Key Topics
The Story of Lycopene
A genetically enhanced tomato that boosts healthful lycopene in tomatoes could reduce cancer risks.
By Milly Ryan-Harshman, PhD, RD
Nutrition Consultant
FEAST Enterprises
Lycopene, the pigment that gives ripe tomatoes their bright red colour, has emerged as a key antioxidant in the last decade. Antioxidants slow down the cell damage associated with aging and disease, and lycopene is thought to be one of the more powerful antioxidants. Lycopene is a carotenoid like beta carotene, but lycopene does not have any vitamin A activity.
In earlier nutrition research, scientists focused on carotenoids such as beta carotene or vitamins such as A and C to determine their effects on cancer. Epidemiological evidence has firmly established that diets high in vegetables and fruit can cut cancer risk in half. Now, though, scientists have begun to explore the roles of phytochemicals such as lycopene rather than the roles of traditional vitamins.
In 1996, a landmark study was published by the Harvard Health Professionals Follow-Up Study group that found that prostate cancer risk was a third lower in men who ate tomato-based products more than 10 times a week than in men who ate them less than twice a week.
Lycopene is the most abundant carotenoid, but it is found almost exclusively in tomatoes and tomato-based food products (see table below). In the Harvard study, three of the four foods significantly associated with prostate cancer risk reduction were tomato sauce, tomatoes and pizza. The fourth food was strawberries; however, the red colour of strawberries is due to a different pigment.
Other studies have shown that lycopene may play an important protective role in aging and Alzheimer's disease, cancers of the digestive tract and possibly heart disease by preventing the oxidation of bad or low-density lipoprotein (LDL) cholesterol. In the human body, singlet oxygen molecules (one type of free radical which damages tissues) are formed during normal bodily processes. Lycopene is a singlet oxygen quencher whose activity is almost twice as high as beta carotene. Consumers have become very interested in lycopene for its health benefits, but the best dietary advice — to consume 10 or more servings of tomato-based products weekly — may not appeal to all consumers.
Agricultural biotechnology, though, can help consumers meet their desire for increased lycopene intake. Already, scientists at Purdue University and the USDA have developed a tomato with enhanced lycopene. Imagine a tomato with 2 1⁄2 times the lycopene whose development was accidental! The researchers were attempting to improve the shelf life of tomatoes by inserting a yeast gene into the plants that would increase the production of polyamines. Polyamines protect plants by helping to prevent the cell death of chromoplasts where lycopene is stored. Preventing cell death ensures that the tomato's membranes will stay stronger so the lycopene-enhanced tomato can ripen on the vine longer.
The benefit of this technology is that consumers will be able to eat five or less servings of tomatoes or tomato products weekly to achieve the same level of cancer risk reduction. Other products have been developed with special health benefits. In Europe, the same antisense technology used to develop the Flavr Savr tomato has resulted in a tomato with twice the lycopene and four times the beta carotene, and in Spain, researchers are working with antisense technology to improve peppers. The next step for scientists may be to transfer genes involved in the production of beneficial phytochemicals into other plants. Whether cauliflower or the colour of a tomato has broad consumer appeal remains to be seen, but if there are individuals who have a high risk of chronic disease and dislike tomatoes, then the cauliflower may be worth trying!
The development of foods with special health benefits or functional foods using agricultural biotechnology is still in its infancy. As scientists identify more genes with specific functions that can improve the nutritional value of vegetables and fruit, the dietary habits of Canadians will change. In addition to their usual diet, Canadians will be able to purchase novel foods that complement their diet. These specialty crops will be carefully managed by plant breeders, farmers and the regulatory authorities to ensure the continuing safety of the food supply.
Reading List
- Diplock AT. Antioxidant nutrients and disease prevention: An overview. American Journal of Cinical Nutrition 1991;53(suppl);189S-193S.
- Giovannucci E, et al. Intake of carotenoids and retinol in relation to risk of prostate cancer. Journal of the National Cancer Institute 1995;87:1767-1776.
- DiMascio P, Kaiser S, Sies H. Lycopene as the most efficient biological carotenoid singlet oxygen quencher. Archives of Biochemictry and Biophysics 1989;274:532-538.
- Mehta RA, et al. Engineered polyamine accumulation in tomato enhances phytonutrient content, juice quality, and vine life.
- Tonucci LH, Holden JM, Beecher GR, et al. Carotenoid content of thermally processed tomato-based food products. Journal of Agriculture and Food Chemistry 1995;43:579-586.
- Shi J, Le Maguer M. Lycopene in tomatoes: Chemical and physical properties affected by food processing. Critical Reviews in Biotechnology 2000;20:293-334.in Biotechnology 2000;20:293-334.