Tomatoes may provide protection against UV light and reduce the risk of skin cancer.
The research was conducted by Tatiana Oberyszyn, a professor of pathology at The Ohio State University in Columbus, co-author Jessica Cooperstone, a research scientist in the Department of Food Science and Technology in the College of Food, Agricultural, and Environmental Sciences at the university, and their colleagues. Their findings were published in the journal Scientific Reports.
Unprotected sun exposure is a major risk factor for skin cancer. Keratinocyte carcinoma (KC) skin cancer is the most common cancer, with 5.4 million new cases diagnosed in 2012. Basal cell carcinomas account for around 80 percent of KC cases, and around 20 percent of cases are squamous cell carcinomas.
While KCs are associated with a low mortality rate, the financial impact of treating skin cancers in the United States is around $8.1 billion and rising. In a bid to reduce skin cancer cases and their treatment costs, the U.S. Department of Health and Human Services released The Surgeon General's Call to Action to Prevent Skin Cancer in 2014.
As a result of the Call to Action report, alternative methods of protection against skin cancer have been investigated, with protection using nutritional interventions being a potential candidate for modulating skin cancer risk.
Previous evidence has shown that consuming tomato paste may reduce sunburn, and that dietary carotenoids - which are "pigmenting compounts that give tomatoes their color" - left behind in human skin after eating the paste may be responsible for its protective effect against ultraviolet (UV) light damage.
"Lycopene, the primary carotenoid in tomatoes, has been shown to be the most effective antioxidant of these pigments," says Cooperstone.
Other research indicates that lycopene intake from eating a tomato in its whole food form is more effective at preventing sunburn than lycopene administered from a synthesized supplement. This suggests that other compounds in tomatoes may contribute to the overall effect.
Tomato-fed mice had lower skin cancer risk
The new study aimed to determine whether consuming the tangerine or red variety of tomatoes would significantly reduce skin cancer tumors in male and female mice that had been chronically exposed to UV light.
No significant difference in the number of tumors were identified in the female mice in the study, the researchers say.
However, the team found that when male mice were fed a 10 percent tomato powder diet every day for 35 weeks and then exposed to UV light, they experienced a 50 percent reduction in skin cancer tumors when compared with the control group of mice that were fed no tomato.
Differences noted between the male and female mice could be explained by previous studies that report that male mice develop tumors quicker after UV exposure than female mice, and their tumors are larger, more aggressive, and more abundant.
"This study showed us that we do need to consider sex when exploring different preventive strategies," comments Prof. Oberyszyn. "What works in men may not always work equally well in women and vice versa."
Prof. Oberyszyn, Cooperstone, and their collaborators discovered that only the male mice fed dehydrated red tomatoes experienced a decrease in tumors. Male mice fed with the tangerine variety of dehydrated tomatoes - shown to have higher bioavailable lycopene levels - had fewer tumors than those in the control group, but the difference was not notable.
"Alternative methods for systemic protection, possibly through nutritional interventions to modulate risk for skin-related diseases, could provide a significant benefit. Foods are not drugs, but they can possibly, over the lifetime of consumption, alter the development of certain diseases."
Cooperstone is currently working to determine whether other compounds in tomatoes may have any significant health benefits.