Most people think that a casual exposure to sun or diet is enough to fulfil their daily vitamin D needs. That’s not true. In today’s modern, indoor and urban world, optimizing your relationship with the sunlight is essential – too much of it is harmful and too little can make you pallid and unhealthy. While vitamin D is necessary for healthy bones and muscles, there has been good epidemiologic evidence between increased vitamin D uptake and decreased risks of many autoimmune diseases such as lupus, multiple sclerosis (MS), psoriasis, and rheumatoid arthritis (RA).
Role of Vitamin D in autoimmune diseases
People with lupus, an autoimmune disease that leads to organ damage, have significantly lower vitamin D levels. It is also more common among people with a high melanin (body’s natural sunscreen) concentration in the skin.
People who live at higher latitudes are more likely to have MS than people who are born below 35°N latitude and lived at or below that latitude for the first 10 years of their lives. This is attributable to a decrease in UVB (the ultraviolet light necessary to make vitamin D) exposure. It was observed that increases in vitamin D intake were related to decreases in MS incidents.
Vitamin D, when applied as an ointment has reduced the effects of psoriasis, an autoimmune skin disease.
In RA, activity level, weather, and joint pain have been associated with vitamin D levels. The Iowa Women’s Health Study showed that women who took vitamin D supplements were less likely to develop RA.
Low levels of UV rays in winter, and thus low levels of vitamin D synthesis by your skin, are unable to inactivate the environmental viruses making you more susceptible to infections like flu.
Sources of Vitamin D
Very few foods naturally contain vitamin D, and only a few foods are fortified with it. Natural sources are cod liver oil, fortified milk and cereal products, sun-dried or irradiated mushrooms (mushrooms naturally contain some vitamin D and when exposed to sunlight, the amounts increase substantially), oily fish such as salmon, tuna, sardine, mackerel, and whole egg. Potential overdosing can occur with supplementation as opposed to over sun exposure.
There is no “one size fits all” to individual vitamin D levels. How much you need depends on your
- Age: A 70-year old makes less vitamin D than a 20-year-old.
- Geographic latitude: Above 37° there is marked decreases in the UVB light and D synthesis. Below 37° and closer to the equator, more synthesis occurs in the skin throughout the year.
- Skin coloration: People with high melanin pigmentation require longer exposures to sunlight to make the same amount of vitamin D, compared with light-skinned people.
- Season of the year: In winter, through the months of November to February, D synthesis is low compared to summer.
The latitude of San Francisco County is a little over 37°; hence it is essential for people living here (and everywhere) to have an outdoor lifestyle, and actively seek sunlight as a nutrient. If you don’t do that, you could be living right on the equator and still be D deficient!