Natural Foods Merchandiser

A tomato a day

When customers come in asking how to get their daily dose of disease-fighting lycopene, you can steer them to either the supplements aisle or toward the piles of pink, red and orange fruits and vegetables that line the produce section. Studies show that lycopene—found in such colored foods—can help prevent and fight various types of cancer, lower the chances of cervical abnormalities, help decrease the risk of heart disease and even work as a sunscreen.

Lycopene is part of the family of nutrients known as carotenoids, naturally occurring plant pigments with potent antioxidant powers. What?s more, among the common dietary carotenoids, lycopene has the highest oxygen-quenching capacity in vitro.1 Although not produced in the body, lycopene is readily available in the diet from tomatoes—the best known source—as well as in watermelon, pink and red grapefruit, guava, and papaya.

Once eaten and absorbed, lycopene results in high concentrations in the liver, kidneys and lungs2—as well as the adrenal glands, prostate and testes.1 Low levels of this nutrient have been linked to a number of illnesses such as cancer and heart disease.

Cancer killer
The mechanism behind lycopene?s cancer-fighting ability is thought to be twofold, according to a 2002 review published in Experimental Biology and Medicine. First is its antioxidant role in neutralizing cancer-causing free radicals—those highly reactive molecules that damage cells and cause disease. Second, lycopene has been found to inhibit cancer-cell proliferation, which is regulated by an elaborate cellular process called ?the cell cycle.? Lycopene may help prevent the transformation of a normal cell into a cancer cell. A special structure in the cell membrane, termed a ?gap-junction,? functions as a communication channel between cells. Most tumor cells have few of these structures. Lycopene has been found to induce the formation of the protein connexin 43, one of the major building blocks of these channels, and thereby restores the gap junctions necessary for healthy cells. In other words, lycopene helps cells maintain the communication they need to stay well.3

To date, lycopene?s biggest claim to fame has been its ability to fight prostate cancer. Back in 1995, a study published in the Journal of the National Cancer Institute reported that men eating 10 or more servings of tomato-based foods per week were 45 percent less likely to develop prostate cancer. Those who ate four to seven servings of tomato foods were 20 percent less likely to develop the disease.4

These findings are consistent with other studies that have reported a low incidence of prostate cancer in Mediterranean countries, such as Greece and Italy, where tomato consumption is high.5

It appears that tomatoes cooked in oil?like those in spaghetti sauce—are more readily absorbed than other forms. The explanation seems to be that cooking breaks down the tomatoes? cell walls, releasing more lycopene. In addition, oil enhances absorption of the fat-soluble carotenoid.6,7

Perhaps even more dramatic is lycopene?s ability to fight existing cancer. In a small 2001 study, researchers found that prostate cancer patients who took 15 mg of lycopene two times a day had decreased cancer-cell growth compared with those not taking lycopene.8 Another study in 2002 also showed lycopene helped men who already had prostate cancer.9

Lycopene has also shown promise in combating other cancers. In a review of 72 studies, 57 associations were made between tomato intake or blood lycopene levels and decreased cancer risk. Of these associations, 35 were statistically significant. The benefit was strongest for prostate, lung and stomach cancers, although protective associations were also found for cancers of the pancreas, colon, rectum, esophagus, oral cavity, breast and cervix.10

In particular to women?s issues, the carotenoid has been shown to reduce the risk for precancerous changes of the cervix (dysplasia such as cervical intraepithelial neoplasia),11,12 although one study examined black women only, so this particular carryover to other races is not clear. A few studies, including one in Cancer Causes & Control, also suggested high dietary lycopene might help protect against breast cancer.13,14

Moreover, the findings of a recent animal study presented at the 2004 Experimental Biology Meeting revealed lycopene can reduce the size and incidence of fibroid tumors in quail. (Fibroids are benign growths of uterus muscle cells that, in humans, occur in about 25 percent of women). In this new trial, researchers from Firat University in Turkey, the University of Maryland and the Karmanos Cancer Institute at Wayne State University in Detroit supplemented the basic diet of Japanese quail with either 100 mg or 200 mg lycopene per kg of food. After 10 months, the supplemented quail had fewer fibroids compared with a control group fed only the basic diet. In addition, the average diameter of the tumors was significantly smaller in the supplemented groups.15

Although more research clearly needs to be conducted, lycopene appears to be a promising potential aid in the prevention and treatment of a number of cancerous conditions.

Promoting heart health
Heart disease is the leading cause of death in the United States, and lycopene appears to help fight it. For example, in a 2002 review study published in Experimental Biology and Medicine, researchers suggested that lycopene helps prevent heart disease by lowering the amount of artery-clogging, oxidized low-density lipoprotein and by inhibiting the enzymes that produce cholesterol. The study revealed that men with higher blood levels of lycopene had less atherosclerosis and suffered fewer strokes and heart attacks.16

Women can gain heart protection, too. A recent study in The Journal of Nutrition revealed that women who consumed seven or more servings of tomato-based foods were nearly 30 percent less likely to develop cardiovascular disease than women who ate less than one and a half servings per week.17

Lycopene?s newest feats
A relatively new development in terms of lycopene?s benefits for women is its ability to help prevent preeclampsia, a potentially dangerous condition during pregnancy marked by high blood pressure, swelling in the face, hands and feet, and large amounts of protein in the urine.

In a random, double-blind study, 250 women in New Delhi, India, were given either 2 mg of lycopene (from a tomato extract) twice a day or a placebo, beginning at around 16 weeks of gestation until delivery. The incidence of preeclampsia and the average blood pressure in the lycopene group was significantly lower than in the placebo group.18 Although more research is needed, it appears that a simple preventive measure for pregnant women is to take approximately 1-1/2 ounces of tomato juice (about 4.5 mg lycopene), one-half tablespoon of tomato paste (about 4 mg lycopene), or between 1-1/2 to two tablespoons of tomato sauce or ketchup (about 3.75 mg to 5 mg of lycopene) per day to increase the odds of a healthier pregnancy. Interestingly, lycopene might also help protect against sun damage. A study conducted by German researchers suggests that foods rich in the carotenoid might protect the skin from ultraviolet rays. The trial involved giving volunteers close to three tablespoons of tomato paste (about 24 mg of lycopene) a day for 10 weeks. Afterwards, the volunteers were able to withstand up to 40 percent more artificial sunlight before burning.19

The exact amount of lycopene needed to fight disease is not yet known; however, studies demonstrating cancer prevention have utilized up to 6.5 mg per day. Although high-quality lycopene supplements are available, there is some evidence that food sources of lycopene may exert a stronger effect. For example, a study published in the Journal of the National Cancer Institute revealed that rats fed a diet containing whole tomato powder had a lower risk of death from prostate cancer than those given pure lycopene.20 Fortunately, a number of foods can easily provide this amount (see sidebar below), so eat up.

Linda Knittel is a freelance writer in Portland, Ore.

Where to find lycopene
How can you make sure you are getting enough lycopene? The following list of tomato-based foods reveals a ballpark amount of lycopene per ounce.21 (For conversion purposes, there are two tablespoons per ounce.)

Average Milligrams of Lycopene

Per Ounce

Tomato paste

16 mg

Tomato ketchup

5 mg

Spaghetti sauce

5 mg

Tomato sauce

5 mg

Tomatoes, canned

3 mg

Tomato soup

3 mg

Tomato juice

3 mg


1 mg

Pink grapefruit

1 mg

Ode to the watermelon
Tomato products represent nearly 80 percent of lycopene intake in the U.S. diet. However, a study published in The Journal of Nutrition has shown that watermelon juice might even be a more powerful source of this nutrient. Not only is the mean lycopene concentration of watermelon about 40 percent higher than the year-round mean for raw tomato, but the lycopene in watermelon juice also appears to be equally as bioavailable as that of tomato juice.22 Cooked tomatoes up the ante, but it?s still worth taking note.

1. Gerster, H. The potential role of lycopene for human health. J. Amer Coll Nutr 1997;16:109-126.
2. Schmitz HH, et al. Concentrations of selected carotenoids and vitamin A in human liver, kidney and lung tissue. J Nutr. 1991;121(10):1613-21.
3. Heber D, et al. Overview of mechanisms of action of lycopene. Exp Biol Med 2002;227(10):920-3.
4. Giovannucci E, et al. Intake of carotenoids and retinol in relation to risk of prostate cancer. J Natl Cancer Inst 1995;87:1767?76.
5. Bosetti C, et al. Fraction of prostate cancer incidence attributed to diet in Athens, Greece. Eur J Cancer Prev. 2000;9(2):119-23.
6. Stahl W, Sies H. Uptake of lycopene and its geometrical isomers is greater from heat-processed than from unprocessed tomato juice in humans. J Nutr 1992;122:2161-6.
7. Giovannucci, E. [Correspondence] Response: Re: tomatoes, tomato-based products, lycopene, and prostate cancer: review of the epidemiologic literature. J Natl Cancer Inst. 1999;91(15):1331A.
8. Kucuk O, et al. Phase II randomized clinical trial of lycopene supplementation before radical prostatectomy. Cancer Epidemiol Biomarkers Prev 2001;10(8) 861-8.
9. Kucuk O, et al. Effects of lycopene supplementation in patients with localized prostate cancer. Exp Biol Med 2002;227:881-5
10. Giovannucci E. Tomatoes, tomato-based products, lycopene, and cancer: review of the epidemiologic literature. J Natl Cancer Inst 1999;91:317?31.
11. Van Eenwyk J, et al. Dietary and serum carotenoids and cervical intraepithelial neoplasia. Intl J Cancer 1991;48:34?8.
12. Kanetsky PA, et al. Dietary intake and blood levels of lycopene: association with cervical dysplasia among non-hispanic, black women. Nutr Cancer 1998;31:31?40.
13. Dorgan JF, et al. Relationships of serum carotenoids, retinol, alpha-tocopherol, and selenium with breast cancer risk: results from a prospective study in Columbia, Missouri. Cancer Causes & Control 1998;9:89?97.
14. Jarvinen R, et al. Diet and breast cancer in a cohort of Finnish women. Cancer Lett 1997;114:251?3.
15. Sahin K, et al. Lycopene supplementation prevents the development of spontaneous smooth muscle tumors of the oviduct in Japanese quail. Nutr Cancer 2004;50(2):181-9.
16. Rao AV, et al. Lycopene, tomatoes, and the prevention of coronary heart disease. Exp Biol Med 2002;227(10):908-13.
17. Sesso HD, et al. Dietary lycopene, tomato-based food products and cardiovascular disease in women. J Nutr 2003 Jul;133(7):2336-41.
18. Sharma JB, et al. Effect of lycopene on pre-eclampsia and intra-uterine growth retardation in primigravidas. Int J Gynaecol Obstet 2003;81:257-62.
19. Stahl W, et al. Carotenoids and protection against solar UV radiation. Skin Pharmacol Appl Skin Physiol 2002;15(5):291-6.
20. Boileau TW, et al. Prostate carcinogenesis in N-methyl-N-nitrosourea (NMU)-testosterone-treated rats fed tomato powder, lycopene, or energy-restricted diets. J Natl Cancer Inst 2003;95(21):1578-86.
21. Lycopene: Tomato Power. The Miracle Nutrient That Can Prevent Aging, Heart Disease and Cancer. By James F. Scheer and James Balch, M.D. Advanced Research Press, Hauppauge, NY, 1999.
22. Edwards A, et al. Consumption of watermelon juice increases plasma concentrations of lycopene and beta-carotene in humans. J Nutr 2003;133:1043-50.

Natural Foods Merchandiser volume XXVI/number 3/p. 110, 112

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