Taurine is a non-proteinogenic (i.e., it is not incorporated into proteins during translation) sulfur-containing beta-amino acid that is omnipresent in the body and is particularly abundant in electrically excitable tissues such as the heart, retina, brain, and skeletal muscle.^[2]

A small amount of taurine is produced in the liver from the metabolism of cysteine (which is itself derived from the essential amino acid methionine). Taurine can also be obtained directly from certain foods like beef, dark-meat poultry, and, most abundantly, shellfish such as scallops and mussels.^[3][4]

Taurine is considered a conditionally essential nutrient, meaning that we can produce it in our bodies, but under certain conditions may not produce enough to meet all of our functional needs. Because taurine can be produced in the body, the average adult probably doesn’t need to be concerned about overt symptoms of taurine deficiency.^[5] (In this, humans are unlike cats and monkeys, who develop retinopathy and cardiomyopathy with inadequate taurine intake.^{[6][7][8][9][10][11]}) However, low plasma taurine levels are associated with various conditions, such as cardiovascular disease and type 2 diabetes.^[12][13][14]

In accordance with its ubiquitous presence in the body, taurine has diverse physiological functions. It is known as a cell-protecting agent and is involved in osmoregulation, modulation of mitochondrial function and endoplasmic reticulum stress, cell membrane stabilization, conjugation of bile acids, calcium homeostasis, energy metabolism, neuromodulation, and anti-inflammatory and antioxidant actions.^[15][16][2]

Interest in taurine primarily stems from its potential beneficial effects on athletic performance and potential mitigation of cardiovascular risk factors.

Taurine was first used to treat heart failure patients and demonstrated the ability to improve symptoms — as evidenced by improved cardiac output and stroke volume — which spurred research to determine whether it elicited other cardioprotective effects.^[17] While some evidence supports the use of taurine in the treatment of heart failure,^[18] there are few studies on the topic^[19] and further high-quality randomized controlled trials are needed to confirm potential benefits.

More recent evidence demonstrates that taurine modestly reduces blood pressure, and it seems to be more effective in people with prehypertension or hypertension.^[20][21][1] Taurine may also reduce total cholesterol and triglyceride levels.^[21]

Taurine is a common component of energy drinks, which have been shown to enhance various aspects of physical performance (e.g., endurance exercise performance, vertical jump height).^[22] However, energy drinks also contain caffeine, among other ingredients, so it is unclear how much of their benefit can be attributed to taurine.

Because taurine levels are much higher in type I (“slow twitch”) than type II (“fast twitch”) muscle fibers, most studies have investigated whether taurine supplementation improves endurance exercise performance.^[23] Taurine appears to have a small positive effect on time to exhaustion in both untrained healthy people and older adults with heart failure.^[24] In contrast, taurine does not seem to benefit time trial performance.

Research on whether taurine improves muscle strength and power is limited and inconclusive,^[25] and the effect of taurine on reducing symptoms of delayed onset muscle soreness and accelerating recovery following exercise is equivocal and requires further research.^{[26][27][28][29]}

Serious adverse effects have not been reported with taurine supplementation.^[30] The highest dose used in a human trial was 10 grams per day for 6 months, and the longest human trial was 12 months and used a dose of 0.5–1.5 grams per day. Based on the available evidence, it’s suggested that 3 grams per day can be consumed indefinitely without risk of side effects.^[30]

Most of taurine’s benefits are thought to derive from its role as a cell-protective agent: it regulates cell volume, calcium homeostasis, and stabilizes cell membranes, and also exerts antioxidant effects. The primary mechanism by which taurine acts as an antioxidant is unclear. Taurine may have the ability to directly scavenge free radicals,^[31] but it’s more likely that taurine works by regulating antioxidant enzymes and inhibiting the generation of mitochondrial reactive oxygen species.^[16][32][33]

Taurine may provide cardioprotective effects by decreasing oxidative stress and a few other mechanisms. It can modify blood lipids by binding to bile acids and facilitating the breakdown and excretion of cholesterol.^[32][21] Additionally, it reduces blood pressure by enhancing vasodilation (i.e., by relaxing of blood vessels), leading to an increase in blood flow.^[20][34] Taurine may also reduce blood pressure by reducing the production of angiotensin II, a potent vasoconstrictor.^[35]

Muscle contraction is triggered by the release of calcium from the sarcoplasmic reticulum. Taurine may improve physical performance by increasing the calcium-storing ability of the sarcoplasmic reticulum, as well as increasing the sensitivity of force-generating proteins (i.e., actin and myosin) to calcium, thus increasing muscle force.^[36][37]

With special reference to endurance exercise, taurine may aid performance by increasing the use of fat for fuel and reducing the contribution from glycogen, as well as improving mitochondrial function.^[36]