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Everything You Need To Know About Walnuts

Walnuts have been enriching our diets for many centuries, with archeological evidence indicating that we have been eating these nutrient-packed parcels for more than 8000 years - that’s a very long time! A lot may have changed since then, but one thing is for sure, walnuts remain an essential part of the human diet, providing a whole host of nutrients that are essential for our gut microbiome and our overall health. 

Shelled and unshelled walnuts beside each other on a bright wooden table


But where did walnuts originate? How are they grown? What nutritional benefits do they have, and why should you incorporate them into your diet? - We’ll answer these questions and many more in this article, so read on to learn everything you need to know about walnuts. 

What are walnuts? 

Walnuts are in fact, not a nut at all, but are technically the seed of a drupe from any tree in the Juglandaceae family, but don’t let this confuse you. Botanists define nuts as a ‘dry, one-seeded fruit encased in a hardened ovary wall’ making Walnuts, Cashews, Brazil nuts, Pecans, Almonds, Peanuts and Pistachios all technically not nuts! It would be pretty confusing to turn back and to change the classification of all of these not-nuts now, and so instead, we allow them to keep their common name. 


Naming confusion aside, there are around 50 species of plants within the Juglandaceae family; however, the two that produce the walnuts that you are most likely to have eaten are called the Juglans regia, also known as the Persian, English or Common walnut, and the Juglans nigra, also known as the Black walnut. 

Close up of a bunch of unshelled english walnuts

Juglans regia - The English Walnut

The English Walnut is the most common variety of cultivated walnut, favoured for its relatively thin shell, large seed and sweet, mild, nutty flavour. You may also hear the English walnut referred to as a Persian walnut, particularly in South Africa and Australia, or the Common walnut, in Britain. Although the English Walnut may have many names, they all refer to the nut harvested from the Juglans regia tree. Botanists have found it very difficult to pinpoint the exact origin of the English walnut, because the tree is native across a vast expanse of space, from the Balkans all the way eastward to the Himalayas and southwest China, and is now cultivated extensively across much of Europe. There is some speculation that the variety may have originated from Kyrgyzstan, a landlocked country bordered by Kazakhstan to the north, and Uzbekistan to the west and southwest, only due to the extraordinary number of English walnut trees that grow naturally in the area. In contrast, others simply state that the variety began in Persia, hence the name, Persian walnut. Regardless of where the English walnut variety began, it has now made itself at home in countries all across the world, including the US, China, France, Spain and the UK. 

Close up of a bunch of unshelled black walnuts

Juglans nigra - The Black Walnut

Black walnuts are prized for their very intense walnut flavour but are not as popular as their English cousins due to their hard shells and poor hulling characteristics that make them harder to harvest and process. The Juglans nigra species is native to North America and prefers to grow in riparian zones, that is next to a river or a stream as they like the moist conditions, which also makes them harder to grow in cultivated orchards. The Black walnut variety was introduced into Europe in the mid 16th century and is still cultivated for its flavoursome nuts as well as its quality wood today. Although it may not be as popular as the English walnut, it remains the second most profitable walnut variety. 

Walnuts through history

Walnuts have a deep and rich history and have been providing sustenance to humans and animals for many years, with some sources claiming walnuts to be the oldest form of tree food in the world. The first archaeological evidence of humans eating walnuts is from a Neolithic site in southwest France, where roasted walnut shells were uncovered dating back as far as 8000 years. Our ancient ancestors were likely choosing to roast their walnuts to make it easier for them to break through their tough shells, ultimately enjoying the nutritious roasted nut within one the husks had become dry and brittle. 


In terms of walnut cultivation, our first historical account of walnut trees being grown for their nuts dates back to 2000BC in Babylon (now known as Iran), with the selective breeding of walnuts beginning later with the Ancient Greeks who valued them as a nutrient-packed addition to their diets. 


As the popularity of the walnut grew, it was transported and cultivated across Europe and into parts of North Africa by the Romans on the Silk Road, eventually being cultivated in the north of England by the middle ages. Despite people eating English walnuts all across the world for many centuries, America had to wait until the early 1800s for their first taste of the Juglans regia variety, which was transported from England to the US by ship, hence the name English Walnut in this region. 


Today, walnuts are cultivated on a colossal scale, with the annual harvest totalling more than 3.8 million tonnes! China remains the single largest walnut producer, followed by the USA, Iran and Turkey, with Ukraine, Romania, France and Italy producing significant quantities in Europe. Despite its name as the English Walnut, the British walnut industry has been declining steadily since the 18th century and now only continues on a small scale in a very select few counties. 


To maximise yield and to reduce susceptibility to disease, a lot of research has been put into the selective breeding of more than 300 cultivars of the Juglans regia walnut, producing walnut trees that can be cropped at a young age and whose fruit ripens early to produce more yield. A lot has changed for the walnut tree since its first cultivation by the ancient Greeks, but thankfully the delicious nutrient-packed snack waiting within its husk remains mostly the same and unchanged.

Walnut fruit on walnut tree

How are walnut trees grown and how are walnuts produced? 

Walnut trees are prized for their nuts and for their wood, but to ensure a maximum yield of both products, high-quality nuts and beautiful walnut wood are generally not harvested from the same tree. The walnut cultivation process is not a short one, with most walnut trees taking approximately ten years to begin processing nuts and a further 20 years to reach their maximum production. Grafting and selective breeding have helped to reduce this time, but in most cases, a thriving walnut orchard will take several decades to begin bearing a profit. For those looking to harvest wood, it can take up to 50 years for a tree to mature enough for harvest, with some of the best trees growing for more than 80 years before being cut!


Once mature, walnut trees become ready to harvest annually in the late summer and early fall months, typically between August and November for those varieties grown in the USA. During these warmer months, the green hull that surrounds the in-shell walnut begins to dry and crack, making it easier to extract the nut within. Although harvesting can be done by hand, in large scale production walnuts are shaken onto the ground using a mechanical shaker that vigorously shakes the walnut tree, separating the walnuts from the branches. Once on the ground, the walnuts are then gently swept into rows between the trees where they are then collected by mechanical harvesters who sweep them up into boxes and transport them to the processing plant. 


Next, it’s time to remove the remaining green husks from the walnuts using a huller, leaving the in-shell nut for processing. To help prevent deterioration of walnuts at this stage, many processors then dry their nuts to their optimum moisture level of 8%, keeping them safe from rot. Finally, if the walnuts are destined to be sold shelled, then they are cracked, and the shells mechanically removed to keep as many of the nuts in their perfect ‘half’ formation as possible. A series of cameras and manual sorters ensure that no shell remains in the final product, and any broken walnut halves are discarded to be sold as walnut pieces. 


Whether in the shell or shelled, American walnuts are graded according to USDA standards and sorted by size, colour and quality, which will determine their future market. Because of their strict quality standards, US walnuts are now widely considered to be some of the most premium walnuts in the world. 

How healthy are walnuts?

Walnuts may be small, but they sure are mighty and are packed with an abundance of vitamins, minerals and nutrients that support a healthy diet. Without their shells, 100 grams of walnuts contains: 


  • Calories - 654Kcal 
  • Carbohydrates - 13.71g
  • Protein - 15.23g
  • Fat - 65.21g
  • Cholesterol - 0mg
  • Fibre - 6.7g

At first glance, many people are put off by the high-looking fat content of walnuts; however, unlike other fat sources such as those from animal products, walnuts contain heart-healthy monounsaturated fats including alpha-linoleic acid (ALA), a type of omega-3 fatty acid, that has been found to reduce inflammation and oxidation in the body and even to help the body cleanse itself after an unhealthy fatty meal. 


In addition to providing heart-healthy fats, a good source of protein and essential dietary fibre, walnuts are also a fantastic source of vitamins including Vitamin E, thiamin and folates, potassium and minerals such as copper, iron, manganese and zinc. 

The health benefits of eating walnuts

As you can see, there’s a reason why walnuts have formed an essential role in the diets of people for many centuries - they’re incredibly nutrient-dense and are good for the body. Here are some of the key health benefits of eating walnuts regularly as a part of your diet. 


They help to reduce your harmful cholesterol levels

Not all cholesterol is bad for you and walnuts can help to ensure that you only carry the good stuff. Walnuts are a rich source of monounsaturated fatty acids and omega-3’s, meaning that they can help to lower the levels of bad cholesterol in the body and increase levels of good cholesterol in the blood. Studies have even shown that eating walnuts can help to remove unhealthy cholesterol from the blood after a high-fat meal.  

They can help balance your microbiome 

When your microbiome is happy, your body is happy, and thanks to their fibre content walnuts are great at providing our good gut bacteria with the food they need to do their job. The regular consumption of walnuts has also been found to increase the number of microbes that produce butyrate, a beneficial metabolite for colonic health, and can, therefore, help to reduce the risk of colon cancer. 

They’re good for cognitive health 

Aside from looking a bit like a brain, walnuts also contain many nutrients, including vitamin E and polyphenols that can help to reduce oxidative damage and inflammation. Although studies are still ongoing, preliminary tests have shown significant improvements to the memory and learning ability of subjects that ate walnuts daily and so there’s no harm in eating one or two before a big brain day.  

They can improve your skin 

Vitamin E isn’t just great for your brain but can help to prevent oxidative damage all over the body, including in your skin. Vitamin E works by stabilising free radicals that would otherwise damage skin cells and can, therefore, help to reduce signs of aging such as those caused by the sun. Vitamin E is often added to expensive face creams, but you can also reap the benefits of this magical vitamin by eating a serving of walnuts a day or by applying walnut oil to your skin. 

They can help to reduce your risk of diabetes

Walnuts may be calorically dense, but studies have also found them to help suppress appetite and to aid those who are dieting with controlling food urges, making them a portion of great weight-loss food. In addition to assisting people in losing weight, walnuts also help to control blood sugar levels and so are often recommended to those who are at risk of diabetes or who are trying to reduce their reliance on type 2 diabetes medication. 

They can even help to prevent cancer 

That’s right, as well as being a great weight-loss food, reducing the signs of aging, improving your brain and heart health, and making your skin glow; walnuts can also help to reduce your risk of developing certain cancers. Walnuts are a great source of polyphenols which can be transformed in the microbiome to create urolithins which are anti-inflammatory. The anti-inflammatory properties of urolithins can help to protect you against colorectal cancer as well as reducing the risk of hormone-related cancers such as breast and prostate cancer. 

Want to read more about the health benefits of walnuts? You can do so here!

Which is healthier - The Black or the English walnut?

The Black and the English walnut are both very closely related, but they do still have some differences in their nutritional makeup. Here’s how they compare side by side:


  • Calories

The English walnut wins this round, with slightly more calories per 1oz (28g) serving than the Black walnut.  

  • Fibre

Both nuts come out neck and neck when it comes to fibre, boasting 2 grams per 1oz serving. 

  • Protein

When it comes to protein, the Black walnut comes out on top, with a whopping 7g of protein per 1oz serving compared with the English walnuts 4g - still a significant amount. 

  • Carbohydrates

If you’re watching your total carbs, then the Black walnut narrowly wins again, with 3g of carbohydrate compared to 4g for the English walnut. If it’s Net carbs your after then remove the 2g fibre value, and you’ll find that Black walnuts have 1g of net carbs, compared with the English walnuts 2g. 

  • Omega-3’s

If it’s heart-healthy fats you’re looking for, then the English walnut wins this round, with 2.5g per 1oz serving, as opposed to the Black walnuts 1.5g. 

  • Vitamin E

But when it comes to Vitamin E, the powerful antioxidant responsible for reducing aging, Black walnuts pull ahead once more, providing 3% of your RDA per serving as opposed to the English walnuts 1%. These may both seem like minimal values, but every little helps!

So who wins?

Well, side by side, there’s not a lot in it. The English walnut may be a better source of Omega 3’s and calories, but the Black walnut comes ahead in other areas including for protein and Vitamin E, and at the end of the day, both are extremely good for you and can offer many health benefits. So rather than putting them against one another, we recommend enjoying them both and finding the flavour you prefer. 

Are walnuts suitable for a ketogenic diet?

A ketogenic diet is one that is high in fat and low in carbs, putting the body into a state of ketosis in which it burns fat rather than sugar. For those on a ketogenic diet, walnuts are a great source of nutrients that also fit within ketogenic macros. High in fat and low in carbs, walnuts are one of the few plant foods that have a minimal impact on blood sugar levels, and also provide a much-needed source of fibre and protein as well as health-boosting vitamins and antioxidants. As one of the king nuts of keto, a 1oz serving of walnuts contains just 2g of Net carbs but 18g of fat, making them one of the lowest carbohydrate and highest fat nuts you can eat. 

How to add walnuts into your keto diet

Walnuts can be incorporated into a keto diet in so many different ways. Firstly, they make a great snack on their own and can be eaten as a portion of convenience food. They are also great chopped and sprinkled on top of other keto dishes for some extra fat and crunch, and can even be ground into a flour to be used in baking as a replacement for wheat flour. For maximum fat and minimum carbs, you can also enjoy walnuts as an oil, simply drizzle on salads or other keto dishes but bear in mind that as oil you do lose some of the other nutritional components. Looking for more keto snacks that are high in protein? We've listed 5 of them here!

Where can I buy good quality walnuts?

3.8 million tonnes of walnuts may be harvested each year from countries all over the world, but not all walnuts are created equal. Walnuts can very quickly become stale, ruining their flavour and damaging their nutritional profile, meaning that it is vital to consume the very best fresh, quality walnuts that you can find. Thanks to government food standards, most countries now impose strict guidelines on the quality of walnuts that can be produced for sale, but that doesn’t mean that every walnut you buy from the grocery store is the same. 


Finding the best quality walnuts is about finding a trusted supplier, someone who knows their nuts and who can shop around depending on where the harvest is best that year, and thanks to the internet it’s now easier than ever to source the very best quality walnuts from a trusted supplier, even if they are not local to you. Here at Ayoub’s we like to think that with more than 40 years of experience we know a thing or two about sourcing the best quality walnuts, and only choose the very best premium quality raw nuts to sell to our customers. All of our premium raw walnuts are sourced from either California or Chilli, depending on the quality of the year’s harvest, and meet the very strictest walnut inspection standards, ensuring that you as the customer receive a product that is as fresh as it was the day it was harvested and is still filled with maximum flavour and nutrition. 

How to store your walnuts to stop them going rancid

If you’ve eaten a rancid nut before then, you’ll know that it’s not an experience that you will want to repeat. Rancid nuts taste bitter and nasty, not to mention they can also begin to grow mould which is not good for your health. Sadly, due to their high omega-3 content, walnuts are one of the most temperamental nuts and can go rancid very quickly if stored in the wrong conditions, so here’s how to store yours properly to keep them fresher for longer. 


Heat and humidity are two of the critical enemies of walnuts, which is why, during processing, walnuts are often dried to an 8% moisture level and are always stored in a cool environment. In-shell walnuts have more protection against environmental factors than their shelled sisters, which is why walnuts are often stored in-shell until they are needed. 


When buying shelled walnuts online or from a store they will likely already be packaged in an air-tight bag or container to help control their humidity levels, but once this seal is broken, you must store them correctly if you don’t want them to go bad. When storing walnuts at home, always place them in an air-tight container with a tightly fitted lid, such as a jar or a vacuum-sealed packet, this will stop any air or moisture getting to the nuts and will also prevent them from absorbing any unwanted flavours. 


Next, depending on how long you wish to store them for, you will want to choose between placing them in the pantry away from direct sunlight, in the fridge, or even in the freezer. In the pantry, sealed walnuts will typically last for six months past their best before date, this is extended to 1 year in the fridge and up to two years in the freezer, though we wouldn’t recommend eating them more than a year past their date unless necessary. If you live in a hot climate, then it’s more important to store your walnuts in the fridge as they dislike warm temperatures and will go rancid a lot more quickly. 

How to tell if a walnut has gone rancid

The healthy fats found in walnuts are easily perishable and can go rancid very quickly if they become hot or moist. Although eating a rotten nut won’t make you sick immediately, they do taste pretty bad, and if you eat enough of them, then you may start to feel some not-so-nice side effects. If you’ve got an old jar of nuts in the back of your cupboard or a packet in the back of your fridge, then here’s how to tell if they’re good to eat, or only good enough for the bin. Before you read how to find out if a walnut has gone rancid, check out our post on how to store your nuts correctly to ensure maximum freshness!


Check their date

Nuts usually have a ‘best before date’ rather than an expiry date which means you have a little bit of leeway when it comes to them surpassing it. If you’ve decanted your walnuts into your storage containers, then always be sure to re-label them with their current ‘best before’ date so that you can tell if they have gone beyond it and by how far. As a general rule, sealed walnuts will last six months past their ‘best before’ date in the pantry, one year in the fridge and up to two in the freezer. If they’ve gone beyond this, then you may wish to buy a fresh pack. 

Use your nose

Our bodies are usually pretty good at detecting when food has gone bad, and you should be able to tell if you walnuts have gone rancid by merely smelling them. When walnuts go stale, they start to undergo a chemical change which alters how they smell. Rather than smelling fresh and nutty, they will smell chemically like paint or nail polish remover, and if they are stored in a plastic container, then they may start to smell like old plastic.

Try one

Sometimes bold flavours like chilli or smoked paprika can make it difficult to smell if a walnut has gone rancid, in which case, you may want to bite the bullet and just to try one. A rancid nut will taste rancid, so spit it out and then throw away the rest of the batch. If in doubt - throw it out. 

Look out for mould

If your walnuts have been exposed to moisture, then they may also start to grow mould. Mould often looks like a powdery substance coating the outside of the nut but can be hard to spot if the nut is coated in seasoning. You can usually smell mould inside a packet, so trust your nose and give them a sniff and if they smell musty then throw them out. 

Read our blog post with tips on making sure you're getting walnuts fresh ...

Shelled walnuts and fresh spinach in a food processor on a dark table surrounded by garlic cloves, various herbs and a teaspoon of salt

How to use walnuts in your everyday cooking 

The best way to ensure that your walnuts don’t go rancid is by devouring them, and if you’re going to start eating a 1oz serving a day, then this shouldn’t be too hard to achieve. Walnuts are incredibly versatile and can be used in many dishes from sweet to savoury, hot to cold, and even in drinks and smoothies. Here are some ways that you could incorporate walnuts into your everyday recipes. 

As on-the-go snacks

Whether it’s in your kids’ lunchbox for school, in your lunch for work, or in your handbag during a long day out, walnuts are the perfect grab-and-go snack. Filling and nutritious, they can help to keep you fuller for longer and offer a satisfying crunch that can replace other unhealthy snacks. Keep them sealed in an air-tight pot and munch away on the go. 

As a topper

Chopped into smaller pieces, walnuts make the perfect topper for oatmeal, salads, cereal, fish and even stir-fries, adding a delicious texture and nutty flavour. Sprinkle over oatmeal to add some extra protein to your breakfast, or add to salads in place of bread croutons, and you can even use them to replace peanuts or cashews to garnish Asian dishes. 

As sweet treats

Although walnuts are a savoury snack in themselves, their mild flavour makes them perfect for adding to baked goods too. Add them to muffins or cakes for a crunchy nutrient boost, or grind them up into a flour for fussier eaters. If you want something indulgent, then you can even candy them in some honey or treacle and then bake them in the oven. Find a delicious candied walnuts recipe here

As a smoothie booster

If you’re looking for a way to add healthy fats and omega-3’s into your morning smoothies, then crumble in some walnuts or pop a dollop of walnut butter into your blender. Walnuts blend up quickly in a high-powered blender, and with their mild flavour, they make a great partner to fruits and vegetables. 

And that’s just about everything you need to know about walnuts

From beginning to end, we think it’s pretty clear that walnuts are a fantastic food and we hope you agree. If you’ve been inspired to give them a try or to incorporate them back into your diet, then let us help by delivering our premium raw walnuts directly to your door. Sourced only from the very best growers and from the very best harvests we’re confident that our walnuts can deliver a taste like none other you’ve experienced from the supermarket. Still unsure? Read these 5 reasons why you should eat more walnuts!

November 25, 2020 by Gillian Brady
Tags: walnuts
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