Supplements A–Z (2026): Evidence-Based Comparison Guides

By Erin Rose · Updated July 10, 2026 · Methodology · About Us

• Alpha-Lipoic Acid (ALA)

  Only the R-(+) enantiomer is the active form — and most "alpha-lipoic acid" is racemic (50/50), so a "600 mg" cap is really ~300 mg active R. But here is the counter-intuitive part the cost math reveals: priced per mg of actual active R, bulk racemic is the CHEAPEST source of R; premium R-ALA and stabilized sodium-R-lipoate cost several times more per mg of R — you pay for better absorption, not more active. The R-vs-racemic truth, the "R-ALA Complex" label trap, and the honest evidence (strong for IV diabetic neuropathy, weak long-term oral).

• Ashwagandha

  KSM-66 vs Sensoril vs generic, stress, sleep.

• Astaxanthin

  Real but narrow evidence: screen/eye fatigue, UV/skin tolerance, inconsistent exercise data, and modest lipid markers — plus why the "2 mg EFSA limit" you may have read about does not apply to the natural extract sold as a supplement.

• B-Complex

  A B-complex helps mostly when you are correcting a deficiency — outside that, the "energy" and heart-protection claims do not hold up: lowering homocysteine with B vitamins did not cut cardiovascular events in the big trials. Two things separate a good one: active/methylated forms (methylfolate, methylcobalamin, P5P) vs cheap folic acid and cyanocobalamin, and dose — the popular "B-50"/"B-100" products put B6 at 50-100 mg, right at the upper limit tied to nerve damage. What the evidence really shows, active vs cheap forms, and the megadose trap.

• Beetroot / Dietary Nitrate

  The active compound in beetroot is inorganic nitrate — converted to nitric oxide for blood pressure and endurance. Real evidence at ~6-13 mmol/day (372-800 mg nitrate), but the catch: nitrate content varies >200x between products and almost none disclose it, so "beetroot 1000 mg" tells you nothing about the dose that matters. The mmol-to-mg math, the cost per actual nitrate, and why the marketed milligrams are the wrong number.

• Berberine

  Dosing, dihydroberberine, blood sugar, safety.

• Beta-Alanine

  The carnosine-loading amino acid for high-intensity exercise — solid evidence for 1-4 minute efforts, but useless under 60 seconds or for pure strength. The 4-6 g/day loading dose, the cost per gram, and the label trap: most pre-workouts underdose it, and the tingle you feel is NOT proof of an effective dose.

• Biotin

  Hair and nails evidence, dosing, lab-test interference.

• Boron

  Real-but-modest evidence: mineral/bone plausibility, a small short-term hormone shift (not replicated in athletes), and CFB-specific joint data — plus the boric-acid/borax scare that does not apply to supplement-dose boron.

• Boswellia

  Boswellia (Indian frankincense) has real, relatively fast-acting evidence for knee osteoarthritis — but only from extracts standardized to AKBA, the boswellic acid that actually inhibits inflammation. The catch: the trial-grade products disclose an AKBA % or a branded extract (5-Loxin, Aflapin, ApresFlex), while cheap ones print only "65% boswellic acids" (a generic spec) or a bare milligram — and lab testing has found commercial AKBA content ranging from 3.8% down to nearly zero. What the evidence shows, AKBA vs total boswellic acids, and cost by disclosure tier.

• Calcium

  Citrate vs carbonate, absorption with/without stomach acid.

• Chondroitin

  Osteoarthritis evidence and how it pairs with glucosamine.

• Chromium

  Chromium is sold for blood sugar and weight, but the honest evidence is modest and mixed — meta-analyses in people with diabetes disagree, and it is not an established treatment for anyone. Three things the label gets wrong: picolinate is the most-studied form but no better absorbed than the others (all absorb ~1%); every product is 6-29x the ~35 mcg you actually need; and the identical picolinate dose sells for wildly different prices, which is brand, not formulation. What the evidence shows, the forms, and the cost.

• Collagen

  Types, skin and joint evidence, dosing.

• Colostrum

  The one spec that decides quality is IgG — and most brands, including ARMRA, hide it. Disclosed IgG %, cost per gram of IgG, and an honest read on what the evidence supports.

• CoQ10

  Ubiquinol vs ubiquinone, absorption, statins.

• Cordyceps

  Most US "cordyceps" is mycelium-on-grain — mycelium dried on a rice or oat substrate, largely starch, low in the actives. Premium products are fruiting body / Cordyceps militaris that disclose a real beta-glucan % (the validated active) and cordycepin; the rest hide behind a big "milligram" number or a "polysaccharide %" that just counts grain starch. You can even spot-check it at home with an iodine drop. The fruiting-body-vs-mycelium truth, the beta-glucan test, and the honest (modest) evidence.

• Cranberry

  The compound studied for UTI prevention is the A-type proanthocyanidin (PAC), and the studied dose is ~36 mg PAC/day. But only a handful of products disclose PAC in milligrams; the rest sell a meaningless "25,000 mg equivalent" number that says nothing about the compound that matters. The 2023 Cochrane reversal (a real reduction in recurrent-UTI risk for women), the 36 mg PAC dose, and cost per day at the dose the trials actually used — for prevention, not treatment.

• Creatine

  Monohydrate vs HCl, dosing, what actually works.

• Curcumin

  Bioavailability problem, enhanced forms, joint pain.

• Elderberry

  The honest version: elderberry has real but small and mixed evidence for shortening cold/flu symptoms — several small (mostly industry-funded) trials found a benefit, but the single most rigorous independent trial found none. On the shelf, the marker actives are anthocyanins, and only one product in our set discloses an anthocyanin % — the rest sell a bare milligram, an "equivalent" number, or a sugar-forward gummy. What the evidence really shows, the anthocyanin-disclosure problem, and the raw-berry and autoimmune safety notes.

• Electrolytes

  Sodium/potassium/magnesium ratios, sugar-free picks, keto and sweat loss.

• Fiber

  Psyllium vs inulin vs methylcellulose vs wheat dextrin — why the type matters more than the gram count, who each one helps (and harms), and the cost per gram of soluble fiber.

• Garlic

  Garlic modestly lowers blood pressure in people with hypertension — but most garlic pills may deliver almost none of the active. Allicin isn't in the clove; it forms from alliin when garlic is crushed, and the enzyme that makes it is destroyed by stomach acid, so 83% of even enteric-coated brands were found to release under 15% of their labeled allicin. Two routes actually work: enteric-coated allicin, and aged garlic extract (the form with the real BP trial data). Why "1000 mg garlic" tells you nothing, which products deliver, and the honest blood-pressure evidence.

• Ginkgo Biloba

  The honest headline first: the strongest, most independent evidence is negative — the Cochrane review calls the benefit "inconsistent and unreliable," and two large trials show ginkgo does NOT prevent dementia. The narrow positive signal is EGb 761 (the specific trial extract, 240 mg/day) for treating — not preventing — dementia. So which product matters: only Nature's Way Ginkgold is that trial extract; and only a couple of brands disclose their ginkgolic-acid level (the allergenic contaminant capped at <5 ppm). What the evidence really shows, EGb 761 vs generic, and the bleeding-risk caution.

• Glucosamine

  Osteoarthritis evidence, sulfate vs HCl, dosing.

• Glycine

  One identical molecule that costs up to 12x more from some brands. The 3 g sleep dose (honestly graded), cost per gram, and the glycine you already get from magnesium glycinate and collagen.

• Iron

  Ferrous sulfate vs bisglycinate, low ferritin, tolerability.

• L-Carnitine

  It comes in four forms with different jobs — but they're all sold as generic "energy and fat burning." L-carnitine L-tartrate (LCLT) has the exercise-recovery evidence; acetyl-L-carnitine (ALCAR) crosses into the brain for cognition and nerve pain; propionyl-L-carnitine (PLC) is the circulation form for claudication; plain L-carnitine is the base. Buy the wrong form and you paid for the wrong evidence. Which form for which goal, the cost per gram, and the honest read on the TMAO heart question.

• L-Citrulline

  The nitric-oxide / pre-workout amino acid, judged honestly: modest blood-pressure and small performance evidence — and the label trap that "6,000 mg citrulline malate" is not 6,000 mg of citrulline. The clinical dose vs label dose, cost per actual gram, and why independent testing found most "2:1" products under-deliver.

• L-Glutamine

  The honest version: L-glutamine is a cheap commodity amino acid your body already makes in abundance, and the "seals leaky gut / heals your gut" marketing isn't supported — controlled trials show no effect on gut permeability at normal doses, none in athletes, and high doses were actually linked to higher mortality in critical illness. Its one FDA-approved use is reducing sickle-cell crises. So the real questions are just: cheapest gram (it's all the same molecule), powder vs capsule, and whether you need a sport certification.

• L-Theanine

  Calm-focus evidence, dosing, and stacking with caffeine.

• L-Tyrosine

  A real but narrow tool: tyrosine improves cognition under acute stress (cold, sleep loss, heavy load) but does nothing at rest — it is not a daily focus pill. And the dose is the story: trials used ~2 g up to 7-13 g of plain L-tyrosine, so a 500 mg capsule is a fraction of a studied dose and powders cost a fraction per gram. Plus the NALT trap: N-acetyl-L-tyrosine is marketed as "more bioavailable" but is poorly converted to usable tyrosine. What works, the dose gap, and why the fancy form is worse.

• Lion's Mane

  What the human evidence actually shows, and how to tell a real fruiting-body extract from grain filler by its beta-glucan.

• Magnesium

  Forms compared, sleep/anxiety/cramps picks, dosage, deficiency signs.

• Melatonin

  How much to take (less is often more), timing for sleep vs jet lag, and the label-accuracy problem.

• Methylfolate

  Vs folic acid, MTHFR, pregnancy dosing.

• Milk Thistle (Silymarin)

  The active is silymarin — and the milligram number on the front of the bottle usually tells you nothing about it. Quality products disclose an 80% silymarin standardization (so you can compute the actual active); cheap ones headline "1000 mg" or "3000 mg / 4:1 / full-spectrum" with no silymarin figure, and independent testing found silymarin content varying ~2,800% between brands. The evidence is real but modest (lower ALT/AST; no confirmed mortality benefit), the standardization gap is the moat, and IV silibinin (the real mushroom-poisoning antidote) is not the same as an oral capsule.

• MSM

  MSM (methylsulfonylmethane) is a commodity — the identical molecule in every bottle — with modest, mixed evidence for knee osteoarthritis (physical function improves; pain often does not reach significance). So the only thing worth comparing is cost per gram, which ranges widely, and powder is far cheaper than capsules. The one quality signal is OptiMSM (a branded, distilled MSM) vs generic — and joint blends bury a tiny MSM dose at a much higher effective price. The honest evidence, the cost-per-gram math, and OptiMSM vs generic.

• Multivitamins

  Who actually needs one, what to look for, best picks.

• Myo-Inositol

  PCOS evidence, the 40:1 ratio, and dosing.

• NAC

  Liver/glutathione and mental health, dosing.

• Nicotinamide Riboside (NR)

  NAD+ reliably rises in all 8 trials, but five independent, non-industry RCTs each testing a different organ system found the functional/clinical endpoint null or underpowered. NR's regulatory story is NMN's opposite: never excluded, never delisted. Only two products cleared the ASIN gate — a near-duopoly, disclosed honestly.

• NMN (Nicotinamide Mononucleotide)

  Blood NAD+ reliably rises and a walking-speed/muscle-function signal replicates across several small trials — but a 2024 meta-analysis of 8 RCTs found no glucose/lipid benefit, and the FDA excluded then reinstated NMN as a legal supplement (2022-2025). Ranked by purity/third-party testing, not just price.

• Omega-3

  EPA vs DHA, triglyceride vs ethyl ester, best fish oil.

• Panax Ginseng

  The active compounds are ginsenosides — found ONLY in true Panax ginseng (Asian) and Panax quinquefolius (American). "Siberian ginseng" (Eleuthero) is not a ginseng and has ZERO ginsenosides. Most labels list "ginseng root mg" with no ginsenoside % (content varies 15-36x vs label), and evidence is real-but-modest: an ED benefit tempered by a low-certainty Cochrane review, memory (not overall cognition), and a small glucose effect. The species trap, the standardization gap, and what the evidence actually shows.

• Potassium

  Why OTC pills are capped at 99 mg (2% of what you need), who should never supplement it (kidney disease, blood-pressure meds), and how to actually raise your intake.

• Probiotics

  Strain-specific evidence, condition matching.

• Protein

  Whey vs plant, dosing, protein for GLP-1 users and weight loss.

• Rhodiola

  The adaptogen with real-but-modest evidence — dose-dependent endurance/VO2max gains above ~600 mg/day and honest, mixed anti-fatigue data — plus a hard buying problem: rosavins are the R. rosea species fingerprint, yet many products disclose only salidroside (or nothing), and surveys have found 20-40% of R. rosea products mislabeled or the wrong species. The studied dose, the rosavin standardization moat, and the evidence graded honestly.

• Saffron

  The mood spice with unusually real evidence — small trials find saffron extract comparable to SSRIs for mild-to-moderate depression (studied for, not a treatment) — and a hard buying problem: saffron is one of the most adulterated commodities on earth, and most products never disclose their crocin/safranal potency. Dose, the standardization moat, and the honest depression evidence.

• SAMe

  Depression evidence, dosing, and stability caveats.

• Saw Palmetto

  The honest headline first: the strongest, most independent placebo-controlled trials (STEP, CAMUS) and the Cochrane review found saw palmetto no better than placebo for prostate/urinary (BPH) symptoms — even at 2-3x the dose — and it does not lower PSA. The one nuance is that standardized extracts (the ~85-95% fatty-acid, 320 mg/day form the trials used, and the European "Permixon" extract) are a different, better-characterized product than the cheap non-standardized "berry powder" most brands sell. What the evidence really shows, standardized vs berry powder, and the honest read on hair loss.

• Sea Moss

  What the evidence really shows (almost no human trials), the iodine/thyroid risk nobody labels, heavy metals, and how to buy a tested one instead of a 16-in-1 blend.

• Selenium

  Thyroid (Hashimoto’s) evidence, dosing, and the narrow safe range.

• Shilajit

  What the thin human evidence really shows, and the moat almost no one covers: heavy metals (including thallium), the fulvic-acid % confusion, and how to buy a tested one.

• Spermidine

  Kiechl's dietary-intake mortality association vs SmartAge's null primary memory endpoint (n=100, RCT) — autophagy is a mouse/yeast mechanism, not human proof. Ranked by disclosed actual spermidine mg, not wheat-germ-extract weight.

• Spirulina

  Cultivated Arthrospira with real-but-modest evidence for cholesterol, blood pressure and fasting glucose — and a widely misunderstood safety story. The microcystin scare belongs to WILD "blue-green algae" (AFA), not true spirulina, which tests clean; the real quality axis is cultivation source + heavy-metal testing, which most labels hide behind a vague "third-party tested." What the evidence shows, the AFA vs Arthrospira distinction, and how to tell a transparent source from marketing.

• Taurine

  The energy-drink amino acid, judged honestly: caffeine (not taurine) drives the "energy" buzz, but taurine has real, separately-earned wins for blood pressure and exercise. Dose by goal, the cost-per-gram (one identical molecule, ~8x price spread), and what the 2023 longevity paper actually showed.

• Tongkat Ali

  Testosterone evidence, dosing, tongkat vs fadogia.

• Urolithin A

  A replicated muscle-endurance/strength signal across 7 human RCTs — but 5 of 7 are funded by the company that sells the ingredient (Zhao 2024 is the lone independent trial). The trial-grade product (Timeline Mitopure, 500mg free UA) isn't reliably buyable on Amazon; both live Amazon options are compromised (under-dosed or the wrong molecule).

• Vitamin B12

  Methylcobalamin vs cyanocobalamin, energy, deficiency risk.

• Vitamin B6

  Vitamin B6 is the rare water-soluble vitamin with a real toxicity ceiling: chronic high doses cause sensory nerve damage, so the tolerable upper limit is 100 mg/day — yet many products sell exactly 100 mg, thousands of percent over the ~1.7 mg you need. The other axis is pyridoxine HCl vs P5P (the active coenzyme form, marketed as superior on thin evidence). Where B6 actually helps (PMS, pregnancy nausea), the dose that is risky, and how to buy a sane one.

• Vitamin C

  Forms, the absorption ceiling, immune evidence.

• Vitamin D

  D2 vs D3, dosing (1000–5000 IU), K2 pairing, deficiency.

• Vitamin E

  Vitamin E is a "more is not better" vitamin: the biggest, most independent trials found no heart or cancer prevention and signals of harm at the 400 IU dose most products sell — a heart-failure signal, increased prostate cancer, and higher all-cause mortality at high doses. The one proven use is a narrow liver condition (NASH) at high dose. On the label, natural d-alpha is ~twice as active as synthetic dl-alpha, and gamma/tocotrienol forms are a different product entirely. What the evidence really shows, natural vs synthetic, and why the dose matters.

• Vitamin K2

  MK-7 vs MK-4, how much to take with vitamin D, and the calcium-routing (bone vs artery) evidence.

• Zinc

  Forms, copper balance, immunity and colds, upper limits.

How we compare supplements

We pull product label data from the NIH Dietary Supplement Label Database, clinical evidence from PubMed systematic reviews, and third-party certifications from USP and NSF. Read our methodology and editorial standards.