Vitamin D May Reduce Cancer Risk

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Canadian Cancer Society Recommends Vitamin D to Reduce Cancer Risk

After reviewing a growing body of evidence suggesting a strong link between Vitamin D and lowered risk for various cancers, the Canadian Cancer Society has announced the first ever Vitamin D supplement advisory as a cancer preventive measure.

Who should take Vitamin D supplements?

In a press release dated June 8, 2007, the Canadian Cancer Society recommends that:


  • Adults living in Canada should consider taking Vitamin D supplementation of 1,000 IU a day during the fall and winter.
  • Adults likely to have lower Vitamin D levels should consider taking Vitamin D supplementation of 1,000 IU/day all year round.

This group includes people who:

  • are older
  • have dark skin
  • don’t go outside often
  • wear clothing that covers most of their skin

Mounting Evidence on Vitamin D’s Role in Cancer Prevention

We are not surprised by the Canadian Cancer Society’s recommendation. Indeed, mounting evidence has suggested daily intake of vitamin D should be raised from 400 IU to 1000 IU.

In December 2005, we reported a Vitamin D review study. Researchers from the University of California found that oral intake of 1000 IU vitamin D can reduce the risk of colon, breast, and ovarian cancers by as much as 50 percent. Since it is difficult to obtain 1000 IU of Vitamin D daily from food sources alone, the author recommended taking 1000 IU of the active form Vitamin D (D3 supplement) daily.

Another study published in the Journal of the National Cancer Institute in April 2006 conducted by the Harvard School of Public Health examined cancer incidence and Vitamin D exposure in over 47,000 men. Researchers found that a high level of Vitamin D (~1500 IU daily) was associated with a 17 percent reduction in all cancer incidences. The benefit of 1500 IU of Vitamin D was even greater in digestive cancers, with a 45 percent reduction of deaths from digestive cancers.

A recent study published in The American Journal of Clinical Nutrition in June 2007 found that taking Vitamin D supplements (1100 IU) and calcium substantially reduces risk of all cancers in post-menopausal women.

What about the Sun?

The Canadian Cancer Society does not recommends relying on the sun to obtain Vitamin D. In their press release, Heather Logan, Director, Cancer Control Policy of the Society said, “It’s possible that just a few minutes of unprotected sun exposure every day could increase skin cancer risk for some people.” Using sunscreen with SPF 15 or higher is recommended at all times.


Vitamin D and Cancer

Study affirmed Vitamin D may reduce the risk of breast, colon and ovarian cancer

On December 28, 2005, researchers from the University of California released their most recent findings on the possible role that Vitamin D may play in cancer prevention. Researchers reviewed 63 observational studies published between 1966 and 2004 and investigated vitamin D status in relation to cancer risk. They found that oral intake of 1000 IU vitamin D can reduce the risk of colon, breast and ovarian cancers by as much as 50 percent. The results of this study will be published in the American Journal of Public Health in February 2006.

Editor’s Note – Vitamin D and Cancer

Currently, Vitamin D recommendations for people of 1 – 50 years of age is 200 IU daily; 400 IU for adults of 51 – 69 years of age. After age 70, 600 IU of vitamin D are recommended each day. This finding of the role of Vitamin D in cancer prevention is exciting, but not conclusive yet. This study did not take into consideration the amount and length of sun exposure or address the decreased ability of the elderly population to convert Vitamin D.

The tolerable upper intake level (UL) for Vitamin D is 2000 IU for people age 1 and above – in other words it is safe to consume up to 2000 IU of vitamin D daily. If you would like to adopt a healthy eating pattern to reduce cancer risk, try eating a lower fat diet rich in antioxidants and fiber with plenty of fruits & vegetables as well as whole grains.

Another Study affirmed High Levels of Vitamin D Lowers Cancer Risk

Researchers from the Harvard School of Public Health examined cancer incidence and vitamin D exposure of over 47,000 men in the Health Professionals Follow-Up Study. They found that a high level of Vitamin D (~1500 IU daily) was associated with a 17 percent reduction in all cancer incidences. The benefit of 1500 IU of Vitamin D was even greater in digestive cancers, with a 45 percent reduction of deaths from digestive cancers. Results of this study were published in the Journal of the National Cancer Institute on April 5, 2006.

Editor’s Note – Increase Vitamin D Intake?

Recent studies have suggested daily intake of vitamin D should be raised from 400 IU to 1000 IU. In December 2005, we reported a Vitamin D review study. Researchers from the University of California found that oral intake of 1000 IU vitamin D can reduce the risk of colon, breast and ovarian cancers by as much as 50 percent. Since it is difficult to obtain 1000 IU of Vitamin D daily from food sources alone, the author recommended taking 1000 IU of the active form Vitamin D, i.e. D3 supplement, daily.

Similarly, the author of this study also suggested a daily supplementation of 1500 IU of Vitamin D to optimize benefits on cancer risk. These recommended levels are much higher than the current recommendations. The current Vitamin D recommendations for people of 1 – 50 years of age is 200 IU daily; 400 IU for adults of 51 – 69 years of age. After age 70, 600 IU of vitamin D are recommended each day. The tolerable upper intake level (UL) for Vitamin D is 2000 IU – in other words it is safe to consume up to 2000 IU of vitamin D daily.

If you would like to adopt a healthy eating pattern to reduce cancer risk, try eating a lower fat diet rich in antioxidants and fiber with plenty of fruits & vegetables as well as whole grains.

The Bottom Line

It is difficult to obtain 1000 IU of Vitamin D daily from food sources alone. One glass of milk contains 100 IU of Vitamin D. The author of this study recommended taking 1000 IU of active form Vitamin D, i.e. D3 supplement daily. He also suggested that our skin can produce 2,000 to 5,000 IU of vitamin D when we spend 10 to 15 minutes in the sun on a sunny day without sunscreen if 40% of the body is exposed. However exposure to the sun without sunscreen is not recommended in light of skin cancer issues.

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