The Cold & Flu Vitamin

In January 2018, a study was published in the Pediatric Infectious Disease Journal demonstrating something I have been sharing with my patients, family, and friends for years:

Vitamin D is a cold and flu killer.

The study focused on infants with influenza, but results are similar for older children and adults, too. The multi-center, randomized, controlled, clinical-based trial showed that low and high dose vitamin D was effective and safe in treating infants with infulenza A. Common symptoms like fever, cough, and wheezing were proven to be shorter in duration in both groups, but significantly shorter in the high dose group. 

10 years ago Dr. John Cannell, founder of the Vitamin D Council, put forth the idea that vitamin D deficiency may be a root cause of influenza. Subsequent studies based on this hypothesis did show that individuals who were vitamin D deficient experienced significantly more colds and flu. In February of last year Time Magazine wrote the article “Here’s How to Avoid Catching Colds and Flu” which summarizes the findings of a meta analysis of 25 studies covering 11,000 people. Daily or weekly vitamin D supplementation reduced colds and flu by half in those with the lowest level of vitamin D. Even people with the highest level of vitamin D saw a 10% reduction in respiratory infection including colds and flu which makes it as effective as the flu shot.

Other studies have revealed that it requires 40 people to be treated with a flu vaccine to prevent one case of flu, 33 people treated with vitamin D to prevent one case of flu, and only 4 people if they are vitamin D deficient to prevent one case of flu. Therefore, for those who are vitamin D deficient, a vitamin supplement is 10 times more effective than the flu shot.

Vitamin D is produced naturally from exposure to sunlight, rendering us most susceptible to vitamin D deficiency in the winter months when the days are shortest and it may be too cold for outdoor activities. Working indoors, wearing sunscreens, or having darker skin pigmentation can further reduce our vitamin D levels which should be taken into account when considering supplementation. Some people may require as much as 6000-10000 IU of vitamin D3 supplementation to maintain a healthy level of vitamin D. One may further consider increasing vitamin K2 and magnesium which help optimize vitamin D levels.


Adults: Vitamin D3 50,000 IU once a day for three days.

Children: A proportional fraction of vitamin D3 50,000 IU based on an average adult weight of 150lbs. For example a 30lb child would receive 1/5th of the adult dose or 10,000 IU once a day for three days.

The vitamin D3 should be started within 24-36 hours of the onset of first symptoms.

You should consult with your physician before initiating this protocol as you may have a medical condition precluding vitamin D at these doses.

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