Tomatoes May Lower Cancer Risk
Tomatoes and tomato products may substantially reduce the risk of a variety of cancers, according to a comprehensive scientific review paper published in the February 17 issue of the Journal of the National Cancer Institute. The review paper, titled "Tomatoes, Tomato-Based Products, Lycopene, and Cancer: Review of the Epidemiologic Literature" by Edward Giovannucci, M.D., Sc.D., of Harvard Medical School and Harvard School of Public Health, evaluated 72 studies regarding tomato and tomato product intake, blood lycopene levels, and their association to cancer risk reduction.
"The review indicated that individuals who consumed higher levels of tomato products or had higher blood levels of lycopene, a compound found primarily in tomatoes, had a lower risk of several types of cancers," said Dr. Giovannucci. "Increasing evidence indicates that a diet high in fruits and vegetables may contribute to a lower risk of a variety of cancers. These findings extend this evidence to tomato and tomato products, and support recommendations to include tomatoes and tomato products as part of a diet high in fruits and vegetables."
Dr. Giovannucci suggested that lycopene and other carotenoids may account for a protective association between tomatoes, tomato products and various cancers. One explanation may be that carotenoids exhibit strong antioxidant properties. Serving-for-serving, chemical analyses have shown that tomato-based products are a more concentrated source of lycopene than fresh, unprocessed tomatoes. (Click here to read related article).
The potential benefits of lycopene first came to the attention of the public in December 1995, when Dr. Giovannucci and his colleagues at Harvard Medical School found an inverse association between dietary lycopene and prostate cancer.The study showed that the risk of prostate cancer was a third lower in men who consumed lycopene-rich foods (tomatoes, tomato sauce and pizza) more than 10 times a week compared to those who consumed these products less than twice a week.
Dr. Giovannucci's 1999 review paper examined epidemiologic evidence from hospital-based and population-based case-control studies for associations between consumption of tomato products and risk reduction of various cancers. Highlights from this review include:
• Prostate Cancer. The evidence supports a very specific benefit of tomato products, especially those that provide high lycopene availability. In a large dietary comprehensive study, tomato sauce had the strongest inverse association with prostate cancer out of 131 food items assessed. An analysis of the research did not support a general benefit of overall fruit and vegetable consumption.
• Pancreatic Cancer. An inverse association between consumption of tomato products and pancreatic cancer was shown. Two small studies showed a four- to five-fold risk increase among study subjects with low intake of tomato products.
• Lung Cancer. The literature suggests that several fruit and vegetable groups, including tomatoes, are associated with lower cancer risk. Ten of the 14 studies in the analysis showed an inverse relationship between consumption of tomato products and risk of lung cancer.
• Colorectal Cancer. Case-control studies in populations that consume large amounts of tomato products reported a 60% reduction in risk of both colon and rectal cancers associated with higher tomato consumption.
"This is a very significant report for the scientific and health community," notes Steven Clinton, M.D., Ph.D., director of cancer prevention at The Ohio State University Comprehensive Cancer Center. "Because the review paper looked at all the human studies conducted to date, which incorporated diverse populations and a variety of study designs, it is unlikely that there are any consistent biases or uncontrolled confounding factors common to this collection of studies. As a result, this review provides valuable insight into the role of tomato products in a healthy diet and cancer prevention."