by Taylor Wolfram, MS, RDN, LDN and Jack Norris, RD
Depending on the laboratory, a normal range for white blood cell count (WBC) is about 3.5 to 12.5 billion per liter. One cross-sectional study showed vegans have a lower white blood cell count than omnivores, though in the normal range at 5.8 (Haddad, 1999). It appears that many vegans, however, have a lower than normal white blood cell 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 white blood cell 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 white blood cell counts, which their doctors are rarely concerned about. In contrast, the published research (below) shows vegans to have normal white blood cell counts, though typically lower than omnivores.
A study of 83 American vegetarians, including 13 vegans, found that white blood cell count tended to decrease in men with decreasing animal products in the diet (Dong & Scott, 1982). Many of the participants in this study followed a “natural hygiene” diet consisting mainly of raw vegetables, fruits, nuts, and seeds with minimal grains, legumes, dairy, and dietary supplements.
A study of 25 vegans and 20 meat-eaters found that vegans had lower levels of white blood cells (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) and lymphocytes (1.56 ± 0.39 × 109/l in vegans compared to 1.90 ± 0.59 × 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 white blood cell count went from an average of 5.7 to 5.0 (Bloomer, 2010).
A cross-sectional study from Britain included 398 vegans among 447,726 white participants and 5,237 Indian participants. Among the white participants they found that non-smoking vegans’ white blood cell count (6.22 x 109 cells/l, 95% CI 6.01 to 6.43 x 109 cells/l) was significantly lower than the 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). Vegans’ white blood cell count was within the reference range. White vegetarians had a significantly lower white blood cell count (6.69 x 109 cells/l, 95% CI 6.63 to 6.74 x 109 cells/l) than white meat, fish, and poultry eaters. However, the Indian vegetarians’ white blood cell count (7.30 x 109 cells/l, 95% CI 7.21 to 7.39 x 109 cells/l) didn’t differ significantly from the Indian meat-eaters.
A randomized controlled trial put meat-eaters on a vegan diet for 4 weeks and their total leukocyte count dropped from 6.0 ± 1.4 to 5.4 ± 0.9 x 109/l. The leukocyte count of those on a vegan diet was significantly lower than the comparison group on a meat-based diet but remained within the reference range (Lederer, 2020).
So why do vegans have lower white blood cell counts than omnivores? There are several hypotheses:
- Zinc deficiency — zinc plays a role in the production of white blood cells although vegans didn’t 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 white blood cell count.
- 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; 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 a significantly lower white blood cell count 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 a lower white blood cell count.
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.