Hematological parameters and prevalence of anemia in white and British Indian vegetarians and nonvegetarians in the UK Biobank

The long term exclusion of animal foods may result in inadequate intakes of some essential nutrients that are not readily available from plant sources, such as haem iron or vitamin B12. Given the crucial roles of haem iron in haemoglobin production and vitamin B12 in various cellular processes, people who exclude animal foods from their diets may exhibit differences in haematological parameters from people who consume meat or dairy regularly. We examined this using data collected on close to 500,000 people in the United Kingdom (UK) Biobank study, who had a complete blood count measured at recruitment. We examined haemoglobin concentrations, red and white blood cell counts, and platelet counts and volume, in 212,831 regular meat-eaters (>3 times/week of red and processed meat consumption), 213,092 low meat-eaters, 4,815 poultry-eaters, 10,042 fish-eaters, 6,548 vegetarians, and 398 vegans of white ethnicity, and 3,875 meat-eaters and 1,362 vegetarians of British Indian ethnicity.

We found that in both white and British Indian populations, compared with regular meat-eaters (or meat-eaters in Indians), the other diet groups had up to 3.7% lower age adjusted haemoglobin concentrations (difference not significant in white vegan women), and were generally more likely to have anaemia (e.g. 8.7% of regular meat-eaters versus 12.8% of vegetarians in white premenopausal women). In the white population, compared with regular meat-eaters, all other diet groups had significantly lower counts of total white cells and most white cell subtypes, after accounting for differences in age and sex; but in British Indians, there was no significant difference in any of the white cell counts by diet group. Compared with white regular meat-eaters, the low meat-eaters, poultry-eaters, fish-eaters, and vegans had significantly lower platelet counts and higher platelet volume, while both white and British Indian vegetarians had higher platelet counts and lower platelet volume compared with the respective meat-eaters. The reasons for these differences should be further investigated.