Jan. 14, 2003 -- Small changes in diet during puberty can have a big effect on levels of estrogen and other hormones that have been implicated in boosting breast cancer risk in women, raising hope that girls may be able to eat their way to a lower risk decades later.
And it doesn't appear to take much. Years of consuming just slightly less saturated and total fat calories than today's typical "heart-healthy" recommendations helped slash some hormone levels in teenaged girls by as much as 50%, according to a new study. In adults, elevated levels of these hormones are associated with an increased breast cancer risk.
"The real take-home message of this study is indeed, the quality of diet during puberty seems to have some sort of influence on hormones," says researcher and study author Linda Van Horn, PhD, RD, professor of preventive medicine at Northwestern University's Feinberg School of Medicine. "Whether that will translate to breast cancer prevention down the road, we don't know. But it's long been suspected that diet surrounding the time of puberty might influence breast tissue development."
Her study, reported in the Jan. 15 issue of the Journal of the National Cancer Institute, is actually a secondary finding from the ongoing Dietary Intervention Study in Children (DISC), a federally-funded trial that began in 1987 to test the efficacy and safety of cholesterol-lowering diets in young children.
"When DISC began, the idea of putting growing children -- even those with high cholesterol -- on a so-called 'low-fat' diet was quite controversial," Van Horn tells WebMD. "The popular notion was that it would hurt their growth."
DISC monitored hundreds of boys and girls with high LDL "bad" cholesterol levels from the time they were 8 to 10 to their late teens. All the kids were of normal weight. The researchers placed the girls on an eating plan that limited total fat intake to about 28% percent,, with about 8% from saturated fat (the kind that increases LDL "bad" cholesterol), and the rest from unsaturated fats. Cholesterol was limited to 75 mg for every 1,000 calories consumed. Another group of girls and their families were given written material on nutrition recommended by the American Heart Association.
Today, most Americans are urged by the American Dietetic Association and the American Heart Association to follow a diet similar the DISC plan -- with no more than 30% of total calories coming from all fat sources and no more than 10% from saturated fats.
"While we were studying all these boys and girls to see how diet affected their cholesterol, we decided to take some extra blood for hormone assays to see if diet might also influence hormonal changes," says Victor Stevens, PhD, a psychologist also involved in the DISC study. "Then we called the girls up to get their menstrual cycle data."
The researchers found that estrogen levels during the menstrual cycles were significantly lower in the girls who had consumed a diet with a lower total fat and saturated fat content. The average progesterone level during the later part of the cycles were also significantly lower.
"This is a great finding because there have been some studies saying there is no correlation between dietary fat intake and breast cancer risk. But the problem is that all of those studies have been on adults -- we really don't know what happens at the prepubescent stage, when breast tissue is developing," says Wahida Karmally, PhD, a Columbia University nutritionist and spokeswoman for the American Dietetic Association. "Cancer doesn't happen overnight, it takes years or decades to develop. The age when girls go into puberty might be a very important time to watch fat and monitor diet in order to reduce this risk."
So what can parents do for their young daughters?
"The keys to getting your kids to eat more healthfully is to control what food is in the house and to show by example," says psychologist Stevens. "Of course, we started working with these kids when they were 8 to 10, and that age, parents have a lot of control over what kids eat. But even with teenagers, controlling the food that is in the house is the top strategy for getting kids to eat more healthfully. If you have junk food in the house, they will eat it. If there is fruit, they will eat that. But if you show them you are eating healthy, they will most likely eat that way, too."