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You, UV and vitamin D
 The debate and confusion over vitamin D supplements, cancer prevention and sun exposure continues: what are the benefits of vitamin D? How much do we need? And what is the connection between UV radiation, vitamin D and cancer prevention?
There is strong evidence about the harms of exposure to UV radiation from the sun and other sources, including results of skin cancer, melanoma and some cataracts. However, there is also strong evidence about the benefits of adequate vitamin D, which can be obtained from the sun.
Richard Gallagher, head of the BC Cancer Agency’s Cancer Control Research Program, has studied the relationship between the environment and cancer for thirty years. We recently talked to Richard about what you should know about vitamin D and your health:
Q: What does vitamin D do for you?
- It boosts calcium and potassium levels in our bodies
- It is critical to bone health; a lack of it can lead to rickets in children and to osteoporosis and fractures in older adults.
- Some studies suggest that vitamin D may help prevent some cancers.
Q: How important is sunlight as a source of vitamin D?
- UV-B rays in sunlight are crucial to the formation of vitamin D. They trigger the natural process of vitamin D production in our skin.
- The amount of vitamin D we can get from the sun varies according to the time of day, season, geographic location and cloud cover, as well as your skin type and age.
- Ten to fifteen minutes of sun exposure three times a week is usually sufficient to provide adequate vitamin D.
- In Canada, because of the lack of sunshine from late fall until early spring, our vitamin D levels are often lower than they should be.
Q: Is food a good source of vitamin D?
- We can get 10 to 15 per cent of the normal daily requirement of vitamin D from our diet.
- Best dietary sources are: vitamin D enriched milk, salmon, cod, mackerel, sardines and cod liver oil, egg yolk also contains some vitamin D.
Q: Should you be taking vitamin D supplements?
- Yes, if you are a teenager or older, the recommended minimum is 400(IU) daily.
- 1,000 IU daily is adequate for adults. The maximum safe daily amount is 2,000 IU.
- The best supplement source is vitamin D3.
Q: Can taking mega-doses of vitamin D be harmful?
- Yes, vitamins can produce side effects. Mega doses of vitamin D can cause formation of calcium deposits (hypocalcaemia).
Q: Do older adults need more vitamin D than younger adults?
- Yes. Our skin manufactures vitamin D from sunlight less efficiently as we age, making supplements particularly important for the elderly, especially if they cannot get outdoors.
Q: Do people with lighter and darker skins need different amounts of vitamin D?
- Dark-skinned people can take more sun than lighter-skinned people, but don’t produce vitamin D as efficiently, so they are at a greater risk of vitamin D deficiency, especially in winter.
- Lighter-skinned people are recommended to obtain vitamin D through supplements, rather than through increased sun exposure which increases their risk of skin cancer.
More research is needed to determine the optimal amount of vitamin D supplementation required to prevent health problems or prevent cancer. In the meantime, make sure your vitamin D supplement levels are appropriate; avoid tanning beds; and wear protective clothing and sunscreen when out in the sun.
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