Bonnie - just like we cannot get excited about a medication that shows great results in a small study, the same applies in this case.
The skin makes vitamin D when exposed to sunlight's ultraviolet rays. This study used that same form of the vitamin, known as D3 or cholecalciferol. Multivitamins usually carry a much weaker variant known as D2, but D3 is available in stand-alone dietary supplements.
Bonnie - any multivitamin worth its salt contains vitamin D3.
This study, published Friday in the American Journal of Clinical Nutrition, is the first time that researchers significantly boosted — and measured — blood levels of vitamin D and then followed identical groups of patients from start to finish. That's why, despite its modest size, the research was generating excitement. Nearly all other work has compared disparate groups of patients. The researchers at Creighton University in Omaha focused on 1,179 seemingly healthy women with an average age of 67. The women were divided into three groups: 446 got calcium and vitamin D3 supplements, a similar number got calcium alone, and 288 took dummy pills. The research team gave 1,000 daily international units of vitamin D, more than current guidelines calling for 200 to 600 units depending on a person's age. The researchers intended to check mainly for the effects of calcium on bone health. Their interest in cancer risk was secondary. But the lower cancer risk stood out. Only 13 women, or 3 percent, developed cancer over four years of calcium and vitamin D supplements. With calcium alone, 17 women, or 4 percent, got cancer. With dummy pills, cancer appeared in 20 women, or 7 percent. That shows a 60 percent lower cancer risk over four years in the group taking both supplements, compared to patients taking placebos. And when the first-year cancers were excluded — the ones mostly likely present before the study began — the findings were stronger still: a 77 percent lower risk for the combo group. While the calcium-only group lowered its four-year cancer risk by 47 percent compared to the untreated group, it did no better when early cancers were excluded. That suggests calcium alone may have done little in this experiment, the researchers said.
Bonnie - this is a good example of how calcium, to be properly allocated and utilized in the body, requires adequate vitamin D.
As with any nutrient, dosage varies based upon the individual and should be assessed by a licensed health professional.