Side Effects of Eating Too Much Watermelon

Loaded with potassium, magnesium and vitamin C, watermelon keeps you hydrated and balances your electrolyte levels — but you still need to be mindful of portion sizes. Eating too much watermelon may cause bloating and digestive discomfort, among other symptoms.

Consuming large amounts of watermelon might cause side effects in some people. (Image: Anaiz777/iStock/GettyImages)

Watermelon Nutrition Facts

If you've ever been on a diet, you know that watermelon can be a good ally in the battle against the bulge. This refreshing summer fruit is over 90 percent water, filling you up quickly. Plus, it's chock-full of vitamins, minerals and antioxidants that fuel your energy and support overall health.

The calories in watermelon are negligible. A large wedge (about 9.8 ounces), which equals one serving, has only 84 calories and 21 grams of carbs, including 1 gram of fiber and 17 grams of sugars. Although this fruit is low in protein, it boasts high doses of vitamin A, vitamin C and minerals. Each serving provides the following nutrients:

  • 84 calories
  • 21.1 grams of carbs
  • 1.7 grams of protein
  • 0.4 grams of fat
  • 1.1 grams of fiber
  • 25 percent of the DV (daily value) of vitamin C
  • 9 percent of the DV of vitamin A
  • 8 percent of the DV of thiamin
  • 13 percent of the DV of copper
  • 7 percent of the DV of potassium
  • 7 percent of the DV of magnesium
  • 5 percent of the DV of manganese
  • 2 percent of the DV of calcium

As you see, watermelon is particularly high in vitamin C. This nutrient supports normal growth and development, tissue repair, iron absorption and wound healing, reports the U.S National Library of Medicine. It also serves as an antioxidant, protecting your cells from free-radical damage.

Vitamin C also benefits your brain, according to a December 2015 review published in Frontiers in Physiology. It promotes neuronal survival and differentiation while protecting the brain against oxidative stress. Low vitamin C levels may put you at risk for anemia, joint pain, gingivitis and weight gain, as the U.S National Library of Medicine points out.

Too much of anything can harm your health — and watermelon is no exception. Despite its high nutritional value, this fruit isn't free of side effects.

Watermelon and Diarrhea

Diarrhea is a common side effect of eating too much watermelon. This digestive problem can have several causes.

The Illinois Department of Public Health warns about the dangers of pre-cut melons. These fruits might be contaminated with Salmonella, a bacterium that causes stomach pain, fever and severe diarrhea. To stay safe, purchase whole melons and wash them thoroughly before consumption.

This fruit is also rich in lycopene, a potent antioxidant that may protect against diabetes, hypercholesterolemia, osteoporosis and other health conditions due to its free radical scavenging activity. According to a June 2014 review featured in the EXCLI Journal, red-fleshed watermelon contains 40 percent more lycopene than tomatoes.

This naturally occurring compound, though, may cause gas, diarrhea and bloating in some individuals. Nausea and vomiting are common too. In a study cited by the National Cancer Institute, these symptoms subsided when lycopene was taken with food. However, researchers used lycopene supplements, which are more concentrated than watermelon and other lycopene-rich fruits and hence more likely to cause side effects.

Digestive Discomfort and Cardiovascular Problems

In addition to diarrhea, eating too much watermelon may cause bloating and digestive distress. That's mostly due to its high water content. If you eat three or four wedges in one serving, you'll ingest about 27 to 36 ounces of water plus fiber. Therefore, it's normal to feel bloated and gassy afterward.

Luckily, watermelon boasts high doses of vitamin C, which acts as a natural diuretic, reports Johns Hopkins Medicine. This means that you'll eliminate the excess water quite fast and regain your flat tummy.

Other adverse reactions are related to high potassium intakes. Each serving of watermelon provides 7 percent of the daily recommended allowance for this mineral, so overdosing is unlikely.

However, if your diet is already high in potassium and you eat too much watermelon, you may develop hyperkalemia. Individuals with kidney disease or poorly controlled diabetes are at greater risk. The same goes for those taking medications that prevent the kidneys from excreting potassium.

According to the American Heart Association, excess potassium in the bloodstream may affect cardiovascular function, leading to arrhythmias (irregular heartbeat). You may also experience diarrhea, abdominal pain, numbness and mood changes.

The best thing you can do is to prevent these issues in the first place. Enjoy watermelon in moderation as part of a healthy diet. Beware of its sugar content, too. If you overindulge, you might end up gaining weight.

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