Tomatoes could help boost levels of a hormone that plays an important role in sugar and fat metabolism, a small new study suggests, potentially lowering the risk of breast cancer among women already at risk for the condition.
Research published in the Journal of Clinical Endocrinology & Metabolism shows that women who were randomly assigned to eat 10 weeks of tomato products (that contained 25 milligrams of lycopene each day) also experienced higher levels of this metabolism-regulating hormone, adiponectin.
"The advantages of eating plenty of tomatoes and tomato-based products, even for a short period, were clearly evident in our findings," study researcher Adana Llanos, Ph.D., MPH, an assistant professor of epidemiology at Rutgers University, said in a statement. "Eating fruits and vegetables, which are rich in essential nutrients, vitamins, minerals and phytochemicals such as lycopene, conveys significant benefits."
The researchers also noted that the increase in adiponectin could help to protect against breast cancer, since obesity is a known risk factor for breast cancer.
"Based on this data, we believe regular consumption of at least the daily recommended servings of fruits and vegetables would promote breast cancer prevention in an at-risk population," Llanos added in the statement.
The study is based on 70 postmenopausal women at known risk for breast cancer (this was determined by either having a body mass index between 25 and 42 -- indicative of overweight or obesity -- or having a first-degree relative who has had breast cancer).
The women first went two weeks without eating any tomato or soy products, and then ate tomato products for 10 weeks. After that, they went another two weeks without eating any tomato or soy products, and then consumed 40 grams of soy protein a day for 10 weeks.
Researchers found that at the end of the tomato-eating period, adiponectin levels increased 9 percent, with the effect being stronger among the women with a lower body mass index.
Meanwhile, adiponectin levels seemed to decrease after the women ate the soy products for 10 weeks.
"There are no clear explanations for the observed decrease in adiponectin following the soy intervention," the researchers wrote in the study. "It may be that the protective effects of soy against breast cancer are limited to certain subgroups (e.g., Asian women, whose soy consumption typically begins in utero and who have relatively lower BMI). It is also possible that the mechanism(s) of protection does not involve adiponectin. Further studies are required to clarify these mechanisms."
They noted that while their focus for this study was on lycopene in tomatoes, it's highly possible that other phytochemicals in tomatoes could be beneficial, and that more study is needed.