Vitamin D, popularly known as the “sunshine vitamin” is well-known for its role in bone health. It works by regulating calcium and phosphorus in the body, and there is some evidence that it helps to prevent certain types of cancer and other diseases. You can get vitamin D from a variety of food sources. In addition, your skin produces vitamin D in response to exposure to sunlight. Finally, you can obtain vitamin D from a dietary supplement.
However, despite all these options for obtaining vitamin D, a surprisingly large number of people suffer from vitamin D deficiency. Studies have found that up to three quarters of American adults have vitamin D levels below the recommended value (1). There are a number of risk factors which can significantly increase the risk of vitamin D deficiency. Do you get enough vitamin D through your everyday habits? Read on to find out and decide whether you need more of this important vitamin.
Why does it matter?
First, why should you care about your vitamin D levels? If so many people have vitamin D deficiency, how harmful can it really be? As it turns out, vitamin D has even more roles in the human body than originally thought, and a lack of it can have a variety of long-term, detrimental effects.
The most well-known role of vitamin D is its support of bone health. Vitamin D helps bone growth by regulating calcium in the body so it can be used for building bones. Vitamin D deficiency in children is associated with rickets. This disease causes the bones to become softened and weakened leading to skeletal deformities. Symptoms of vitamin D deficiency are usually subtle or absent, and may include bone pain and muscle weakness.
However, vitamin D deficiency has been associated with some serious health conditions over the long term. Low blood levels of vitamin D are correlated with increased risk of death from cardiovascular disease, cognitive impairment in older adults, severe asthma in children, and cancer. On a positive note, studies have suggested that vitamin D may be used to prevent or treat type 1 and type 2 diabetes, hypertension, glucose intolerance, and multiple sclerosis (2).
Vitamin D is clearly essential for bone growth for a variety of other functions in the human body. Some of these functions are just starting to be explored through scientific research. One thing is certain: many of us are not getting enough vitamin D to function optimally.
Populations at risk
Certain populations are particularly at risk for vitamin D deficiency. Often, the risk is related to an inability to synthesize enough vitamin D from sunlight. People with darker skin are more likely to be vitamin D deficient because melanin protects against the UV rays which are needed for vitamin D synthesis. Those living in northern latitudes, such as in Canada and the northern United States, are also at risk. Of course, if you have dark skin and live in the northern hemisphere, the risk is compounded.
Elderly people are also at risk for vitamin D deficiency for a variety of reasons. For one, they have fewer receptors in their skin that facilitate vitamin D synthesis. They also are more likely to stay indoors, may consume less vitamin D in their diet, and may have trouble with absorption.
Certain medical conditions, such as Crohn’s disease, cystic fibrosis, and celiac disease, interfere with the absorption of dietary nutrients, including vitamin D. Finally, excessive fat cells related to obesity can impair the release of vitamin D into the bloodstream (2).
It may seem that the simple solution to vitamin D deficiency is to spend more time in the sun. But, it is important to balance the benefits and risks of sun exposure. A general guideline is that to get enough vitamin D, you only need to be in the sun two to three times per week for one-fourth of amount of time it would take to become sunburned (3). Obviously, this value varies widely depending on location, cloud cover, skin type, and other factors.
If you are curious, you can use this calculator from the Norwegian Institute of Air Research to figure out how much time you need to spend outside on any given day to maintain healthy vitamin D levels. I found out that where I live, I would need to spend no more than five minutes outside on a typical summer day to get enough vitamin D. But with a lower UV index or darker skin, the required time would be much longer.
You can obtain some vitamin D from your diet as well as from sunlight, but it can be difficult. Most natural dietary vitamin D sources are animal-based, so vegans may be less likely to consume enough vitamin D. If you want a completely natural, vegan dietary source of vitamin D, the best choice is certain types of mushrooms, including maitake, portobello, and chanterelle. These mushrooms synthesize vitamin D when exposed to UV radiation, similarly to how we do (4).
Do note that mushrooms produce vitamin D in the form of D2, whereas humans produce it in the form of D3. There is evidence that D2 is less effective than D3 in raising blood levels of vitamin D. However, many plant-based foods are fortified with D3, including almond milk, cereal, and tofu.
How do you get your vitamin D?
As I have shown in this article, vitamin D deficiency is a widespread problem and should be a cause for concern for people everywhere. Hopefully, this issue will become less prevalent with increased availability of information. The most important information to be aware of is the amount of sun exposure needed for the skin to synthesize vitamin D. If you aren’t spending enough time outside, you may want to eat more of the food sources of vitamin D.
Finally, if you have one or more of the risk factors for vitamin D deficiency, you may want to talk to your doctor and consider starting a dietary supplement. To see what the options are, read my review of the best vitamin D supplements on the market. With some awareness and planning, you can obtain the ideal amount of vitamin D as a part of any lifestyle.
Do you think you are at risk for vitamin D deficiency, or do you have some insight to share? Please feel free to comment below and share your thoughts.