Women and men who have stomach reduction surgery to lose weight may be losing bone even when they take daily calcium supplements, putting them at risk for osteoporosis and bone fracture. These findings from a University of Pittsburgh study were presented Sunday in San Diego at the American Society of Nutritional Sciences program, part of the Experimental Biology 2003 meeting. "While previous studies in the early days of stomach reduction surgery found bone loss following major weight loss, our current study found something surprising - that daily supplements of 1,000 mg of calcium and a vitamin D-rich multivitamin do not prevent the imbalance in bone cell turnover in post-surgical patients resulting in subsequent bone loss," said the researcher who presented the results, Penelope Coates, M.D., postdoctoral fellow at the University of Pittsburgh Medical Center's Osteoporosis Prevention and Treatment Center.
Participants in the study included 18 women and nine men who had undergone successful stomach reduction operations 10 months before and a control group of morbidly obese men and women who were waiting for the same type of surgery.
Measurements of certain metabolic proteins in the urine showed that the heavier, pre-operative patients were keeping their bone cells in balance, with new cells replacing old cells in equal amounts - a normal and continuous process in healthy adults. On the other hand, the post-operative research participants, who had been losing 8 to 10 pounds a month since their surgery, showed significant imbalance in bone turnover, with the regeneration of new cells lagging behind the destruction of old cells.
Dr. Coates and her colleagues then followed six individuals from the control group, measuring blood proteins and getting bone density readings at the hip and spine before their surgery and at three and six months following surgery. The researchers found that at six months, the study participants experienced up to an 8 percent drop in bone density in their hips. While such a difference can be normal for people losing significant amounts of weight, it could have devastating effects if the bone loss continued at that rate while a person continued to drop pounds.
The researchers also found that those who lost the most weight had the greatest imbalance in bone turnover, placing that group at greatest risk of bone loss and osteoporosis. Age, sex and hormone status, including whether women were pre- or post-menopausal, were not factors.
Dr. Coates and the research team are now trying to determine if the weight loss itself causes the problem or if the patients who lost the most weight are less efficient in absorbing calcium.
"Regardless of the reason for the imbalance in bone turnover, this study sends a clear message that major weight loss requires ongoing calcium and vitamin supplementation, as well as early and regular monitoring for bone loss," Dr. Coates said. "These are young patients, and many of them have 40 or 50 years of life in front of them. At a time when they are losing weight and looking forward to new opportunities, they don't want to have problems with osteoporosis."
