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      Causes of Vitamin B12and Folate Deficiency

      Food and Nutrition Bulletin
      SAGE Publications

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          Abstract

          This review describes current knowledge of the main causes of vitamin B12 and folate deficiency. The most common explanations for poor vitamin B12 status are a low dietary intake of the vitamin (i.e., a low intake of animal-source foods) and malabsorption. Although it has long been known that strict vegetarians (vegans) are at risk for vitamin B12 deficiency, evidence now indicates that low intakes of animal-source foods, such as occur in some lacto-ovo vegetarians and many less-industrialized countries, cause vitamin B12 depletion. Malabsorption of the vitamin is most commonly observed as food-bound cobalamin malabsorption due to gastric atrophy in the elderly, and probably as a result of Helicobacter pylori infection. There is growing evidence that gene polymorphisms in transcobalamins affect plasma vitamin B12 concentrations. The primary cause of folate deficiency is low intake of sources rich in the vitamin, such as legumes and green leafy vegetables, and the consumption of these foods may explain why folate status can be adequate in relatively poor populations. Other situations in which the risk of folate deficiency increases include lactation and alcoholism.

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          Review of the magnitude of folate and vitamin B12 deficiencies worldwide.

          Human deficiencies of folate and vitamin B12 result in adverse effects which may be of public health significance, but the magnitude of these deficiencies is unknown. Therefore, we examine the prevalence data currently available, assess global coverage of surveys, determine the frequency with which vitamin status assessment methods are used, and identify patterns of status related to geographical distribution and human development. Surveys were identified through PubMed and the Vitamin and Mineral Nutrition Information System at the World Health Organization (WHO). Since different thresholds were frequently used to define deficiency, measures of central tendency were used to compare blood vitamin concentrations among countries. The percentage of countries with at least one survey is highest in the WHO Regions of South-East Asia and Europe. Folate and vitamin B12 status were most frequently assessed in women of reproductive age (34 countries), and in all adults (27 countries), respectively. Folate status assessment surveys assessed plasma or serum concentrations (55%), erythrocyte folate concentrations (21%), or both (23%). Homocysteine was assessed in one-third of the surveys of folate and vitamin B12 status (31% and 34% respectively), while methylmalonic acid was assessed in fewer surveys of vitamin B12 status (13%). No relationship between vitamin concentrations and geographical distribution, level of development, or population groups could be identified, but nationally representative data were few. More representative data and more consistent use of thresholds to define deficiency are needed in order to assess whether folate and vitamin B12 deficiencies are a public health problem.
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            Hyperhomocysteinemia and elevated methylmalonic acid indicate a high prevalence of cobalamin deficiency in Asian Indians.

            In India, most people adhere to a vegetarian diet, which may lead to cobalamin deficiency. The objective was to examine indicators of cobalamin status in Asian Indians. The study population included 204 men and women aged 27-55 y from Pune, Maharashtra, India, categorized into 4 groups: patients with cardiovascular disease (CVD) and diabetes, patients with CVD but no diabetes, patients with diabetes but no CVD, and healthy subjects. Data on medical history, lifestyle, and diet were obtained by interviews and questionnaires. Blood samples were collected for measurement of serum or plasma total cobalamin, holotranscobalamin (holoTC), methylmalonic acid (MMA), and total homocysteine (tHcy) and hemetologic indexes. MMA, tHcy, total cobalamin, and holoTC did not differ significantly among the 4 groups; therefore, the data were pooled. Total cobalamin showed a strong inverse correlation with tHcy (r = -0.59) and MMA (r = -0.54). Forty-seven percent of the subjects had cobalamin deficiency (total cobalamin 15 micromol/L), and 73% had elevated serum MMA (>0.26 micromol/L). These indicators of impaired cobalamin status were observed in both vegetarians and nonvegetarians. Folate deficiency was rare and only 2.5% of the subjects were homozygous for the MTHFR 677C-->T polymorphism. About 75% of the subjects had metabolic signs of cobalamin deficiency, which was only partly explained by the vegetarian diet. If impaired cobalamin status is confirmed in other parts of India, it may have important health implications.
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              Vitamin Status and Intake as Primary Determinants of Homocysteinemia in an Elderly Population

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                Author and article information

                Journal
                Food and Nutrition Bulletin
                Food Nutr Bull
                SAGE Publications
                0379-5721
                1564-8265
                June 22 2008
                June 2008
                June 22 2008
                June 2008
                : 29
                : 2_suppl1
                : S20-S34
                Article
                10.1177/15648265080292S105
                18709879
                23be69b8-624e-4c00-9ad6-b684eced2ce4
                © 2008

                http://journals.sagepub.com/page/policies/text-and-data-mining-license


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