Leaner Body, Stronger Bones

Osteoporosis is a big concern for postmenopausal women. Menopause is marked by a significant decrease in estrogen production, and remaining estrogen levels are direct indicators of bone mineral density in postmenopausal women. This is just one of the reasons that so many women were encouraged to start hormone replacement therapy at menopause - to help prevent osteoporosis. Other factors, like body fat, how long it's been since a woman started menopause, whether or how much a woman smokes (or did smoke), and their dietary calcium intake also factor into a woman's risk of bone loss.

Of course, another strong indicator of bone mineral density in women after menopause is... wait for it... their bone density before menopause. Some studies have indicated that the amount of fatty acids in a woman's diet can have negative effects on her bone density. What about other variables, such as Body Mass Index, hormone levels or even ethnicity? Researchers at the University of Texas Medical Branch designed a study to assess womens' bone density in relation to these and other factors (J Nutr 2009;139(2): 250-256).

They recruited 242 healthy women in their thirties and forties from the area surrounding the university. The women represented a good cross-section of the ethnicities in the area, being just about half white, 32% Hispanic, 13% African-American, and the rest Asian, American Indian, or of unspecified ethnicity. About 70% of the women were either overweight or obese (as assessed by their Body Mass Index), while just over 3% were underweight and the rest of normal weight. None of the women were pregnant, breast-feeding or taking any contraceptives, and all were having regular menstrual periods.

The researchers collected blood samples from each woman and asked them to fill out questionnaires on three separate occasions that asked what each woman had eaten in the last 24 hours. Their bone mineral density was measured both at the hip and at the lower spine, and their lean body mass, body fat, and total body mass were measured using highly sensitive equipment.

Of all of the measurements taken and compared with the womens' bone density, the only one that was most consistently related to stronger bones was their level of lean body mass. A higher lean body mass meant higher bone mineral density. Estrogen levels, however, did not appear to have much effect on bone mineral density. The authors of this study suggest that this may mean that estrogen functions to help only maintain bone density - regardless of whether a women is pre- or postmenopausal.

What this means for you

Certainly there are things you can do to help prevent osteoporosis after menopause. It appears, however, that one of the best things you can do is to make sure that your bones are strong before menopause - and one of the easiest things you can do, both for your bones and your health as a whole, is to maintain a healthy body weight with a normal amount of lean body mass.

First posted: April 15, 2009