Participants in a randomized controlled trial who received a monthly dose of 100,000 IUs of vitamin D3 did not have a significantly reduced incidence or severity of upper respiratory tract infection, according to a New Zealand-based study.
The finding contradicts some previous data that suggested a possible inverse association between serum vitamin D level and the incidence of colds, the researchers said.
David R. Murdoch, MD, of the University of Otago in New Zealand, and colleagues conducted a randomized trial of 322 healthy adults between February 2010 and November 2011. Participants were randomly assigned to receive an initial dose of 200,000 IU oral vitamin D3, then 200,000 IU one month later, then 100,000 IU monthly for a total of 18 months; or placebo administered in an identical dosing regimen.
The average 25-hydroxyvitamin D (25-OHD) level of participants at the beginning of the study was 29 nanograms per milliliter. Vitamin D supplementation resulted in an increase in serum 25-OHD levels that was maintained at greater than 48 ng/mL throughout the study. There were 593 episodes of upper respiratory tract infection in the vitamin D group and 611 in the placebo group.
The researchers found no statistically significant differences in the number of URTIs per participant (average of 3.7 per person in the vitamin D group and 3.8 per person in the placebo group), duration of symptoms per episode (12 days on average in each group), number of days of missed work as a result of URTIs or severity of URTI episodes.
"The main finding from this study is that a monthly dose of 100,000 IU of vitamin D3 in healthy adults did not significantly reduce the incidence or severity of URTIs," the authors wrote. "This result remained unchanged when the analysis included winter season or baseline 25-OD levels.
"Further research is required to clarify whether there is benefit from supplementation in other populations and with other dosing regimens."
The study appears in the Oct. 3 issue of JAMA and is available at http://jama.jamanetwork.com/article.aspx?articleid=1367547.
Vitamin D has been in the news frequently of late, including a report that vitamin D deficiency may be linked to heart disease (http://news.nurse.com/article/20120930/NATIONAL02/110010029).
The finding contradicts some previous data that suggested a possible inverse association between serum vitamin D level and the incidence of colds, the researchers said.
David R. Murdoch, MD, of the University of Otago in New Zealand, and colleagues conducted a randomized trial of 322 healthy adults between February 2010 and November 2011. Participants were randomly assigned to receive an initial dose of 200,000 IU oral vitamin D3, then 200,000 IU one month later, then 100,000 IU monthly for a total of 18 months; or placebo administered in an identical dosing regimen.
The average 25-hydroxyvitamin D (25-OHD) level of participants at the beginning of the study was 29 nanograms per milliliter. Vitamin D supplementation resulted in an increase in serum 25-OHD levels that was maintained at greater than 48 ng/mL throughout the study. There were 593 episodes of upper respiratory tract infection in the vitamin D group and 611 in the placebo group.
The researchers found no statistically significant differences in the number of URTIs per participant (average of 3.7 per person in the vitamin D group and 3.8 per person in the placebo group), duration of symptoms per episode (12 days on average in each group), number of days of missed work as a result of URTIs or severity of URTI episodes.
"The main finding from this study is that a monthly dose of 100,000 IU of vitamin D3 in healthy adults did not significantly reduce the incidence or severity of URTIs," the authors wrote. "This result remained unchanged when the analysis included winter season or baseline 25-OD levels.
"Further research is required to clarify whether there is benefit from supplementation in other populations and with other dosing regimens."
The study appears in the Oct. 3 issue of JAMA and is available at http://jama.jamanetwork.com/article.aspx?articleid=1367547.
Vitamin D has been in the news frequently of late, including a report that vitamin D deficiency may be linked to heart disease (http://news.nurse.com/article/20120930/NATIONAL02/110010029).
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