Townsend Letter, December 2012
Two recent randomized, double-blind, placebo-controlled trials provide evidence that vitamin D supplementation reduces the incidence of respiratory infections in children. Vitamin D, which regulates immune response, is made in human skin exposed to sunlight. Without supplementation, D levels decline during the dark days of winter – the season of colds and flu.
A 2010 Japanese trial, led by Mitsuyoshi Urashima, tested the effect of vitamin D supplements on verified influenza. The research team followed 334 schoolchildren from December 2008 through March 2009. Half of these children (n = 167) were given 1200 IU of D3 per day. This group had fewer confirmed cases of influenza A: 10.8% (n = 18) compared with 18.6% (n = 31) in the placebo group. Only two children in the vitamin D group had asthma attacks compared with 12 in the placebo group. This study showed no significant difference between the D3 and placebo groups in the incidence of influenza B or influenzalike illness.
Instead of focusing on influenza, a 2012 trial looked at vitamin D supplementation’s effect on acute respiratory tract infections. This study enrolled 247 Mongolian children in late January. Serum 25-hydroxyvitamin D was measured at baseline and at the study’s conclusion seven weeks later. Both groups started with a very low median serum D concentration of 7 ng/mL (17 nmol/L). Researchers fortified local milk with vitamin D (300 IU/day) and gave it to 143 children. The remaining 104 participants received unfortified milk. Median serum D concentration in the supplemented group rose to 19 ng/mL (47 nmol/L) by study’s end. The incidence of respiratory infections, according to parent reports, was about 50% lower in the vitamin D group compared with the control group.
Dr. Carlos Camargo, who led the study, explains: “‘ … The large benefit was undoubtedly related to the low baseline vitamin D levels of these children, so I would not expect the supplement to provide similar benefit in children who start with healthy levels of vitamin D. The key question for future research is at what initial vitamin D level would children no longer receive benefit from winter supplementation?'”
Camargo CA, Ganmaa D, Frazier AL et al. Randomized trial of vitamin D supplementation and risk of acute respiratory tract infection in Mongolia [abstract]. Pediatrics. Epub August 20, 2012. Available at http://pediatrics.aappublications.org/content/early/2012/08/15/peds.2011-3029.abstract. Accessed October 3, 2012.
Rattue P. Vitamin D supplements may lower risk of respiratory problems in kids [online article]. Medical News Today. August 22, 2012. http://www.medicalnewstoday.com/articles/249297.php. Accessed September 17, 2012.
Urashima M, Segawa T, Okazaki M et al. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr. 2010;91:1255–1260. Available at http://ajcn.nutrition.org/content/91/5/1255.full.pdf+html. Accessed September 17, 2012.
Vitamin D supplementation cuts childhood colds and flu in half. Life Extension. August 28, 2012. Available at www.lef.org. Accessed October 3, 2012.