Editor’s Note: Each month, HerbalEGram highlights a conventional
food and briefly explores its history, traditional uses, nutritional profile,
and modern medicinal research. We also feature a nutritious recipe for an
easy-to-prepare dish with each article to encourage readers to experience the
extensive benefits of these whole foods. With this series, we hope our readers
will gain a new appreciation for the foods they see at the supermarket and
frequently include in their diets.
The basic materials for
this series were compiled by dietetic interns from Texas State University in
San Marcos and the University of Texas at Austin through the American Botanical
Council’s (ABC’s) Dietetic Internship Program, led by ABC Education Coordinator
Jenny Perez.
We would like to acknowledge Perez, ABC Special Projects Director Gayle Engels,
and ABC Chief Science Officer Stefan Gafner, PhD, for their contributions to
this project.
By Hannah Baumana and Becky Nicholsba HerbalGram Assistant Editor b ABC Dietetics Intern (TSU, 2013)
History and Traditional Use Range and Habitat
The watermelon is the largest edible fruit grown in the United States: an
annual trailing plant with fruits that can can grow from 5-50 pounds and vines
that can reach up to 20’ in length.1,2 Each fruit forms from a
yellow flower, and the spherical or ovoid fruit is typically smooth and green,
or green with lighter banded stripes. The watermelon is native to the Kalahari
Desert in Africa, and it thrives in well-draining, sandy soil. Currently, watermelons
are cultivated all over the world, with Asia producing 60% of watermelons
globally.2,3 The United States ranks fifth in global watermelon
production.4 Forty-four states grow watermelons, including Texas,
Florida, Georgia, and California, which collectively produce 2/3 of all the
watermelons domestically.
Phytochemicals and Constituents
Watermelon contains an array of important vitamins and minerals including
vitamin A, vitamin C, vitamin B-6, potassium, and beta-carotene.1,5,6
Watermelon also contains the important bioactive compounds citrulline and
lycopene. Vitamin C acts as an antioxidant and anti-cancer agent.7-9
Watermelon’s vitamin C content may be linked to reducing blood pressure, as
does its smaller amounts of vitamins B6 and E.8 The human
body converts beta-carotene into vitamin A, which promotes healthy eyes, a
strong immune system, and healthy skin.10 Vine fruits like
watermelon are a good source of potassium, a crucial electrolyte for nerve and
muscle function. Potassium is an essential nutrient as the body ages, as it decreases
high blood pressure and reduces the risk of kidney stones, stroke, and bone
density loss.11,12
Citrulline is a precursor to the amino acid arginine and is involved in the
process of removing nitrogen from the blood and eliminating it through urine.13,14
Arginine is a precursor for the synthesis of nitric oxide in the body, which is
a vasodilator (blood vessel-widening agent). Conditions that benefit from
vasodilation, such as cardiovascular diseases, erectile dysfunction, and
headaches may benefit from increased arginine intake. Arginine also helps the
body make protein, which boosts muscle growth, enhances wound healing, combats
fat accumulation, and stimulates the immune system.
Though the tomato (Solanum lycopersicum)
is more well-known as a source for lycopene (and in fact, its name is derived
from lycopersicum), lycopene is a
carotenoid found in many red foods, including watermelon, papaya (Carica papaya), pink grapefruit (Citrus x paradisi), and red carrots (Daucus carota subsp. sativus).15 A powerful
antioxidant, lycopene may help prevent heart disease and has shown a potent
ability to protect the body from “free radicals,” which may play a role in the
development of heart disease, Alzheimer’s disease, and many cancers. Lycopene
may also boost sperm counts and lower the risk of prostate cancer.
Historical and Commercial Uses
Though native to the African Kalahari desert, where the watermelon gourd was
often used as a canteen, the cultivation of watermelon spread quickly, and
other cultures adopted it as a beneficial, healing food. Ancient Egyptians used
watermelon to treat reproductive problems such as erectile dysfunction and
prostate inflammation. The peoples of Russia and Central Asia used watermelon
as a diuretic and to cleanse the blood.16,17 In Traditional Chinese
Medicine, watermelon is considered cooling and moistening, producing a diuretic
effect, and commonly is used to treat thirst, edema, and inflammation of the
kidney and urinary tracts.18 Because watermelon is 92% water, many
traditional uses of watermelon overlap with current uses, including hydration,
cleansing, and eliminating impurities.4 Since watermelon is digested
relatively quickly, the folk traditions of the Papua New Guinea aborigines
known as Onabasulu advised against eating watermelon and other juicy fruits after
a heavy meal or if suffering from a stomachache.19
African cuisine treats the watermelon as a vegetable and uses the entire fruit:
seeds, rinds, and flesh.20 The seeds are eaten as snacks, added to
dishes, or ground into flour for use in baked goods. The rind can be stir-fried,
stewed, candied, pickled, or grilled. The flesh is eaten or juiced, but it can
also be fermented into alcohol; in the southern part of Russia, the juice is
combined with hops to make beer.
Modern Research
The traditional uses for watermelon as a medicine are beginning to gain
scientific confirmation, particularly in regards to its applications against
erectile dysfunction, dehydration, kidney disease, and anti-aging concerns. Watermelon’s
antioxidant and nutrient content defends against many different conditions.
Current research shows that citrulline in watermelons has beneficial effects on
the heart, dilating the blood vessels and improving blood flow.6 In
one clinical study, obese participants with pre-high blood pressure or
stage-one high blood pressure significantly reduced their ankle and brachial
systolic blood pressure, diastolic blood pressure, mean arterial pressure, and
carotid wave reflection with ingestion of citrulline from watermelons.21
A review of consumption of citrulline from watermelon demonstrated improvements
in glycemic control and circulatory problems in diabetics, a reduction in
cardiovascular risk factors, and increased levels of arginine, an essential
amino acid. Because arginine is involved in maintaining the health of the
reproductive, pulmonary, renal, gastrointestinal, hepatic, and immune systems,
citrulline is of increasing interest in the realm of scientific study. Studies
show that citrulline is more bioavailable in the body than arginine, making it
a better candidate for arginine deficiency diseases such as renal carcinoma,
chronic inflammatory diseases, or blood cell diseases like sickle cell anemia
and malaria.14,22 Citrulline research also has shown promising
results of becoming a biomarker for bowel problems of the small intestine as
well as kidney failure.13
Lycopene’s powerful antioxidant properties have been shown to reduce the risks
of prostate, lung, gastric, and colorectal cancers. However, due to its
antioxidant effect it seems to interfere with chemo and radiation therapy.7,23
In addition to being an antioxidant, lycopene has been shown to be heart-protective
and lowers LDL cholesterol.23 In one study, lycopene ingestion
showed a reduction in the risk for stroke, especially ischemic strokes in men.24
Finally, lycopene has been linked to a reduction in cardiovascular risks.25
Nutrient Profile26
Macronutrient Profile (Per 1 cup diced watermelon [approx. 152 g]):
46 calories 1 g protein 11.5 g carbohydrate 0.2 g fat
Secondary Metabolites (Per 1 cup diced watermelon
[approx. 152 g]):
Excellent source of:
Vitamin C: 12.3 mg (20.5% DV) Vitamin A: 865 IU (17.3% DV)
Very good source of:
Potassium: 170 mg (4.9% DV)
Also provides:
Magnesium: 15 mg (3.8% DV) Vitamin B-6: 0.07 mg (3.5% DV) Thiamin: 0.05 mg (3.3% DV) Vitamin E: 0.08 mg (3% DV) Manganese: 0.06 mg (3% DV) Dietary Fiber: 0.6 g (2.4% DV) Iron: 0.4 mg (2.2% DV) Phosphorus: 17 mg (1.7% DV) Folate: 5 mcg (1.3% DV) Calcium: 11 mg (1.1% DV)
DV = Daily Value as established by the US Food and Drug
Administration, based on a 2,000-calorie diet.
Recipe: Pickled Watermelon Rinds
Adapted from Bon Appétit27 For an equally delicious condiment without the wait, use these ingredients to
make watermelon rind chutney: increase sugar to 1 ½ cups, water to 1 cup, and
finely mince the ginger. Bring all ingredients to a boil in a large pan, then
simmer for 45-60 minutes until the rind is translucent and tender and the
liquid reduces and thickens. Remove whole spices before serving.
Ingredients:
-
4 lbs of watermelon
- 1 serrano chili, thinly sliced,
seeds removed if desired
- 1-inch piece of fresh ginger,
peeled and thinly sliced
- 2 star anise pods
- 1 tablespoon kosher salt
- 1 teaspoon black peppercorns
- 1 cup sugar
- 1 cup apple cider vinegar
Directions:
- Using a vegetable peeler, remove the tough green outer rind
from watermelon; discard.
- Slice watermelon into 1”-thick slices. Cut away all but 1/4” of
flesh from each slice; reserve flesh for another use. Cut rind into 1”
pieces for roughly 4 cups of rind.
- Bring chili, ginger, star anise, salt, peppercorns, sugar,
vinegar, and 1/2 cup of water to a boil in a large, non-reactive saucepan,
stirring to dissolve sugar and salt.
- Add watermelon rind. Reduce heat and simmer until just tender,
about 5 minutes. Remove from heat and let cool to room temperature,
setting a small lid or plate directly on top of rind to keep submerged in
brine, if needed.
- Transfer rind and liquid to an airtight container; cover and
chill at least 12 hours.
References
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- Watermelons
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- Kiple AF,
Ornelas KC. The Cambridge World History
of Food. Cambridge, UK: Cambridge University Press; 2000.
- FAQs: Fun
Facts. National Watermelon Promotion Board site. Available here. Accessed June 22, 2015.
- Pons L.
Exploring Important Medicinal Uses for Watermelon Rinds. February 21, 2003.
United States Department of Agriculture website. Available here. Accessed June 22, 2015.
- Santa Ana R.
Watermelon May Have Viagra-Effect: Secrets of Phyto-nutrients Are Being
Unraveled. June 30, 2008. AgriLife website. Available here. Accessed June 22,
2015.
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RB, Pajkovic N. Multitargeted therapy of cancer by lycopene. Cancer Letters. 2008;269(2):339-351.
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Exploring the actions of vitamin C. US
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Beta-carotene. June 21, 2013. University of Maryland Medical Center website.
Available here. Accessed June 22,
2015.
- Sefcik, L. Why is
Potassium Important in the Diet? February 18, 2015. Livestrong.com website.
Available here. Accessed June 22, 2015.
- Seth A,
Mossavar-Rahmani Y, Kamensky V, et al. Potassium intake and risk of stroke in
women with hypertension and nonhypertension in the Women's Health Initiative. Stroke. 2014;45(10):2874-80.
- Bahri S, Zerrouk N,
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therapeutic use. Nutrition.
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- Diaz M, Viegas J,
Martins M, Aguayo E. Bioactive compounds from flesh and by-product of fresh-cut
watermelon cultivars. Journal of the
Science of Food and Agriculture. 2010;91(5):805-812.
- Weil, A. Vitamin
Library: Lycopene. Andrew Weil, MD website. Available here. Accessed June 22, 2015.
- Gordestsky J,
O’Brien J. Urology and the scientific method in ancient Egypt. Urology. 2009;73(3):476-479.
- Pieroni A, Gray C.
Herbal and food folk medicines of Russlanddeutschen living in
Kunzelsau/Talacker, south-western Germany. Phytotherapy
Research. 2008;22(7):889-901.
- Pitchford P. Healing with Whole Foods. Berkeley,
California: North Atlantic Books; 1993.
- Meyer-Rochow V. Food
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- An African Native of
World Popularity. Our Vegetable Travelers.
Texas A&M University; 2000. Available here. Accessed June 22, 2015.
- Figueroa A,
Sanchez-Gonzalez M, Wong A, Arjmandi B. Watermelon extract supplementation
reduces ankle blood pressure and carotid augmentation index in obese adults
with prehypertension or hypertension. American
Journal of Hypertension. 2012;25(6):640-643.
- Morris M. Arginases
and arginine deficiency symptoms. Curr
Opin Clin Nutr Metab Care. 2012;15(1):64-70.
- Seren S, Liberman R,
Bayraktar U, et al. Lycopene in cancer prevention and treatment. American Journal of Therapeutics.
2008;15(1):66-81.
- Karppi J, Laukkanen
J, Sivenius J, Ronkainen K, Kurl S. Serum lycopene decreases the risk of stroke
in men: A population-based study. Neurology.
2012;79(15):1540-1547.
- Palozza P, Catalano
A, Simone RE, et al. Effect of lycopene and tomato products on cholesterol
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Watermelon, raw. Agricultural Research Service, United States Department of
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