During the winter months reduced levels of vitamin D can occur due to a lack of sun exposure. Of course this is also the time of year when there is a rise in upper respiratory infections such as colds and the flu. Could there be a connection between low vitamin D levels and an increased risk of infection? Recent research in this area has shed some light on this topic and may have you running toward the sunlight this winter.
Vitamin D is well known for its role in keeping bones healthy but this hormone “vitamin” also plays an important role in regulating our immune system. Vitamin D provides anti-inflammatory properties while also boosting mucous membrane immune function. It also encourages expression of anti-microbial peptides such as cathelicidin. In both the gastrointestinal tract and respiratory tract, vitamin D dependent immune pathways have been shown to provide anti-bacterial, anti-viral, and anti-inflammatory properties.
Observational studies suggest that low vitamin D levels may increase the risk of respiratory tract infections. There is a growing interest in studying vitamin D’s impact on these infections. A 2012 study published in the British Medical Journal looked at whether 4000 IU of supplemental vitamin D3 could reduce the need for antibiotics in those with frequent respiratory infections. Infections were significantly reduced in the vitamin D group compared to the placebo group. The researchers concluded that vitamin D supplementation may be a strategy to reduce symptoms and antibiotic use in those with frequent respiratory infections. (BMJ Open 2012;2:e001663) A related study involving 644 Australians age 60-84 were randomly assigned to a placebo, a monthly dose of 30,000IU vitamin D, or a 60,000IU dose of vitamin D. Those over the age of 70 did experience a significant reduction in antibiotic use in the high dose supplementation group. There was no effect in those under 70. Experts note the potential and need for further research in this area. (Am J Clin Nutr. 2013 Oct 9)
The “D3” form is recommended for daily supplementation. Current recommendations are 400 IU/day for infants and 600 IU/day for those 1 to 70. Those over 70 should get 800 IU of vitamin D per day. In the winter months when sun exposure is minimal or in house-bound elderly, higher doses may be appropriate. The safe upper limit for adults is set at 4000 IU/day. According to the Vitamin D Council, a healthy human adult body uses 3,000 to 5,000 IU of vitamin D per day. A 25 Hydroxy-vitamin D test, also known as a 25(OH)D, can tell you if you need higher dose supplementation. You will want to work closely with your healthcare provider to determine your needs based on your medical history and test results.
2013 Megan Witt, RD, LD
References:
Vitamin D and Mucosal Immune Function
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2955835/
Vitamin D3 supplementation in patients with frequent respiratory tract infections: a randomized and double-blind intervention study
http://bmjopen.bmj.com/content/2/6/e001663.full
Effect of vitamin D supplementation on antibiotic use: a randomized controlled trial
http://ajcn.nutrition.org/content/early/2013/10/09/ajcn.113.063271.short?rss=1
The Vitamin D Council
www.vitamindcouncil.org