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Can You Overdose on Nuts?

Woman pouring a variety of nuts into her hand

When your stomach rumbles between meals, a handful of nuts is a quick snack that’s tasty and good for you. Delicious and nutritious, nuts are full of fiber, high in protein and contain minerals, antioxidants, healthy fats and other compounds that can greatly benefit your health. And unlike other popular snacks, they are more likely to satisfy your appetite and keep you from reaching for more, less healthy foods.

Nutty for Nuts? Don’t Overdo It

The expression “everything in moderation” is especially important when talking about nut consumption. Because they are such a nutrient- and calorie-dense food, portion control is essential to avoid excess weight gain. More importantly, eating too many nuts can actually lead to food toxicity which can range from mild symptoms to severe illness. In addition, many nut varieties contain the amino acid L-Arginine, which can cause mouth ulcers if you over-indulge.

The health benefits of nuts vary depending on which type you eat, but a daily serving of nuts generally helps to:

  • Support heart and vascular health
  • Reduce risk of stroke
  • Enhance digestion
  • Contribute to healthier skin
  • Reduce blood clotting
  • Help curb the appetite

In addition, some studies have shown that when a handful of nuts is eaten as a replacement for less-healthy foods, it may help prevent obesity.

In general, one ounce of nuts a day is the guideline most dietitians recommend for people without medical contraindications or nut allergies. Some common snack nuts are discussed in more detail below:

Almonds are often referred to as a “super food” and rightly so. They contain high amounts of calcium, vitamin E, potassium and magnesium and some research suggests that consuming almonds daily may help reduce blood levels of bad (LDL) cholesterol and triglycerides.

Eating too many, too often, however, can affect the efficiency of the liver and contribute to kidney stones.

Recommendation: One ounce (24 almonds) per day.

Brazil Nuts – Proceed with Caution
These large, tropical nuts are the exception to the one-ounce-of-nuts-a-day rule because they contain highly concentrated amounts of the trace mineral selenium. In fact, one ounce of Brazil nuts (approximately 8 medium nuts) contains 544 micrograms of selenium, which is 777 percent of the recommended daily allowance. 

Eating too many Brazil nuts can lead to toxic levels of selenium in the body (selenosis) and cause symptoms such as bad breath, diarrhea, nausea, skin rashes/lesions, nerve pain and fatigue. In rare cases, very high levels can cause kidney failure, cardiac arrest and even death.

Recommendation: No more than one or two Brazil nuts in one day, eaten only occasionally.

One of the most delicious and popular snack nuts, cashews are a good source of protein, healthy fats, fiber and minerals like magnesium, copper, manganese and zinc. Moderate consumption of cashews may help boost the immune system, improve energy levels and support brain and bone health.

Side effects from eating cashews are very rare; however, regularly eating far more than the recommended amount may lead to digestive symptoms such as bloating or constipation/diarrhea, headache and joint swelling. Keep in mind that about 20 percent of the fat content in cashews is saturated fat, which is much higher than most other nuts, so portion size is especially important.

Recommendation: One ounce (18 medium) cashews per day.

Peanuts are probably the most common snack nut, readily available and more affordable than many other nut varieties. They are also an extremely common food allergen – those with a peanut allergy must be very careful not to consume even trace amounts of peanuts. For the non-allergic, peanuts are an affordable and nutrient-rich source of healthy fats, protein, fiber, potassium, phosphorous, magnesium and B vitamins.

Their small size, however, makes it easy to overindulge and eat them by the handful, which can lead to weight gain and/or uncomfortable digestive symptoms. In addition, consumers should make every effort to buy peanuts that have been grown and packaged in the United States. Those produced in parts of Africa and Asia are more likely to have been exposed to aflatoxin – a fungus associated with liver cancer.

Recommendation: One ounce (35) peanuts per day.

Like almonds, pecans are considered by many nutritionists to be a superfood. They are rich in calcium, zinc, magnesium and iron and possess more antioxidants than any other tree nut. Some research suggests that eating pecans regularly can boost your immune system, help fight the development of cancer and cardiovascular disease, and even reduce hair loss. Pecans are also great for vegetarians because they make an excellent, high-protein substitute for meat.

Like many other nuts, pecans contain a high percentage of fat and can lead to diarrhea if too many are eaten in a short amount of time. Over-consumption may also lead to digestive issues like gas and bloating.

Recommendation: One ounce (15-19) pecan halves per day.

Like pecans, walnuts are very high in antioxidants and contain more omega-3 fats than any other nut. Research has shown that eating moderate amounts of walnuts can aid in digestion, reduce risk of heart disease, decrease inflammation and support brain health.

Excessive consumption of walnuts may cause diarrhea, bloating, stomach pain or kidney stones. Due to the phytic acid they contain, too many walnuts may also inhibit the absorption of dietary iron, calcium and zinc.

Recommendation: One ounce (10-14) English walnut halves per day.

How to Safely Add Nuts to Your Diet

“Nuts can be an excellent and healthy addition to your diet. In general, it is safe and beneficial to eat one ounce of most nuts (not Brazil nuts) per day but portion control is essential to avoid side effects and consuming more calories than you need,” says Jessica Jurcak, registered dietitian and Manager of Whole Health and Well-Being for University Hospitals. “A good idea is to buy your nuts in bulk and divide them into single-serving-size portions to avoid eating too many at once,” she adds.

“Follow the serving size recommendations above and always choose unsalted or lightly salted varieties,” says Jurcak. “Too much sodium can, in the short-term, dry out your mouth lining and cause slight inflammation. And, in the long-term, it can contribute to the development of high blood pressure, a serious health condition. To enhance the flavor of unsalted nuts, I recommend combining them with another food group, such as almonds and berries, pecans and low-fat Greek yogurt, or peanuts and dark chocolate,” she adds.

Because nuts are such a common food allergen, when trying a nut for the first time, start with a small amount and watch for any reaction. In addition, it may be possible that some of the compounds in certain nuts may interact with some medications. If you have any concerns, talk to your doctor or pharmacist about which nuts can safely be added to your diet.

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University Hospitals has a team of clinical dietitians with the knowledge and experience to help you achieve total, balanced nutrition; reach or maintain an optimum weight; and prevent or manage chronic health conditions through dietary strategies.