Watermelon Juice a Rich Source of Lycopene and Beta-Carotene
Regular consumption of watermelon juice can increase blood concentrations of lycopene and beta-carotene, according to a study in Journal of Nutrition (2003;133:1043–50). Studies suggest that these potent antioxidants may have protective effects against heart disease and certain cancers, such as prostate, bladder, and cervical cancer.
Lycopene and beta-carotene are compounds called carotenoids, which are highly colored pigments that help protect plants against damage from sunlight. Carotenoids are important to humans because they have antioxidant activity and prevent free radicals from causing harm to the body, similar to other types of antioxidants such as selenium and vitamins C and E. Some carotenoids are also converted to vitamin A, which is necessary for normal immune function and development of cells. Other significant carotenoids include lutein and zeaxanthin, which play a role in visual function.
In the study, 23 healthy adults between 36 and 69 years old consumed three of four possible diets that each lasted three weeks. All participants completed the first two treatments, which included consuming daily (1) a controlled diet, low in lycopene and (2) the controlled diet plus watermelon juice containing 20 mg of lycopene and 2.5 mg of beta-carotene. As a third treatment, participants were assigned to consume either (3) the controlled diet plus watermelon juice that was twice as concentrated as in the second treatment or (4) the controlled diet and tomato juice containing 18 mg of lycopene and 0.6 mg of beta-carotene. The quantities of watermelon and tomato juice needed to provide the amounts of lycopene and beta-carotene used in this study were approximately 3 cups of diced watermelon and 1 cup of tomato juice. Blood levels of lycopene and beta-carotene were measured at the beginning and completion of each three-week treatment period.
The watermelon juice diet increased blood concentrations of lycopene and beta-carotene almost five-fold and two-fold, respectively, compared with the diet without watermelon juice. However, there was no significant increase in lycopene or beta-carotene levels when the amount of watermelon juice was doubled. Consumption of tomato juice produced a similar increase in blood lycopene concentrations, but failed to increase beta-carotene levels.
Although the current study shows watermelon juice increases lycopene and beta-carotene blood levels, the long-term health benefits consuming watermelon have yet to be investigated. Several studies have shown that lycopene from tomatoes reduces the risk of heart attacks and may help prevent prostate cancer. Although the lycopene concentration in watermelon is 40% higher than the amount found in tomatoes, it is unknown whether consumption of watermelon will produce similar results. Other food sources of lycopene include guava, pink grapefruit, apricots, persimmons, and papaya.
Darin Ingels, ND, MT (ASCP), received his bachelor’s degree from Purdue University and his Doctorate of Naturopathic Medicine from Bastyr University in Kenmore, WA. Dr. Ingels is the author of The Natural Pharmacist: Lowering Cholesterol (Prima, 1999) and Natural Treatments for High Cholesterol (Prima, 2000). He currently is in private practice at New England Family Health Associates located in Southport, CT, where he specializes in environmental medicine and allergies. Dr. Ingels is a regular contributor to Healthnotes and Healthnotes Newswire.
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