1. Human milk contains about 7 times more taurine than cow’s milk, which on average has an essential nutrient content about 3 times greater than human milk. This 21-fold relative nutrient enrichment is almost certainly not an accident. It is highly likely that taurine is a required nutrient for infants and should be in all infant formulas.
2. Is taurine essential for adults? It is made from essential nutrient methionine via cysteine, but it is likely that it is not made in sufficient quantities in at least some adults. The popularity of several energy drinks containing taurine attests to either a perceived benefit from supplementation or to a mass placebo effect.
3. For vegans especially, taurine could be essential. Found only in animal products, taurine is obtained by faithful vegans only through de novo synthesis. Since methionine is low in plant products generally, vegans must rely on an untested salvage pathway from plant betaines to keep their limited methionine pools at sufficiently high levels to supply all of the downstream products. In theory, most vegans would benefit from strong taurine supplementation.
4. The wide-ranging effects of taurine on metabolism argue that demand for it might get particularly acute, making it conditionally essential in those cases.
5. For more information, see Yamori et al. “Taurine in health and diseases,” Journal of Biomedical Science 2010, 17 Suppl 1: S6.(http://www.jbiomedsci.com/content/17/S1/S6) and “The Sulfur-Containing Amino Acids: An Overview.” J. Nutr. 136: 1636S–1640S, 2006