Ms. Nutrition: Shiney vitamin D

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There is a lot of buzz about vitamin D these days and it has become quite the hot supplement over the last few years. But is this stardom warranted?

Initially our understanding was that vitamin D primarily helps us manage the complex flow of calcium and phosphorus through our bodies, thus preventing a bone disease known as rickets. However, hundreds of studies of this once humble vitamin have made it increasingly clear that it plays a bigger and more important role than we thought. Deficiencies of vitamin D in the body have been associated with several health problems, including autoimmune diseases such as multiple sclerosis and rheumatoid arthritis, risk of prostate and other cancers, and heightened susceptibility to asthma and some infectious diseases.

The trick is that, unlike most vitamins, vitamin D is very hard to get from food. The best way for us to get vitamin D is to expose our bare, sunscreen-free skin to ultraviolet B (UVB) rays from the sun.

Exposing the full body to the noon summer sun for 20 to 30 minutes stimulates the skin to produce as much as 10,000 international units (IU) of vitamin D, 50 times the US government’s recommended 200 IU per day. The amazing thing is that you cannot overdose on vitamin D made by the skin – built in regulators keep your skin from making too much. However, you can get too much from taking vitamin D supplements orally.

But overdosing isn’t the main problem with vitamin D. Recent studies indicate that current recommendations for vitamin D intake are actually too low to address the body’s needs. In November, the American Institute of Medicine will issue new guidelines for vitamin D, and many experts are hoping that the new guidelines will encourage higher intake.

Unfortunately, these days many people do not get enough vitamin D from the sun, and may need to supplement in order to maintain optimal levels. Indoor life and Beijing’s harsh, windy winters mean that most of us will not be spending much time outdoors over the next few months. Also, people with darker skin tones tend not to benefit as much from sunlight exposure. Lighter skin responds better to the UVB rays that trigger vitamin D production. As a result, vitamin D levels for most of us are likely to be far below what they should be, especially during darker months.

So how much vitamin D should we take while living in Beijing? How much vitamin D we need varies individually based on factors such skin tone, age, body weight, sunlight exposure and medical factors. However, a good generalization for Beijing winters is that healthy children under the age of 1 can take 1,000 IU of vitamin D3 per day, while older children can take 1,000 IU vitamin D3 per day for every 11kg of body weight. Healthy adults and adolescents can take up to 5,000 IU of vitamin D3 per day with little ill-effect.

So if you find yourself missing the sun this summer, check your multivitamins and supplements to make sure you’re getting enough vitamin D3. It won’t make up for a long winter, but it can make for a healthier one.

 

Got a question? Singaporean Olivia Lee (olivianutrition@gmail.com) has an MSc in nutrition and provides nutrition counseling.

 

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