Just "D" Facts about Vitamin D

Benefits of Moderate UV Sunshine Exposure

Vitamin D as Cancer Fighter?

Posted by D3forU on February 23, 2008

Big doses showed promising results
Vitamin D.
CREDIT: Dan Janisse / Windsor Star / Canwest News Service
Vitamin D.

Most vitamins have proven disappointing in the area of cancer prevention when subjected to rigorous scientific evaluation. There appears to be one important exception, however, and this edition of HealthWatch takes a look at one of last year’s hottest health topics.

Vitamin D has long been espoused as important in maintaining bone health, particularly in climates like ours, in which sunlight is scarce during winter. Last year, a landmark study on Vitamin D took a different slant by indicating that taking larger than usual amounts of it can actually prevent cancer. However, conclusions drawn were confusing as different organizations issued conflicting recommendations.

What exactly is Vitamin D?
Vitamin D is a fat-soluble vitamin found in fatty fish, egg yolks and milk, but sunshine is the main source for most people. Ultraviolet (UV) rays from sunlight trigger Vitamin D synthesis in the skin, while the liver and kidneys convert it to an active form.

Vitamin D maintains normal blood levels of calcium and phosphorus and promotes calcium absorption from the intestine. In severe deficiency conditions, the bones become brittle and misshapen; milder deficiencies promote and worsen osteoporosis.

What about the connection to cancer?
For decades, population studies suggested a lower cancer incidence in regions with greater sun exposure, and that people with inadequate Vitamin D intake are at greater risk of developing cancer.

The study
Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial by Joan M. Lappe et al. American Journal of Clinical Nutrition, June 2007.What did the study reveal?
The study, conducted by Creighton University, followed 1,179 healthy, post-menopausal women from rural Nebraska over four years. The participants were divided into three groups randomly assigned to receive: a) 1,400-1,500 mg of supplemental calcium per day; b) supplemental calcium plus 1,100 international units (IU) Vitamin D3 per day; or c) placebo.

The results were dramatic: women assigned to the Vitamin D and calcium group had a 60 per cent lower risk of developing breast, lung, colon and other cancers. When the researchers eliminated the first-year results from their analysis on the premise that some women could have entered the study with undiagnosed cancers, the results were even more dramatically positive: a 77 per cent cancer risk reduction in women assigned to Vitamin D and calcium.

The dose of Vitamin D administered was nearly three times the North American recommended daily intake for middle-aged adults.

How do these results fit in with what we already know about this subject?
One earlier clinical trial was carried out to test for an anti-cancer effect of Vitamin D. It failed to demonstrate a reduction in cancer risk, but the Vitamin D dose was only 400 IU per day. Many studies have indicated that mild Vitamin D deficiency is associated with a higher risk of certain cancers; this study is the first to show that a higher than usual dose can reduce cancer risk.

What can we conclude about these results and their importance?
Another way to look at the benefits suggested in this study is that 20 post-menopausal women would need to take high-dose Vitamin D for three or four years to prevent one new cancer. That may not seem like much of an effect, but this is what a 60-per-cent to 70-per-cent risk reduction translates into. A risk reduction that great is potent when compared with other disease preventative strategies that have been proposed.

These study results are very promising and will spark more studies to learn if the findings are reliable, and to determine which cancers are most preventable with Vitamin D and which kinds of people can most benefit.
Post-menopausal women in Nebraska are probably quite similar to those in Canada, especially in terms of limited annual sun exposure, which is a cause of low Vitamin D levels. We have long known that cancer rates are higher in northern climates and this might be part of the puzzle.

Are there any caveats?
One important point to emphasize is that the major benefits seen in this trial occurred when Vitamin D was used along with 1,500 mg of calcium supplementation per day. It may prove that the maximum benefit depends on taking both Vitamin D and calcium simultaneously.

The jury is still out on whether pre-menopausal women and men of all ages can benefit from Vitamin D. However, it’s worth noting that natural Vitamin D is regarded as safe in a daily dose up to 2,000 IU per day (even higher doses may be relatively safe) and that calcium intake of up to 1.5 grams per day does not cause kidney stones as was a common belief in the past.

Vitamin D is readily available without a prescription and is inexpensive. On the basis of current knowledge, it makes sense for middle-age and older adults to increase their intake of Vitamin D by taking a daily supplement, especially if they have a strong family history of cancer.

How much is enough?
The Canadian Cancer Society now recommends Vitamin D supplementation for prevention, in consultation with one’s healthcare provider:
– Adults living in Canada should take 1,000 (IU) per day during the fall and winter.
– Adults at higher risk of having lower Vitamin D levels should take 1,000 IU per day all year round. This includes people who are older; with dark skin; who don’t go outside often; and who wear clothing that covers most of their skin.
– The cancer society does not have a recommendation for Vitamin D supplementation for children.


(The authors thank John Hoffer, an internist and PhD in clinical nutrition at the SMBD Jewish General Hospital, for his input.)

The material provided in HealthWatch is designed for general educational purposes only and does not pertain to individual cases. The information included should not replace necessary medical consultations with your own doctor or medical professional.


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