Writing in the Journal of Clinical Endocrinology & Metabolism, the new longitudinal cross-over study examined the effects of lycopene- and isoflavone-rich diets on serum adipokines - which play a vital role in regulating fat and sugar metabolism.
Led by Dr Adana Llanos from Rutgers University, the explained that breast cancer risk rises in postmenopausal women as their body mass index climbs. As such lifestyle changes or interventions that modify the metabolism of sugar and fat may help to reduce BMI and the risk of cancer.
The study found eating a diet high in tomatoes had a positive effect on the level of hormones that play a role in regulating fat and sugar metabolism.
“The advantages of eating plenty of tomatoes and tomato-based products, even for a short period, were clearly evident in our findings,” said Llanos. “Eating fruits and vegetables, which are rich in essential nutrients, vitamins, minerals and phytochemicals such as lycopene, conveys significant benefits."
"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," she commented.
The team assessed the effects of both tomato-rich and soy-rich diets in a group of 70 postmenopausal women.
For 10 weeks, the women ate tomato products containing at least 25 milligrams of lycopene daily, while in a second 10-week period they consumed at least 40 grams of soy protein daily.
Before each test period began, the women were instructed to abstain from eating both tomato and soy products for two weeks.
Participants following the lycopene-rich diet were found to have higher levels of adiponectin – a hormone involved in regulating blood sugar and fat levels - by 9%.
The effect was slightly stronger in women who had a lower body mass index, the team revealed.
“The findings demonstrate the importance of obesity prevention,” Llanos said. “Consuming a diet rich in tomatoes had a larger impact on hormone levels in women who maintained a healthy weight.”
The soy diet, however, was linked to a reduction in participants’ adiponectin levels.
Source: Journal of Clinical Endocrinology & Metabolism
Published online ahead of print, doi: 10.1210/jc.2013-3222
"Effects of Tomato and Soy on Serum Adipokine Concentrations in Postmenopausal Women at Increased Breast Cancer Risk: A Cross-Over Dietary Intervention Trial"
Authors: Adana A. Llanos, Juan Peng, et al