Nutrients. 2014 Aug; 6(8): 3259–32
Vegan Diet, Subnormal Vitamin B-12 Status and Cardiovascular Health
Metabolic vitamin B-12 deficiency is prevalent in vegetarians and, in particular, in vegans. Those subjects with normal or relatively high salt intake may be associated with unhealthy early vascular changes in function and structure, which have not been well documented in the past. In individuals with subnormal vitamin B-12 status, vitamin B-12 supplementation may significantly improve such vascular changes. Regular monitoring of vitamin B-12 profile may thus be beneficial for early detection and treatment of metabolic vitamin B-12 deficiency, and possibly prevention of atherosclerosis-related diseases.
Vegetarians, in particular vegans in India and China, have a high prevalence of metabolic vitamin B-12 deficiency.
Restriction or exclusion of all animal food, including dairy and egg products, in strict vegans may result in lower intake of vitamin B-12, and subsequently metabolic vitamin B-12 deficiency and adverse vascular surrogates (brachial FMD and carotid IMT).
Vegetarian diets are protective for cardiovascular risk and events. Vegan diets are more protective compared with lacto-ovo-vegetarian diets for body mass index, and prevalence of diabetes mellitus, hypertension and hyperlipidemia. However, in cohorts with normal or relatively high salt intake and subnormal vitamin B12 status, such as in Chinese vegans, there is an adverse impact of vegan diets on atherosclerosis surrogates (arterial endothelial function and carotid intima-media thickness), which is potentially ameliorable by vitamin B-12 supplementation. Whether this benefit could be extended to other vegans with lower salt intake and better blood pressure profiles will remain to be confirmed.
Hence vegetarians in particular vegans need to be advised to carefully plan their diets, and to monitor their plasma vitamin B-12 on a more regular basis, to facilitate early detection of low vitamin B-12 status, and if necessary to take vitamin B-12 fortified food, B-12 supplementation, or milk products
there are few data concerning the possible cardiovascular effects of a vegan diet (with no meat, dairy or egg products). Vitamin B-12 deficiency is highly prevalent in vegetarians; this can be partially alleviated by taking dairy/egg products in lact-ovo-vegetarians. However, metabolic vitamin B-12 deficiency is highly prevalent in vegetarians in Australia, Germany, Italy and Austria, and in vegans (80%) in Hong Kong and India, where vegans rarely take vitamin B-12 fortified food or vitamin B-12
supplements. Similar deficiencies exist in northern Chinese rural communities consuming inadequate meat, egg or dairy products due to poverty or dietary habits. Vascular studies have demonstrated impaired arterial endothelial function and increased carotid intima-media thickness as atherosclerosis surrogates in such metabolic vitamin B-12 deficient populations, but not in lactovegetarians in China. Vitamin B-12 supplementation has a favourable impact on these vascular surrogates in Hong Kong vegans and in underprivileged communities in northern rural China. Regular monitoring of vitamin B-12 status is thus potentially beneficial for early detection and treatment of metabolic vitamin B-12 deficiency in vegans, and possibly for prevention of atherosclerosis-related diseases.
Toohey et al. reported that cardiovascular risk factors are more favourable in African-American vegans, compared with lacto-ovo-vegetarians, with significantly lower body mass index (24.7 ± 1.9 vs. 26.4 ± 0.45 kg/m2), lower total cholesterol (3.75 ± 0.12 vs. 4.51 ± 0.1 mmol/L), and lower low-density lipoprotein (LDL) cholesterol levels (2.06 ± 0.13 vs. 2.65 ± 0.09 mmol/L), p < 0.0
