by Jack Norris, RD, and Taylor Wolfram, MS, RDN, LDN
Depending on the laboratory, a normal range for white blood cell (WBC) count is about 3.5 to 12.5 billion per liter. One cross-sectional study showed vegans have a lower WBC count than omnivores, though in the normal range at 5.8 (Haddad, 1999). It appears that many vegans, however, have a lower than normal WBC count. We don’t really know why this is, but it appears to be common and not indicative of any obvious problem. If you have a WBC count below normal, you should talk to your doctor about whether to be concerned.
White Blood Cells
Also known as leukocytes, white blood cells are needed to fight foreign invaders, including bacteria, viruses, and cancerous cells. During infections, they typically increase in number. A concise explanation of the various white blood cells, along with some interesting pictures, can be found on Britannica (link).
White Blood Cells in Vegans
Anecdotally, many vegans report having low WBC counts, which their doctors are rarely concerned about. In contrast, the published research (below) shows vegans to have normal WBC counts, though typically lower than omnivores.
A study of 25 vegans and 20 meat-eaters found vegans had lower levels of certain types of WBC (Haddad, 1999). Vegans had significantly lower concentrations of leukocytes (4.96 ± 0.91× 109/l in vegans compared to 5.83 ± 1.51 × 109/l in meat-eaters), lymphocytes (1.56 ± 0.39 × 109/l in vegans compared to 1.90 ± 0.59 × 109/l in meat-eaters), and platelets (235 ± 60 × 109/l in vegans compared to 270 ± 55 × 109/l in meat-eaters) These values are all within the normal ranges. After considering other immune-related parameters, the authors concluded, “It is not possible to determine from these findings whether the immune status of vegans is compromised or enhanced compared with other groups.”
A clinical trial from the University of Memphis placed mostly healthy and some vegetarian subjects on a “Daniel Fast” for 21 days, eating only plant foods with no processed or packaged foods, and their WBC went from an average of 5.7 to 5.0 (Bloomer, 2010).
A cross-sectional study of 447,726 white British and 5,237 British Indian participants (including 398 vegans in the white sample) found non-smoking white vegans’ WBC (6.22 x 109 cells/l, 95% CI 6.01 to 6.43 x 109 cells/l) was significantly lower than white participants who were regular meat eaters (7.02 x 109 cells/l, 95% CI 7.01 to 7.03 x 109 cells/l), low meat eaters (6.80 x 109 cells/l, 95% CI 6.79 to 6.81 x 109 cells/l), poultry eaters (6.55 x 109 cells/l, 95% CI 6.49 to 6.61 x 109 cells/l), and vegetarians (6.69 x 109 cells/l, 95% CI 6.63 to 6.74 x 109 cells/l), but not significantly lower than fish eaters (Tong, 2019). Vegan WBC was still within the reference range.
White vegans had significantly lower platelet count (238.2 x 109 cells/l, 95% CI 232.5 to 243.9 x 109 cells/l) and significantly higher platelet volume (9.73 fL, 95% CI 9.63 to 9.84 fL) than all other diet groups.
White vegetarians also had significantly lower WBC (6.69 x 109 cells/l, 95% CI 6.63 to 6.74 x 109 cells/l) than white participants who ate meat, fish, and poultry. However, Indian vegetarians’ (this does not include vegans) WBC (7.30 x 109 cells/l, 95% CI 7.21 to 7.39 x 109 cells/l) did not different significantly from Indian meat eaters.
A randomized controlled trial found that after putting meat-eaters on a vegan diet for 4 weeks, their leukocyte, neutrophil, monocyte and platelet counts dropped (though still within reference ranges) and were significantly lower than the comparison group on a meat diet (Lederer, 2020). The drop in leukocytes for those on the vegan diet was from 6.0 ± 1.4 to 5.4 ± 0.9 x 109/l.
So why do vegans have lower white blood cell counts than omnivores?
There are several hypotheses for why vegans may have lower WBC compared to other diet groups:
- Zinc deficiency. Zinc plays a role in the production of white blood cells (though vegans did not have significantly lower zinc intakes or serum zinc levels than meat-eaters in Haddad et al.).
- Insufficient intake of branched chain amino acids (BCAA). BCAA play a role in lymphocyte functionality (Lederer et al. hypothesize that the mTOR signaling pathway downregulates white blood cell production when BCAAs are in low supply).
- Lower IGF-1 levels. IGF-1 plays a role in the production of white blood cells (McCarty suggests that vegans have lower IGF-1 levels which may contribute to their lower WBC).
Low vitamin A levels. Vitamin A plays a role in the production of white blood cells, and vegans may have lower levels of vitamin A due to no direct dietary source, and potentially low carotenoid and/or fat intake (though vegans did not have lower or insufficient intakes of vitamin A, in retinol equivalents, than meat-eaters in Haddad et al.)
- Vitamin B12 deficiency. B12 plays a role in the production of white blood cells (though vegetarians, who also have low B12 intakes, didn’t have significantly lower WBC than meat-eaters in Tong et al.).
None of these hypotheses have been well-studied or proven. So for now, we cannot with any certainty say why vegans tend to have lower WBC.
Last updated April 2021
Bloomer RJ, Kabir MM, Canale RE, Trepanowski JF, Marshall KE, Farney TM, Hammond KG. Effect of a 21 day Daniel Fast on metabolic and cardiovascular disease risk factors in men and women. Lipids Health Dis. 2010 Sep 3;9:94.
Craddock JC, Neale EP, Peoples GE, Probst YC. Vegetarian-Based Dietary Patterns and their Relation with Inflammatory and Immune Biomarkers: A Systematic Review and Meta-Analysis. Adv Nutr. 2019 May 1;10(3):433-451. Not cited.
Haddad EH, Berk LS, Kettering JD, Hubbard RW, Peters WR. Dietary intake and biochemical, hematologic, and immune status of vegans compared with nonvegetarians. Am J Clin Nutr. 1999 Sep;70(3 Suppl):586S-593S.
Lederer AK, Maul-Pavicic A, Hannibal L, Hettich M, Steinborn C, Gründemann C, Zimmermann-Klemd AM, Müller A, Sehnert B, Salzer U, Klein R, Voll RE, Samstag Y, Huber R. Vegan diet reduces neutrophils, monocytes and platelets related to branched-chain amino acids – A randomized, controlled trial. Clin Nutr. 2020 Nov;39(11):3241-3250.
Tong TYN, Key TJ, Gaitskell K, Green TJ, Guo W, Sanders TA, Bradbury KE. Hematological parameters and prevalence of anemia in white and British Indian vegetarians and nonvegetarians in the UK Biobank. Am J Clin Nutr. 2019 Aug 1;110(2):461-472.