Can Walnuts Upset Your Digestive Tract?

Walnuts contain more natural antioxidants and heart-healthy polyunsaturated fats than other types of nuts. In spite of their nutritional benefits, walnuts can upset your digestive tract. They have enough fiber to cause side effects in some cases, and might cause problems if you're especially vulnerable to gastrointestinal distress or you have a walnut intolerance or allergy.

Wallnuts cracked open on a table. (Image: Voyagerix/iStock/Getty Images)

Walnut Intolerance

A food intolerance means you can't properly digest a particular food, reports the American Academy of Allergy, Asthma and Immunology. If you're sensitive to walnuts, they can cause stomach pain, gas and bloating. You may also experience nausea or diarrhea. Even if you have a walnut intolerance, you may not have to miss out on their nutritional benefits. Many people with a food intolerance find that they can enjoy small portions of the food without triggering symptoms. Limiting your intake works well with walnuts considering they're so high in calories: You'll get 185 calories in a 1-ounce serving.

Tree Nut Allergies

Walnuts cause more allergies than any other type of tree nut, according to a report in the International Archives of Allergy and Immunology in 2003. If you're allergic to peanuts, you're at a higher risk for a walnut allergy, and nut allergies may cause life-threatening reactions. Food allergies are known for causing hives, itching and swelling, but gastrointestinal problems can also appear. Symptoms in the digestive tract include nausea, vomiting, cramps, stomach pain and diarrhea. If you have a walnut allergy, you must keep them out of your diet, which includes eliminating walnut-containing processed foods such as baked goods, candies, cereals and granola bars.

Effect of Fiber

The fiber in walnuts is one of their nutritional benefits. On the flip side, they contain just enough fiber to potentially cause side effects. A handful of walnuts, or about 1 ounce, has nearly 2 grams of fiber, which is 8 percent of the daily value based on a 2,000-calorie-a-day diet, according to While the fiber in one portion probably won't cause problems, consuming several servings, or eating walnuts together with other high-fiber foods such as a salad, may cause gas, diarrhea and cramps. Fiber from walnuts can also lead to uncomfortable gas and bloating in people diagnosed with irritable bowel syndrome, reports McKesson Health Solutions.

Suggestions and Benefits

When fiber is the source of your digestive distress, you can still enjoy walnuts by getting your body accustomed to digesting extra fiber. Eat one small serving and wait a few days before eating more, then slowly increase serving size and frequency, up to about 1 to 1.5 ounces daily. In addition to fiber, walnuts provide protein, folate, vitamin B-6, copper and manganese. They have more healthy polyunsaturated fats than other nuts, and they're the only nut with a significant amount of omega-3 fatty acids. One ounce of walnuts delivers more than 100 percent of your recommended daily intake for omega-3s, which fight inflammation and help lower cholesterol.

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