Beneficial compounds in tomatoes may help lower the risk of breast cancer for postmenopausal women, according to a new study. The researchers show that the lycopene found in tomatoes may modify levels of adipokine hormones, which have been linked to obesity and inflammation.
“This is important because obesity and inflammation are both known to be associated with increased breast cancer risk, especially among women who are postmenopausal,” lead author Adana Llanos, PhD, MPH, of the Rutgers Cancer Institute of New Jersey, told Cancer Network. The study, published in the Journal of Clinical Endocrinology & Metabolism, is the first to examine the effects of a lycopene-rich diet in postmenopausal women, according to Llanos.
The researchers examined the effects of both lycopene and isoflavone-rich diets on serum levels of adipokines. The 70 postmenopausal women at higher risk for breast cancer who participated in the study first ate a tomato-based diet for 10 weeks. After a wash-out period of 2 weeks, the same participants ate a diet rich in soy protein (more than 4 g of soy daily) for 10 weeks. The researchers measured the effects of the diet on biomarkers that have been linked to inflammation and obesity such as adiponectin and leptin.
Eating the lycopene-rich fruit resulted in an increase serum levels of adiponectin by an average of 9%, particularly among the nonobese women in the study. Adiponectin is a hormone known to regulate glucose levels and has been shown to influence the risk of breast cancer. The strongest effects were among women with lower body mass indices.
Following the soy-rich diet, the participants had lower levels of the hormone. No detectable changes in leptin levels were seen.
“Lycopene has powerful antioxidant properties, which are important for blocking the action of free radicals that are damaging to the cells in our bodies,” said Llanos. Previous studies have shown that lycopene can prevent growth of breast cancer cells in mouse models. But, the role of consuming lycopene-rich foods in women at risk for breast cancer has not previously been studied.
“Among postmenopausal women who are at increased risk of breast cancer, increased consumption of fruits and vegetables, particularly tomatoes, which are high in nutrients, vitamins, minerals, and phytochemicals like lycopene, could be an important practical strategy to promote breast cancer prevention,” said Llanos.
Still, the results are preliminary and based on a small, nonrandomized cohort of women. How exactly lycopene or other phytochemicals benefit as putative chemopreventive agents is not yet known.
The authors tested the role of soy in modulating hormone levels because soy is a staple of the Asian diet and may be part of the reason Asian women have lower rates of breast cancer compared to their Western counterparts. Previous studies connecting soy consumption and breast cancer have been mixed.
“My colleagues and I would like to continue future studies that examine longer-term effects of dietary lycopene and other phytonutrients, separately and in combination with exercise interventions, that may prove useful in breast cancer prevention,” said Llanos. “Additional areas of research we are interested in include understanding the underlying molecular mechanisms linking obesity and breast cancer risk.”
Original study: http://press.endocrine.org/doi/abs/10.1210/jc.2013-3222