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Sunday, May 31, 2015

Vitamin D: Should We Get it From Food, Supplements, or the Sun?

A new study found that vitamin D levels made a difference in the survival of patients with advanced colorectal cancer. The individuals who had higher levels of vitamin D in their bloodstream before they were treated with chemotherapy and biologic drugs lived longer, on average, compared to people with lower levels of vitamin D.

There's no doubt that vitamin D is important. It's a key nutrient for several systems in the body including the cardiovascular, neurological, and immune systems. And it regulates the activity of more than 3,000 different genes. Many people are deficient in vitamin D and for them the question is: Should it come from food, supplements, or the sun?


Few foods are good sources of vitamin D. The best ones are fatty fish like salmon and mackerel and their livers. In the United States, fish livers are difficult to find in forms other than cod liver oil supplements. (In France they’re sold on grocery store shelves alongside other canned fish products.) Smaller amounts of vitamin D are found in canned sardines, beef liver, egg yolks, cheese, and some mushrooms. Some foods may be fortified with added vitamin D like milk, yogurt, and orange juice.  


Vitamin D is fat-soluble, so when your body has more than it needs, extra vitamin D is stored for future use. Taking too much in supplement form can cause it to accumulate to toxic levels, so it's a good idea to be tested. Your doctor can tell you how much to take, based on your current level, and re-test as necessary to ensure that supplementation is effective and that levels don’t exceed the upper limit of the normal range. A recent study found that excessively high levels of vitamin D were associated with an increased risk of dying from a stroke or heart attack. 

People who are deficient in vitamin D also need the co-factors required for it to work properly, including vitamin A, vitamin K, magnesium, zinc, and boron. The best way to get these nutrients is by eating at least one serving of dark green leafy vegetables and a handful of raw nuts or seeds every day. If that isn't possible, these nutrients can also come from a quality multiple vitamin-mineral supplement.

The Sun

Upon exposure to sunlight, our skin turns cholesterol into vitamin D. At the same time, several related compounds are also created. Because we can’t get these related compounds from other sources, safe sun exposure can have bigger benefits than food or supplements.

Exactly how much vitamin D your skin makes depends on several different factors: 
  • How far you live from the equator (the intensity of the sun is strongest at the equator)
  • The season of year (sunlight is more direct and lasts longer in the summer)
  • The color of your skin (darker skin tones contain more melanin, which blocks sunshine)
  • Your age (the older you get, the less vitamin D you make)
  • How much time you spend in the sun
We can't get too much vitamin D from the sun like we can from supplements, but we can get too much ultraviolet radiation. I usually recommend ten to twenty minutes of early morning sunshine each day, depending on the UV index. 

The UV index is a scale from 1 to 11 that estimates the risk of harm that the sun's rays can have on unprotected skin:
  • 1 and 2 = low risk
  • 3, 4, 5 = moderate risk
  • 6 and 7 = high risk
  • 8, 9, 10 = very high risk
  • 11 = extremely high  risk
The UV index is highest in the summer and in the middle of the day. It's lowest in the winter and during early morning and late afternoon hours. It's easy to check the UV index with free smart phone apps like "EPA's SunWise UV Index" from the United States Environmental Protection Agency or "UV US - Weather Forecast, UV Index, and Alerts" from MetaOptima Technology Inc.

When the UV index is low, it's safe to be outside without using sunscreen. When the UV index is moderate, wear sunscreen outdoors. Use the 2015 Guide to Sunscreens from the Environmental Working Group to learn more about the sunscreen you have and find good choices that are free of harmful chemicals.

When the UV index is high, stay out of the sun. If you can't seek shade, cover your skin with long sleeves, long pants, and a hat. Strong sun can also damage your eyes and increase the risk of developing macular degeneration, so it’s also a good idea to wear sunglasses when you’re outdoors, especially when the UV index is moderate or high.

Early morning is the best time to be outside. Not only are the sun’s rays are least intense and least likely to increase the risk for skin cancer, but early morning sunshine also stimulates the production of hormones and neurotransmitters that help regulate sleep, energy, mood, appetite, blood sugar levels, and even the way our bodies store fat. 

The bottom line?

Safe sun exposure can be a good way to treat the whole person. This is true whether or not vitamin D comes from food or supplements.

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