A fresh box of Timbits appears in the office kitchen. One co-worker selects a chocolate and a honey glazed to go with her morning coffee. Her colleague hovers over the treats, fretting and deliberating. She pulls herself away, but returns later to claim the last two Timbits. Who enjoys better health?
Faculty of Land and Food Systems (LFS) research suggests that diet anxiety over the long run may end up chipping away at women’s bone health.
In a recent study, Jennifer Bedford discovered links between cognitive dietary restraint (CDR)—the constant worry over eating choices—and women’s cortisol levels, menstrual cycle function and bone density.
Bedford carried out her doctoral research, which was supported by the Canadian Institute of Health Research, with Susan Barr, a professor in the LFS Food, Nutrition and Health program who has been investigating the health impacts of CDR over the past 20 years. Barr explains that CDR is more about the attitude toward food than actual behaviour.
Bedford adds, “Women with higher CDR levels do not necessarily eat more or less than those with lower CDR, but they do experience stress from constantly monitoring what they eat in an effort to achieve a perceived ideal weight.”
Over a two-year period, Bedford tracked study participants: 123 women aged 19-35, all healthy and experiencing a wide range of CDR levels. Bedford tested the women’s bone density at the beginning and end of the study. She also measured their blood pressure and cortisol levels at regular intervals.
Cortisol is a stress hormone that is beneficial during acute stress, but erodes bone strength when chronically elevated. When out of balance, cortisol can have far-reaching effect, from how well the body absorbs calcium to negatively impacting bone formation.
“This area of research is important since about one in four Canadian women over the age of 50 is currently affected by osteoporosis,” notes Barr.
Bedford’s findings suggest that even slightly elevated levels of cortisol can take their toll. “Our data shows a correlation between cortisol levels that are still within the normal range and reduced bone density.”
The study also monitored for the prevalence of subclinical ovulatory disturbances, which refer to subtle changes that women are not aware of since their menstrual cycles appear to be completely normal. But even as women experience a regular monthly period, they may not have sufficient levels of estrogen and progesterone—reproductive hormones that are critical for optimal bone health.
This was indeed the case for study participants with increasing levels of CDR, says Bedford. “These women had more subclinical ovarian disturbances, which appear to be associated with reduced bone density over the two years of our study.”
However, her research also yielded some positives, says Bedford, who completed her PhD thesis earlier in the year. “Our data shows that physical activity can be effective for increasing bone density and reducing stress.”
Now undertaking a one-year dietetic internship at LFS, Bedford says she is mindful of the “big picture” when it comes to people’s health and well being. “It’s not just about how much butter someone spreads on their toast, but how the person feels about food and their relationship to their body.”
