There are five main sources of vitamin D.
In the previous article we discussed supplementation for those who have a serious Vitamin D Deficiency or cannot get it from the sun and other sources. In this article we discuss four potential sources: The sun, which is our primary source, as well as other sources. These include real foods, as well as “fortified” foods (such as milk and many processed foods), which are actually not a good source of Vitamin D. Finally, artificial light is also discussed as a source for those in colder climates where optimal sun exposure is limited.
It’s especially important to obtain adequate vitamin D from sun exposure throughout the warmer summer months to build stores of vitamin D for the winter. But without sufficient exposure beginning early in the season that brings vitamin D levels in the body to moderate or high levels, the amount of vitamin D stored for winter may be inadequate and additional sources necessary.
How much sun and for how long depends on each person’s individual needs. For many fair-skinned people, exposing arms and legs to sunlight for 20-30 minutes — more in northern climates and less as you get closer to the equator during high sun (between the hours of 10 a.m. and 3 p.m.) throughout the week without sunscreen should be adequate to start the process of building adequate vitamin D levels. In a healthy person, this amount of sun can produce 5,000 to 10,000 units of vitamin D — and this amount is healthy, not excessive.
While it’s possible to burn from too much sun, we cannot overdose on vitamin D from the sun like we can with all other sources.
As skin tans, longer periods of sun exposure will be needed to build vitamin D stores for the winter months. Those in more northern (and extreme southern) climates may need much more. And, those with darker skin will require even more sun exposure throughout the year. In general, more exposure may be better as long as you avoid the most important sun stress, sunburn. And, as your levels of vitamin D rise and normalize, the risk of sunburn diminishes.
Foods containing vitamin D are secondary sources that only help contribute to normal vitamin D levels. While food won’t get your levels to normal if you’re deficient, they can help maintain them. The best vitamin D-containing foods are from animal sources. These include:
- Wild salmon, sardines and tuna.
- Egg yolks.
Vegetable sources of vitamin D are less adequately utilized by the body, with shiitake mushroom being a modest source.
Foods fortified with vitamin D are not a good source for several reasons. First, the levels are quite insignificant when compared to what we can get from the sun. Relying on the consumption of vitamin D-fortified foods has clearly failed to prevent abnormal low levels and associated disease and other problems in the population.
The synthetic fortification of milk is a common example. Most people would need 10 or 12 glasses a day — or more — to consume adequate amounts of vitamin D; something most would, and should, not consume. And, this form is vitamin D2.
This vitamin D2 is ergocalciferol. In humans, it’s not utilized as well as natural forms, such as from fish, and not as well absorbed. And, the foods that are fortified are usually unhealthy processed products, such as cereal, margarine and processed cheese, and other items that are generally best avoided.
For most people, relying on food to obtain sufficient vitamin D is difficult without adequate sun exposure. If your blood levels of vitamin D are low, and you’re spending time in the sun, addition supplementation from cod liver oil may be necessary.
Tanning or sun beds, happy lights and other sources of UVB rays, can increase vitamin D levels. These are readily available for home use and in tanning salons. I don’t recommend them as a replacement for sun exposure, except for those who may be unable to spend adequate time in the sun. This is especially true in winter months in cold climates, and those who work indoors all day. With adequate sun exposure in warm weather, cod liver oil supplements and a tanning bed once a week, even people in Canada, northern Europe and other sun deficient areas, for example, can help maintain healthy levels of vitamin D.
Other Nutrients Associated with the Sun and Vitamin D
The body requires a variety of other nutrients to help regulate vitamin D. Those consuming a healthy diet can usually obtain most of these nutrients. However, many people don’t even obtain minimum levels, such as RDA levels, of some nutrients — even when they include supplements! Magnesium is a common example, and a very important nutrient to help the body regulate vitamin D. This mineral is often low, particularly in athletes. In fact, having done a dietary analysis on almost all athletes I’ve seen over decades of work, magnesium is one of the more common deficiencies. The best food sources are organically grown vegetables, and raw nuts and seeds.
These foods will also help you obtain other nutrients needed for better utilization of vitamin D; they include zinc, and the vitamins A and K. In the case of vitamin A, however, you’ll need egg yolks and other animal foods such as fish since plant foods don’t contain vitamin A (they contain large amounts of beta carotene which the human body can convert to vitamin A but not very efficiently as other animals). Most cod liver oil supplements also contain vitamin A.
As research continues we’ll find out more regarding the nutrients that we need to protect us when spending time in the sun. Various naturally occurring antioxidants from foods, and omega-3 fats, for example, are used by the body in helping to protect us from possible harm of overexposure, so these nutrients will be needed in adequate amounts especially in sunny seasons.
For a long time it’s been known that sun exposure reduces the body’s folate levels (usually known as folic acid), another reason to consume 10 servings of vegetables and fruits each day, which should provide sufficient folate.