The word carnitine comes from the Latin word for meat because red meat—even if it’s lean—is by far the richest dietary source. Pork and lamb also have fair amounts; chicken, fish and dairy products contain small amounts. The biologically active form is called L-carnitine. The body makes carnitine from amino acids (lysine and methionine), which are building blocks of protein.
Carnitine plays a crucial role in the mitochondria—the energy-producing structures in cells—notably in muscles, including heart muscle. It also acts as an antioxidant. As we age, carnitine levels drop and mitochondrial function becomes impaired, which may contribute to some adverse effects of aging as well as to some diseases. Thus, it’s hoped, carnitine supplements may help prevent these problems.
L-carnitine is sold as a supplement. It’s in many “healthy-aging” products and formulas claiming to improve athletic performance and build muscle. It’s also promoted as a treatment for many disorders, including heart disease, diabetes and dementia, and is supposed to boost energy, improve memory and promote weight loss. Most of this is just marketing hype or wishful thinking.