Ingredients, compared by dose
Creatine monohydrate
Creatine helps muscles regenerate energy (ATP) during short, intense efforts. It is one of the most studied sports supplements: short-term use often increases strength and power, and longer-term use supports adaptations to training.
10 products compared
Caffeine
A stimulant that can improve endurance, strength and power and reduce how hard exercise feels.
12 products compared
Beta-alanine
An amino acid that raises muscle carnosine, which helps buffer acid during hard exercise. The evidence for performance benefits is limited.
8 products compared
L-citrulline
An amino acid the body converts to arginine and then nitric oxide — the basis of "pump" marketing. Research supporting it as a performance aid is limited and conflicting.
8 products compared
Betaine
Also called trimethylglycine; found in beets, spinach and whole grains. Small studies in men show conflicting results and modest improvements at best.
5 products compared
BCAAs (leucine, isoleucine, valine)
Three essential amino acids that make up about a quarter of the amino acids in complete-protein foods. Studies have not consistently shown that BCAA supplements improve performance, build muscle or speed recovery — complete protein supplies them automatically.
11 products compared
Whey protein
The fast-digesting protein fraction of milk. Isolate is filtered to more protein and less lactose and fat than concentrate.
10 products compared
L-theanine
An amino acid found in tea, often paired with caffeine to smooth out the jittery edge or used on its own for relaxation. Research is early: a small 2019 randomized trial (30 adults, 200 mg a day for four weeks) found improvements in self-reported stress and sleep measures.
13 products compared
Magnesium
A mineral involved in hundreds of enzyme reactions, including muscle and nerve function. Forms that dissolve well in liquid, such as citrate, lactate and chloride, are absorbed more completely than oxide and sulfate.
13 products compared
Vitamin D
Helps the body absorb calcium and maintain bones. It is made in skin exposed to sunlight and found naturally in few foods.
10 products compared
Vitamin B12
Needed for nerve function and red blood cell formation. It occurs naturally only in animal foods, so vegans — and many older adults, who absorb it less well — rely on fortified foods or supplements.
12 products compared
Vitamin C
An antioxidant needed to make collagen and support immune function.
8 products compared
Folate
A B vitamin needed to make DNA and for healthy cell division — especially important before and during early pregnancy.
8 products compared
Zinc
A mineral involved in immune function, wound healing and protein synthesis.
10 products compared
Iron
Needed to make hemoglobin, which carries oxygen in the blood. People who menstruate, are pregnant or eat no meat are most likely to fall short.
3 products compared
Biotin
A B vitamin heavily marketed for hair, skin and nails. Benefits are clearest in people who are deficient, which is uncommon.
5 products compared
Omega-3 (EPA & DHA)
EPA and DHA are long-chain omega-3 fats found mainly in fatty fish and algae.
6 products compared
Probiotics
Live microorganisms whose effects depend on the specific strain — results for one strain don’t carry over to another.
17 products compared
Melatonin
A hormone that helps regulate the sleep–wake cycle. Research suggests it may help with jet lag and some circadian rhythm sleep disorders.
3 products compared
Electrolytes (sodium & potassium)
Sodium and potassium are the main electrolytes lost in sweat; they help the body hold on to fluid and keep muscles and nerves working.
9 products compared
Fiber (psyllium, inulin, glucomannan)
Soluble fibers absorb water, add bulk and — in the case of prebiotics like inulin — feed gut bacteria.
15 products compared
Collagen peptides
Hydrolyzed collagen, usually from bovine hide or fish skin. Research on skin elasticity and joint comfort is promising but mixed, and many trials are industry-funded.
7 products compared