March 1st, 2017

// Study finds Vitamin D effective for reducing flu and colds

Study finds Vitamin D effective for reducing flu and colds 

People who boost their vitamin D levels with supplements reduce their risk of respiratory tract infections, such as the flu, by up to 12%, according to a new systematic review and meta-analysis study of 25 randomised controlled trial (RCT) studies published recently in the British Medical Journal (BMJ).


The study reported that this equates to one person being spared a respiratory tract infection (RTI) for every 33 taking vitamin D supplements. The benefit is greater in those receiving daily or weekly vitamin D versus bolus or monthly dosing, with the number needed to treat dropping to 20. The impact in Canada, based on a population of 35 million people, shows vitamin D could spare 1.75 million people having one RTI per year.


“The results are likely to change the cost/benefit analysis relating to fortification of foods with vitamin D significantly,” said Adrian Martineau, clinical professor of respiratory infection and immunity at Queen Mary University of London.


The magnitude of potential healthcare savings is great when you consider the impact of RTI’s such as time off work, doctor appointments, and prescription costs. Just last year a study found if Canadians could raise their mean level of vitamin D to at least 100 nmol/L, it would prevent approximately 23,000 premature deaths and save $12.5 billion annually in direct healthcare and related costs.


Vitamin D researchers have suspected for a long time that RCT studies which used bolus or monthly dosing and reported minimal benefits were diminishing the true positive effects of vitamin D especially in systematic review and meta-analysis. This new study by Martineau et al. was able to prove that bolus or monthly dosing is ineffective. It found:


  • 12% reduction of respiratory tract infections based on all studies and all dosing regimens
  • 19% reduction of respiratory tract infections for those receiving daily or weekly vitamin D doses
  • No statistically significant effect on risk of respiratory tract infections for those receiving bolus or monthly dosing
  • 70% reduction in respiratory tract infections for those with low vitamin D blood levels below 25 nmol/L and receiving weekly or daily dosing of vitamin D


“You can’t expect a monthly bolus dose of vitamin D to provide adequate blood levels of 25(OH)D to respond to daily infectious attacks,” said Dr. Gerry Schwalfenberg, a scientific advisor to the Vitamin D Society and an Assistant Clinical Professor at the University of Alberta. “Vitamin D levels would spike immediately from the bolus dosing and then drop throughout the month back to low untreated levels leaving you open to infections. You need daily vitamin D intake for best results and immune response.”


In Canada, 35% of people or approximately 12 million people have vitamin D levels below 50 nmol/L. This increases to 40% in winter. More than 50 vitamin D scientists recommend that you reach a vitamin D blood level of between 100-150 nmol/L for optimal health.


“This study proves that by increasing your vitamin D blood levels through daily intake you could significantly prevent flu, colds and other respiratory infections,” said Perry Holman, Executive Director of the Vitamin D Society. “One of the reasons we have more flu and colds in the winter is due to the lack of UVB sun exposure and the resulting lower vitamin D levels.”


About the Vitamin D Society:

The Vitamin D Society is a Canadian non-profit group organized to increase awareness of the many health conditions strongly linked to vitamin D deficiency; encourage people to be proactive in protecting their health and have their vitamin D levels tested annually; and help fund valuable vitamin D research. The Vitamin D Society recommends people achieve and maintain optimal 25(OH)D blood levels between 100 – 150 nmol/L (Can) or 40-60 ng/ml (USA).

To learn more about vitamin D, please visit


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