Adequate intake of vitamin D has a myriad of benefits, especially in disease prevention. It has been associated with lower risk of e.g. osteoporosis, cardiovascular disease, both types of diabetes, many autoimmune diseases and many types of cancer, even depression and influenza.
Based on the current research it would not be far-fetched to compare vitamin D deficiency as a health risk to smoking. Deficiency is very common, but luckily fairly easy to fix.
Sunlight as a Source of Vitamin D
Sunlight (more specifically, UVB light) produces vitamin D on the skin when the sun is high enough – an UV index of three is needed. In many countries it is only possible to obtain vitamin D from the sun a few months a year.
In just 15 to 30 minutes, sunlight can produce 10,000-20,000 IU (250-500 mcg) on the skin. This shows how laughably inadequate most recommendations for vitamin D requirements are: in most countries the RDA is between 200 and 800 IU (or 5-20 mcg).
Sunscreen blocks the production of vitamin D, so it is recommended to also spend some time outdoors without sunblock, if at all possible. Showering and bathing can also wash away some of the vitamin D produced in the sun.
Some (but not all) solariums also produce light in the UVB spectrum, so one may be able to get vitamin D from tanning. However, there are safer ways to satisfy one's requirement than sun beds.
Some people are found to be deficient in vitamin D despite frequent exposure to the sun, suggesting that their skin does not produce it effectively enough. Dark-skinned and the elderly produce it much less effectively than fair-skinned youth. This is one reason why blood testing is often recommended.
Food Sources of Vitamin D
Many people believe that by eating healthily they can meet their requirement of all vitamins. Some foods do naturally contain vitamin D, including eggs, dairy fat, liver and fish. Wild mushrooms are the only natural vegan source. Vitamin D is also added to margarine and dairy products in many countries, sometimes also to cereal.
However, the amounts one can acquire from food are generally insignificant. For example, 100 g/3.5 oz of salmon contains about 320 IU (8 mcg) of vitamin D and 100 g of cooked chanterelle mushrooms contains 640 IU (16 mcg). Eaten daily, they could be used to mee the official RDA, but they are a far cry from the amounts obtained from just brief sun exposure.
Vitamin D Supplementation
Those who do not get plenty of bright sunlight several times a week need vitamin D supplements. Most vitamin D researchers recommend at least 4,000 IU (100 mcg) a day, but even that isn't enough for many people. The best way to ensure adequate intake is to get a blood test and adjust the dose accordingly.
There are two different forms of vitamin D: D2 or ergocalciferol and D3 or cholecalciferol. D2 is vegan while D3 is usually acquired from wool. D3 is thought to be the more effective form, though the research is conflicting whether the difference is slight or major.
Vitamin D should always be supplemented as oil capsules or in liquid form dissolved in oil, never as tablets, because as a fat soluble vitamin it needs fat for proper absorption.
Cod liver oil cannot be recommended as a source of vitamin D, because of the very large doses of vitamin A it also contains. Vitamin A can be harmful even in doses slightly above the RDA and can counteract some of the benefits of vitamin D.
There is a common misconception that if one takes vitamin D, they also must take calcium. This is not true, but some other nutrients are important for the proper utilization of vitamin D, most importantly magnesium – which many people are also deficient in.
Join the Conversation