 2025 meta-analysis of 38 RCTs, PMID 41000008) confirm a modest, statistically significant reduction in systolic and diastolic BP; the effect is clinically meaningful mainly in hypertensive or hypomagnesemic populations and does not consistently reach significance in normotensive individuals (Grade B). For sleep, small RCTs show statistically significant but modest effects on insomnia severity; a 2021 systematic review (PMID 33865376) rates the overall evidence quality as low-to-very-low, and two more recent trials on magnesium L-threonate (PMID 39252819) and bisglycinate (PMID 40918053) show small effect sizes; benefits are plausible but should not be overstated (Grade C). For constipation, magnesium oxide and citrate at pharmacological doses are well-established osmotic laxatives, confirmed in a 2019 RCT (PMID 31587548); this is the highest-evidence use but is form-specific and dose-dependent (Grade A). For migraine prevention, a 2024 meta-analysis (PMID 39404918) supports oral magnesium as a meaningful preventive option with reduced attack frequency, severity, and monthly migraine days (Grade B). Form matters enormously across all uses: oxide is cheap and labels high elemental magnesium but is poorly absorbed (roughly 4% bioavailability) and drives GI side effects. Glycinate, bisglycinate, malate, and citrate are substantially better absorbed. ConsumerLab 2024 testing found products that label themselves as glycinate but appear to contain oxide, which is the core transparency problem this vertical addresses.

Vitamin D supplementation is strongly supported for deficiency correction: supplemental D3 reliably raises serum 25(OH)D in deficient individuals, with roughly 100 IU per day raising levels by approximately 1 ng/mL; this relationship is mechanistic, dose-dependent, and not contested (Grade A; PMID 26183416). For bone health and fracture reduction, vitamin D alone shows no consistent fracture-risk reduction; combined with adequate calcium (400-800 IU D3 plus 1,000-1,200 mg calcium), the evidence supports a modest 6% reduction in any fracture and 16% reduction in hip fracture in older deficient populations (PMID 31860103; Grade B). Primary prevention of cancer and cardiovascular disease is NOT supported by the best available evidence: the VITAL trial (25,871 participants, 5.3-year follow-up, PMID 30415629) found no reduction in cancer incidence (HR 0.96, p=0.47) or major cardiovascular events (HR 0.97, p=0.69) at 2,000 IU D3 per day; this is a pre-specified primary endpoint result, not a post-hoc analysis (Grade D). Falls prevention evidence is mixed and dose-dependent: high-dose daily vitamin D (at least 700 IU) combined with calcium reduced fall risk by 17% in a 38-RCT meta-analysis (PMC 9399608), but low-dose and bolus dosing show no significant effect; benefit is primarily relevant to older adults with baseline deficiency (Grade C). Label accuracy is a specific concern: the LeBlanc 2013 JAMA Internal Medicine study (PMID 23400578) found OTC cholecalciferol products ranged from 52% to 135% of labeled dose, and ConsumerLab 2024 testing found products delivering up to 200% of labeled dose, which raises hypercalcemia risk for consumers already taking multiple D-containing supplements.

This is the weakest and most commercially conflicted vertical in the NutraTested coverage set. Electrolyte (carbohydrate-electrolyte) solutions have qualified evidence of advantage over plain water for rehydration during and after sustained exercise, particularly in heat: a 2025 systematic review (PMID 38116803) found 4-9% carbohydrate-electrolyte solutions may be effective for exercise-associated dehydration, and a 2020 RCT (PMID 33333771) showed better fluid retention with high-electrolyte ORS versus plain water (Grade B). Sodium supplementation for hyponatremia prevention in endurance events is biologically plausible and recommended in some ultra-endurance contexts, but current evidence indicates that avoiding overhydration with hypotonic fluids is the primary prevention strategy; salt supplementation alone has not been shown to reduce exercise-associated hyponatremia incidence in clinical trials per StatPearls (NBK572128; Grade B). For everyday use, adrenal support, or hangover recovery in sedentary or moderately active individuals, there is no meaningful clinical evidence base: the adrenal fatigue framing used in some marketing does not reflect a recognized medical diagnosis (PMID 30182895), and no RCT has shown electrolytes reduce hangover severity (Grade D). The independent testing layer is the thinnest of any supplement vertical covered here: the largest product-level sweep is Labdoor 2017 (16 products, now aging), ConsumerLab's electrolyte review is from 2022 and paywalled, and the most notable recent finding is a single advocacy-tester lead result on LMNT Raw Unflavored (27 ppb in dry powder, November 2024). The dominant mass-market brands including LMNT and Liquid I.V. carry no NSF Certified for Sport or Informed Sport certification. Expert recommendations in this category are heavily entangled with paid sponsorships and equity investments: Huberman is a paid LMNT sponsor, and Attia holds disclosed LMNT equity.