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Don’t Forget Vitamin D this Cold and Flu Season

Vitamin D And Cold & Flu Season
  • Vitamin D deficiency is prevalent during the winter months
  • Low vitamin D levels are associated with cold and flu season
  • Vitamin D3 supplementation may decrease the incidence and symptoms of colds and flus

Vitamin D plays a key role in immune regulation

In most places in America, wintertime naturally means getting fewer UVB rays from the sun, which leaves many people with diminishing vitamin D levels. In addition, spending less time outdoors and using more clothing adds to the factors that contribute to a potential vitamin D deficiency. 

Vitamin D deficiency influences overall health any time of the year, but we see affects more clearly during the cold and flu season since vitamin D plays a key role in immune regulation. It helps stimulate expression of naturally occurring antimicrobial peptides (e.g. cathelicidin and defensins), which helps protect the body by destroying invading microbes.1 These peptides are in immune cells throughout the body and specifically in cells lining the upper and lower respiratory tract, which means they can directly fight off viruses and bacteria that cause common immune and respiratory infections like cold and flu.2,3 For more information about vitamin D, refer to “An Introduction to Vitamin D”.

Low vitamin D levels are linked to increased incidence of colds and flu

Research indicates that lower vitamin D levels are associated with an increase in the incidence of colds and flu.4,5 On the other hand, higher vitamin D levels reduce their occurrence and diminish their symptoms if they do occur3. Even more, the benefits of vitamin D span all age groups. 

  • A research evaluation of 25 clinical trials with 11,321 participants between the ages of 0 and 95 years found that vitamin D supplementation promoted normal respiratory tract function.6 The greatest benefits were experienced by patients who were very vitamin D deficient (<10 ng/mL or 25 nmol/L), along with those taking daily amounts of vitamin D, compared to those taking big doses (30,000 IU or more) every one to three months.
  • Researchers reported that children 6–15 years of age who took 1200 IU of vitamin D per day were significantly less likely to acquire seasonal respiratory complications (10.8%) than children in the placebo group (18.6%).7 The reduction was most prominent with children who were not supplementing with vitamin D otherwise and who began nursery school after 3 years of age.
  • Another study showed that after 3 years of vitamin D supplementation (800 IU/day in the first year, 2000 IU/day the second and third years of the study) in women 50–85 years of age (208 participants) self-reported incidences of seasonal respiratory complications were significantly lower compared to placebo.5,8,9

Incorporate daily vitamin D

Considering the research, incorporating or increasing daily vitamin D intake may help the entire family stay well this winter. Vitamin D testing can help determine your specific daily vitamin D requirements. It includes a simple blood test that can be requested through your doctor or online. 

For general dosing guidelines, view below:

Vitamin D RecommendationsIOMFDAEndocrine Society
(RDA)(RDI)(Daily Allowance)
0-6 months400 IU400-1000 IU
6-12 months400 IU400-1000 IU
1-3 years600 IU600 IU600-1000 IU
4-8 years600 IU800 IU600-1000 IU
9-18 years600 IU800 IU600-1000 IU
19-70 years600 IU800 IU1500-2000 IU
>70 years800 IU800 IU1500-2000 IU
14-18 years600 IU600 IU600-1000 IU
19-50 years600 IU600 IU1500-2000 IU
14-18 years600 IU600 IU600-1000 IU
19-50 years600 IU600 IU1500-2000 IU

*4000–6000 IU/day is mother’s required intake if infant is not receiving 400 IU/day.

IOM = Institute of Medicine; RDA = Recommended Dietary Allowance; RDI = Recommended Dietary Intake; IU = International Units.

[Table is modified from Evaluation, Treatment, and Prevention of Vitamin D
Deficiency: an Endocrine Society Clinical Practice

Denise John, PhD is a Science Researcher and Writer for Nordic Naturals. A published author, Denise holds a Doctorate in Neuroscience from Florida State University, and is passionate about sharing science to help others make informed choices and live better lives.

1. Aranow C. J Investig Med. 2011. 59(6): p. 881-6.
2. Gombart AF. Future Microbiol. 2009. 4(9): p. 1151-65.
3. Wacker M, Holick MF. Nutrients. 2013. 5(1): p. 111-48.
4. Ginde AA, et al. Arch Intern Med. 2009. 169(4): p. 384-90.
5. Cannell JJ, et al. Epidemiol Infect. 2006. 134(6): p. 1129-40.
6. Martineau AR, et al. BMJ. 2017. 356: i6583.
7. Urashima M, et al. Am J Clin Nutr. 2010. 91(5): p. 1255-60.
8. Aloia JF, et al. Arch Intern Med. 2005. 165(14): p. 1618-23.
9. Aloia JF, Li-Ng M. Epidemiol Infect. 2007. 135(7): p. 1095-6.