Lycopene Antioxidant: The Rediscovered Carotene

According to the Linus Pauling Institute of Micronutrient Information Center, lycopene antioxidant activity is extremely important to plants, but the importance to human health is still unclear. Partly because of this, there has been no established lycopene daily requirement.
Beta-carotene from carrots is known for its antioxidant action. But did you know that there are over 600 known carotenoids besides beta? About 40 are found in the human diet, and not all of them turn into vitamin A. Lycopene is one that does not convert to vitamin A. Studies have shown that eating foods with lycopene provides stronger antioxidant protection against certain types of free radicals and does reduce the risk of some types of cancer and possibly heart disease. The carotenoid lycopene is the most common carotenoid found in the human body yet very little research has been done on it.
Carotenoids are organic chemicals that give plants their colors. Plant foods with lycopene are red like tomatoes, watermelons, grapefruits and papaya. A pigment synthesized by some plants and animals to protect them from the sun, lycopene evolved as a weapon against certain types of free radicals. Lycopene is so effective at quenching free radicals; it beat out vitamin E in one study on oxidized fat. This suggests that lycopene might have importance in preventing heart disease, which involves oxidized LDL cholesterol. The first evidence for a protective effect in heart disease was reported in the journal Lipids A group from Canada demonstrated that lycopene significantly lowers LDL oxidation in human blood. Lycopene works better in combination with lutein, another carotenoid which is found mostly in spinach and corn. (Lutein is associated with maintenance of the macula.) People with high cholesterol have been found to have high levels of free radicals and low levels of lycopene and beta-carotene. Humans get most of their lycopene from tomatoes, by far the richest source, yet tomato products offer a more concentrated source of lycopene than the fresh fruit itself. For example, tomato powder contains approximately 120 milligrams per 100 grams of fruit whereas fresh tomatoes have about 2 milligrams per 100. Since lycopene is a nutrient that can stand the heat, cooked tomato products, such as tomato paste, provide more of it than fresh tomatoes. It has been theorized that heating tomatoes makes their lycopene more absorbable.
Researchers are realizing that the cancer-preventive effects of the Mediterranean diet, which have been attributed to olive oil, may in fact be due to lycopene. Lycopene's cancer protection is in part due to its antioxidant protection. But some studies show that it may also modulate immunity, inhibit angiogenesis and affect hormonal effects in human.
There are no known lycopene antioxidant deficiency diseases. The reason that it is included in some dietary supplements, however, is because of scientific studies that indicate it may reduce the risk of some life threatening diseases and improve health. The FDA regulates health claims made by manufacturers of dietary supplements and food stuffs. In 2005, they addressed the issue of a lycopene daily requirement and proposed health claims of foods with lycopene. Their conclusion was that the limited scientific evidence suggests that consuming one-half to one cup of tomatoes or tomato sauce per week may reduce the risk of prostate cancer.
The carotenes are lipid soluble-they must have fat to be absorbed. It has been consistently demonstrated that foods with fat in them deliver more lycopene into the body. Lycopene is carried in the blood by the lipoprotein molecule (LDL) that also carries cholesterol. Drugs that lower cholesterol can drastically interfere with the carotenes. In one study, cholestyramine (Questran) decreased lycopene by 30% in the blood. It also reduced beta-carotene by 40% and vitamin E by 7%.
Other parts of the body besides the prostate that accumulate lycopene are the adrenal glands, liver, colon and testes. Aging reduces levels of lycopene in the blood. Elderly people are consistently deficient in nutrients, including ones that interact with lycopene such as vitamins C and E.
Lycopene: Promote Prostate Health
Epidemiological evidence strongly suggests that lycopene consumption contributes to prostate cancer risk reduction. Preclinical studies show that lycopene acts via different mechanisms, which have the potential to cooperate in reducing the proliferation of normal and cancerous prostate epithelial cells, in reducing DNA damage, and in improving oxidative stress defense. The mechanisms include inhibition of prostatic IGF-I signaling, IL-6 expression, and androgen signaling. Moreover, lycopene improves gap-junctional communication and induces phase II drug metabolizing enzymes as well as oxidative defense genes. These findings provide plausible explanations for the epidemiological findings how lycopene can contribute to reduced prostate cancer risk. The novel finding that lycopene reduces local androgen signaling in the prostate suggests also efficacy in prevention of benign prostate hyperplasia.
Lycopene: Implication in Other Cancers
Lycopene appears to be protective against cancer of the digestive tract. Several studies have found a lower risk for colorectal cancer in people who eat a lot of tomato products and/or have higher levels of lycopene in their blood. More direct evidence has been provided by researchers in Japan who did a study on colon cancer in rats. It's important to note, however, that pure lycopene did not. The authors of the study speculate that lycopene's action depends on other factors present in the juice that is missing in pure lycopene. Recent thinking in carotene research is that the carotenes are both interdependent and dependent on other vitamins and minerals, and this must be taken into account when studying them.
One of the largest and most important cancer/diet studies ever done shows the importance of the carotenes in digestive cancers. The study was begun in 1980 in Linxian, China. Linxian has one of the highest rates of esophageal and gastric cancer in the world. Its population also has subnormal levels of vitamins C, E, A, riboflavin and the carotenes. In an effort to see whether supplementation would cut the cancer rate, over twenty-nine thousand people were given four different nutrient combinations in the Linxian study. Four different combinations were tested: riboflavin, niacin; vitamin C, molybdenum; retinol, zinc; or beta-carotene, vitamin E, selenium. After five years, the results showed that the beta-carotene, Vitamin E, selenium combination cut the cancer rate and overall mortality. The others did not. Reduction in risk began to occur one to two years after supplements were begun. It was also discovered that men who took the combination had a lower risk of stroke, and better immune response.
Another cancer that may relate to lycopene is pancreatic cancer. Researchers at Johns Hopkins tested the stored blood of twenty-two people with pancreatic cancer for levels of certain vitamins and selenium before treatment began. The levels of these were lower in patients than controls. In hamsters, palm carotene (which contains lycopene) inhibits pancreatic cancer.