In a population-based study, 1180 Caucasian women older than 55, were randomized to receive a daily placebo, calcium or calcium plus 1000 IU of vitamin D (cholecalciferol). Â Health status and compliance to the regimen were assessed every 6 months over 4 years and serum vitamin D was measured at baseline and annually. 1024 women actually completed the study. Â
Fifty women developed cancers that were not skin cancers. Â The risk for cancer in the calcium-plus vitamin-D group was less than half that in the placebo group (RR 0.4; P=0.013). Â The calcium only group had no statistically significant risk reduction. Â Researches adjusted for the possibility that cancers detected during the first year of the study, had been present but silent, at baseline and analyzed these separately. Â Â
Women in the calcium plus vitamin D group had higher serum vitamin D levels that correlated with lower cancer risk, both at baseline and at one year. Adherence to the study doses was 86%.
Lappe J, et al. Â Vitamin D and calcium supplementation reduces cancer risk: Results of a randomized trial. Â Am J Clin Nut 2007; une 85: 1586-1591
Commentary: Â Itâ€™s reassuring to see that the benefits of higher than recommended dosing of vitamin D is catching on. Â Many women in the U.S. are vitamin D deficient- estimated to be about 60%, no matter where they live. Â The current adult daily recommendations Â for vitamin D in women 51 to 70 isÂ 400 IU -800 iu per day. Â Doses up to 2000 IU are considered safe and to be without significant risk for adverse events. Many practitioners are advising even higher doses, but I would recommend this only after assessment for medical need, serum testing, and evaluation for risk of side effects. Â
Calcium and Vitamin D Intake and Risk for Breast CancerÂ
The relationship between vitamin D and breast cancer was prospectively assessed among 10,000 premenopausal and 20,000 postmenopausal women who were enrolled in the Womenâ€™s Health Study. Â Intake of calcium and vitamin D was determined from self-reported questionnaires about diet and vitamin use.
During an average follow-up of 10 years, the overall incidence of invasive breast cancer was 2.6% among premenopausal women and 3.6% among postmenopausal women. Â Among premenopausal women, the risk of developing breast cancer was significantly lower for Â women in the highest versus lowest quintiles of calcium use and 0.65 for vitamin D intake. Â No benefit was seen for these nutrient intakes and breast cancer risk in postmenopausal women.
Lin J et al. Â Intakes of calcium and vitamin D and breast cancer risk in women.Â Arch Intern Med 2007, May 28; 167:1050-1059.
Commentary: This is a very large, prospective study which once again demonstrates important findings for vitamin D, at least for premenopausal women. Â A higher intake of calcium and vitamin D was associated with a lower risk for breast cancer among premenopausal women, but not for postmenopausal women. Â While the numbers were statistically significant, Â the absolute reduction in risk was small. Â Being a population based study using only self-reported questionnaires, the usefulness of the findings in this study are limited, especially since the amount was only recorded only once at baseline. Â In addition, there could easily be other variables that explain the findings. Â None the less, it supports the trend to advise women about adequate intakes of calcium and vitamin D, both in the diet and in supplement form.