Long-term ovo-lacto vegetarian diet impairs vitamin B-12 status in pregnant women

How common is vitamin B-12 deficiency?

In considering the vitamin B-12 fortification of flour, it is important to know who is at risk of vitamin B-12 deficiency and whether those individuals would benefit from flour fortification. This article reviews current knowledge of the prevalence and causes of vitamin B-12 deficiency and considers whether fortification would improve the status of deficient subgroups of the population. In large surveys in the United States and the United Kingdom, approximately 6% of those aged > or =60 y are vitamin B-12 deficient (plasma vitamin B-12 < 148 pmol/L), with the prevalence of deficiency increasing with age. Closer to 20% have marginal status (plasma vitamin B-12: 148-221 pmol/L) in later life. In developing countries, deficiency is much more common, starting in early life and persisting across the life span. Inadequate intake, due to low consumption of animal-source foods, is the main cause of low serum vitamin B-12 in younger adults and likely the main cause in poor populations worldwide; in most studies, serum vitamin B-12 concentration is correlated with intake of this vitamin. In older persons, food-bound cobalamin malabsorption becomes the predominant cause of deficiency, at least in part due to gastric atrophy, but it is likely that most elderly can absorb the vitamin from fortified food. Fortification of flour with vitamin B-12 is likely to improve the status of most persons with low stores of this vitamin. However, intervention studies are still needed to assess efficacy and functional benefits of increasing intake of the amounts likely to be consumed in flour, including in elderly persons with varying degrees of gastric atrophy.

Causes of Vitamin B12 and Folate Deficiency

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.

Nutritional counseling for vegetarians during pregnancy and lactation

A woman's nutritional status directly affects pregnancy outcome and the quality of breast milk after birth. Clinicians who provide prenatal care have an important role in assessing the nutritional status of women and directing them to appropriate resources while respecting their choices. Vegetarian and vegan diets may present with unique nutrient deficiencies that can be addressed during prenatal nutritional counseling.

Longitudinal study of the effect of pregnancy on maternal and fetal cobalamin status in healthy women and their offspring

Compromised cobalamin status during pregnancy may put both mother and child at risk of deficiency during lactation and subsequent development. We investigated whether changes in cobalamin status during pregnancy are associated with impaired status in the mother and the cord. Plasma cobalamin, methylmalonic acid (MMA), and holotranscobalamin (holoTC) concentrations were determined in 92 women at preconception, 8, 20, and 32 wk of pregnancy, at labor, and in the cord. All variables [geometric mean percentiles 10, 90 (P(10), P(90))] were significantly reduced from preconception [cobalamin: 293 (155, 535) pmol/L; holoTC: 63 (38,98) pmol/L; MMA: 0.12 (0.09, 0.17) micromol/L] by 20 wk of pregnancy [cobalamin: 230 (123, 432) pmol/L; holoTC: 48 (34,78) pmol/L; MMA: 0.11 (0.08, 0.15) micromol/L P < 0.001]. Plasma cobalamin and holoTC remained lower throughout the remainder of pregnancy [32 wk: 198 (107, 339); labor: 224 (117, 444); P < 0.001] and [32 wk: 45 (26,82); labor: 40 (23,79); P < 0.05], respectively. By 32 wk, MMA was greater than preconception [0.14 (0.09, 0.20) micromol/L; P < 0.01]. Plasma holoTC at 32 wk and at labor was negatively correlated with cord MMA (r = -0.51, P < 0.001 and r = -0.40, P < 0.01, respectively). Women with lower holoTC at preconception had greater increases in MMA at 32 wk and at labor. Maternal MMA at 32 wk and at labor was significantly and independently associated with cord MMA only in women with lower holoTC at preconception (regression models: R(2) = 0.707, 0.682, respectively; P < 0.01). The moderate increases observed in the cobalamin biomarker, MMA, during pregnancy may indicate a functional depletion in intracellular cobalamin status.

Diagnosis of megaloblastic anaemias

There are a large number of causes of megaloblastic anaemia. The most frequent are disorders resulting in vitamin B(12) or folate deficiency. The diagnostic process often consists first of establishing the presence of B(12) or folate deficiency and then of determining the cause of deficiency. The blood count, blood film, serum B(12) assay, and red cell and serum folate assays are the primary investigations. Other useful investigations include serum/plasma methylmalonic acid (MMA), plasma total homocysteine (tHCYS) and serum holo-transcobalamin II assays. All currently used tests have limitations regarding specificity or sensitivity or both and the metabolite assays are not widely available. An understanding of these limitations is essential in formulating any diagnostic strategy. The wide use of serum B(12) and metabolite assays has resulted in the increasingly early diagnosis of B(12) deficiency, often in patients without B(12)-related symptoms (subclinical deficiency). Food cobalamin malabsorption is the most frequent cause of a low serum B(12). At least 25% of low serum B(12) levels are not associated with elevated metabolite levels and may not indicate B(12) deficiency. Some of these are caused by partial deficiency of transcobalamine I.

One-third of pregnant and lactating women may not be meeting their folate requirements from diet alone based on mandated levels of folic acid fortification

Many women are advised to consume a folic acid-containing prenatal supplement for the duration of pregnancy and lactation. Whether this remains necessary after folic acid fortification of the food supply in North America has yet to be determined. Our objective was to assess the dietary folate intake of a sample of pregnant and lactating women at mandated and predicted folic acid-fortification levels and determine the prevalence of inadequate and excessive intakes. Weighed food records (for 3 d) were collected from predominantly university-educated women (32 +/- 4 y of age) at 36 wk of pregnancy (n = 61) and at 4 and 16 wk of lactation (n = 60). Dietary folate intakes during pregnancy and lactation, assuming fortification at mandated levels (140-150 micro g/100 g), were 562 +/- 106 and 498 +/- 99 micro g/d dietary folate equivalents (DFE), respectively. The prevalence of inadequacy for folate, or the proportion of individuals with usual folate intakes less than their nutrient requirement, was 36% for women during pregnancy (estimated average requirement of 520 micro g/d DFE), and 32% during lactation (estimated average requirement of 450 micro g/d DFE). Assuming fortification at twice the mandated level, mean dietary intakes during pregnancy and lactation were 786 +/- 132 and 716 +/- 150 micro g/d DFE, respectively, producing only a 3% prevalence of folate inadequacy. Grains contributed approximately 41% of total folate intake followed by fruits and vegetables (approximately 21%). To conclude, at mandated levels of fortification many pregnant and lactating women are unlikely to meet their folate requirements from dietary sources alone; however, the actual level of inadequacy cannot be determined until the level of folic acid in the food supply is known with greater precision.

Health effects of vegetarian and vegan diets

Vegetarian diets do not contain meat, poultry or fish; vegan diets further exclude dairy products and eggs. Vegetarian and vegan diets can vary widely, but the empirical evidence largely relates to the nutritional content and health effects of the average diet of well-educated vegetarians living in Western countries, together with some information on vegetarians in non-Western countries. In general, vegetarian diets provide relatively large amounts of cereals, pulses, nuts, fruits and vegetables. In terms of nutrients, vegetarian diets are usually rich in carbohydrates, n-6 fatty acids, dietary fibre, carotenoids, folic acid, vitamin C, vitamin E and Mg, and relatively low in protein, saturated fat, long-chain n-3 fatty acids, retinol, vitamin B(12) and Zn; vegans may have particularly low intakes of vitamin B(12) and low intakes of Ca. Cross-sectional studies of vegetarians and vegans have shown that on average they have a relatively low BMI and a low plasma cholesterol concentration; recent studies have also shown higher plasma homocysteine concentrations than in non-vegetarians. Cohort studies of vegetarians have shown a moderate reduction in mortality from IHD but little difference in other major causes of death or all-cause mortality in comparison with health-conscious non-vegetarians from the same population. Studies of cancer have not shown clear differences in cancer rates between vegetarians and non-vegetarians. More data are needed, particularly on the health of vegans and on the possible impacts on health of low intakes of long-chain n-3 fatty acids and vitamin B(12). Overall, the data suggest that the health of Western vegetarians is good and similar to that of comparable non-vegetarians.

Vitamin–mineral supplement use by low-income Brazilian pregnant adolescents and non-adolescents and the predictors for non-use

OBJECTIVES

To determine (1) the intake of vitamin-mineral supplements by 855 low-income Brazilian pregnant adolescents and non-adolescents in three interviews (gestational ages < or =16, 20-26 and 30-36 weeks), (2) the relationship between vitamin-mineral supplementation and toxic exposure, and nutritional, psychological, socio-economic, demographic and obstetric characteristics of the women.

DESIGN

Longitudinal cohort study.

SETTING

Jundiaí city, São Paulo, Brazil.

SUBJECTS

A total of 855 pregnant adolescents and non-adolescents who attended antenatal care from September 1997 to August 2000.

METHODS

A general questionnaire was utilized three times in pregnancy (gestational ages < or =16, 20-26 and 30-36 weeks) to investigate the vitamin-mineral supplements ingested by the women, their smoking habit and alcohol intake, anthropometric measurements (pre-pregnancy and actual weight, height, mid-upper arm circumference) and psychological (anxiety, stress and distress), socio-economic (per capita income), demographic (education, age, marital status) and obstetric (gravidity) characteristics. The associations between vitamin-mineral supplementation and maternal characteristics were assessed in 12 multiple logistic regression models, stratifying the women by age and per capita income.

RESULTS

Iron and vitamin C were the most ingested supplements by adolescents and non-adolescents, in the three interviews. Logistic regression analysis revealed that the maternal predictors for non-use of vitamin-mineral supplementation were acute anxiety and alcohol intake for adolescents, and low education, single without partner, distress (anxiety, depression, etc.) and stress for non-adolescents.

CONCLUSIONS

These are important data to identify groups of low-income pregnant women in need of supplementation guidance and nutrition education. Stress/distress was a predictor for non-use of vitamin-mineral supplements for both adolescents and non-adolescents pregnant women.