Cancer Nutrition Network for Texans
Lycopene is one of the latest ‘wonder’ elements commonly found in tomatoes and giving them their distinctive red color. It is an antioxidant carotenoid of the family that contains, alpha and beta – carotene, lutein, zeaxanthin, and beta-cryptoxanthin. This family of substances has numerous biological properties that may underpin a role for them as chemopreventive agents in the avoidance of cancer, the most common is their conversion in the body to Vitamin A. Lycopene is thought to work by neutralizing harmful substances in the body called, ‘free radicals’, molecules that result from normal cell metabolism. Lycopene as a dietary supplement also has shown promise in reducing the risk of coronary heart disease and in reducing other types of cellular oxidative damage. It may have wide- ranging health benefits associated with suppression of HPV and HIV infections.
A review of 72 population studies was conducted to determine the relationship between tomato-rich diets, lycopene levels in the blood, and the risks of various cancers. In 57 of the studies, diets rich in tomatoes and tomato products produced protective effects from the risks of cancer with 35 of the 57 showing statistically significant associations. None of these studies showed any risk of higher tomato consumption or blood lycopene levels and increased risk of cancer at a defined anatomical site. The evidence for a benefit was strongest for cancers of the prostate, lung, and stomach. The data from these studies were suggestive of protection for cancers of the pancreas, colon and rectum, esophagus, oral cavity, breast, and cervix. What makes for excitement about the potential of lycopene as a chemopreventive is the strength of this association found in diverse populations. However, it must be kept in mind that many other potentially beneficial compounds are present in tomatoes and these or some as yet unknown but complex interactions among multiple components may contribute to the anticancer properties of tomato-rich diets.
A clue as to how the lycopene might work has been reported as antiproliferative action associated with cell differentiation – in lay terms, lycopene has something to do with regulating cell growth to reduce the numbers of changes that normally arise thereby reducing the number of copy errors that can occur. Lycopene has been shown to have a synergistic effect with other natural anticancer compounds, such as, 1,25-dihydroxyvitamin D3, a compound that when used alone is effective against cancer cells but is toxic. When this agent is used with low levels of lycopene it is as effective but at much lower doses. This combination of lycopene and 1,25-dihydroxyvitamin D3 produces an additive effect on cell cycle progression – in lay terms, these compounds together are thought to kills cells with errors readily while keep the cell working through its cycle in a timely, orderly manner. This laboratory work has been shown with experimental leukemic cells, and cells from the lung, colon, endometrium, breast, prostate, and pancreas.
Further research on lycopene bioavailability, pharmacology, biochemistry, and physiology must be done to discover the mechanisms of action of lycopene coming from the human diet. This need for more information will not stop people from producing, selling, buying, and taking lycopene as a dietary supplement even though the pharmacokinetics (i.e., how it works as a drug) are poorly understood. The best advice from the experts is to get your lycopene from natural dietary sources – fresh or cooked tomatoes or tomato purees or juices. A serving a day (about a half cup of tomato or spaghetti sauce or one medium-sized whole tomato) is probably sufficient. Fresh tomatoes are full of lycopene but cooking makes it easier for your body to use it. Including a little fat with cooked tomatoes can improve absorption of the lycopene.
Other, although less rich, food sources of lycopene are watermelon and pink grapefruit. For those of us in Texas, who enjoy salsas, and for all whom like fresh salads with tomatoes will find these good sources of dietary lycopene. Even pizza-lovers and ketchup aficionados find something beneficial in their dietary choices. Remember that foods are not medicine and a prudent diet based on the national food guidelines is the best bet for a health.
Billy U. Philips, Jr., Ph.D., Professor, Department of Preventive Medicine and Community Health at the University of Texas Medical Branch at Galveston.