Ideally, before the flu season begins, find out your vitamin D status. A study involving 18, 883 participants, 12 years and older, found that people with the lowest blood level of vitamin D reported having significantly more recent colds or flu. The analysis adjusted for demographics and clinical factors–season, body mass index, smoking history, asthma, and chronic obstructive pulmonary disease.1
Vitamin D helps to activate your inactive immune responses. Your body produces natural antibiotic-like compounds called antimicrobial peptides in the white blood cells. Bio-active vitamin D dramatically increases the activity of these antimicrobial compounds found in white blood cells and epithelial cells of the respiratory tract. 2,3
Vitamin D is crucial to activating our immune defenses. Without sufficient intake of the vitamin, the killer cells of the immune system (killer T lymphocytes) will not be able to react to and fight off serious viral infections.4 Low levels of vitamin D impair the immune system in the gut.5,6 Gut bacteria is important for the immune response in the lungs.7 Rodent studies indicate that a healthy population of gut bacteria improves the efficacy of certain flu vaccines.8
Unfortunately, nutritional epidemiologists estimate that as many as 50% of North Americans and Europeans have an insufficient amount of vitamin D. To solve this problem, get at least 20 minutes of sunlight a day and consider taking a vitamin D supplement, especially if you are indoors most of the day, are elderly, or have dark skin, as these factors substantially increase your risk for vitamin D deficiency.
- Ginde, AA. Association between Serum 25-Hydroxyvitamin D Level and Upper Respiratory
- Tract Infection in the Third National Health and Nutrition Examination Survey. Arch Intern Med. 2009; 169(4):384-390.
- Bartley J. Vitamin D, innate immunity and upper respiratory tract infection.
- Cannell J.J., et al, Epidemic influenza and vitamin D. Epidemiol Infect, 134(6):1129-40, 2006. J Laryngol Otol. 2010 May; 124(5):465-9.
- University of Copenhagen. “Vitamin D crucial to activating immune defenses.” ScienceDaily. ScienceDaily, 8 March 2010. www.sciencedaily.com/releases/2010/03/100307215534.htm
- Jun Sun. Vitamin D and mucosal immune function. Curr Opin Gastroenterol. 2010 Nov; 26(6): 591–595.
- Ichinohe T. (2011). Microbiota regulates immune defense against respiratory tract influenza A virus infection. Proceedings of the National Academy of Sciences of the United States of America, 108 (13), 5354-9 PMID: 21402903.
- Oh J Z. TLR5-Mediated Sensing of Gut Microbiota Is Necessary for Antibody Responses to Seasonal Influenza Vaccination. Volume 41, Issue 3, p478–492, 18 September 2014.