In the first study ever to evaluate catalase (CAT) genotypes and breast cancer, researchers at Roswell Park Cancer Institute in Buffalo, New York, found that women with the most common genotype for reducing oxidative stress are at a reduced risk of developing breast cancer. Further, they can diminish their breast cancer risk even more by including ample fruits and vegetables in their diets.
Fruits and vegetables are well known to reduce the risk of some cancers through their antioxidant properties, which inhibit reactive oxidant species. These free radicals form naturally in the course of cell respiration and metabolism, but have been linked with disease-causing damage to tissue and changes in DNA that can lead to malignancies.
While this oxidative stress is considered to be a major causative factor for breast cancer, prominent research including the Nurses Health Study has shown no link between increased consumption of fruits and vegetables and decreased breast cancer risk. Because the evidence on whether fruits and vegetables reduce the risk of breast cancer is not clear, the investigators from Roswell Park thought that effects might be limited to women with specific genotypes related to protection from oxidative stress.
Jiyoung Ahn, a pre-doctoral research associate in the department of epidemiology at Roswell Park, and a Ph.D student at Cornell University, noted that catalase (CAT) is one of the most effective enzymes in the body for reducing oxidative stress. It converts hydrogen peroxide into water and oxygen, thus neutralizing reactive oxygen species.
Ahn theorised that if higher levels of the endogenous antioxidants that course through the human blood stream naturally - like those resulting from the CAT C (CC) allele - might provide some degree of antioxidant protection against breast cancer, and if the risk might be further diminished by the consumption of fruits, vegetables and specific antioxidants.
Ahn evaluated this hypothesis in a population-based, case-control study of 1,037 women with breast cancer and 1,086 healthy subjects. Each woman was interviewed at home to assess suspected breast cancer risk factors over the course of her lifetime, and completed a food frequency questionnaire to determine dietary intake the preceding 12 months.
The women were genotyped, with the most common genotype the CAT C (CC), present in a little more than 60 per cent of the cases and the controls. A CT polymorphism exists in the (CAT) gene in about 33 per cent of participants, and all others - some 4 percent - have the TT genotype.
Women with the CC genotype and a diet rich in fruits and vegetables had a 30 per cent reduced risk of breast cancer. There was only a 5 per cent lower risk in women with the CC genotype who ate very few fruits and vegetables, according to the study (abstract 2313), presented this week at the American Association for Cancer Research annual meeting.
"With so many women having the CC genotype," said Ahn. "Our study potentially has a very important public health impact. Of course, none of us knows our exact genetic make-up, but since eating a diet high in fruits and vegetables is known to contribute to a healthy lifestyle anyway, women can consider it a viable means of reducing their breast cancer risk, as well."