With sufficient sun exposure, the body is able to make enough vitamin D on it's own. Nonetheless, some people who live very far north or very far south, i.e. far from the equator, might be deficient in vitamin D. That's why medical professionals recommend taking vitamin D as a supplement. Today our focus is this question: Is it still necessary to take vitamin D supplements in the summertime?
When the skin is exposed to sunlight (UVB), the body can make sufficient vitamin D. The body transports this form of vitamin D from the skin to the liver and the kidneys, where it is then converted into active vitamin D. Only after this conversion can the vitamin D start to fill its role in the body. According to some scientific evidence, vitamin D – actually a hormone and not a vitamin – should play a role in the prevention of a number of chronic illnesses like cancer and multiple sclerosis, and it also can make bones stronger.
Which illnesses can vitamin D prevent?
Even though the scientific evidence that taking vitamin D in pill form can be helpful in countering chronic illnesses might not be reproducible and consistent, there is indeed some scientific evidence that a vitamin D deficiency can cause rickets and a softening of the bones. The reason for this is that vitamin D supports the uptake of calcium in the intestinal tract, thus it performs an important function in relation to the building of bone. Rickets and bone softening are of course rare, but they still present a risk for some populations.
When does vitamin D deficiency occur?
Everyone who is outside in the afternoon at least twice a week and gets sun on their arms and legs for 5 to 30 minutes has gotten "enough" sunlight to prevent a vitamin D deficiency. The skin can even produce vitamin D on cloudy days, although anything that blocks direct sunlight – clouds, shade, air pollution – can reduce vitamin D production by 50% to 60%. Getting sunlight through glass also hinders vitamin D synthesis, and sun-blocking lotions or sun creams likewise reduce the amount of vitamin D that the body produces. People with lighter skin convert sunlight into vitamin D more easily than people with darker skin. Last but not least, people who are overweight tend to have more problems with vitamin D. This is likely because the vitamin D that the body produces via the skin is stored in the fat tissue, so it's not able to do its job in the body.
When are good vitamin D supplements recommended?
- Anyone who goes outside at least twice per week and gets sun exposure on their arms and legs for roughly 5 to 30 minutes (depending on skin type, weight, ethnicity) does not need to take vitamin D supplements in the summertime.
- In the winter, people who live quite far from the equator – north or south – should have their blood checked for vitamin D, and when there is a risk for vitamin D deficiency, 1,000 to 2,000 IE of vitamin D in the form of a high quality supplement should be taken.
- If you are someone who generally fits the high risk group for vitamin D deficiency (e.g. not much time outside, limited sun exposure due to clothing, excess body weight, darker skin), then taking 1,000 to 2,000 IE of vitamin D in the less sunny months is recommended.
- You should always check with your doctor when taking a vitamin D supplement, as taking too much can have toxic effects. We do not recommend carelessly or haphazardly taking vitamin D supplements. Getting a blood test in the summer and winter will give you a clear guide as to whether or not you are in a high risk group.
In summary, it can be said that for most people, taking a vitamin D supplement in the summer should not be necessary, but in the wintertime some people – especially those living further from the equator – there may be a need for supplementation. Getting a blood test in the summer and winter, along with advice from your doctor, will give you the information you need to make the best choice.
Source: Dr. Thomas Campbell, The China Study Solution, New York 2015
Dr. Thomas Campbell is the coauthor of a book entitle "The China Study Solution", which presents some of the most important research into the connection between diet and the occurrence of chronic disease. In the book, recommendations are presented for various health-related topics – all of them stemming from the scientific discoveries made in the course of a long-term study conducted in China. Dr. Thomas Campbell is the son of one of the most well-known and renowned dietary researchers in the world, Dr. Colin Campbell.
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