Supplement & Nutrient Encyclopedia

Supplements for metabolic health: what the human evidence shows

14 supplements in our encyclopedia have at least one graded human outcome for metabolic health. Each row shows the strongest one, ranked by grade and then by the number of people studied. A high grade means the research is solid, not that the effect is large: open the row for the size of the effect and the dose tested.

Strongest evidence per supplement

Supplements with graded human evidence for metabolic health, strongest first
SupplementStrongest outcomeGradeStudy
Carnitine (L-carnitine, L-carnitine L-tartrate, acetyl-L-carnitine)Body weight, BMI and fat massWorsenedForm tested: L-carnitineGrade Bmeta-analysis · n = 2,292 · 2020
Zinc (picolinate vs gluconate vs bisglycinate)Fasting blood sugar and related markersWorsenedForm tested: various zinc saltsGrade Bmeta-analysis · n = 1,700 · 2019
TaurineBlood pressure, fasting glucose and triglyceridesWorsenedForm tested: taurineGrade Bmeta-analysis · n = 1,024 · 20242 graded rows for this goal
PsylliumFasting blood sugar, HbA1c and insulin resistanceWorsenedForm tested: PsylliumGrade Bmeta-analysis · n = 962 · 20242 graded rows for this goal
Berberine (vs dihydroberberine)Fasting glucose and HbA1cImprovedForm tested: berberineGrade BRCT · n = 116 · 20082 graded rows for this goal
Vitamin D3 vs D2Blood-sugar progression in adults with elevated blood sugarMixedForm tested: vitamin D3Grade CRCT · n = 2,423 · 2019
Selenium (selenomethionine vs selenite)Developing high blood sugar over 7.7 yearsImprovedForm tested: selenium (form not specified in abstract)Grade CRCT · n = 1,202 · 20072 graded rows for this goal
FenugreekFasting and 2-hour blood sugar and HbA1cWorsenedForm tested: Fenugreek (preparations varied by trial)Grade Cmeta-analysis · n = 706 · 2023
Magnesium glycinateFasting glucose (people with diabetes)ImprovedForm tested: Oral magnesium (forms varied by trial)Grade Cmeta-analysis · n = 670 · 2016
ResveratrolFasting glucose, insulin and HbA1cMixedForm tested: ResveratrolGrade Cmeta-analysis · n = 388 · 20142 graded rows for this goal
NMN (nicotinamide mononucleotide)Fasting glucose, insulin, HbA1c and lipidsNo effectForm tested: NMNGrade Cmeta-analysis · n = 342 · 2024
Reishi mushroomHbA1c, cholesterol and body-mass indexNo effectForm tested: Ganoderma lucidum vs placeboGrade Cmeta-analysis · n = 130 · 2015
Nicotinamide riboside (NR)Insulin sensitivity and glucose metabolismNo effectForm tested: Nicotinamide riboside vs placeboGrade CRCT · n = 40 · 20182 graded rows for this goal
QuercetinBlood lipids and glucoseNo effectForm tested: QuercetinNo effectmeta-analysis · n = 896 · 2020

Grades follow our methodology. A “no effect” grade means good trials found no benefit. Amounts in trials are what was studied, not advice for you.

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Educational information only, not medical advice. Dietary supplements are not intended to diagnose, treat, cure or prevent any disease.