Six Little-Known Risks Linked to Overeating Watermelon

Watermelon is celebrated for its summer sweetness and 92 percent water content, yet researchers and clinicians say the fruit can trigger adverse reactions in certain people—especially when consumed in large quantities or used as the foundation of single-food “cleanse” diets.

Below are six documented concerns:

1. Digestive distress  

Watermelon is high in fructose. Individuals with irritable bowel syndrome or a hereditary fructose-intolerance disorder may experience bloating, cramps, constipation or diarrhea after eating the fruit. In rare untreated cases of fructose intolerance, excess fructose can contribute to kidney or liver damage.² ³

2. Potassium overload  

One cup of diced watermelon supplies roughly 170 mg of potassium. For most people that is harmless, but patients with chronic kidney disease, heart failure or Type 1 diabetes—and anyone taking potassium-sparing diuretics—could accumulate too much of the mineral, leading to hyperkalemia. The condition can disrupt heart rhythm, cause muscle weakness and in severe cases require emergency care.⁶ ⁷

3. Blood-sugar spike  

Watermelon’s glycaemic-index score ranges from 74 to 80. Large servings may temporarily raise blood glucose, although the overall glycaemic load remains modest at 8. Experts advise people with diabetes to treat the fruit as an occasional, portion-controlled carbohydrate source.⁸ ⁹

4. Allergic reactions  

Allergy is uncommon but possible, particularly among individuals sensitive to grass or ragweed pollens. Symptoms can range from oral itching to full anaphylaxis. One published case described an 11-year-old boy who experienced repeated anaphylactic episodes after eating watermelon seeds.¹⁰–¹³

5. Migraine triggers  

Watermelon is rich in tyramine, an amino-acid derivative implicated in some food-induced migraines. In a survey of nearly 4,000 adults, about 30 percent reported headache onset within minutes of eating the fruit.¹⁴

6. Temporary skin discoloration  

Excessive intake of Lycopene-rich foods, including watermelon, can cause Lycopenemia—a benign orange tint to the skin. The discoloration fades once Lycopene consumption is reduced.¹⁵ ¹⁶

How much is safe?  

U.S. dietary guidelines recommend 1.5 to 2 cups of fruit per day; moderate watermelon portions fit comfortably within that allotment and can aid hydration and heart health.17-19 Nutritionists caution, however, that “watermelon-only” cleansing regimens lack protein, vitamin E and several B-vitamins, posing a risk of nutrient deficiency.

Consumers who experience gastrointestinal upset, unusual fatigue, tingling or discoloration after eating watermelon should consult a clinician to rule out underlying conditions and to discuss balanced dietary alternatives.