Vitamin D Facts Studies And Tips

August 2011

I was recently dismayed by the reaction an allopathic physician had with a family member regarding vitamin D use. He explained to the practitioner that he had been taking Vitamin D as well as Vitamin C since experiencing a fever and sore throat but since it was persisting he was concerned it was bacterial. The doctor with eyes rolling explained that vitamin D is an unlikely hero against colds and the flu and it wouldn’t help.  Clearly this practitioner is unaware of the benefits of Vitamin D beyond bone health so from this came the topic for this month’s newsletter. Oh and by the way…it was strep throat.

Vitamin D Facts and Commonly Known Roles

Vitamin D is a fat soluble vitamin found naturally in fatty fish such as salmon tuna and mackerel and other foods such as beef liver cheese egg yolk and mushrooms exposed to UV radiation. In addition the body when exposed to sunlight makes vitamin D. Its most commonly known role is with bone health. Vitamin D aids calcium absorption and maintains proper calcium and phosphate ratios in the blood. This results in normal bone growth and development. Healthy levels of vitamin D help protect against bone disorders such as rickets and osteoporosis. Aside from this a growing list of research exists pointing out that vitamin D is a key player in preventing a host of ailments including autoimmune cardiovascular and infectious diseases and type 2 diabetes. In this article I am going to focus on vitamin D’s role in virus protection.

Vitamin D and Cold and Flu Prevention

Is it a coincidence that the flu peaks in the winter months when because of the location of the sun vitamin D levels are at their lowest? Or that seasonal allergies peak in early spring when vitamin D is also low? These are popular topics for debate. Vitamin D is required for immune system regulation and seems to have an effect on our ability to fight viral infections. In a multicenter randomized double blind placebo-controlled parallel group trial published in 2010 Urashima et al. researched the effect of vitamin D supplementation on the incidence of seasonal influenza A on school children. 334 children between the ages of 6 and 15 were involved. The intervention group received a 1200 IU supplement per day for 4 months and the control group received a placebo. During the study 18 children in the supplementation group acquired the flu versus 31 in the placebo group. Statistically this equates to vitamin D reducing the risk of getting the flu by 42% when compared to the placebo group. In addition the same study showed that the children previously diagnosed with asthma who were taking the vitamin D supplement had a relative risk reduction of having an asthma attack by 93% compared to the placebo group. Another interesting study by Sabetta J. R. et al found that healthy adults with a 25-hydroxyvitamin D level of greater than or equal to 95 nmol/l had a reduced risk of viral respiratory tract infections. These are just a couple of the many studies that support vitamin D’s protective qualities against viruses.  Vitamin D functions as a hormone as well as a vitamin and is involved in numerous bodily functions. In an article published in the International Journal of Epidemiology in 2011 Vitamin D was found to be inversely related to all-cause mortality in a group of US adults. The National Institutes of Health Dietary Supplements Fact Sheet on Vitamin D states that in addition to bone health Vitamin D has other roles in the body including modulation of cell growth neuromuscular and immune function and reduction of inflammation. And that many genes encoding proteins that regulate cell proliferation differentiation and apoptosis are modulated in part by vitamin D.

Another Reason Why Grandma Was Right

Does anyone remember the days when a dose of cod liver oil was a daily staple? Or maybe you heard stories from your parents or grandparents about an unpalatable spoonful forced on them. Well once again the previous generations knew a thing or two about health. Cod liver oil is packed with vitamin D vitamin A (another flu fighter) and the always-important omega 3s. I wonder if flu season had a softer blow on the cod liver oil-taking households?  Vitamin D enhances natural killer cells. It potentiates the phagocytic activity of macrophages the white blood cells that go after viruses bacteria and fungi.

Supplementation and Recommended dosages

Vitamin D dosing depends on your age and health status. For example the elderly pregnant and obese are typically in need of greater amounts of vitamin D than the average healthy adult. Recently the FDA upped the vitamin D dosage levels to 600IU per day for all ages up to 70 and 800 IUs per day starting at age 71. In addition they raised the safe upper limit to 4000 IU per day for adults and 3000 IU per day for children. However many expert vitamin D researchers believe these levels are still too low. Dr. Walter Willett chair of the Harvard School of Public Health Department of Nutrition publicly declared that these levels are still too low. Michael Holick Ph.D. M.D. Professor of Medicine Physiology and Biophysics at Boston University School of Medicine suggests dosages for children at 1000 IU per day and teenagers and adults at 2000 IU per day. Higher yet Dr. John Cannell of the vitamin D council recommends 5000 IU per day for adults.


If you are reading this then you are on the right track you are committed to the health and wellbeing of you and your family. Aside from vitamin Ds viral fighting qualities it is great for all around health improvements. If you don’t know where your Vitamin D level stands ask your doc to check your 25 (OH) Vit D level. It should definitely be above 30 and can range to 100. I have seen many patients overall health improve just by getting their vitamin D ranges into the normal range. So as you continue to bask in the glow of the northeast summer sun embrace the natural vitamin D your body is producing cause cold and flu season will be knocking on your door in no time. Including a vitamin D supplement into your diet for the late fall and winter months may help you to endure the season. Remember if your number is in the low normal range at this time of year after the past 3 months of sun then it will only be decreasing as the days grow shorter.

Additional Reference - Michael F. Holick. Health Benefits of vitamin D and sunlight: a D-bate. Nat. Rev. Endocrinol. 7 73–75 (2011).

Thanks to Geri's graduate intern Debra Wolf for her help preparing this article.