Vitamin D: More Than Bone Heath

Recent studies have established the importance of vitamin D for cancer prevention. It is now clear that all women should have their vitamin D levels monitored for bone health and for cancer prevention. This is especially important for premenopausal women to prevent breast cancer. Here is why:A study of 1180 women (older than 55 years) showed that calcium and 1100 IU/day of vitamin D resulted in higher vitamin D levels and half as many cancers over a 4 year period, compared with women who used placebo (pills without any vitamin D or calcium). (Am J Clin Nut 2007. 85:1586-1591)

A second study was published from data derived from the Women’s Health Initiative. This study showed that vitamin D and calcium supplementation lowered the incidence of breast cancer in premenopausal women. No change was found for the 20,000 postmenopausal women; however, the vitamin D dose was small, only 400 U/day, and these older women were likely deficient at the start of the study. Unfortunately, vitamin D levels were not followed (as they were in the earlier mentioned study) so there is no way to determine if vitamin D deficiency was improved in both groups. (Arch Intern Med, 2007. 167: 1050-1059).

Less than ten years ago vitamin D used to be considered a potentially dangerous vitamin supplement, and recommendations were to use no more than 400 U/day. Research has since shown that an estimated 60% of all women in the United States, regardless of where they live, are deficient in vitamin D, and it can be supplemented safely in 1000- 2000 U/day (many doctors are using much higher doses). Vitamin D is vital to build strong bones and is also important for immune function and cancer prevention.

Ask your doctor for a blood test of your 25 OH D level, and aim for a level of 50 nmol/L. How much vitamin D you take depends on how low your level is. Taking 1,000 U/day will raise your level by 15-25 nmol/L. The best form to take is cholecalciferol, D3 (preferred to ergocalciferol D2). Always take vitamin D with food to improve absorption. If you are taking it and your level is not improving consider taking a pancreatic enzyme (that contains lipase) with your meals. Also remember vitamin D is made from sunlight on our skin- so get 20 to 30 minutes of outdoor sunlight every day if possible.

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  1. I have been taking 1,000 Ui a day of D3, but my level is still low. I take Lipase and now have moved up to 2,000 UI a day of D3 per my naturopathic Dr’s recommendation. But I’m worried it might make me toxic. Also, I’m trying to conceive. Is that a concern?


  2. Jennifer,

    It is safe to use up to 2,000 U vitamin D while trying to conceive as long as you are monitoring your levels every 2 to 3 months. You want you vitamin D level to be greater than 30nmol/L. If your level is not improving ask your doctor to check a digestive test on your stools while on the lipase to ensure that you are absorbing fats adequately.

    Dr. P

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