Posted 25 February 2009 - 06:57 PM
The popular press version:
Vitamin D may protect people -- especially those with asthma and other chronic lung conditions -- from colds and other respiratory tract infections, according to the largest study to date to look at the link.
People with low blood levels of vitamin D were more likely to have had a recent cold.
Unlike other vitamins, a deficiency of vitamin D (which is known as the sunshine vitamin because sun exposure triggers production in the body) is quite common in the United States -- particularly in winter.
At least 50 percent of people in the new study, which included nearly 19,000 people 12 and older, had levels that suggested less-than-optimal protection against respiratory tract infections, according to the report in the Archives of Internal Medicine.
"People think that if they have a good, balanced diet that they will get enough vitamin D, and that's actually not true," said Dr. Michal Melamed, an assistant professor at Albert Einstein College of Medicine in New York. "Unless you eat a lot of fish and drink a lot of milk, you can't get enough vitamin D from diet."
In the study, Dr. Adit Ginde of the University of Colorado Denver School of Medicine and colleagues at Harvard Medical School and Children's Hospital Boston found that people who had low blood levels of vitamin D were more likely to report having had a recent cold than those with higher amounts. What's more, the risk of a recent cold or other respiratory infection seemed to rise as vitamin D levels dropped. Overall, 24 percent of people with the lowest levels (under 10 ng/ml) had had a recent cold, compared with 20 percent of those with slightly higher levels (10 to 29 ng/ml) and 17 percent of those with the highest levels (30 ng/ml or more). The link was even stronger in people with asthma, who had about six-fold greater risk of colds with low vitamin D, and in those with chronic obstructive pulmonary disease, who had a two- to three-fold greater risk.
and the original study:
Arch Intern Med. 2009 Feb 23;169(4):384-90.
Association between serum 25-hydroxyvitamin d level and upper respiratory tract infection in the third national health and nutrition examination survey.
Ginde AA, Mansbach JM, Camargo CA Jr. Emergency Medicine Network, Massachusetts General Hospital, 326 Cambridge St, Ste 410, Boston, MA 02114. ccamargo@partners.org.
BACKGROUND: Recent studies suggest a role for vitamin D in innate immunity, including the prevention of respiratory tract infections (RTIs). We hypothesize that serum 25-hydroxyvitamin D (25[OH]D) levels are inversely associated with self-reported recent upper RTI (URTI). METHODS: We performed a secondary analysis of the Third National Health and Nutrition Examination Survey, a probability survey of the US population conducted between 1988 and 1994. We examined the association between 25(OH)D level and recent URTI in 18 883 participants 12 years and older. The analysis adjusted for demographics and clinical factors (season, body mass index, smoking history, asthma, and chronic obstructive pulmonary disease). RESULTS: The median serum 25(OH)D level was 29 ng/mL (to convert to nanomoles per liter, multiply by 2.496) (interquartile range, 21-37 ng/mL), and 19% (95% confidence interval [CI], 18%-20%) of participants reported a recent URTI. Recent URTI was reported by 24% of participants with 25(OH)D levels less than 10 ng/mL, by 20% with levels of 10 to less than 30 ng/mL, and by 17% with levels of 30 ng/mL or more (P < .001). Even after adjusting for demographic and clinical characteristics, lower 25(OH)D levels were independently associated with recent URTI (compared with 25[OH]D levels of >/=30 ng/mL: odds ratio [OR], 1.36; 95% CI, 1.01-1.84 for <10 ng/mL and 1.24; 1.07-1.43 for 10 to <30 ng/mL). The association between 25(OH)D level and URTI seemed to be stronger in individuals with asthma and chronic obstructive pulmonary disease (OR, 5.67 and 2.26, respectively). CONCLUSIONS: Serum 25(OH)D levels are inversely associated with recent URTI. This association may be stronger in those with respiratory tract diseases. Randomized controlled trials are warranted to explore the effects of vitamin D supplementation on RTI.
PMID: 19237723