The Way You Eat May Affect Your Risk For Breast Cancer

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http://www.sciencedaily.com/releases/2009/08/090804071404.htm

The Way You Eat May Affect Your Risk For Breast Cancer

ScienceDaily (Aug. 6, 2009) — Cancer researchers have long studied the role

of diet on breast cancer risk, but results to date have been mixed. New

findings published in Cancer Prevention Research, a journal of the

American Association for Cancer Research, suggest the

method by which calories are restricted may be more important for cancer

protection than the actual overall degree of calorie restriction.

" Understanding how calorie restriction provides protection against the

development of mammary tumors should help us identify pathways that could be

targeted for chemoprevention studies, " said Margot P. Cleary, Ph.D.,

professor at the Hormel Institute, University of Minnesota. " Further

identification of serum factors that are involved in tumor development would

possibly provide a way to identify at risk individuals and target

interventions to these people. "

Previous studies have shown that intermittent calorie restriction provided

greater protection from mammary tumor development than did the same overall

degree of restriction, which was implemented in a chronic fashion. The

researchers compared changes of a growth factor (IGF-1) in relationship to

these two calorie restriction methods — chronic and intermittent — and tumor

development beginning in 10-week old female mice at risk to develop mammary

tumors. Their hope was to explain why intermittent restriction is more

effective.

The overall degree of restriction was 25 percent reduction compared to

control mice. Mammary tumor incidence was 71 percent in the control mice who

ate the amount of food they wanted, 35 percent among those who were

chronically restricted and only nine percent in those who intermittently

restricted calories.

The researchers were initially surprised by these findings for several

reasons. First, the prevailing wisdom is that the degree of protection from

calorie restriction is proportional to the degree of mammary tumor

prevention. Second, they originally thought that intermittent calorie

restriction might enhance tumor growth due to growth factors being secreted

in response to re-feeding, Cleary said.

In an accompanying editorial also published in Cancer Prevention Research,

Pollak, M.D., stated that some major challenges of pharmacologic

approaches to cancer prevention and/or treatment include defining the

underlying causes and determining the relevance of these caloric restriction

methods. Pollak is professor of oncology at McGill University and director

of the Cancer Prevention Center at the Jewish General Hospital, both in

Montreal.

This study " contributes to accumulating evidence that caloric restriction

acts by altering hormone levels rather than by directly starving cancers of

energy. In particular, lower levels of insulin are associated with reduced

food intake, and this may be protective, " said Pollak, who is also an

editorial board member for Cancer Prevention Research.

In the editorial Pollak wrote: " there is reason for concern that the

'obesity epidemic' may lead to an increased prevalence of a hormonal profile

associated with elevated cancer risk and/or an adverse cancer prognosis.

Therefore, in addition to its well-known general health benefits,

maintaining an ideal body weight is also important in the specific contexts

of cancer prevention and improving the prognosis of cancer patients. "

Based on varied findings from clinical trials, Pollak suggested that

lifestyle and pharmacologic methods to reduce IGF-1 and insulin deserve

ongoing investigations. Cleary agreed, stating that these results may

provide interest to more aggressively pursue cancer prevention studies

related to calorie restriction.

" Humans frequently regain lost weight discouraging the application of

calorie restriction protocols for disease prevention, " she said. " We hope

these studies will identify biomarkers and/or pathways that could be used in

human studies to determine agents that would mimic calorie restriction. "

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Adapted from materials provided by American Association for Cancer Research,

via EurekAlert!, a service of AAAS.