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

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

Before you browse, it's worth asking whether you need a supplement at all — see how to decide what you actually need, including a short starting list to discuss with your clinician (and what to skip).

Check price →

• Algal Omega-3

  The vegan branch of the omega-3 family — algal-oil DHA is bioequivalent to fish-derived DHA on the biomarker level (Arterburn 2008 ran it head-to-head against cooked salmon) and has been compared with fish oil at high doses. Two honest caveats: most algal oil is DHA-heavy or DHA-only (only 1 of 5 verified products discloses its EPA:DHA split), and no algal-oil product has run a hard cardiovascular-outcome trial.

• Alpha-GPC

  An acetylcholine precursor with small sports-performance studies — and a 2021 observational study (12M+ people) that linked use to higher stroke risk. Ranked by disclosed actual-mg, not label mg, exposing the industry-wide 50%-blend gap.

• 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 what the research covers.

• Ashwagandha

  KSM-66 vs Sensoril vs generic, and the doses studied.

• Astaxanthin

  Narrow research: eye fatigue, skin, exercise, and lipid markers, with inconsistent results — 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

  Outside of correcting a low intake, "energy" and heart-protection claims for B-complex are not well supported: lowering homocysteine with B vitamins did not change cardiovascular events in large 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. Active vs cheap forms and the megadose trap.

• Beetroot / Dietary Nitrate

  The active compound in beetroot is inorganic nitrate — converted to nitric oxide in the body. Studied for blood pressure and endurance 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, and safety.

• Beta-Alanine

  The carnosine-loading amino acid for high-intensity exercise — studied mainly for 1-4 minute efforts, with little expected for very short or pure-strength work. 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.

• Betaine HCl (Betaine Hydrochloride)

  Not betaine/TMG — betaine HCl is an acidic stomach-acid salt, usually sold with pepsin. The one solid finding (Yago et al., UCSF) is narrow: 1,500mg transiently re-acidified the stomach in a small volunteer study. No RCTs were found in healthy people. The capsule-titration "warmth test" is unvalidated. Do not use with an ulcer history, NSAIDs, or acid-reducing drugs without asking a doctor. Ranked by cost per capsule — plain vs. with-pepsin vs. with-gentian.

• Biotin

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

• Boron

  Modest evidence on the mineral, plus the boric-acid/borax scare that does not apply to supplement-dose boron.

• Boswellia

  Boswellia (Indian frankincense) has been studied in knee osteoarthritis — but only with extracts standardized to AKBA, a boswellic acid. 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. AKBA vs total boswellic acids, and cost by disclosure tier.

• Bromelain

  A pineapple-stem enzyme dosed in activity units (GDU/MCU/FIP), not just mg — identical 500mg labels here carry a 2.5x potency spread (1,200-3,000 GDU). Post-surgical swelling and other uses have been studied with split results, and one osteoarthritis trial (Bolten 2015) tested an enzyme combination product, not bromelain alone.

• Calcium

  Citrate vs carbonate, absorption with/without stomach acid.

• Carnosine (L-Carnosine)

  Oral L-carnosine is largely broken down by serum carnosinase before it reaches muscle — for raising muscle carnosine, beta-alanine is the established, better-evidenced route (Harris 2006). Beyond muscle: modest, mixed research (one trial positive, one null) and lab chemistry that has not been shown in human outcomes. Ranked by verified cost per day, with a combo-formula product flagged, not ranked as plain carnosine.

• Choline

  An essential nutrient — about 90% of Americans fall short of the Adequate Intake. TMAO is a noted nuance in the research. Ranked by elemental choline mg, not bitartrate salt weight.

• Chromium

  Chromium is marketed for blood sugar and weight, but the research is modest and mixed, and meta-analyses disagree. 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. The forms and the cost.

• Citicoline (CDP-Choline)

  Two Cognizin-funded trials looked at attention and memory in healthy adults, and the largest citicoline RCT (ICTUS, n=2,298) was null. Ranked by cost per mg; a Cognizin-branded pick, not a generic, turns out cheapest per mg.

• Citrus Bergamot

  Bergamot polyphenols (BPF) has been studied for cholesterol markers in short Italian trials — but the biggest effects come from studies with commercial or institutional ties to the extract, and the one independent systematic review found the evidence "quite limited." A CYP3A4/statin interaction caution applies; ask your prescriber. Ranked by disclosed polyphenol standardization, not just price.

• CLA (Conjugated Linoleic Acid)

  The classic animal-vs-human-gap supplement: large effects in animals, but two human meta-analyses find only a small effect (~0.09 kg/week), and some trials reported unwanted lab changes. Rare liver case reports exist.

• Cod Liver Oil

  The real safety constraint is the vitamin A load, not the omega-3 — some disclosed servings already use 8-25% of the adult UL before a multivitamin is added. Cod-liver-oil-specific evidence is thin: a small number of trials, some combining it with a multivitamin. Only 2 of 5 tracked products disclose vitamin A to a number.

• Collagen

  Types, what has been studied, and dosing.

• Colostrum

  The one spec that decides quality is IgG — and most product labels do not state it. Disclosed IgG %, cost per gram of IgG, and a plain read on what the research covers.

• Copper

  The honest headline is a warning, not a benefit: most iron-replete adults already exceed the 900mcg RDA from food, and the usual reason to look at it is high-dose zinc, which competes with copper absorption. Anyone with Wilson's disease should not supplement copper. Ask a doctor first. "Copper reverses gray hair" and oral GHK-Cu peptide anti-aging drops are marketing overreach with no human RCT support.

• CoQ10

  Ubiquinol vs ubiquinone, absorption, and dosing.

• Cranberry

  The compound studied in cranberry research 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 36 mg PAC dose and cost per day at the dose the trials used.

• Creatine

  Monohydrate vs HCl, dosing, and what the research covers.

• Curcumin

  Bioavailability problem and enhanced forms.

• D-Mannose

  Early trials looked promising, but the largest trial to date (MERIT, 2024, 598 women, JAMA Intern Med) found no benefit. Cost per 2 g studied dose and the capsule under-dosing trap.

• Digestive Enzymes

  Enzymes differ by type: lactase and alpha-galactosidase (Beano-type) have RCTs behind them; pancreatic enzyme replacement is a prescription medicine, not an OTC product; broad-spectrum "digestive enzyme complex" blends have thin, small-trial evidence, one 100% manufacturer-authored (DigeZyme/Sami-Sabinsa).

• Elderberry

  The honest version: elderberry has small and mixed research on cold and flu symptoms — several small (mostly industry-funded) trials reported a benefit, but the most rigorous independent trial did not. 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. The anthocyanin-disclosure problem and the raw-berry safety note.

• Electrolytes

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

• Essential Amino Acids (EAA)

  A "complete" alternative to BCAAs — free-form EAAs stimulate muscle protein synthesis more than an equivalent amount of intact protein, gram for gram, but whey is already ~45-50% EAA by weight, and two trials found small EAA doses matched much larger whey doses for MPS. Largely redundant for anyone eating adequate protein. Ranked by cost per gram — bulk powder is far cheaper than premium capsules.

• Fiber

  Psyllium vs inulin vs methylcellulose vs wheat dextrin — why the type matters more than the gram count, the trade-offs of each one, and the cost per gram of soluble fiber.

• GABA

  Whether oral GABA meaningfully crosses the blood-brain barrier is genuinely disputed (Boonstra 2015) — the mechanism itself is unresolved, not just "the trials are small." The stress/sleep trial base is small, short, and mostly industry-funded (Pharma Foods International, maker of PharmaGABA); most positive trials used ~100mg of the branded fermented form, while most retail capsules are synthetic GABA at 500-750mg, 5-7.5x the tested dose.

• Garlic

  Garlic has been studied for blood pressure — 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 forms have been used in trials: enteric-coated allicin and aged garlic extract. Why "1000 mg garlic" tells you nothing, and which products disclose the active.

• Ginkgo Biloba

  The honest headline first: the strongest, most independent evidence is negative — the Cochrane review calls the benefit "inconsistent and unreliable." The trials used a specific extract, EGb 761 (240 mg/day). 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). EGb 761 vs generic, and the bleeding-risk caution.

• Glycine

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

• Grape Seed Extract

  Three independent meta-analyses (Feringa 2011, Zhang 2016, Foshati 2022) report a small blood-pressure change, but a well-designed single RCT (Ras 2013, 300mg/day) found no significant effect. Ranked by disclosed OPC/proanthocyanidin standardization, with a mild antiplatelet-mechanism caution for anyone on blood thinners.

• HMB (β-Hydroxy β-Methylbutyrate)

  HMB's widely cited muscle-gain trials (Wilson 2014, Lowery 2016) were funded by and co-authored with Metabolic Technologies Inc., the company that patented and sells HMB — and independent researchers with no MTI tie found trivial-to-null effects in the same trained-athlete population (Rowlands 2009, Sanchez-Martinez 2018). Some smaller studies looked at untrained lifters, older adults, and bed rest. Ranked by cost per 3g/day dose — cheap Ca-HMB powder beats the pricier HMB-FA form on price, with no proven outcome advantage for FA.

• Hyaluronic Acid (Oral)

  Oral HA capsules are a separate product from HA dermal fillers and topical serums — oral evidence never transfers. Small, replicated skin-hydration trials (mostly Kewpie-funded, the Hyabest maker) at 120mg/day; thinner joint research with inconsistent doses. Ranked by trial-matched ingredient vs generic, then cost per mg.

• Inulin

  The best-evidenced prebiotic fiber — and the one most likely to bloat you. A fermentable chicory-root fiber that feeds Bifidobacteria (not a bulking/viscous fiber like psyllium or glucomannan), with an ingredient-manufacturer conflict of interest on its flagship meta-analysis and a real gas/bloating downside. See the Fiber hub for how it compares to other fiber types.

• Iron

  Ferrous sulfate vs bisglycinate, ferritin tests, tolerability.

• Krill Oil

  The phospholipid "better absorbed" edge over fish oil is real but small and inconsistent (positive, non-significant, and null results across three trials) — the bigger issue is density: krill delivers only 108-240mg EPA+DHA per gram of oil vs 300-500mg+/g in concentrated fish oil, so you often pay more for less omega-3. Half the products checked don't even disclose EPA+DHA mg.

• L-Citrulline

  The nitric-oxide / pre-workout amino acid, judged honestly: modest blood-pressure and small performance findings — 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

  L-glutamine is a cheap commodity amino acid your body already makes, and gut-health marketing claims for it are not well supported by trials. 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

  Dosing and how it is used with caffeine.

• Lactoferrin

  Two of the most-cited trials behind it were retracted in 2023. What the remaining research covers, and how to compare products.

• 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.

• Lutein & Zeaxanthin

  AREDS2 was a large trial in people who already had intermediate or advanced AMD. It does not support claims for healthy eyes or the "blue light" screen-strain story most marketing borrows. The 10mg:2mg AREDS2 ratio vs what is actually on shelves, and the honest CREST read on meso-zeaxanthin "triple carotenoid" formulas.

• Magnesium

  Forms compared, picks for sleep and other uses, dosage, and low-intake signs.

• MCT Oil

  One measurable effect (C8-driven ketone elevation), often oversold with weight and cognition claims. The GI-tolerance titration ramp, cost per gram of C8 (the ketogenic driver most labels hide), and why coconut oil is not the same product.

• Melatonin

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

• Methylfolate

  Vs folic acid, forms, and label doses.

• 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 modest, the standardization gap is the main buying problem, and hospital IV silibinin is not the same as an oral capsule.

• MSM

  MSM (methylsulfonylmethane) is a commodity — the identical molecule in every bottle — with modest, mixed research in knee osteoarthritis. 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 cost-per-gram math and OptiMSM vs generic.

• Multivitamins

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

• Myo-Inositol

  The 40:1 ratio, dosing, and what has been studied.

• NAC

  Forms, dosing, and what has been studied.

• Nicotinamide Riboside (NR)

  Nicotinamide riboside label facts, cost and testing: Tru Niagen and Thorne NiaCel are both listed in NSF Certified for Sport, and they were the only two NR products with a buyable Amazon listing when we checked.

• NMN (Nicotinamide Mononucleotide)

  NMN label facts, cost per 500 mg and third-party testing: which NMN products sold on Amazon are in NSF or Informed Choice, which post lab reports by lot, and how capsules, powder and liposomal forms compare on cost.

• 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: small studies on memory and other outcomes, mostly low-certainty. The species trap, the standardization gap, and what the evidence actually shows.

• Phosphatidylserine (PS)

  The FDA's 2003 "qualified health claim" is the weakest tier FDA issues — and the trials behind it used bovine-cortex PS, discontinued for decades. Every product sold today is soy or sunflower, a different substance; the direct soy replication of the classic 300mg dose (Jorissen 2001) was null. Ranked by disclosed source (soy/sunflower/undisclosed) and branded vs generic raw material, then cost per mg.

• Pine Bark Extract (Pycnogenol)

  Nearly all human pine bark evidence is on one patented, industry-funded ingredient — Pycnogenol® — and the one fully independent review (Cochrane 2020, 27 RCTs) found no definitive conclusions. Three blood-pressure meta-analyses of overlapping trials disagree (null, modest-positive, positive-but-not-in-well-designed-trials). A generic pine bark extract has never been tested head-to-head against Pycnogenol, so equivalence is unproven — ranked by genuine-vs-generic split, not price alone.

• Potassium

  Why OTC pills are capped at 99 mg (2% of what you need), who should talk to a doctor before supplementing it, and how to raise your intake from food.

• PQQ (Pyrroloquinoline Quinone)

  Small cognitive/attention/cerebral-blood-flow signals cluster around 20mg BioPQQ trials — but nearly every positive trial traces back to Mitsubishi Gas Chemical (BioPQQ's maker) or a Cepham-affiliated author, and the mitochondrial-biogenesis mechanism is mouse/cell-culture: in the one human trial that measured it in muscle (Hwang 2020), the biomarker rose with ZERO functional benefit. Ranked by BioPQQ-branded vs generic disodium, then cost per mg.

• Probiotics

  Strain-specific research and how to read a label.

• Protein

  Whey vs plant, dosing, and protein per dollar.

• Psyllium

  One of the best-studied fiber supplements: the FDA-authorized soluble-fiber label claim, what trials have looked at, and the husk-vs-powder-vs-capsule buying math. See the Fiber hub for how psyllium compares to other fiber types.

• Quercetin

  Three meta-analyses report a small blood-pressure change that only reached significance at 500mg/day plain quercetin — but plain and phytosome (Quercefit) forms deliver very different absorption per mg (Riva 2019: ~20x), so a milligram isn't a milligram across forms.

• Rhodiola

  The adaptogen with real-but-modest evidence — small endurance findings at higher doses and mixed 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 and rosavin standardization.

• Saffron

  Small trials have looked at mood, with mixed and limited results, and most saffron products do not state their crocin/safranal potency. Dose, standardization, and what the research covers.

• Saw Palmetto

  The largest independent placebo-controlled trials (STEP, CAMUS) and the Cochrane review found no difference from placebo for urinary symptoms. 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. Standardized extract vs berry powder, and cost per day.

• 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

  Dosing and the narrow range between the RDA and the upper limit.

• 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.

• Spirulina

  Cultivated Arthrospira with modest evidence on some lab markers — and a widely misunderstood safety story. The microcystin scare belongs to WILD "blue-green algae" (AFA), not cultivated spirulina, which tested negative for microcystin in the screens we cite; 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, and taurine itself has been studied separately 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.

• Tocotrienols

  The other vitamin E — structurally distinct from tocopherols. The early cholesterol findings were small, 1990s, and industry-linked, and later independent trials did not confirm them. Annatto (tocopherol-free) vs palm (full-spectrum) is a real, evidence-grounded sourcing distinction, not just marketing.

• Tongkat Ali

  Dosing, standardization, and tongkat vs fadogia.

• Urolithin A

  Muscle-endurance and strength measures 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 product (Timeline Mitopure, 500mg free UA) is sold direct to consumers; the two Amazon products we track differ from it in dose per serving or molecular form.

• Vitamin A

  Preformed vitamin A (retinol/retinyl esters) is a proven human teratogen at high doses in pregnancy (Rothman 1995, ~10,000 IU/day threshold — the same number as the adult UL) and, in chronic excess, causes liver and bone toxicity. Most people are already replete from food and don't need a supplement; provitamin-A beta-carotene is a different, non-teratogenic substance covered separately.

• Vitamin B12

  Methylcobalamin vs cyanocobalamin, dosing, and who tends to run low.

• 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). The doses that are risky, and how to buy a sensible one.

• Vitamin C

  Forms, the absorption ceiling, and dosing.

• Vitamin D

  D2 vs D3, dosing, K2 pairing, and the upper limit.

• Vitamin E

  Vitamin E is a "more is not better" vitamin: large independent trials reported no benefit and safety signals at the 400 IU dose most products sell. On the label, natural d-alpha is ~twice as active as synthetic dl-alpha, and gamma/tocotrienol forms are a different product entirely. Natural vs synthetic, and why the dose matters.

• Vitamin K

  K1 vs K2, how much you actually need (90/120 mcg AI), and the one warning that matters: vitamin K interacts with warfarin, so check with your prescriber. See the Vitamin K2 hub for MK-7 detail.

• Vitamin K2

  MK-7 vs MK-4, how much to take with vitamin D, and what has been studied.

• Zinc

  Forms, copper balance, and 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.