L-Arginine
L-arginine is the amino acid the body uses to make nitric oxide. A meta-analysis found gram-level doses modestly improved mild to moderate erectile dy...
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Ingredient type
Amino Acids
Building blocks of protein and related compounds, such as L-carnitine and L-theanine, used in supplements for energy metabolism, focus and relaxation.
L-Arginine
L-Citrulline DL-Malate
L-citrulline is an amino acid that the body converts into arginine. It raises blood arginine better than arginine itself, and a small study found 1.5 ...
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D-Aspartic Acid
D-aspartic acid is an amino acid sold as a testosterone booster. Animal studies are positive, but human results are inconsistent, and a 2024 review fo...
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Taurine
Taurine is the most abundant amino acid in the retina and is essential for photoreceptor health in animal studies. There is little human evidence that...
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5-HTP
5-HTP is the direct precursor of serotonin. Evidence for sleep is limited to small studies, and it can interact with antidepressants and other seroton...
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GABA
GABA is the brain's main calming messenger. A systematic review found limited evidence for stress and very limited evidence for sleep benefits from or...
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Betaine
Betaine is a nutrient from beets and whole grains involved in methylation and liver metabolism. Meta-analyses disagree on body fat and show no effect ...
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L-carnitine
L-carnitine helps transport fatty acids into mitochondria. A meta-analysis of 37 trials found a small average weight reduction, mainly in people with ...
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L-theanine
L-theanine is an amino acid from tea. Combined with caffeine, it produces small short-term improvements in attention and reaction time, but it has no ...
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