Free radical induced oxidative damage and chronic diseases: Protection by dietary lycopene

Cancer and coronary heart disease are two of the leading causes of death in North America. Nutritionists and other health professionals have long championed the role of fruits and vegetables in reducing risk for these diseases. It now appears that one particular vegetable (actually fruit) may be especially effective. The case for increasing tomato and tomato-based product consumption is getting stronger and stronger as more and more scientific studies support the health benefits of tomatoes (1-4).

The secret to the tomato's success may lie with lycopene - the carotenoid responsible for red colour and present in high amounts. Results from a number of population studies show that people with high lycopene intake or high lycopene levels in the body are at a lower risk for developing certain types of cancers (5). Lycopene's ability arises from its antioxidant power (6).

Free radicals are electron hungry molecules naturally produced by the body during aerobic metabolism. These free radicals and the damage that they cause have been implicated as a major player in the development of chronic diseases (7, 8). Although free radicals are naturally produced, their formation can be greatly influenced by a number of factors. Infection, disease and lifestyle factors such as smoking, exposure to radiation and environmental pollution can increase free radical production. In the end, irrespective of how and why they are formed, they are extremely harmful and can damage important molecules within the body such as lipids, proteins and DNA.

Within the body there are many types of lipids, or fat molecules. One type is responsible for maintaining the structural integrity of the cell membrane. Free radicals can cause damage to the cell membrane by oxidation thereby making them leaky (9). Free radical oxidation of another type of lipid, the low-density-lipoprotein, is considered to play a major role in the development of atherogenesis (the thickening of arterial walls) (10).

Free radicals also cause damage to proteins and genes. Some proteins serve as important enzymes that regulate metabolic reactions. Free radicals can interfere with protein functions, leading to irregular and abnormal metabolism (11). DNA is the genetic material responsible for heredity. Oxidative damage to DNA over time can cause changes to both the structure and function of chromosomes. These changes in the genetic code may lead to cancer and other chronic diseases (8, 12-14).

How can we protect ourselves against free radical damage? Science has found that antioxidants can help. Antioxidants are important molecules that act as free radical scavengers. They trap the free radicals and give up own electrons, thus preventing free radical oxidation of other molecules (15, 16). Our body naturally has a very elaborate network of antioxidants that help to protect us. However, the body cannot produce enough to do all the work that needs to be done and needs help. Diets rich in fruits and vegetables are good sources of dietary antioxidants which include vitamin E, vitamin C and carotenoids like beta-carotene and lycopene. These dietary antioxidants are effective bodyguards, giving us protection from free radical damage (15 - 17). Lycopene, found in high levels in tomatoes and tomato products, has been found to be one of the most potent and effective dietary antioxidants (18).

Increasingly, science is discovering that lycopene can play an important role in disease prevention. A good example of lycopene in action is its possible role in prostate cancer prevention. Studies have shown that these patients have less lycopene and more oxidized lipids and proteins in their body (19). Diets rich in tomatoes and tomato products may protect DNA from oxidative damage (20, 21). Science has also found that people who consume tomato juice or sauce every day for one week in addition to their regular diet are able to increase their blood lycopene and reduce the amount of oxidized lipids, protein and DNA (22, 23). This suggests to us that lycopene from traditional tomato products can be absorbed into the body where they protect us from oxidative damage.

The future of lycopene and disease prevention looks very exciting and promising. Studies involving patients and those that are at risk for certain chronic diseases are underway. More work needs to be done for us to fully understand and discover the mechanism of dietary lycopene in disease prevention. However based on what we know, it appears that "a tomato a day can keep the doctor away".


References

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