Anemia occurs when the body has a low number of red blood cells (RBCs). These cells carry oxygen throughout the body. Fewer RBCs limit the body’s oxygen level.
Risk factors for anemia include:
- Low dietary iron and folate (vitamin B) intake
- Serious illnesses including internal bleeding, kidney disease, cancer, diabetes, HIV/AIDS, and liver disease
- Low vitamin D levels
Sunlight exposure and risk
Dr. John Cannell of the Vitamin D Council presented data on oxygen-carrying capacity of athletes from the mid-1950s. The data showed that the blood’s ability to carry oxygen peaks in late summer, suggesting that UVB during the summer increased RBC count.
Vitamin D and anemia
Vitamin D levels
There are a number of studies linking lower vitamin D levels and higher anemia risk:
- In an Australian study of people with noncholestatic chronic liver disease, lower vitamin D levels were associated with anemia.
- Pregnant women in Tanzania with low vitamin D levels were compared to those with adequate vitamin D levels. The women with low levels had a much higher risk of anemia.
- In the United States, 41% of patients with chronic kidney disease had anemia. Lower vitamin D levels were associated with lower hemoglobin levels and anemia.
- A study in Los Angeles found a link between vitamin D deficiency and anemia.
- A U.S. study compared people with and without anemia. Those with anemia were more likely to have low vitamin D levels.
- Another study reported a direct connection between vitamin D levels and maximum oxygen consumption.
How vitamin D works
It is not known how vitamin D affects red blood cells.
There are no reported studies of vitamin D preventing anemia. However, based on results for other diseases, vitamin D levels above 30–40 ng/mL (75–100 nmol/L) may increase RBCs and oxygen in the blood.
According to studies, RBCs rebuild more quickly in people who have higher vitamin D levels. These studies also used iron and other agents to stimulate RBCs. Anyone with anemia should seek medical care.
This evidence summary on anemia was written by:
William B. Grant, Ph.D.
Sunlight, Nutrition, and Health Research Center (SUNARC)
P.O. Box 641603
San Francisco, CA 94164-1603, USA
Complete bibliography of research used in this summary
The research we have cited in our summary is listed below, with links to PubMed abstracts and full-text for those who wish to explore further.
- Brancaccio, D. Cozzolino, M. Gallieni, M. Hyperparathyroidism and anemia in uremic subjects: a combined therapeutic approach. J Am Soc Nephrol. 2004 Jan; 15 Suppl 1S21-4.
- Branda, R. F. Eaton, J. W. Skin color and nutrient photolysis: an evolutionary hypothesis. Science. 1978 Aug 18; 201 (4356): 625-6.
- Cannell, J. J. Hollis, B. W. Sorenson, M. B. Taft, T. N. Anderson, J. J. Athletic performance and vitamin D. Med Sci Sports Exerc. 2009 May; 41 (5): 1102-10.
- Constantini, N. W. Arieli, R. Chodick, G. Dubnov-Raz, G. High prevalence of vitamin D insufficiency in athletes and dancers. Clin J Sport Med. 2010 Sep; 20 (5): 368-71.
- Fisher, L. Fisher, A. Vitamin D and parathyroid hormone in outpatients with noncholestatic chronic liver disease. Clin Gastroenterol Hepatol. 2007 Apr; 5 (4): 513-20.
- Fleming, A. F. Iron deficiency in the tropics. Clin Haematol. 1982 Jun; 11 (2): 365-88.
- Fukuwatari, T. Fujita, M. Shibata, K. Effects of UVA irradiation on the concentration of folate in human blood. Biosci Biotechnol Biochem. 2009 Feb; 73 (2): 322-7.
- Gaweda, A. E. Goldsmith, L. J. Brier, M. E. Aronoff, G. R. Iron, inflammation, dialysis adequacy, nutritional status, and hyperparathyroidism modify erythropoietic response. Clin J Am Soc Nephrol. 2010 Apr; 5 (4): 576-81.
- Heldenberg, D. Tenenbaum, G. Weisman, Y. Effect of iron on serum 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D concentrations. Am J Clin Nutr. 1992 Sep; 56 (3): 533-6.
- Jablonski, N. G. Chaplin, G. Colloquium paper: human skin pigmentation as an adaptation to UV radiation. Proc Natl Acad Sci U S A. 2010 May 11; 107 Suppl 28962-8.
- Kiss, Z. Ambrus, C. Almasi, C. Berta, K. Deak, G. Horonyi, P. Kiss, I. Lakatos, P. Marton, A. Molnar, M. Z. Nemeth, Z. Szabo, A. Mucsi, I. Serum 25(OH)-Cholecalciferol Concentration Is Associated with Hemoglobin Level and Erythropoietin Resistance in Patients on Maintenance Hemodialysis. Nephron Clin Pract. 2010 Nov 12; 117 (4): c373-c378.
- Lac, P. T. Choi, K. Liu, I. A. Meguerditchian, S. Rasgon, S. A. Sim, J. J. The effects of changing vitamin D levels on anemia in chronic kidney disease patients: a retrospective cohort review. Clin Nephrol. 2010 Jul; 74 (1): 25-32.
- McGillivray, G. Skull, S. A. Davie, G. Kofoed, S. E. Frydenberg, A. Rice, J. Cooke, R. Carapetis, J. R. High prevalence of asymptomatic vitamin D and iron deficiency in East African immigrant children and adolescents living in a temperate climate. Arch Dis Child. 2007 Dec; 92 (12): 1088-93.
- Mehta, S. Giovannucci, E. Mugusi, F. M. Spiegelman, D. Aboud, S. Hertzmark, E. Msamanga, G. I. Hunter, D. Fawzi, W. W. Vitamin D status of HIV-infected women and its association with HIV disease progression, anemia, and mortality. PLoS One. 2010; 5 (1): e8770.
- Park, K. Kersey, M. Geppert, J. Story, M. Cutts, D. Himes, J. H. Household food insecurity is a risk factor for iron-deficiency anaemia in a multi-ethnic, low-income sample of infants and toddlers. Public Health Nutr. 2009 Nov; 12 (11): 2120-8.
- Patel, N. M. Gutierrez, O. M. Andress, D. L. Coyne, D. W. Levin, A. Wolf, M. Vitamin D deficiency and anemia in early chronic kidney disease. Kidney Int. 2010 Apr; 77 (8): 715-20.
- Perlstein, T. S. Pande, R. Berliner, N. Vanasse, G. J. Prevalence of 25-hydroxyvitamin D deficiency in subgroups of elderly persons with anemia: association with anemia of inflammation. Blood. 2011 Jan 14;
- Sim, J. J. Lac, P. T. Liu, I. L. Meguerditchian, S. O. Kumar, V. A. Kujubu, D. A. Rasgon, S. A. Vitamin D deficiency and anemia: a cross-sectional study. Ann Hematol. 2010 May; 89 (5): 447-52.
- Wu, S. G. Jeng, F. R. Wei, S. Y. Su, C. Z. Chung, T. C. Chang, W. J. Chang, H. W. Red blood cell osmotic fragility in chronically hemodialyzed patients. Nephron. 1998; 78 (1): 28-32.