Vegetarian diets can provide high levels of antioxidants and a lipid profile that can help prevent coronary disease. However, there can be some associated problems. Blood samples were taken from a large group of volunteer subjects who were vegans (strict vegetarians; no animal products), lacto-vegearians (vegetarians who eat dairy products), or omnivores (individuals with a normal, varied diet including meat). In each case, the volunteers had followed the diet for several years. The blood levels of both homocysteine and methylmalonate were elevated in the vegan group, somewhat lower in the lactovegetarian group, and much lower in the omnivore group.

Choose the best explanation for the elevated blood levels of homocysteine and methylmalonate. A. Vitamin B12 (cobolamin) is missing from the vegan diet and very low in the lactovegetarian diet. B. Vitamin B9 (folic acid) is missing from the vegan diet and very low in the lactovegetarian diet. C. Vitamin B6 (pyridoxine) is missing from the vegan diet and very low in the lactovegetarian diet. D. Antioxidants in the both the vegan and lactovegetarian diets inhibit the formation of methionine from homocysteine