Walnuts are one of the most nutritious tree nuts, known for their brain-like shape and high omega-3 content. They’re often used in baking, salads, snacking, and breakfast dishes. But how many calories is a walnut and how does it fit into a healthy diet?

Calories by Weight and Portion Size

Walnuts are energy-dense, meaning they pack a lot of calories into a small volume. A single whole walnut (shelled) weighs around 2.5g and contains approximately 26 calories.

Here’s a general calorie breakdown:

  • 1 whole walnut (shelled, 2.5g): 26 calories
  • 1g of walnut: approx. 10.5 calories
  • 28g (a standard handful or ~14 halves): 185–190 calories
  • 100g walnuts: approx. 650–690 calories

If you’re snacking on them or adding to meals, portion control is key due to their high calorie density.

Nutritional Breakdown of Walnuts

For a standard 28g (1oz) serving of shelled walnuts (about 14 halves), the nutritional profile is:

  • Calories: 185
  • Fat: 18g
  • Saturated fat: 1.7g
  • Monounsaturated fat: 2.5g
  • Polyunsaturated fat: 13g (includes omega-3 ALA)
  • Carbohydrates: 3.9g
  • Of which sugars: 0.7g
  • Fibre: 1.9g
  • Protein: 4.3g
  • Salt: 0g
  • Omega-3 ALA: 2.5g
  • Magnesium: 45mg
  • Vitamin E: 0.2mg

Walnuts are high in healthy fats, particularly alpha-linolenic acid (ALA), an essential omega-3 fatty acid.

Benefits of Walnuts

Walnuts are one of the healthiest nuts you can eat. They support heart health, brain function, and inflammation control thanks to their high polyunsaturated fat content especially omega-3s. ALA in walnuts has been linked to reduced cholesterol and improved blood vessel function.

They also contain antioxidants, magnesium, fibre, and plant-based protein, making them a great food for vegans, vegetarians, and anyone following a Mediterranean-style diet. Eating a small handful regularly has been associated with better weight management and cardiovascular outcomes.

Downsides of Walnuts

Despite their health benefits, walnuts are high in calories and fat. It’s easy to eat a large number of them quickly, which can lead to calorie overconsumption especially when used in trail mixes, desserts, or baking.

They’re also a common allergen, and for those with nut allergies, even a small amount can trigger serious reactions. Additionally, rancidity is a risk with walnuts due to their high fat content, so they should be stored in a cool, dark place or in the fridge for long-term freshness.

Dietary Impact and the GI Index

Walnuts have a glycaemic index (GI) of zero, as they contain very little carbohydrate and do not cause spikes in blood sugar. They are a perfect food for people with diabetes, pre-diabetes, or anyone following a low-GI or low-carb diet.

The fats and fibre in walnuts actually help slow digestion and improve satiety, making them a helpful addition to meals aimed at stabilising energy and appetite.

How Are Walnuts Processed or Prepared?

Walnuts are harvested from the walnut tree and typically sold either in-shell or shelled. The shelled variety is more convenient and more commonly used in cooking and baking. They can be eaten raw, toasted, chopped, or ground.

They are often included in cereals, salads, granola bars, pesto, and plant-based spreads. Roasting enhances flavour but does not significantly change the calorie content—though added oil or salt during roasting will raise calories and sodium levels.

Healthy Alternatives to Walnuts

If you're looking for similar nutrition with slightly fewer calories, almonds, pistachios, or cashews may be good alternatives. For omega-3s, chia seeds and flaxseeds are also excellent plant-based sources.

If you're aiming to reduce calories, using chopped walnuts instead of whole halves lets you stretch smaller amounts through a recipe.

Summary

A single walnut contains around 26 calories, while a standard handful (28g) comes in at 185–190 calories. Rich in healthy fats, protein, and fibre, walnuts are one of the most nutritious nuts available. They have a glycaemic index of zero, making them ideal for blood sugar control. Though high in calories, small portions offer significant health benefits especially for the heart, brain, and metabolism when eaten as part of a balanced diet.

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