The watermelon is a large fruit, known scientifically as Citrullus lanatus.
It originates from southern Africa, and is related to cantaloupe melons, zucchinis, pumpkins and cucumbers.
Watermelon is packed with water and nutrients, contains very few calories and is exceptionally refreshing and juicy.
It is also a good dietary source of both citrulline and lycopene, two very powerful plant compounds.
Eating watermelon or drinking watermelon juice may have several health benefits, including lower blood pressure, improved insulin sensitivity and reduced muscle soreness.
While watermelons are most commonly eaten fresh, they can also be made into juice or added to smoothies.
Watermelon consists mostly of water (91%) and carbs (7.5%). It contains almost no protein or fat, and is very low in calories.
The table below contains information on all the main nutrients in watermelon ().
Watermelon contains 7.5 grams of carbs in 100 grams, or 12 grams of carbs per cup.
The carbs are mostly simple sugars, such as glucose, fructose and sucrose. Watermelon also contains a small amount of fiber.
The glycemic index of watermelons ranges from 72-80, which is high (). It is a measure of how quickly foods raise blood sugar levels after meals.
However, each serving of watermelon is relatively low in carbs, so eating it should not have a major effect on blood sugar levels.
Watermelon is a poor source of fiber (0.4 grams per 100 grams).
However, it is considered high in fermentable short-chain carbohydrates, referred to as FODMAPs.
FODMAPs can cause unpleasant digestive symptoms in individuals who cannot digest them, such as those with irritable bowel syndrome.
Bottom line: Watermelon is low in calories and fiber and consists mostly of water and simple sugars. It also contains FODMAPs, which may cause digestive problems in some people.
Vitamins and Minerals
Watermelon is a good source of vitamin C, and also a decent source of several other vitamins and minerals.
- Vitamin C: An antioxidant that is essential for skin health and immune function (, ).
- Potassium: A mineral that is important for blood pressure control and heart health ().
- Copper: A mineral that is most abundant in plant foods, and often lacking in the Western diet ().
- Vitamin B5: Also known as pantothenic acid. This vitamin is found in almost all foods to some extent.
- Vitamin A: Watermelon contains beta-carotene, which is transformed into vitamin A in the body.
Bottom line: Watermelon is a good source of vitamin C, and contains decent amounts of potassium, copper, vitamin B5 and vitamin A (from beta-carotene).
Other Plant Compounds
Watermelon is a poor source of antioxidants compared to other fruits ().
However, it is a good source of the amino acid citrulline, and the antioxidant lycopene, which have numerous benefits for health ().
Watermelon is the richest known dietary source of the amino acid citrulline. The highest amount is found in the white rind that surrounds the flesh (, , ).
In the body, citrulline is transformed into the essential amino acid arginine.
Both citrulline and arginine play an important role in the synthesis of nitric oxide (NO), which helps to lower blood pressure by dilating and relaxing our blood vessels ().
Arginine is also important for many organs, such as the lungs, kidneys, liver, and the immune and reproductive systems, and has been shown to facilitate the healing of wounds (, , ).
Studies have shown that watermelon juice is a good source of citrulline, and is able to increase blood levels of both citrulline and arginine considerably (, , ).
Despite being one of the best dietary sources of citrulline, one would have to consume about 5 pounds (2.3 kg) of watermelons to meet the recommended daily intake for arginine ().
Watermelon is the best known fresh source of lycopene, a powerful antioxidant responsible for its red color (, , , ).
Lycopene is used to some extent to form beta-carotene in the body, which is converted into vitamin A.
Lycopene is generally associated with tomatoes, but fresh watermelon is actually a better source of lycopene than fresh tomato ().
Human studies have shown that fresh watermelon juice is effective at raising blood levels of both lycopene and beta-carotene ().
Bottom Line: Watermelon is a good source of two beneficial plant compounds, the amino acid citrulline and the antioxidant lycopene.
Health Benefits of Watermelons
Watermelons and watermelon juice have been linked with several health benefits.
Lower Blood Pressure
High blood pressure is a major risk factor for chronic disease and premature death ().
Watermelon is a good source of citrulline, which is converted into arginine in the body. Both of these amino acids help in the production of nitric oxide.
Nitric oxide is a gas molecule that causes the tiny muscles around the blood vessels to relax and dilate. This leads to a reduction in blood pressure ().
Supplementation with watermelon or watermelon juice has been shown to reduce blood pressure and arterial stiffness in people with high blood pressure (, , , ).
Reduced Insulin Resistance
Insulin is a very important hormone in the body, and is tightly involved in blood sugar control.
Insulin resistance is the condition in which the body produces insulin, but the cells become resistant to its effects. This can lead to elevated blood sugar levels and is linked to metabolic syndrome and type 2 diabetes.
Watermelon juice and arginine intake have been linked with reduced insulin resistance in some studies (, , ).
Reduced Muscle Soreness After Exercise
Muscle soreness is a well known side effect of strenuous exercise.
One study showed that watermelon juice was effective in decreasing muscle soreness following exercise ().
Several studies have also investigated the effect of watermelon juice or citrulline on exercise performance.
One study found no effect (), and another study found improved performance in untrained, but not well-trained individuals ().
Bottom line: Watermelon may reduce blood pressure and insulin resistance in some people. It is also linked to reduced muscle soreness after exercise.
Watermelon is well tolerated by most people.
However, it may cause allergic reactions or digestive problems in some individuals.
Allergy to watermelon is rare, but it may cause oral-allergy syndrome in individuals who are sensitive to pollen (, ).
The symptoms include itchy mouth and throat, swelling of the lips, mouth, tongue, throat, and sometimes ears ().
Watermelon contains FODMAPs, short-chain carbohydrates that some people cannot digest.
FODMAPs may cause unpleasant digestive symptoms, such as bloating, gas, stomach cramps, diarrhea or constipation.
Individuals who are sensitive to FODMAPs, such as those with , should consider avoiding watermelons.
Bottom Line: Watermelon may cause oral-allergy syndrome in individuals with pollen allergy. It also contains FODMAPs, which can cause unpleasant digestive symptoms in some people.
Watermelon is an exceptionally healthy fruit.
It is loaded with citrulline and lycopene, two powerful plant compounds that have been linked to lower blood pressure, improved metabolic health and decreased muscle soreness after exercise.
It also has a sweet and delicious taste, and is packed with water, making it excellent for maintaining good hydration.
For the vast majority of people, watermelon is a perfect addition to a healthy diet.
It is particularly refreshing on a hot summer day, and may be considered the ultimate summer fruit.