Comparison of selected nutritional status and disease biomarkers in omnivores, flexitarians, pescatarians, vegetarians, and vegans in the United Kingdom: findings from the Feeding the Future (FEED) study

Background & Aims The adoption of plant-based diets in the United Kingdom (UK) is increasing, which has potential health benefits, but may increase risk of inadequate intakes of some nutrients. We aimed to assess differences in biomarkers of nutritional status and disease across diet groups in UK adults. Methods This cross-sectional analysis included 124 omnivores, 131 flexitarians, 71 pescatarians, 124 vegetarians, and 183 vegans from the Feeding the Future (FEED) follow-up study (2024-2025). Capillary blood samples were collected and analysed for: haemoglobin; lipid measures (low- and high-density lipoprotein cholesterol (LDL-C and HDL-C), non-HDL-C, total cholesterol, and triglycerides); vitamins B12 and D. We estimated age- and sex-adjusted arithmetic or geometric mean concentrations and 95% confidence intervals of these biomarkers across diet groups. Participants taking lipid-lowering medications were excluded for analysis of lipid markers (n = 85). Results We observed differences in concentrations of cholesterol, triglycerides, and vitamin B12 across diet groups (P heterogeneity for all [&le;] 0.03). Cholesterol markers (mmol/L) were lower with greater exclusion of animal foods (omnivores vs vegans, total cholesterol = -0.8; LDL-C = -0.7; HDL-C = -0.2). Triglyceride concentrations (mmol/L) were similar across groups, with slightly higher values in vegetarians (+0.2) and vegans (+0.1) compared with omnivores. Vitamin B12 concentrations (pmol/L) were highest in vegans and lowest in vegetarians compared to omnivores. Supplement users had higher vitamin B12 and D concentrations in all groups (P heterogeneity between strata = <0.001), while non-supplementing vegetarians and vegans had lower, but not deficient, vitamin B12 concentrations compared to omnivores (P heterogeneity between diet groups = <0.001). Conclusions In this contemporary UK cohort, those following plant-based diets had more favourable blood lipid profiles, with little evidence of vitamin B12 or D deficiency, or anaemia. Supplement use was associated with higher vitamin B12 and D concentrations, particularly among vegetarians and vegans.