The World's Healthiest Foods

lycopene

What can high-lycopene foods do for you?

What events and lifestyle factors can indicate a need for more high-carotenoid foods?

Foods highest in lycopene include tomatoes, pink grapefruit, watermelon, and guava. Other foods containing small amounts of lycopene include persimmon and apricots.

Description

Lycopene is a member of the carotenoid family of phytochemicals and is the natural pigment responsible for the deep red color of several fruits, most notably tomatoes. Although tomatoes have been consumed in abundance throughout the world for centuries, the investigation into the health benefits of lycopene did not begin until the last part of the 20th century. However, in a relatively short period of time, scientists have amassed a significant body of laboratory, animal, and population-based research that supports the role of lycopene in human health, specifically in the prevention of cancers of the prostate, pancreas, stomach, breast, cervix and lung, as well as in the prevention of cardiovascular disease, cataracts, and age-related macular degeneration (a chronic eye condition in which light-sensing cells in the center of the retina stop functioning).

How it Functions

Unlike several of its carotenoid cousins, lycopene does not have pro-vitamin A acitvity—in other words, it does not get converted into vitamin A. Consequently, the health benefits of lycopene are attributed primarily to its powerful antioxidant actions. In fact, laboratory experiments indicate that lycopene is a more effective antioxidant than other carotenoids, including beta-carotene. Lycopene is especially effective at quenching a free radical called singlet oxygen. Singlet oxygen is a highly reactive free radical formed during normal metabolic processes that reacts with polyunsaturated fatty acids, which are major constituents of cell membranes. Due to the fact that lycopene is commonly located in cell membranes, it plays an important role in preventing oxidative damage to the membrane lipids, thereby influencing the thickness, strength, and fluidity of the membranes. Cell membranes are the gatekeepers of the cell, allowing nutrients in, while preventing toxins from entering and facilitating the removal of cellular garbage. Maintaining the integrity of cell membranes is a therefore key factor in the prevention of disease.

In addition to its antioxidant activity, lycopene has been shown to suppress the growth of tumors in in vitro (test tube) and in vivo (animal) experiments. One of the ways that lycopene may limit tumor growth is by stimulating cell to cell communication. Researchers now believe that poor communication between cells is one of the causes of the abnormal growth of cells, a condition which ultimately leads to the development of cancerous tumors.

Lycopene is also believed to play a role in the prevention of heart disease by inhibiting free radical damage to LDL cholesterol. Before cholesterol can be deposited in the plaques that harden and narrow arteries, it must be oxidized by free radicals. With its powerful antioxidant activity, lycopene can prevent LDL cholesterol from being oxidized.

Recent research has suggested that lycopene can boost sperm concentrations in infertile men. In one study, a lycopene-supplemented diet resulted in a statistically significant improvement in sperm concentration and motility amongst the 30 infertile men being studied with six pregnancies following as a result of the trial.

Deficiency Symptoms

Inadequate intake of lycopene, and other carotenoids, over a period of many years may set the stage for the development of several chronic diseases, including heart disease and various cancers. One important mechanism for this relationship appears to involve free radicals. Research indicates that diets low in carotenoids can increase the body's susceptibility to damage from free radicals. As a result, over the long term, carotenoid-deficient diets may increase tissue damage from free radical activity, and increase risk of chronic diseases like heart disease and cancers.

Toxicity Symptoms

A high intake of foods containing lycopene is not known to cause any harmful side effects. However, excessive consumption of lycopene can cause a deep orange discoloration of the skin, a harmless condition called lycopenodermia. Although very little is known about the potential for adverse effects from high doses of supplemental lycopene, the Institute of Medicine at the National Academy of Sciences did not establish a Tolerable Upper Intake Level (UL) for carotenoids (including lycopene) when it reviewed these compounds in 2000.

Some research indicates that under certain circumstances, lycopene (and other carotenoids) can become oxidized in the body, and may subsequently behave like free radicals and cause cellular damage. Cigarette smoke, for example, may cause lycopene to become oxidized. This may explain, at least in part, the research findings that cigarette smokers who take carotenoid supplements may have an increased risk of cancer or heart disease.

Impact of Cooking, Storage and Processing

As the interest in the health benefits of lycopene continues to increase, food scientists and manufacturers have focused a tremendous amount of attention on the impact of food processing on the quantity and bioavailability of lycopene in various food products. Although not all scientists agree, it is generally accepted that the availability of lycopene from tomato products is increased when these foods are processed at high temperatures or packaged with oil. If actually true, this means that your body absorbs the lycopene in canned, pasteurized tomato juice and tomato products that contain oil more easily than the lycopene found in a fresh, raw tomato. It appears that more research is necessary in this area.

Vine-ripened tomatoes have a higher lycopene content than tomatoes ripened off the vine.

Factors that Affect Function

Lycopene is a fat-soluble substance, and as such requires the presence of dietary fat for proper absorption through the digestive tract. Consequently, your lycopene status may be impaired by a diet that is extremely low in fat or if you have a medical condition that causes a reduction in your ability to absorb dietary fat such as pancreatic enzyme deficiency, Crohn's disease, celiac sprue, cystic fibrosis, surgical removal of part or all of the stomach, gall bladder disease, or liver disease.

Drug-Nutrient Interactions

The cholesterol-lowering medications referred to as bile acid sequestrants (including cholestyramine and colestipol) lower blood levels of carotenoids, including lycopene. In addition, margarines enriched with synthetic plant sterols such as Benecol (TM) or Take Control (TM) may decrease the absorption of carotenoids. Olestra (TM), a fat substitute added primarily to snack foods, may also decrease the absorption of carotenoids.

Nutrient Interactions

Some research indicates that the various members of the carotenoid family compete with one another for absorption. The example most often cited of this interaction is the reduction in blood levels of lutein that occurs with beta-carotene supplementation. However, one study that measured the absorption of beta-carotene and lycopene found that, when taken at the same time, beta-carotene absorption was not reduced and lycopene absorption was actually enhanced.

Other conflicting research suggests that carotenoids actually work synergistically, and that the antioxidant activity of lycopene is enhanced by the presence of other carotenoids, specifically lutein. More studies are needed to clarify these relationships.

Health Conditions

Lycopene may play a role in the prevention and/or treatment of the following health conditions:

Form in Dietary Supplements

As a dietary supplement, lycopene is available in mixed carotenoid formulations or by itself. Most supplements containing lycopene are oil-based and are sold in soft-gels. One wide-selling category of lycopene supplements are tomato extracts.

Food Sources

Introduction to Nutrient Rating System Chart

The following chart shows the World's Healthiest Foods that are either excellent, very good or good sources of this nutrient. Next to each food name you will find the following information: the serving size of the food; the number of calories in one serving; DV% (percent daily value) of the nutrient contained in one serving (similar to other information presented in the website, this DV is calculated for 25-50 year old healthy woman); the nutrient density rating; and the food's World's Healthiest Foods Rating. Underneath the chart is a table that summarizes how the ratings were devised. Read detailed information on our Nutrient Rating System.

Food Source Analysis not Available for this Nutrient

Public Health Recommendations

To date, no recommended dietary intake levels have been established for carotenoids, including lycopene. However, the National Academy of Sciences supports the recommendations of various health agencies, which encourage individuals to increase their consumption of carotenoid-rich fruits and vegetables.

References