Walnuts are nutrient-dense, containing omega-3 fats, antioxidants, and other compounds that may help protect against brain decline, heart disease, and cancer.

Walnuts, also called Juglans regia, are a type of tree nut. They originated in the Mediterranean region and Central Asia and have been part of the human diet for thousands of years.

There are a few edible walnut species. This article is about the common walnut — sometimes referred to as the English or Persian walnut — which is grown worldwide.

Here’s everything you need to know about the common walnut.

Walnuts are made up of 65% fat and about 15% of protein. They’re low in carbs — most of which consist of fiber.

A typical serving of 7 walnuts provides the following nutrients:

  • Calories: 183
  • Water: 4%
  • Protein: 4.26 grams (g)
  • Carbs: 3.84 g
  • Sugar: 0.68 g
  • Fiber: 1.88 g
  • Fat: 18.3 g

Fats

Walnuts contain about 65% fat by weight.

Like other nuts, most of the calories in walnuts come from fat. This makes them an energy-dense, high-calorie food.

However, even though walnuts are rich in fat and calories, studies indicate that they don’t increase obesity risk when replacing other foods in your diet.

Walnuts are also richer than most other nuts in polyunsaturated fats. The most abundant one is an omega-6 fatty acid called linoleic acid.

They also contain a relatively high percentage of the healthy omega-3 fat alpha-linolenic acid (ALA). ALA is considered especially beneficial for heart health. It also helps reduce inflammation and improve the composition of blood fats.

What’s more, ALA is a precursor for the long-chain omega-3 fatty acids EPA and DHA, which have been linked to numerous health benefits.

Walnuts are an excellent source of several vitamins and minerals, including:

  • Copper. This mineral promotes heart health. It also helps maintain bone, nerve, and immune system function.
  • Folic acid. Also known as folate or vitamin B9, folic acid has many important biological functions. Folic acid deficiency during pregnancy may cause birth defects.
  • Phosphorus. Walnuts contain phosphorus, a mineral that is mainly present in bones. It has numerous functions, including helping the formation of bones and teeth.
  • Manganese. This trace mineral is found in the highest amounts in nuts, whole grains, fruits, and vegetables.
  • Vitamin E. Compared to other nuts, walnuts contain high levels of a special form of vitamin E called gamma-tocopherol.

Walnuts contain a complex mixture of bioactive plant compounds.

They’re exceptionally rich in antioxidants, including:

  • Ellagic acid. This antioxidant is found in high amounts in walnuts, along with other related compounds like ellagitannins. Ellagic acid may reduce your risk of heart disease and cancer.
  • Catechin. Catechin is a flavonoid antioxidant that may have various health benefits, including promoting heart health.
  • Melatonin. This neurohormone helps regulate your body clock. It’s also a powerful antioxidant that may reduce your risk of heart disease.
  • Phytic acid. Phytic acid, or phytate, is a beneficial antioxidant, though it can reduce the absorption of iron and zinc from the same meal — an effect that’s only of concern for those following imbalanced diets.

Walnuts are linked to a number of health benefits. They have been associated with a reduced risk of heart disease and cancer, as well as improved brain function.

Heart health

Heart disease — or cardiovascular disease — is a broad term used for chronic conditions related to the heart and blood vessels.

In many cases, your risk of heart disease can be reduced with healthy lifestyle habits, such as eating nuts.

Walnuts are no exception. In fact, eating walnuts may combat risk factors for heart disease by:

  • lowering LDL (bad) cholesterol
  • reducing inflammation
  • improving blood vessel function, thus cutting the risk of plaque buildup in your arteries

These effects are likely caused by the beneficial fat composition of walnuts, as well as their rich antioxidant content.

Cancer prevention

Cancer is a group of diseases characterized by abnormal cell growth.

Your risk of developing certain types of cancer can be reduced by eating healthy food, exercising, and avoiding unhealthy lifestyle habits.

Since walnuts are a rich source of beneficial plant compounds, they could be an effective part of a cancer-preventive diet.

Walnuts contain several bioactive components that may have anticancer properties, including:

  • phytosterols
  • gamma-tocopherol
  • omega-3 fatty acids
  • ellagic acid and related compounds
  • various antioxidant polyphenols

Research in animals has linked the regular consumption of nuts to a lower risk of colon, breast, and prostate cancer.

However, before any solid conclusions can be reached, these effects need to be confirmed by clinical studies in humans.

Brain health

Several studies indicate that eating nuts may improve brain function. They also show that walnuts can help with depression and age-related decline in brain function.

These effects on brain health are likely due to the high antioxidant content of walnuts, though their omega-3 fatty acids may play a role as well.

In general, walnuts are considered very healthy, but some people need to avoid them due to allergies.

Walnut allergy

Walnuts are among the most allergenic foods.

Symptoms of a walnut allergy are typically severe and can include allergic shock (anaphylaxis), which can be fatal without treatment.

Individuals with a walnut allergy need to avoid these nuts completely.

Reduced mineral absorption

Like all seeds, walnuts are high in phytic acid.

Phytic acid, or phytate, is a plant substance that impairs the absorption of minerals — such as iron and zinc — from your digestive tract. This only applies to meals that contain high-phytate foods.

Individuals who follow imbalanced diets rich in phytic acid are at a higher risk of developing mineral deficiencies, but most people shouldn’t need to worry.

Walnuts are rich in heart-healthy fats and high in antioxidants.

What’s more, regularly eating walnuts may improve brain health and reduce your risk of heart disease and cancer.

These nuts are easily incorporated into your diet, as they can be eaten on their own or added to many different foods.

For example, you can add walnuts to oatmeal, salads, or yogurt for an extra crunch. You can incorporate it into a homemade trail mix with dried fruit and seeds.

Simply put, eating walnuts may be one of the best things you can do to improve your health.