The bioavailability of L-carnitine The homeostasis of L-carnitine is maintained through biosynthesis, efficient reabsorption in the kidneys and food intake, particularly from meat and dairy products. The physiological range of different L-carnitine concentrations in various tissues is maintained by complex transporter systems. The biosynthesis of L-carnitine from the amino acids lysine and methionine proceeds in the liver, kidney and testis, with ┛-butyrobetaine (GBB) being an intermediate precursor. It has been estimated that in the case of a non-vegetarian diet, only about 25% of the necessary L- carnitine is biosynthesised, and 75% is ingested from food. Interestingly, the blood plasma concentration in women is about 20% lower than in men. Additionally, in vegetarians, the L-carnitine concentration in the blood serum is 20- 30% lower than that in the reference population