Question of the Week

October 27, 2008


Everyone needs vitamin D. As winter approaches, it can become more difficult for those in northern climates to get what they need without taking supplements.

"There are three sources of vitamin D: natural sunlight, fortification of dietary foods, particularly dairy products and some cereals and oily fish. The radiation that converts vitamin D in the skin is the same wavelength that causes sunburn, so careful application of sunscreen can inhibit vitamin D production. At northern latitudes, there is not enough radiation to convert vitamin D, especially during the winter. After the age of 70 the skin does not convert vitamin D effectively."

While natural sunlight can be a primary source of vitamin D, obstacles such as a person's age, how a person's body converts sun exposure into vitamin D, and lack of skin exposure to direct sunlight can make it difficult for some people to maintain enough vitamin D in their blood for optimum health.

Food sources can be another way for people to get some vitamin D, but not all people eat enough vitamin D rich foods, and not all vitamin D is created equal.

"Vitamin D is found in many dietary sources such as fish, eggs, fortified milk, and cod liver oil. The sun also contributes significantly to the daily production of vitamin D, and as little as 10 minutes of exposure is thought to be enough to prevent deficiencies. The term 'vitamin D' refers to several different forms of this vitamin. Two forms are important in humans: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Vitamin D2 is synthesized by plants. Vitamin D3 is synthesized by humans in the skin when it is exposed to ultraviolet-B (UVB) rays from sunlight. Foods may be fortified with vitamin D2 or D3. The major biologic function of vitamin D is to maintain normal blood levels of calcium and phosphorus. Vitamin D aids in the absorption of calcium, helping to form and maintain strong bones."

While one of the most well known functions of vitamin D is to aid in the absorption of calcium for strong bones, recent studies have found that vitamin D is involved in many more aspects of good health.

"It has long been known as the vitamin that cured rickets. But today, vitamin D is being hailed for being able to do much more than that. Scientists have known for some time about vitamin D's role in helping the body absorb calcium, in maintaining bone density, and in preventing osteoporosis. But new research suggests it may also help protect against chronic diseases such as cancer, type 1 diabetes, rheumatoid arthritis, multiple sclerosis, and autoimmune diseases. Yet many adults have low blood levels of vitamin D. Vitamin D is not abundant in our usual food choices, so we get most of the vitamin from sun exposure and multivitamins. The problem is that the sun is not a reliable source for everyone. The season, time of day, geography, latitude, level of air pollution, color of your skin, and your age all affect your skin's ability to produce vitamin D. Further, the form of Vitamin D found in most multivitamins is vitamin D2, which does not deliver the same amount of the vitamin to the body as the more desirable D3 form."

Finding the right foods and multivitamins to complement or replace the vitamin D that a person might otherwise get from the sun can be complicated.

"Adequate levels of vitamin D, also known as 'the sunshine vitamin', are metabolised by the human body from as little as 15 minutes sun exposure during the summer months. The vitamin plays a role in the absorption of calcium, which is crucial for bone health, and in overall health and development. However during the winter limited sunlight and absence of ultraviolet light at the right wavelength (290 to 310 nm) in the north of the UK mean that many people - especially those with darker skin or those who cover up most of the body for religious reasons - are susceptible to deficiency. While vitamin D does also occur naturally in foods like oily fish, eggs and fortified breads and cereals, the warning is that 'these may still be inadequate when sunshine hours are limited'."

Whatever the source, vitamin D has shown that it can play a major role in helping people improve both their mental and physical health.

"'Basically, what vitamin D does is increase levels of the [chemical] serotonin in the brain,' he tells WebMD. Many antidepressant medications work the same way. About 90% of patients in my hospital are vitamin D deficient, and I put them on a vitamin D regimen, and it does improve their mood disorders' ... However, if you are currently taking antidepressants, don't stop taking those drugs if you begin taking the vitamin supplements. 'What this study suggests that is vitamin D deficiency may be an explanation for depression, and that boosting vitamin D levels may help prevent or ease symptoms,' Cannell tells WebMD. 'But how much vitamin D you need depends on several factors, such as the environment you live in, what time of year it is, your skin type, and sun exposure.'"

Doctors can do a blood test to see check the level of vitamin D in a person's blood. This can help patients and doctors to work together to know how what changes, if any, need to be made in order to improve vitamin D levels for optimal health.

Levels can be low for a number of reasons. People convert sunlight into vitamin D at different rates depending upon their age and skin color. Working with a health care professional can help each person determine what lifestyle choices and/or changes they can make in order to be sure they are getting enough vitamin D.

Obstacles that the body faces when attempting to convert sunlight to vitamin D can include:

  • "Dark skin: People with dark-colored skin synthesize less vitamin D on exposure to sunlight than those with light-colored skin. The risk of vitamin D deficiency is particularly high in dark-skinned people who live far from the equator. ...
  • Aging: The elderly have reduced capacity to synthesize vitamin D in skin when exposed to UVB radiation, and the elderly are more likely to stay indoors or use sunscreen, which blocks vitamin D synthesis. ...
  • Covering all exposed skin or using sunscreen whenever outside: Osteomalacia has been documented in women who cover all of their skin whenever they are outside for religious or cultural reasons. The application of sunscreen with an SPF factor of 8 reduces production of vitamin D by 95%.
  • Fat malabsorption syndromes: Cystic fibrosis and cholestatic liver disease impair the absorption of dietary vitamin D.
  • Inflammatory bowel disease: People with inflammatory bowel disease like Crohn’s disease appear to be at increased risk of vitamin D deficiency, especially those who have had small bowel resections.
  • *
  • synthesized in the skin or ingested, it is deposited in body fat stores, making it less bioavailable to people with large stores of body fat."

Questions of the Week:
How can you determine whether or not you need more vitamin D in your life for optimum health? How can you tell whether or not you need to raise the amount of vitamin D you are getting from your diet and/or from your time in the sun? Based upon your age, where you live, and your individual health needs, how can you determine what would be the best sources of vitamin D for you? What factors would influence how your vitamin D blood levels might vary from those of a friend or relative?

Please email me with any ideas or suggestions.
Note: Due to increasing amounts of SPAM sent to this account, please include "QOW" in the subject line when sending me email.

I look forward to reading what you have to say.

Health Community Coordinator
Access Excellence @ the National Health Museum

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