Vitamin B12 and folate intake and biomarker status among omnivore and vegetarian UK-dwelling women of childbearing age: pooled results from the National diet and nutrition surveys (2008-2019).

PURPOSE: Vitamin B12 is crucial for neurological function and maternal health, particularly during pregnancy and lactation. Women of childbearing age (WCBA) following unfortified plant-based diets are at increased risk of B12 deficiency, which can adversely affect both maternal and infant health. This study analysed NDNS data (2008-2019) to: (1) compare vitamin B12 intake and status, and folate intake and status, between omnivores and vegetarians; (2) examine the impact of supplementation; (3) explore predictors of B12 biomarkers, including diet, supplementation, and age, and (4) assess the prevalence of vitamin B12 insufficiency and deficiency in WCBA, per diet group.

METHODS: Data from 2,299 WCBA (2,204 omnivores and 89 vegetarians) in the National Diet and Nutrition Survey (2008-2019) were analysed. Survey-weighted means and 95% confidence intervals (CI) were calculated for nutrient intakes and biomarkers, and t-tests compared omnivores and vegetarians. Vitamin B12 and folate intakes were assessed from food and supplements.

RESULTS: Mean dietary vitamin B12 intake was significantly higher in omnivores (4.3 µg/day; 95% CI: 4.2-4.5) compared with vegetarians (2.9 µg/day; 95% CI: 2.5-3.3; p < 0.0001). Supplement use was more common among vegetarians (27%) compared with omnivores (10%). Mean dietary folate intake was higher in vegetarians (227.4 µg/day; 95% CI: 210.1-244.7) than omnivores (206.9 µg/day; 95% CI: 202.4-211.4; p = 0.025). Serum vitamin B12 concentrations were higher in omnivores (271.3 pmol/L; 95% CI: 260.8-281.7) than vegetarians (231.0 pmol/L; 95% CI: 183.9-278.1; p = 0.1). Holotranscobalamin (HoloTC) was significantly lower in vegetarians (39.8 pmol/L; 95% CI: 33.1-46.5) compared with omnivores (63.1 pmol/L; 95% CI: 60.0-66.2; p < 0.001). Homocysteine concentrations were significantly higher in vegetarians (11.22 µmol/L; 95% CI: 9.21-13.23) than omnivores (8.49 µmol/L; 95% CI: 8.17-8.81; p = 0.009). Serum folate (22.1 vs. 18.1 nmol/L; p = 0.170) and red cell folate (583.4 vs. 528.9 nmol/L; p = 0.484) did not differ significantly between groups.

CONCLUSIONS: Women of childbearing age following vegetarian diets had lower vitamin B12 intakes and holotranscobalamin concentrations than omnivores, despite higher supplement use, with a substantial proportion falling below clinically significant thresholds for deficiency and insufficiency. In contrast, folate intake was higher among vegetarians. These findings highlight the need for targeted dietary guidance and supplementation to support adequate vitamin B12 status in this population.