Tangerine Tomatoes: One Example of the Potential of A Diet Rich in Whole Foods for Reducing Cancer Risk
As we hit the peak of summer, tomatoes are everywhere - in sauces, salads, and even in cocktails. And while this may conjure images of robust red fruits (yes, tomatoes are fruits), consider trying out a different color for flavor, health, and variety.
The different hues of tomatoes come from phytochemicals, which are components synthesized by plants to promote overall plant survival. Some phytochemicals, like vitamins, are nutrients required by humans for health maintenance. On the other hand, there are thousands of phytochemicals that are not nutrients, but may still have biologic effects when consumed. Nutritional scientists are only beginning to grasp how these compounds might be important in health and disease. The tomato plant makes certain phytochemicals to protect itself from constant ultraviolet light and to fight off hungry insects. Phytochemicals also help the tomato plant attract bees and ward off disease. All plants have such chemicals, which interact with each other in complicated ways. As clinical data grows, dietary patterns that include phytochemical-rich plant foods may be powerful tools for cancer prevention, treatment, and survival.
Not all foods are created equal
At the most fundamental level, plant foods provide many different phytochemicals. In laboratory cell culture studies, these phytochemicals demonstrate a variety of ways they may protect us from cancer. Some function as antioxidants, which means they can give extra electrons to damaged molecules that need them without getting damaged in the process. Others function to promote programmed cell death (or apoptosis), inhibit cancer cell proliferation, or favorably modulate the immune system.
Although laboratory studies provide important mechanistic knowledge, they often cannot be directly translated to humans for several reasons. Laboratory conditions are very well controlled and frequently investigate a single purified compound. Human diets, however, are extraordinarily complex with many interrelationships between nutrients and phytochemicals. Additionally, human digestion and metabolism can significantly vary between individuals. Studying whole foods in the context of a varied diet, as well as identifying patterns of dietary intake over many years, offers a broader view of the roles of nutrition and health. Here at The Ohio State University Comprehensive Cancer Center - Arthur G. James Cancer Hospital and Richard J. Solove Research Institute (OSUCCC - James), we've brought together a number of researchers—from nutritionists and agricultural scientists to oncologists and population scientists—to determine the impact of many different foods on health and disease using a food-based approach.
Tomatoes as Part of a Healthy Diet
Large population studies have reported that men who consume at least five servings of tomato foods each week have a lower risk of prostate cancer. Tomatoes are a rich source of hundreds of phytochemicals, including vitamin C and the phytochemical lycopene, which gives tomatoes their red color.
Of the many different components in tomato foods, lycopene has been significantly researched. Recently, our laboratory has been interested in better understanding the factors contributing to lycopene absorption. We know lycopene is a fat-soluble phytochemical and is therefore better absorbed with dietary fat. We also know that genetics and food processing play a role in absorption.
Furthermore, we have recently learned that the chemical structure of lycopene is also important. Tangerine tomatoes are a tomato produced using natural breeding practices that are more orange in hue. They have a different chemical structure of lycopene than red tomatoes, and this structure affects the absorption of lycopene. When my colleagues investigated lycopene in the orange-hued tangerine tomatoes (Solanum lycopersicum), they were found to be particularly rich in a type of lycopene that the body appears to absorb more than eight times more efficiently than the version in red tomatoes. Studies are now underway to evaluate the bioavailability of the tangerine tomato in men with prostate cancer.
And the benefits of tomatoes don't stop with lycopene. Tangerine tomatoes also contain considerable levels of other chemicals (for example, phytoene, phytofluene, ζ-carotene, and neurosporene) that are also being studied.
While understanding lycopene is important, we eat it as one of hundreds of interacting chemicals in every tomato bite. Consuming a single chemical rarely proves effective, which is why many nutritional supplements have not demonstrated benefit in clinical studies.
As such, whole-food research is critical to understanding how patterns of dietary intake over time may benefit health. Fruits and vegetables contain a largely unexplored array of bioactive components not among the 40 essential nutrients necessary for human survival. And yet, understanding the foods is only half of the problem—there is tremendous variation in how different people process what they eat.
It Gets Even More Complicated
In the tangerine tomato study, researchers enrolled a small pool of subjects, just six men and five women. The study required two 12-hour long visits to a research unit, and all subjects followed a controlled diet for one month. This study had multiple funding sources, including support from the National Science Foundation’s Industry University Cooperative Research Center for Advanced Packaging and Processing Studies, The Ohio Agriculture Research and Development Center, the Ohio State University Comprehensive Cancer Center’s Pelotonia Fellowship Program, and Ohio State’s Center for Clinical and Translational Science.
The 11 subjects were of similar age, did not smoke, did not have any known conditions that drastically affect digestion and consumed the same amount of lycopene (10 mg) from either red tomato juice or tangerine tomato juice (produced by the Department of Food Science and Technology at Ohio State). Despite this homogeneity, the range of results after test meals was profound.
Overall, individuals absorbed over 8 times more lycopene when they consumed the tangerine tomato juice-containing meal, as compared to the red tomato juice meal. Men had higher lycopene concentrations than women. For those drinking red tomato juice, there was an 80-fold difference from the person who absorbed the most lycopene to the one who absorbed the least (in the tangerine tomato juice, there was also a wide difference at 20-fold). Additionally, while one subject absorbed less lycopene from the tangerine tomato juice, the other ten participants absorbed a far-ranging greater amount, from 2.3 times to 247 times more lycopene from the tangerine tomato juice compared to the red tomato juice.
All of this is within the context of a study that had a very small number of participants, but the take-home message stands: people absorb and digest foods differently, and the variations can sometimes be significant.
Variety in People, Variety in Nutrition
An important reason for the sprawling results is our genetic code - although humans are nearly genetically identical, the tiny differences between individuals make a difference. Some genes code for different proteins, with one variant helping absorb a given nutrient and another standing in the way.
Many people are frustrated by such seemingly inconsistent nutrition messages. However, there is a significant body of scientific literature that suggests a healthy dietary pattern with a variety of fruits and vegetables each day may aid in the prevention of many different types of cancer.
Several organizations offer evidence-based public health guidelines to help Americans eat healthily, including the recently published 2015-2020 Dietary Guidelines for Americans. These guidelines offer several examples of what a “healthy dietary pattern” looks like, as well as specific guidelines for maintaining good health. Additionally, The World Cancer Research Fund / American Institute for Cancer Research provides a thorough and regularly updated synthesis of diet and cancer research and offers clear diet guidelines for cancer prevention and survivorship. These organizations and others encourage all Americans to eat a diet which includes many different plant foods. Tomatoes (both red and tangerine) are one way to incorporate more plants into your diet and savor the last days of summer.