Walnuts: 5 Major Side Effects + How Many Walnuts To Eat

Reviewed By Dr. Geeta Dharmatti, M.Sc,Ph.D , Clinical Nutritionist and Registered Dietician, MSc, PhD , Registered Dietitian
Written by Ravi Teja Tadimalla , Professional Certificate In Food, Nutrition & Health

Walnuts are one of the richest sources of antioxidants and other essential nutrients. However, not everyone may enjoy their goodness.

Just like any food, walnuts also may cause certain adverse effects. In this post, we will discuss those effects and find out what research states.

What Are The Side Effects Of Walnuts?

1. Can Cause Digestive Issues

The fiber in the nuts may cause gastrointestinal issues if consumed in excess (1). Though walnuts (and nuts in general) may help treat digestive issues, sometimes, they may aggravate the problem. Hence, please consult your doctor before consuming walnuts if you have any digestive problems.

Other common digestive side effects of tree nuts (including walnuts) include bloating, stomach pain, and diarrhea (2).

In other studies involving walnuts, a few participants reported various forms of gastrointestinal distress, including bloating (3). Consuming more than 1 ounce of walnuts may pose this risk. Walnuts have a high fiber and high fat content (30 grams of walnuts have 2 grams of fiber and 20 grams of fat).

2. May Cause Allergies


Allergies to tree nuts are common. The symptoms include nausea, shortness of breath, difficulty in swallowing, itching of the mouth, throat, or the eyes, and nasal congestion (4).

The most dangerous allergic reaction is anaphylaxis. It impairs breathing and sends the body into a state of shock (4). You may experience either a primary or a secondary allergy with walnuts. Primary allergies involve the direct intake of walnuts or their products, which can lead to anaphylaxis. Secondary allergies involve pollen, which reacts with walnuts due to cross-reactivity (this is because of the similarities in the nature of proteins in the pollen and walnuts). Here, the symptoms include itching or swelling of the mouth (5).

An allergy to walnuts doesn’t necessarily mean you would be allergic to other tree nuts as well. But it is essential to check with your doctor before you consume walnuts or any other tree nut – more so if you are easily susceptible to allergies (6).

3. May Lead To Weight Gain

Walnuts (and nuts, in general) are excellent sources of fiber and can help in weight loss. But they also are high in calories.

Seven walnuts pack about 183 calories (7). Eating them in excess would surely mean more calories and may eventually lead to weight gain.

Studies show that a diet supplemented with walnuts can lead to greater daily energy intake. This can lead to weight gain, although not very significant (8).

One way of countering this is to round out your meal with walnuts instead of having the nuts by themselves because just 4 ounces of walnuts contain over 740 calories (9).

Though they are rich sources of protein, you cannot replace your better protein sources (like meat or eggs) with walnuts. Also, nuts, in general, need to be combined with animal proteins for a complete amino acid profile.

However, some sources suggest that eating more walnuts doesn’t lead to weight gain (10).

Other research also states that walnuts may activate a specific brain region involved in impulse control. This means walnuts may help people have better control over their cravings (11).

Given the mixed findings, we suggest you speak to your doctor about consuming walnuts.

4. May Cause Choking In Children


Almost all nuts (and most foods that are firm) carry the risk of choking in children. These foods are difficult for kids to bite through and break down and swallow safely. Instead, they might get stuck in their airways (12).

As walnuts are comparatively larger than other tree nuts, they may pose a higher risk.

If your child is below 7 years of age, avoid giving them whole nuts as they would be at the risk of choking (13).

5. May Aggravate Ulcers

Since nuts, including walnuts, are high in fiber, they may aggravate ulcers in susceptible individuals (14). However, more research is required to establish this fact.

Like all other nuts, walnuts are healthy. A large body of research highlights their anticancer, anti-inflammatory, cardio- and neuroprotective properties (15).

But it is important to take note of the side effects and practice moderation.

How Many Walnuts Can You Consume In A Day?

There is no scientific consensus on the ideal dosage of walnuts. But an ounce of the nuts (7 whole walnuts) a day should do. You can make them a part of your diet and not overindulge.


Making walnuts a part of your daily diet is important. The nuts have excellent benefits. Instead of having them by themselves, include them in your diet in various forms.

But if you have any medical condition, avoid their intake, and consult your doctor.

Frequently Asked Questions

Should we soak walnuts?

It is important you soak walnuts. Walnuts and other nuts contain phytates. These are natural compounds that hinder the absorption of some essential nutrients. Soaking walnuts can help reduce their phytate content, making them all the more nutritious (16).

You can soak walnuts in a container of fresh saltwater overnight (about eight hours).


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Dr. Geeta Dharmatti, M.Sc,Ph.D

(Clinical Nutritionist and Registered Dietician, MSc, PhD )
Dr. Geeta Dharmatti is the Director and Founder of Geeta Nutriheal Consultancy (Nutrition Services Consultancy) and an Executive Member of... more