B-Vitamin Status and Concentrations of Homocysteine in Austrian Omnivores, Vegetarians and Vegans

Abstract

Background: A vegetarian diet is considered to promote health and longevity and reduce the risk of cardiovascular diseases and cancer. However, a vegetarian diet may be deficient in some nutrients. Exclusion of animal products in vegetarian diets may affect the status of certain B-vitamins, and further cause the rise of plasma homocysteine concentration. Objective: The nutritional status of various B-vitamins (B₁, B₂, B₆, B₁₂, folic acid) and the concentration of homocysteine in blood plasma of omnivores (n = 40), vegetarians (n = 36) and vegans (n = 42) in Austria was evaluated. Methods: The evaluation was done using the functional parameters erythrocyte transketolase (ETK), glutathione reductase (EGR) and glutamic oxaloacetic transaminase (EGOT) activation coefficients. Enzyme activity was measured photometrically. The quantity of vitamins B₁, B₂ and B₆ in urine and the concentrations of vitamin B₆ and homocysteine in plasma were determined by HPLC methods with fluorescence detection. Plasma concentration of vitamin B₁₂ and folic acid were measured with radioimmunoassay. Results: Most of the subjects showed a satisfying vitamin B₁ status. Vegans presented a significantly lower mean plasma vitamin B₁₂ concentration than omnivores and vegetarians and deficiency in 2.4% of the volunteers but the highest mean value of plasma folate among the investigated groups. A deficient status of folate was found in 18% of omnivores and in approximately 10% of vegans and vegetarians. The status of riboflavin is considered to be deficient in about 10% of omnivores and vegetarians and in over 30% of vegans. According to the activation coefficient of GOT, approximately one third of all subjects showed vitamin B₆ deficiency. Elevated homocysteine concentration in plasma was observed in 66% of the vegans and about 45–50% of the omnivores and vegetarians. Vegan subjects had significantly higher mean plasma homocysteine levels than omnivores. Conclusion: Thiamin and folate need not be a problem in a well-planned vegan diet. Vitamins B₁₂ and B₂ may need attention in the strict vegan diet, especially regarding elevated homocysteine levels in plasma. Pyridoxine status appeared to be independent of the diet.