By David Liu, PHD

Sunday Spet 02, 2012 (foodconsumer.org) -- Calorie restriction can not only extend a person's lifespan, but also help prevent  chronic diseases such as breast cancer, according to a recent review published in Frontier Physiology.

R. Pallavi of European Institute of Oncology Milan in Italy and colleagues reviewed studies on calorie restriction and cancer and reported in the journal that the anticancer effect  of calorie restriction has been demonstrated in multiple animals and in humans, an eating disorder called anorexia nervosa  has been found associated with lower risk for invasive or lethal breast cancer. A patient with anorexia nervosa has a very low intake of calories.

Cancer cells are more dependent on glycolysis for their energy needs than normal cells and calorie restriction has an effect on the energy-metabolic pathways, the researchers explained.  Glycolysis generates less energy than the normal pathway and produces lactic acid, which explains why cancer patients often feel tired.  This has been well known to cancer researchers.

Calorie restriction can inhibit cancers induced by different carcinogens including cancer transplants, spontaneous mutations, radiation induced mutations and chemically induced carcinogenesis or mutagenesis, the reviewers said.

One example to demonstrate how calorie restriction actually may work to prevent cancer is anorexia nervosa, an eating disorder. The reviewers said women who were treated for anorexia in their early life were found to have a lower risk of breast cancer.

This observation was studied at least by Karin B. Michels, ScD and colleagues who reported their research recently in the Journal of American Medical Association.

Michels et al. studied 7303 Swedish women hospitalized for anorexia nervosa prior to age 40 years and found that compared to the Swedish general population, women treated for anorexia nervosa prior to age 40 were 53 percent less likely to develop lethal breast cancer. Among nulliparous women, those who suffered anorexia nervosa were 23 percent less likely to develop invasive breast cancer. Parous women with anorexia were 76 percent less likely to develop invasive breast cancer.

Michels et al. explained that calorie restriction can protect against cancer through multiple mechanisms including lowering "levels of circulating insulin, insulin-like growth factors I and II, and epidermal growth factor, as well as by modified cellular responsiveness to estrogens, enhanced immunologic responsiveness, alterations in cell cycle regulation, lower rates of cellular proliferation, increased DNA repair, reduced expression of oncogenes, and enhanced expression of tumor suppressor genes."

As a result, calorie restriction decreases the levels of many growth factors, anabolic hormones, inflammatory cytokines, and oxidative markers which are deregulated in several cancers, Pallavi et al. explained.

Michels et al. concluded "Severe caloric restriction in humans may confer protection from invasive breast cancer. Low caloric intake prior to first birth followed by a subsequent pregnancy appears to be associated with an even more pronounced reduction in risk."

It is hard for most women to practise severe calorie restriction, which may cause some undesirable effects.  Two things they can do to drastically reduce their risk for breast cancer, according to amn authorative report released recently, are avoiding medical radiation which is used in diagnostic tools like mammogram screening and radiotherapy and hormone replacement therapy.