The consequences of impaired L-Carnitine ingestion upon vegetarian health and nutrition have received relatively little or no attention to date in humans. This is surprising as the L-Carnitine requirements of the body are met almost exclusively from the consumption of meat, with limited de-novo synthesis. If intake of L-Carnitine is low, however, the body must almost entirely rely on the endogenous synthesis to meet the needs. A vegetarian diet is frequently low in some of the nutrients that are essential for L-Carnitine biosynthesis in the body, such as the amino acids lysine and methionine as well as bioavailable iron. Indeed, humans ingesting a lacto-ovo- or a strict vegetarian diet over years have shown to have decreased plasma L-Carnitine concentrations. High performance athletes such as triathletes have been shown to have lower than normal plasma levels of L-Carnitine, even when maintaining an omnivorous diet. This has been attributed to a higher excretion of esterified L-Carnitine via the kidneys after severe exercise, and, to a lesser extent, via perspiration. Due to the high fat and protein content of meat, however, many athletes wishing to consume a carbohydrate-rich diet often omit meat and may be “silent” vegetarians. Researchers observed that those triathletes who were on a predominantly vegetarian diet had the lowest plasma levels of L-Carnitine. Supplementation with L-Carnitine for 6 weeks increased total L-Carnitine from 27μmol/L to 100μmol/L and free L-Carnitine from 10μmol/L to 85μmol/L. This considerable increase also improved the ratio of Acyl-L-Carnitine to total L-Carnitine, which is a means to express the supply of functionally active L-Carnitine. Vegetarians and anyone following a meat-reduced diet can benefit from additional L-Carnitine. Since L-Carnitine is directly involved in the metabolism of fatty acids and carbohydrates, a good supply is important for active people providing the energy they need.