The watermelon (Citrullus lanatus) is a large, sweet fruit originally from southern Africa. It’s related to cantaloupe, zucchini, pumpkin, and cucumber.

Watermelon is packed with water and nutrients, contains very few calories, and is exceptionally refreshing.

What’s more, it’s a good dietary source of both citrulline and lycopene, two powerful plant compounds.

This juicy melon may have several health benefits, including lower blood pressure, improved insulin sensitivity, and reduced muscle soreness.

While watermelons are predominantly eaten fresh, they can also be frozen, made into juice, or added to smoothies.

This article tells you everything you need to know about watermelon.

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Watermelon consists mostly of water (91%) and carbs (7.5%). It provides almost no protein or fat and is very low in calories.

The nutrients in 2/3 cup (100 grams) of raw watermelon are (1):

  • Calories: 30
  • Water: 91%
  • Protein: 0.6 grams
  • Carbs: 7.6 grams
  • Sugar: 6.2 grams
  • Fiber: 0.4 grams
  • Fat: 0.2 grams

Carbs

Watermelon contains 12 grams of carbs per cup (152 grams).

The carbs are mostly simple sugars, such as glucose, fructose, and sucrose. Watermelon also provides a small amount of fiber.

The glycemic index (GI) — a measure of how quickly foods raise blood sugar levels after meals — of watermelons ranges from 72–80, which is high (2).

However, each serving of watermelon is relatively low in carbs, so eating it should not have a major effect on blood sugar levels.

Fibers

Watermelon is a poor source of fiber, providing only 0.4 grams per 2/3 cup (100 grams).

However, due to its fructose content, it is considered high in FODMAPs, or fermentable short-chain carbohydrates (3).

Eating high amounts of fructose can cause unpleasant digestive symptoms in individuals who cannot fully digest them, such as those with fructose malabsorption (4).

SUMMARY Watermelon is low in calories and fiber and consists mostly of water and simple sugars. It also contains FODMAPs, which cause digestive problems in some people.

Watermelon is a good source of vitamin C and a decent source of several other vitamins and minerals.

  • Vitamin C. This antioxidant is essential for skin health and immune function (5, 6).
  • Potassium. This mineral is important for blood pressure control and heart health (7).
  • Copper. This mineral is most abundant in plant foods and often lacking in the Western diet (8).
  • 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 your body can turn into vitamin A.
SUMMARY Watermelon is a good source of vitamin C and contains decent amounts of potassium, copper, vitamin B5, and vitamin A (from beta carotene).

Watermelon is a poor source of antioxidants compared to other fruits (9).

However, it’s rich in the amino acid citrulline and the antioxidant lycopene, which have numerous benefits for health (10).

Citrulline

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 (9, 11, 12).

In your body, citrulline is transformed into the essential amino acid arginine.

Both citrulline and arginine play an important role in the synthesis of nitric oxide, which helps lower blood pressure by dilating and relaxing your blood vessels (13).

Arginine is also important for many organs — such as your lungs, kidneys, liver, and immune and reproductive systems — and has been shown to facilitate wound healing (14, 15, 16).

Studies note that watermelon juice is a good source of citrulline and can increase blood levels of both citrulline and arginine considerably (15, 17, 18).

Though watermelon is one of the best dietary sources of citrulline, you would have to consume about 15 cups (2.3 kg) at once to meet the Reference Daily Intake (RDI) for arginine (19).

Lycopene

Watermelon is the best known fresh source of lycopene, a powerful antioxidant responsible for its red color (20, 21, 22, 23).

In fact, fresh watermelon is a better source of lycopene than tomatoes (1).

Human studies show that fresh watermelon juice is effective at raising blood levels of both lycopene and beta carotene (24).

Your body uses lycopene to some extent to form beta carotene, which is then converted into vitamin A.

SUMMARY Watermelon is a good source of the amino acid citrulline and the antioxidant lycopene, which play important roles in your body.

Watermelons and their juice are linked to several health benefits.

Lower Blood Pressure

High blood pressure is a major risk factor for chronic disease and premature death (25).

Watermelon is a good source of citrulline, which is converted into arginine in your body. Both of these amino acids aid nitric oxide production.

Nitric oxide is a gas molecule that causes the tiny muscles around your blood vessels to relax and dilate. This leads to a reduction in blood pressure (26).

Supplementing with watermelon or its juice may reduce blood pressure and arterial stiffness in people with high blood pressure (27, 28, 29, 30).

Reduced Insulin Resistance

Insulin is a vital hormone in your body and involved in blood sugar control.

Insulin resistance is the condition in which your cells become resistant to the effects of insulin. This can lead to elevated blood sugar levels and is linked to metabolic syndrome and type 2 diabetes.

Watermelon juice and arginine intake are associated with reduced insulin resistance in some studies (31, 32, 33).

Reduced Muscle Soreness After Exercise

Muscle soreness is a well-known side effect of strenuous exercise.

One study showed that watermelon juice is effective at decreasing muscle soreness following exercise (34).

Research on watermelon juice (or citrulline) and exercise performance gives mixed results. One study found no effect, while another observed improved performance in untrained — but not well-trained — individuals (35, 36).

SUMMARY 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

Allergy to watermelon is rare and usually associated with oral-allergy syndrome in individuals who are sensitive to pollen (37, 38).

Symptoms include itchy mouth and throat, as well as swelling of the lips, mouth, tongue, throat, and/or ears (39).

FODMAPs

Watermelon contains relatively high amounts of fructose, a type of FODMAP that some people do not fully digest.

FODMAPs like fructose may cause unpleasant digestive symptoms, such as bloating, gas, stomach cramps, diarrhea, and constipation.

Individuals who are sensitive to FODMAPs, such as those with irritable bowel syndrome (IBS), should consider avoiding watermelons.

SUMMARY Allergy to watermelons is rare but does exist. This fruit also contains FODMAPs, which may cause unpleasant digestive symptoms.

Watermelon is an exceptionally healthy fruit.

It’s loaded with citrulline and lycopene, two powerful plant compounds linked to lower blood pressure, improved metabolic health, and decreased muscle soreness after exercise.

What’s more, it’s sweet, delicious, and 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.