New study links L carnitine in red meat to heart disease Harvard Health L Carnitine: Benefits, Side Effects, And Dosage, Per Dietitians Revisiting the Role of Carnitine in Heart Disease Through the Lens of the Gut Microbiota If you are like a lot of people, you may have never heard of carnitine but this important nutrient is critical for our body's ability to optimally burn fat required for energy.