Also known as 1,3,7-trimethylxanthine; methylxanthine.  An alkaloid and central nervous system stimulant found in coffee, tea, cola nuts, guarana and yerba mate.  Caffeine can enhance exercise performance, and also has mild thermogenic effects.  Because of these effects, caffeine is added to a wide variety of energy drinks, weight loss supplements and pre-workout boosters.  Caffeine is addictive, and both caffeine intoxication and withdrawal are recognized psychiatric disorders.

A member of the carotenoid family of antioxidants with provitamin A activity.  The vitamin A activity of beta-carotene in food is approx. 1/12 that of retinol (pre-formed Vitamin A).  Beta-carotene is most abundant in orange/yellow vegetables and fruits, such as carrots, pumpkin and winter squash.

For more information, see the beta-carotene review in the Vitamins and Minerals section.

Ilex paraguariensis – see Yerba Mate

Konjac: See glucomannan

Also known as L-alanyl-L-histidine.  A naturally-occurring dipeptide in muscle tissue.  Carnosine has antioxidant activity and can inhibit the formation of harmful advanced glycation end products.  Carnosine also helps to buffer hydrogen ions produced during exercise, and thus delay fatigue.

See also beta-alanine; Paul’s review of H+Blocker for more information.

A non-protein amino acid that’s a precursor to carnosine (beta-alanyl-l-histidine).  Carnosine is a dipeptide that’s highly concentrated in muscle tissue.  It has antioxidant effects, and acts to buffer hydrogen ions produced during exercise, thus delaying muscle fatigue.  Beta-alanine is marketed primarily as a bodybuilding, performance enhancing-supplement.  See Paul’s review of H+Blocker, for more information.

See: L-Arginine.

Also known as AKG or AAKG.  Arginine alpha-ketoglutarate is a salt composed of 2 molecules of the conditionally-essential amino acid L-arginine, plus alpha-ketoglutarate, a Krebs Cycle intermediate and nitrogen transporter (via conversion to L-glutamate).  AKG is frequently used in nitric oxide (NO) boosting bodybuilding supplements to increase muscle pump during workouts.  See Paul’s review, “An Introduction to Nitric Oxide Supplements” for more information.

Other chemical names: L-Arginine 2-oxopentanedioate

A conditionally-essential amino acid that’s a component of proteins, substrate for nitric oxide (NO) synthesis, and urea cycle intermediate.  Experimentally, supplemental L-arginine has been shown to increase resting (but not exercise-induced) growth hormone production and improve exercise tolerance in patients with congestive heart failure.

A member of the carotenoid family of antioxidants with provitamin A activity.  The vitamin A of alpha-carotene is approx. one-half that of beta-carotene, the best-known carotenoid in the family.  Like beta-carotene, alpha-carotene is most abundant in orange/yellow vegetables and fruits, such as carrots, pumpkin and winter squash.