Carnitine is an amino acid that participates in energy metabolism by transporting long-chain fatty acids, particularly triglycerides, to the body cells where they are broken down for fuel for the tissues and organs. Humans get adequate amounts of carnitine either through exogenous sources (outside the body) or endogenous sources (created within the body).
Carnitine can be absorbed from dietary sources through the intestine. The body can also synthesize carnitine in the liver by combining two amino acids: lysine and methionine. If not used immediately by body tissues, carnitine is stored in the skeletal muscles, the heart, the brain and in sperm.
Because the majority of carnitine is found in skeletal muscles, animal products are the most abundant dietary sources. Red meat, particularly lamb, is particularly rich in carnitine, while poultry and fish contain lesser amounts. Carnitine also accumulates in the milk of animals, especially cows, so it is plentiful in dairy products as well.
For infants, breastfeeding is the best natural source of carnitine. Just as in other animals, human breast milk contains sufficient amounts of the amino acid to support the growth of growing babies.
Vegetarians can still obtain carnitine through the diet in foods such as tempeh, nuts and seeds, wheat, asparagus and avocados. Combining foods high in lysine and methionine can also supply the body with an adequate supply of nutrients for the body to make creatine. Foods rich in lysine include nuts, particularly hazelnuts, peanuts and almonds, pumpkin seeds and squash, wheat germ and oats. High methionine foods include tofu, dried beans, spinach, green peas and corn.