Updated: Nov 18, 2020
What is Vitamin D?
It's actually a steroid hormone. It regulates around 5% of our genome making it vitally important in many bodily processes. It plays an important role in your immune system, bones and respiratory health.
How is it made?
Vitamin D is made by the body upon exposure to the sun and is gotten in certain foods like salmon, mushrooms, egg yolks, liver and leafy greens.
What populations are most affected by Vitamin D deficiency?
Elderly: A 70 year old person makes about 4 times less than their 20 year old selves.
Obese: They have greater than 50% less bioavailability of Vitamin D than non obese adults. Because of this, obese people are 3 times more likely to be Vitamin D deficient.
Northern Latitude: We simply get less sun and therefore synthesize less Vitamin D.
Dark skinned: Synthesis of Vitmin D is reduced because the extra melanin acts as a natural sunscreen. African Americans have been show to have 24.6 times more Vitamin D deficiency than non-hispanic whites.
Interestingly, the populations most affected by Covid19 are the same populations with chronically low Vitamin D levels.
A recent CDC study of 1500 people in 14 states that analyzed data from March 1-30 found
- 48% of people hospitalized for Covid19 were obese
-75% were over 50 years old
- 33% of people hospitalized were African American despite only being 13% of the total population
Also, a report out of Sweden said that Somali immigrants who live in Stockholm comprised 40% of the deaths though they are only 0.84% of the population. A number of previous studies found that Somalis in Sweden had extreme Vitamin D deficiency due to overlapping factors of heredity and geography. The authors of this report strongly recommended administration of Vitamin D to high risk populations.
Vitamin D and Acute Respiratory Tract Infection
A meta-analysis of 25 different studies showed that people who had Vitamin D deficiency and supplemented daily or weekly, had a 50% less risk of Respiratory Tract Infections than people who did not supplement. For people who had a normal baseline Vitamin D, when they supplemented, they had a 10% less risk of RTIs.
Vitamin D and the Immune system
Vitamin D is an important contributor to the innate immune response (ie. the first line defenders).
The details of how Vitamin D affects the Immune system and Respiratory Tract is a bit complicated and I won't go into it here, but suffice to say there is more and more data supporting the idea that Vitamin D supplementation is a good idea for those in the high risk categories. Usually, it's recommended that you take 2000-4000iu per day (D2 or D3 are both fine - D2 is from plant sources and D3 is from animal sources). And when you can go outside comfortably and want to get tested to find out for sure, then that might be a good idea as well.
Somalis and Vitamin D https://www.bmj.com/content/368/bmj.m1101/rr-10
Meta Analysis https://www.ncbi.nlm.nih.gov/pubmed/30675873