Free reference
Supplement & Nutrient Encyclopedia
One page per compound or form. Every evidence row is a human trial with its effect direction, grade, participant count, year, the form and dose studied, and a PubMed link. We show the elemental math behind label claims and every published interaction we can source. No product rankings on these pages, and nothing behind a paywall.
A
B
- Berberine (vs dihydroberberine)BotanicalGrade ABerberine is a yellow plant alkaloid from goldenseal, barberry and Coptis; dihydroberberine is a reduced form marketed for better absorption.
- Beta-alanineAmino acidGrade BBeta-alanine is a non-protein amino acid that the body combines with histidine to make carnosine, a buffer of acid in muscle.
C
- Caffeine (capsules, gum and anhydrous powder)OtherGrade BCaffeine is a methylxanthine stimulant found in coffee, tea and cacao that blocks adenosine receptors, raising alertness and reducing fatigue.
- Calcium (carbonate vs citrate)MineralGrade ACalcium is the body's most abundant mineral, stored mostly in bones and teeth and needed for muscle, nerve and blood-vessel function.
- Carnitine (L-carnitine, L-carnitine L-tartrate, acetyl-L-carnitine)Amino acidGrade BCarnitine is an amino-acid-derived compound that carries long-chain fatty acids into mitochondria so they can be burned for energy.
- Choline (bitartrate vs alpha-GPC vs phosphatidylcholine)OtherGrade CCholine is an essential nutrient used to build cell membranes and the neurotransmitter acetylcholine, and to supply methyl groups.
- Citrulline (L-citrulline and citrulline malate)Amino acidGrade CCitrulline is an amino acid made in the body and found in watermelon; the kidneys convert most of it into arginine.
- Collagen peptidesOtherGrade BCollagen peptides are hydrolyzed collagen protein, sold as powders and capsules.
- CoQ10 (ubiquinol vs ubiquinone)OtherGrade CCoenzyme Q10 is a fat-soluble compound the body makes for cellular energy production; supplements sell it oxidized (ubiquinone) or reduced (ubiquinol).
- CordycepsMushroomGrade CCordyceps are parasitic fungi used in traditional East Asian medicine; supplements use several species.
- Creatine monohydrateAmino acidGrade ACreatine is a compound made from amino acids that muscles store as phosphocreatine to recycle energy (ATP) during short, intense effort.
E
F
- FenugreekBotanicalGrade CFenugreek is a clover-like herb whose maple-scented seeds are used as a spice and sold as powders and extracts.
- Folate (methylfolate vs folic acid)VitaminGrade AFolate (vitamin B9) is a water-soluble B vitamin needed to make DNA and RNA and to metabolize amino acids such as homocysteine.
H
I
- Iodine (potassium iodide, kelp)MineralGrade BIodine is a trace mineral the thyroid needs to make the hormones T4 and T3, which regulate metabolism and early brain development.
- Iron (ferrous sulfate vs bisglycinate vs other forms)MineralGrade AIron is an essential mineral that forms part of hemoglobin and myoglobin, which carry and store oxygen in blood and muscle.
L
M
- MagnesiumMineralForms overviewGrade AEssential mineral involved in over 300 enzyme systems; sold as glycinate, citrate, threonate, malate, taurate, oxide and other salts.
- Magnesium citrateMineralGrade CMagnesium salt of citric acid (about 16% magnesium by weight), among the better-absorbed forms in human comparisons.
- Magnesium glycinateMineralGrade AMagnesium bound to the amino acid glycine (about 14% magnesium by weight); studied for sleep in one RCT.
- Magnesium L-threonateMineralGrade CMagnesium salt of L-threonic acid (about 8% magnesium by weight), studied for cognition and sleep in small RCTs.
- MelatoninOtherGrade BMelatonin is a hormone the brain makes in response to darkness; it helps time the body's 24-hour clock and sleep.
N
- NAC (N-acetylcysteine)Amino acidGrade BNAC is an acetylated form of the amino acid cysteine; it supplies cysteine for glutathione and was approved as a drug in 1963.
- Nicotinamide riboside (NR)NAD+ / longevityGrade CNicotinamide riboside is a vitamin B3-family precursor of the coenzyme NAD+.
- NMN (nicotinamide mononucleotide)NAD+ / longevityGrade CNMN is a precursor of the coenzyme NAD+; in rodents, aging and obesity impair NAD+ synthesis.
O
P
- Potassium (chloride vs citrate vs gluconate)MineralGrade APotassium is an essential mineral and electrolyte that maintains cell fluid volume and supports nerve transmission, muscle contraction and kidney function.
- ProbioticsOtherGrade AProbiotics are live microorganisms, named by genus, species and strain, sold in foods and supplements.
- PsylliumBotanicalGrade APsyllium is the husk of Plantago seeds: a soluble, gel-forming fiber sold as powders, capsules and wafers.
Q
R
- Reishi mushroomMushroomGrade CReishi (Ganoderma lucidum, lingzhi) is a fan-shaped mushroom used in traditional Chinese medicine.
- ResveratrolNAD+ / longevityGrade CResveratrol is a plant polyphenol (a stilbene) found in grapes, berries and peanuts.
- Rhodiola roseaBotanicalGrade CRhodiola rosea is a plant from cold, high-altitude regions; its root extract is sold as a supplement.
S
- SaffronBotanicalGrade CSaffron is the dried stigma of the Crocus sativus flower; extracts contain crocin, crocetin and safranal.
- Selenium (selenomethionine vs selenite)MineralGrade CSelenium is an essential trace mineral built into 25 selenoproteins involved in thyroid hormone metabolism, DNA synthesis and antioxidant defense.
- SpermidineNAD+ / longevityGrade CSpermidine is a natural polyamine found in foods such as wheat germ; it induces autophagy in animal models.
T
- TaurineAmino acidGrade BTaurine is a sulfur-containing amino acid that is popular in dietary supplements and in functional foods and energy-type beverages.
- Tongkat aliBotanicalGrade CTongkat ali (Eurycoma longifolia) is a plant widely used in Asia; its root water extract is sold as a supplement.
- Turmeric and curcuminBotanicalGrade BTurmeric is a root spice (Curcuma longa); curcumin is its main yellow curcuminoid.
V
- Vitamin A (retinyl palmitate vs beta-carotene)VitaminGrade AVitamin A is a fat-soluble vitamin, as preformed retinol or provitamin carotenoids, needed for vision, immunity, growth and reproduction.
- Vitamin B12 (methylcobalamin vs cyanocobalamin)VitaminGrade CVitamin B12 (cobalamin) is a water-soluble vitamin needed for red blood cells, nerve function and DNA synthesis; supplements use several cobalamin forms.
- Vitamin B6 (pyridoxine vs P5P)VitaminGrade BVitamin B6 is a group of water-soluble compounds whose active form, PLP, is a coenzyme in over 100 reactions, mostly protein metabolism.
- Vitamin C (ascorbic acid vs buffered vs liposomal)VitaminGrade BVitamin C (ascorbic acid) is a water-soluble vitamin and antioxidant needed to make collagen, some neurotransmitters and carnitine.
- Vitamin D3 vs D2VitaminGrade AVitamin D is a fat-soluble vitamin sold as D3 (cholecalciferol) or D2 (ergocalciferol); the body converts both to 25-hydroxyvitamin D.
- Vitamin E (natural d-alpha vs synthetic dl-alpha tocopherol)VitaminGrade BVitamin E is a group of fat-soluble antioxidants; alpha-tocopherol is the only form the body maintains and the one intake targets cover.
- Vitamin K2 (MK-7 vs MK-4)VitaminGrade CVitamin K2 is a group of menaquinones; supplements mainly use MK-7 (long half-life, microgram amounts) or MK-4 (studied at milligram amounts).
W
Z
Articles: straight answers from the research
- 400 IU of Vitamin E Is Either 268 mg or 180 mg. The "d" or "dl" on the Label Decides
- Alpha-GPC vs Choline Bitartrate: Blood Choline Rose the Same, but One Detail Differed
- Ashwagandha for Stress and Sleep: What the Trials Found, and Why the Results Vary So Much
- Ashwagandha Side Effects: The Liver, Thyroid and Pregnancy Warnings Behind Denmark’s Ban
- B12 After 50 and on Metformin: Why Levels Drop, and What the Trials Say About Fixing Them
- Berberine Side Effects and Drug Interactions: The Liver-Enzyme Problem Nobody Mentions
- Berberine, “Nature’s Ozempic”: What the Trials Actually Show (Hint: About 2 Pounds)
- Beta-Alanine vs Creatine: Different Jobs, Different Time Frames
- Caffeine Before a Workout: 3 mg/kg, 15 to 60 Minutes Out, and Why It Helps Endurance Most
- Calcium Citrate or Carbonate? The 40% vs 21% Label Math, and Why Smaller Doses Absorb Better
- Can Vitamin K2 Keep Calcium Out of Your Arteries? What 14 Trials Actually Show
- Choline in Pregnancy: Most Women Fall Short, and Most Prenatal Vitamins Barely Help
- Citrulline for the Gym: About 3 Extra Reps, Less Next-Day Soreness, No Endurance Edge
- Citrulline Malate vs L-Citrulline: The 56.64% Label Math, and Two Head-to-Head Trials
- CoQ10 With Statins: Statins Do Lower It, but Does Taking It Ease Muscle Aches?
- Cordyceps Benefits: The Endurance Claim Failed Its Best Test
- Creatine After 50: What It Does for Muscle, Memory and Bone (and What It Doesn’t)
- Creatine Loading Phase: Do You Need It, and Why Did the Scale Just Jump?
- Do Calcium Pills Raise Heart Attack Risk? What the 2010 Scare Found, and What Came After
- Does Collagen Count as Protein? It Helps With Training, but Whey Builds More Muscle
- Does Collagen Really Work for Skin? The Benefit Disappears in Independent Trials
- Does Creatine Cause Hair Loss? The One Study Behind the Fear, and the Trial That Finally Checked Hair
- Does Lion's Mane Work? One Small Memory Trial, and Gains That Faded
- Does NMN Work? It Raises NAD, but Pooled Trials Find Little Else So Far
- Does Tongkat Ali Work? Small, Short Trials and Mixed Results
- Does Vitamin D Protect Your Bones? The 25,871-Person Trial That Surprised Everyone
- Electrolyte Drinks vs Water: When the Extra Sodium Matters, and When It Does Not
- Fenugreek and Blood Sugar: Lower Readings in Pooled Trials, Low-Quality Evidence
- Fenugreek Side Effects: Digestive Upset, Low Blood Sugar and a Pregnancy Warning
- Fish Oil After 50: Big Trials Found No Drop in Heart Events, and a Heart-Rhythm Signal Nobody Mentions
- Fish Oil vs Krill Oil vs Algae Oil: Which Omega-3 Is Worth Your Money?
- HMB for Muscle After 50: Small Gains in Mass, Grip and Walking Speed Across 21 Trials
- HMB vs Creatine: In Young Lifters, Creatine Has the Data and HMB Mostly Does Not
- How Many Brazil Nuts a Day Is Too Many? The Selenium Math in One Handful
- How Much Caffeine Is Too Much? 400 mg a Day, 100 mg for Teens, and Why Pure Powder Is Dangerous
- How Much Magnesium Is Too Much? The 350 mg Rule, the Label Trap and Who Should Be Careful
- How Much Melatonin Should You Take? Trials Used 0.5 to 5 mg, and Timing Mattered as Much as Dose
- How Much Protein Builds Muscle? Gains Leveled Off Near 1.6 g/kg a Day
- How Much Vitamin A Is Too Much? The Label Detail That Decides It
- Iodine Before and During Pregnancy: Why Many Prenatals Leave It Out, and What an 832-Woman Trial Found
- Iron After 50: Why Most Men and Postmenopausal Women Shouldn’t Take It Without a Blood Test
- Iron Pills Without the Stomach Upset? The Case for Every-Other-Day Dosing
- Is Cordyceps Safe? Short Trials Found No Problems, but Products Vary by Species
- Is NAC Safe to Take Daily? What Long Trials and FDA's 2022 Policy Say
- Is NMN Legal in the US? FDA Reversed Its 2022 Position on September 29, 2025
- Is Resveratrol Safe? Mild Side Effects in Trials, Open Questions on Interactions
- Is Spermidine Safe? Small Trials up to 40 mg a Day Found No Problems
- Is the Taurine in Energy Drinks Bad for You? The Safety Data Points at the Caffeine
- L-Carnitine for Weight Loss: About 1.2 kg in Pooled Trials, and a Smaller Effect Over Time
- L-Carnitine Side Effects: Stomach Upset and Fishy Odor at 3 g, Plus the TMAO Question
- L-Theanine and Caffeine: What the "Calm Focus" Stack Actually Did in Trials
- L-Theanine for Anxiety and Sleep: The Evidence Is Thinner Than the Marketing
- Lion's Mane Side Effects: Stomach Upset, Headache and Allergy
- Liposomal, Buffered or Ester-C: Is Fancy Vitamin C Worth Paying More For?
- Magnesium Glycinate vs Citrate: The Calm One, the Bathroom One, and What the Label Really Holds
- Melatonin Gummies: 22 of 25 Were Mislabeled, and Child Poison-Center Calls Rose Sixfold
- Methylcobalamin vs Cyanocobalamin: Is the “Active” B12 Worth Paying More For?
- Methylfolate vs Folic Acid: What the MTHFR Gene Hype Gets Wrong
- MK-7 vs MK-4: The Two Kinds of Vitamin K2, and Why Their Doses Differ a Thousandfold
- NAC and Glutathione: What GlyNAC Trials Actually Measured
- Nicotinamide Riboside Benefits: Higher NAD+, One Walking Result, No Metabolic Gains
- NMN vs NR: No Head-to-Head Trial, and Similar Results So Far
- Potassium and Blood Pressure: What the Trials Found, and the Doses They Used
- Probiotic CFU Explained: Why the Strain Name Matters More Than the Billions
- Probiotics With Antibiotics: Two Strains Have the Data, and Strain Is Everything
- Psyllium Husk for Cholesterol: About 13 mg/dL Off LDL Across 28 Trials
- Psyllium Husk Side Effects: The Choking Warning, Medicine Timing and Allergy
- Quercetin and Blood Pressure: A Real but Small Drop of About 2 to 3 mmHg
- Quercetin Phytosome vs Plain Quercetin: Absorption Differs up to 62-Fold
- Reishi Mushroom Benefits: Few Human Trials, and the Biggest Review Found No Effect
- Reishi Mushroom Side Effects: Well Tolerated in Trials, With Rare Liver Case Reports
- Resveratrol Benefits: Mostly Null Results in Human Trials
- Rhodiola Rosea Benefits: Small, Mixed Trials and an NIH "Not Enough Evidence" Verdict
- Rhodiola Side Effects: Dizziness, Insomnia and a Drug-Enzyme Interaction
- Saffron for Sleep: Better Quality Scores in 8 Trials, Low-Certainty Evidence
- Saffron Supplement Side Effects: A Blood-Pressure Dip and Little Long-Term Data
- Salt Tablets for Endurance Racing: The 413-Athlete Ironman Trial Found No Difference
- Selenium for Your Thyroid? What 16 Trials on Thyroid Antibodies Actually Showed
- Smoked in the Past? Why Beta-Carotene Was Pulled From the Classic Eye-Vitamin Formula
- Spermidine Benefits: A Promising Memory Pilot, Then a Null 12-Month Trial
- Switched to Sea Salt or Pink Salt? You May Have Quietly Dropped Your Main Iodine Source
- Taurine Benefits: Small Exercise Gains, Modest Metabolic Shifts, No Memory Boost
- The Anabolic Window: A Meta-Analysis Found Total Protein Mattered More Than Timing
- Tongkat Ali Side Effects: Short Safety Data, a Drug Interaction and Tainted Products
- Too Much Folic Acid After 50? The B12 Problem It Can Hide
- Turmeric and Curcumin Benefits: Modest Signals, Low-Quality Trials
- Turmeric With Black Pepper: Better Absorption, and a Liver Safety Question
- Ubiquinol vs Ubiquinone: Is the Pricier CoQ10 Worth It After 40?
- Vitamin B6 Toxicity: How a “Harmless” Vitamin Can Cause Tingling Feet
- Vitamin C and Colds: What 10,000 People in Trials Taught Us (It’s Not What the Label Implies)
- Vitamin D3 and K2 Together: Smart Pairing or Marketing? What the Research Actually Shows
- Vitamin D3 vs D2: Why the Letter on the Label Changes How Much You Absorb
- Vitamin E for Your Heart? Three Big Trials Found No Benefit, and Some Found Harm
- Why Beta-Alanine Makes Your Skin Tingle, How Long It Lasts, and How Trials Kept It Down
- Why Potassium Supplements Stop at 99 mg (About 2% of the Daily Value)
- Zinc for Colds: About 2 Days Shorter, but Only If You Use It the Way the Trials Did
- Zinc Picolinate, Citrate or Gluconate? The Absorption Data, and Why More Zinc Can Cost You Copper