Taking calcium and vitamin D pills can only provide limited protection against fractures for older women, according to a long-term U.S. study to be published in Thursday's New England Journal of Medicine.

The seven-year national study involving 36,282 postmenopausal women gave each participant 1,000 mg of calcium and 400 units of vitamin D or matching placebos each day. It found better hip bone density in the half given supplements, but no reductions of statistical significance in fractures of all kinds.

Benefit of the supplements was only seen in women above 60 whose chances of hip fracture dropped 21 percent after taking the pills.

Researchers said the study would help correct the important misconception of many women that taking calcium and vitamin D pills can provide full protection against the development of osteoporosis.

Researchers still think sticking with an adequate calcium intake will lay the foundation for bone health. Some also believe higher doses of the supplements are needed to achieve the desired effect.

The study also examined the value of the supplements in preventing colorectal cancer, but no benefit was found. The incidence of colorectal cancer turned out to be nearly the same in each group.

However, as colorectal cancer can take 10 to 20 years to develop, researchers said it may need longer follow-up for the supplements to show a beneficial effect.

Meanwhile, the U.S. study showed a significant side effect with the diet supplements, which increased the risk of kidney stones by 17 percent.

Source: Xinhua