Vegetarians who avoid all sources of animal protein are called vegan. Another recent study adds further support to the growing scientific perception that avoidance of animal protein as in a vegan lifestyle, can help many people avoid coronary artery disease, heart attacks and other disorders. Most animal proteins but very few vegetable proteins contain high levels of the amino acid methionine, which appears to exert negative effects on the circulatory system when converted to the toxic metabolite homocysteine. Vegan diets help prevent this conversion of methionine to large amounts of homocysteine by only offering sparse amounts of methionine to begin, and by providing naturally high concentrations of essential vitamins B6, B12 and folic acid, which help eliminate homocysteine. These vitamins are significantly depleted in meat-eaters, smokers, alcohol and coffee drinkers.