White blood cells, or leukocytes, represent a major protective barrier between you and invading microorganisms and other potentially harmful agents. Five kinds of white blood cells exist in your body, each with a distinct function. Neutrophils are your main defense against bacterial and fungal infections, and a low neutrophil count, also known as neutropenia, increases your risk for diseases caused by these organisms. Many factors can contribute to a low neutrophil count, including nutritional deficiencies caused by a strict vegetarian, or vegan, diet.
Like all white blood cells, neutrophils are produced in your bone marrow before they migrate into your bloodstream and lymphatic system. Neutrophils are the most numerous white cells in your circulation, but they are short-lived, surviving an average of about five days. Therefore, new neutrophils must be made quickly, continuously and in large numbers, a process that requires copious amounts of DNA. Vitamin B-12, an essential participant in DNA synthesis, is often lacking in vegans' diets.
Vitamin B12, or cyanocobalamin, is unique among the B vitamins. It possesses the most complex molecular structure of any vitamin, it is the only vitamin that contains an essential mineral, cobalt, and it is not found in appreciable quantities in any plant food. According to the Linus Pauling Institute at Oregon State University, vitamin B-12 is required for the activity of an enzyme that adds methyl groups to DNA, thereby facilitating the manufacture of chromosomes for new cells.
Vegans who do not supplement their diets with vitamin B-12 are at risk for developing B-12 deficiency. Because your body recycles B-12 fairly efficiently, a deficiency can take many months or even years to emerge. Nonetheless, scientists at the University of Oxford in the United Kingdom showed that half of the vegans enrolled in a large European study were vitamin B-12 deficient. "The Merck Manual of Diagnosis and Therapy" lists vitamin B-12 deficiency as a common cause of a low neutrophil count.
Considerations and Recommendation
Strict vegetarians – those who avoid all animal products – are at risk for developing a low neutrophil count if they do not supplement with vitamin B-12. A low neutrophil count heightens your chances for bacterial and fungal infections. Since vitamin B-12 is limited to animal sources, fortified foods, some fermented products – miso and tempeh, for example – and supplements, vegans must take special care to get enough of this important nutrient. Vitamin B-12 supplements are produced from bacterial fermentation, so this represents an acceptable source of B-12 for vegans. The recommended dietary allowance for vitamin B-12 for non-pregnant adults is 2.4 mcg daily. If you are a vegan, ask your doctor if your vitamin B12 needs are being met.