Caffeine, Genes Tied to Bone Loss in Older Women

Women's Health |

An appetite for coffee and chocolate can take its toll on the bones of elderly women, especially those with a particular genetic mutation, researchers report.

The investigators found that in a group of women whose average age was 71, those who consumed the most caffeine had significantly lower bone mineral density (BMD) after 3 years compared with women who consumed the least. BMD is a marker of bone strength. Women with two copies of a gene with a mutation in the vitamin D receptor were even more prone to bone loss, the report indicates.

The findings add weight to research linking caffeine consumption to the bone-thinning disease osteoporosis, which can raise the risk of fractures in the elderly. However, until doctors are able to more easily determine which patients carry the genetic risk noted in the study, it is too soon to advise people to avoid caffeine, Linda K. Massey, from Washington State University in Spokane, writes in an accompanying editorial.

“On the basis of the studies conducted to date, it seems prudent to recommend both adequate dietary calcium and a moderate caffeine consumption for elderly individuals,” she suggests.

Moderate daily caffeine consumption is about 16 ounces of brewed coffee or 32 ounces of brewed tea.

The study, led by Dr. Prema B. Rapuri from Creighton University in Omaha, Nebraska, included 96 women who did not take calcium or vitamin D supplements. Researchers divided them into two groups–those who consumed less than 300 milligrams (mg) of caffeine daily and those who consumed more than 300 mg daily.

Researchers monitored BMD in the spine, hip and other areas of the skeleton over 3 years.

According to results published in the November issue of the American Journal of Clinical Nutrition, women who consumed more than 300 mg of caffeine a day–about three cups of brewed coffee–were more likely to lose bone in their spine. However, the amount of bone lost was significant only in women who carried two copies of the vitamin D receptor (VDR) gene with a particular mutation.

A woman’s smoking habits, alcohol intake and calcium consumption did not appear to influence the results.

“Caffeine intake (above) 300 mg a day was associated with a higher rate of bone loss in postmenopausal elderly women at most of the skeletal sites studied and significantly so at the spine,” Rapuri and colleagues conclude.