In the previous blog post I briefly spoke about the mechanism of action of vitamin D, and I explained the difference between vitamin D2 and vitamin D3. I also discussed some of the more common health conditions that are affected by a vitamin D deficiency. In this post I’m going to talk about why many people are deficient in vitamin D, and I’ll also discuss how to test for a vitamin D deficiency. I’ll conclude the post by mentioning three ways to increase vitamin D levels.
So why are many people deficient in vitamin D? Well, here are some of the different reasons:
1. Most people don’t get enough sunlight. Many people work indoors and don’t get enough sunlight. This definitely describes me, as while I’d like to say that I take a 30-minute walk in the sun during my lunch break every day, this usually isn’t the case. And keep in mind that the amount of skin that is exposed to the sun plays a big factor. For example, if someone takes a walk in the sun fully clothed then they will produce much less vitamin D when compared to someone who is sunbathing. So I’ll consult with people who take a daily walk outside, or perhaps they work in their garden every day, but because they have a lot of clothing on they aren’t getting enough skin exposure.
2. Latitude. Those who live in northern latitudes have a decreased exposure to sunlight during the winter, and thus are more likely to be deficient in vitamin D.
3. VDR polymorphism. Vitamin D binds to the vitamin D receptor (VDR), which in turn is encoded by the VDR gene. Many people have genetic polymorphisms of the VDR gene, which can increase one’s risk of developing a vitamin D deficiency. And the research shows an association between VDR polymorphisms and thyroid autoimmunity (1) [1] (2) [2].
4. Skin pigmentation. Those with dark colored skin absorb more UVB in the melanin of their skin, and as a result, they require more sun exposure to produce the same amount of vitamin D (3) [3] (4) [4].
5. Air pollution. Air pollution can block the absorption of ultra-violet B (UBV) light. This of course is a factor wherever you live, but if you live in a larger city then chances are you are dealing with a greater amount of air pollution.
6. Age. Aging affects vitamin D metabolism, as the older you get, the less vitamin D is produced by the skin.
7. Frequent use of sunscreen. Many people apply sunscreen whenever they go out in the sun, and since sunscreen blocks the absorption of vitamin D, using it frequently can lead to a vitamin D deficiency. This isn’t meant to suggest that you should never use sunscreen, as I can understand using it if you are planning to be in the sun for many hours, but I would try to get at least 20 to 30 minutes of sun exposure daily without the use of sunscreen.
8. Deficiency in one of the cofactors. Vitamin D works together with numerous cofactors, including magnesium, vitamin K2, zinc, boron, and vitamin A. The vitamin D Council website has an excellent article [5] which discusses the role that each of these cofactors has with regards to vitamin D.
What Are The Symptoms of a Vitamin D Deficiency?
Many people who are deficient in vitamin D don’t experience any noticeable symptoms. If the vitamin D deficiency is severe then they might experience symptoms such as muscle pain or weakness. But other factors can cause such symptoms, and not everyone with depressed vitamin D levels will experience muscle pain or weakness. As a result, the best way to determine if you have a vitamin D deficiency is through testing.
Testing The Vitamin D Levels
25-OH vitamin D is the marker that should be tested through the blood. Some healthcare professionals will test 1,25-dihydroxyvitamin D, and when you consider that this is the active form of vitamin D this might make sense. However, it’s important to understand that 1,25-dihydroxyvitamin D is regulated by parathyroid hormone, and when someone has a vitamin D deficiency this results in a compensatory increase in the parathyroid hormone levels, and this in turn will increase 1,25-dihydroxyvitamin D. And so 1,25-dihydroxyvitamin D is usually normal or elevated, even in the presence of a vitamin D deficiency.
3 Ways To Increase Vitamin D Levels
1) Sunlight. Ideally this is the best way to increase vitamin D levels, as one hundred years ago people didn’t take vitamin D3 supplements as they do today. However, we of course live in a different world, as many people don’t have the opportunity to go outside when it’s sunny, and most who do get regular sun exposure are fully clothed. In addition, air pollution is a big issue, as I mentioned earlier how this affects the absorption of vitamin D.
2) Supplementation. I personally take 5,000 IU/day of vitamin D3 on a wellness basis, and this keeps my levels at a healthy level, which I confirm through annual testing. Does this mean that everyone should take a vitamin D3 supplement on a wellness basis? Not necessarily, as some people do need to supplement with vitamin D3 to correct a deficiency, but are then able to maintain healthy levels through regular sun exposure. Others need to supplement with vitamin D3 but don’t need to take as high of a dosage.
3) Indoor tanning. Using indoor tanning beds can also be an option. This is controversial, as indoor tanning can potentially increase the risk of skin cancer (5) [6] (6) [7]. However, the vitamin D Council considers tanning to be a good option if you take the following two precautions (7) [8]. First, get half the amount of exposure that it takes for your skin to turn pink. And second, use low-pressure tanning beds that have a good amount of UVB light, instead of the high intensity UVA light.
Can Vitamin D Be Obtained Through Diet?
Vitamin D is very low in the food supply, as it is not found in plant materials (i.e. vegetables, fruits, or grains) and it is present in small amounts in meats and other animal food sources, except in rare cases such as fish liver oils (8) [9]. Dairy products are of course commonly fortified with vitamin D, and canned salmon, sardines, and tuna can be good sources of vitamin D (9) [10]. But overall it is very difficult to get enough vitamin D from the diet, and it is almost impossible to correct a vitamin D deficiency through diet alone.
In summary, many people with thyroid and autoimmune thyroid conditions are deficient in vitamin D, and while a big reason for this is due to insufficient exposure to sunlight, other reasons include living in a northern latitude, having a VDR polymorphism, having dark colored skin, air pollution, frequently using sunscreen, and being deficient in one or more of the cofactors of vitamin D. When testing for vitamin D in the blood you want to test for 25-hydroxy vitamin D, as this is more accurate than 1,25-dihyroxyvitamin D. Sunlight and supplementing with vitamin D3 are the two main ways to increase vitamin D levels, although indoor tanning is also an option.