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All about “Walnut”

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Health profile

The nut differs from other shelled and oleaginous fruits by its particularly high content of polyunsaturated fatty acids, mainly in the form of omega-3, whose benefits on cardiovascular health are well demonstrated. When we know that the lipid content of the nut as well as the other active ingredients it contains bring a lot of health benefits, we no longer hesitate to integrate it regularly into our diet.

Active ingredients and properties

For nuts and oilseeds in general
Several epidemiological and clinical studies associate regular consumption of nuts and oilseeds with various health benefits such as a cholesterol-lowering effect 1 , a reduction in the risk of cardiovascular disease 2 and diabetes mellitus. type 2 3 , decreased risk of gallstones 4 and gallbladder removal 5 , and decreased risk of colon cancer in women 6. The amount of shelled and oil seeds related to these benefits is most often equivalent to a weekly intake of about five one-ounce (30 g) servings.

For walnuts (walnut fruit)
Polyunsaturated fatty acids
 . The nut has a particularly high content of polyunsaturated fatty acids (more than 70% of its total lipids), of which almost a fifth is in the form of alpha-linolenic acid , an essential omega-3 fatty acid. Polyunsaturated fatty acids , particularly omega-3 fatty acids, are considered good fats for cardiovascular health, given their positive impact on blood lipid levels . The nut contains the ideal proportion of omega-3 fatty acids (compared to omega-6 fatty acids) to have in our diet (see our sheet Essential fatty acids ).

The nut has been attributed beneficial effects on cardiovascular health, mainly because of its ability to improve the profile of blood lipids and the elasticity of the vessels. It is well established scientifically that replacing saturated fats with polyunsaturated fats in the diet leads to a reduction in blood cholesterol , which provides a protective effect against cardiovascular diseases 7 . But lipids alone cannot fully produce this protective effect, which suggests that other components contained in the nut could lead to cardiovascular health benefits 8 .

  • Blood lipids . A large number of studies have evaluated the impact of nut consumption on blood lipids. In healthy subjects, the consumption of 44 g to 84 g of nuts per day for four weeks decreased total cholesterol from 4% to 12% and LDL cholesterol (“bad” cholesterol) from 9% to 16%, and this, compared to the consumption of a diet without nuts 9,10. It is important to mention that in these studies, nuts were not added, but rather consumed in place of other lipids in the diet. Other similar studies have also seen an improvement in blood lipids upon the integration of nuts in subjects with hypercholesterolemia. In fact, the consumption of 41 g to 56 g of nuts per day for six weeks resulted in a reduction in total cholesterol by 4% and LDL-cholesterol by 6% 11 . The daily integration of nuts has also led to a decrease in cholesterol in certain particles transporting lipids and which are considered to be atherogenic 12. In the majority of these studies, the consumption of nuts did not really affect the concentration of HDL cholesterol (“good” cholesterol) and blood triglycerides 1 . In summary, the daily consumption of 40 g to 84 g of nuts 1 has a significant impact on blood lipids, both in healthy people and in those who already have a deteriorated lipid profile. The alpha-linolenic acid (omega-3) found in nuts is an important compound associated with this effect.

    Elasticity of blood vessels. In a study of people with moderately high cholesterol, replacing some of the fat in the diet with nuts resulted in an improvement in the elasticity (ability to expand and contract) of the vessel wall blood 13 , a critical point in the prevention of coronary heart disease . So far, the precise mechanism is not fully discovered, but alpha-linolenic acid as well as arginine (an amino acid) could be two compounds linked to this effect.

Antioxidants . Antioxidants are compounds that reduce the damage caused by free radicals in the body. These are very reactive molecules which are implicated in the appearance of cardiovascular diseases, certain cancers and other diseases linked to aging. The nut comes in second place among several other plants (fruits, vegetables, nuts, seeds and cereals) in terms of its antioxidant content 14 .

  • Phenolic compounds . The nut contains ellagic acid 15 , a phenolic compound which has demonstrated antioxidant potential in vitro 15 and prevention against certain cancers in animals 16 . On the other hand, these effects do not necessarily transpose to humans. Indeed, researchers have found that, depending on the microbial flora of individuals, some people excrete more than others a byproduct of ellagitannin (a phenolic compound containing ellagic acid) in the urine, after identical consumption of nuts 17. This means that each individual metabolizes ellagitannin differently and therefore that the biological activity of this compound would vary from one individual to another. This information is useful in the context of clinical studies since data on the absorption and metabolism of phenolic compounds will make it possible to validate their activity in vitro.

    In addition to ellagic acid, the nut contains at least nine other phenolic compounds (including gallic acid) 15 . When extracted from nuts, these compounds are effective inhibitors of LDL cholesterol oxidation in vitro 15 . It should be noted that the phenolic compounds of the nut are found in greater concentration in the thin brown filmsurrounding it 15 .

  • Melatonin . The nut contains melatonin, a lesser known antioxidant molecule compared to many other antioxidants 18 . Melatonin is rarely measured in food and nuts are the first shelled fruit to be measured. After consuming nuts, rats had their melatonin levels and antioxidant capacity significantly increase in their blood compared to animals given a diet without nuts 18 . The authors assume that a synergistic effectwould be possible between melatonin and other antioxidant compounds (like vitamin E) present in the nut, thus increasing the total antioxidant capacity. Future studies on the subject will certainly shed light on the role of melatonin as an antioxidant.

Phytosterols . Phytosterols are compounds found in plants and whose structure is related to that of cholesterol. A meta-analysis of 41 clinical trials has shown that taking 2 g of phytosterols daily reduces LDL cholesterol by 10% (“bad” cholesterol) and that this reduction can reach 20% as part of a diet. low in saturated fat and cholesterol 19 . Phytosterols are found in walnut oil and the few varieties of nuts contain different amounts. For example, a 30 g serving of black walnut would contain about 35 mg of phytosterols, compared to about 23 mg for the same serving of common walnut (most commonly consumed)20 . The latter is also one of the shelled and oleaginous fruits least rich in phytosterols 20 . In addition, the amount of phytosterols contained in nut oils vary from one country to another, being higher for nuts from China and lower for walnuts US 21 .

It is practically impossible to reach this quantity of 2 g per day by food alone and for the moment, Health Canada does not allow the marketing of foods enriched with phytosterols. However, even if the effects of phytosterols in walnuts have not been directly evaluated, it is possible to assume that phytosterols found naturally in food remain interesting for cardiovascular health.

Arginine . Vegetable proteins differ from animal proteins in their amino acid composition: they generally have a higher content of arginine and lower content of lysine. In an animal study, adding nuts to the diet decreased the aggregation of blood platelets as well as total blood cholesterol 22 . The decrease in the aggregation of platelets, a preventive factor for cardiovascular disorders, was linked to the low lysine / arginine ratio of the nut, suggesting that this would be decisive in the effect observed. The nut has a particularly high content of arginine 23and from this amino acid, the body makes nitric oxide, a substance that promotes the dilation of blood vessels necessary for good blood circulation. This anti-atherogenic effect linked to the low lysine / arginine ratio has been demonstrated in humans 24 , but not specifically after consumption of nuts.

Dietary fiber . The nut is a source of fiber. Dietary fibers, which are found only in plant products, include a set of substances that are not digested by the body. In addition to preventing constipation and reducing the risk of colon cancer, a high fiber diet can help prevent cardiovascular disease and control type 2 diabetes and appetite 29 . Remember that it is recommended to consume 25 g of fiber per day for women from 19 to 50 years old, and 38 g per day for men of the same age group 30 .

Body weight . Since the nut is rich in lipids, it is possible to believe that its consumption can cause weight gain. In this regard, a study has shown that adding nuts to the diet for six months leads to an increase in weight that is lower than the planned values, taking into account the caloric surplus brought by these 25 . In the same vein, two other studies have found that the weight does not really increase after the consumption of 285 kCal to 400 kCal additional in the form of nuts, and this, for six weeks 12 , 26 . In addition, two large reviews of the scientific literature have also shown that regular consumption of nuts and oilseeds is not associated with weight gain 27,28. This effect is explained by various mechanisms such as increasing the degree of satiety or expenditure , the high content of fiber and polyunsaturated fatty acids in nuts and other shelled fruits, as well as by incomplete absorption of lipids. In summary, even if the consumption of nuts and oilseeds does not seem associated with a higher risk of gaining weight, it must be remembered that it is a greater calorie intake compared to the expense that leads weight gain. It is therefore preferable to substitute these foods for others, rather than adding them to the usual diet, and to maintain a stable level of physical activity on a daily basis.

Other properties

Is the nut antioxidant? Strongly. The TAC index of 30 g of nuts is 4,062 umol.
Is the nut acidifying? Moderately. The PRAL index of 100 g of nuts is 6.8.
Does the nut have a high glycemic load? Data not available.

Most important nutrients

See the meaning of the nutrient source classification symbols

 Manganese . The nut is an excellent source of manganese. Manganese acts as a cofactor for several enzymes that facilitate a dozen different metabolic processes. It also participates in the prevention of damage caused by free radicals .

 Phosphorus . Walnuts are a source of phosphorus (see our Phosphorus nutrient fact sheet ). Phosphorus is the second most abundant mineral in the body after calcium. It plays an essential role in the formation and maintenance of healthy bones and teeth. In addition, it participates among other things in the growth and regeneration of tissues and helps to maintain normal blood pH . Finally, phosphorus is one of the constituents of cell membranes.

 Magnesium . The nut is a source of magnesium. Magnesium participates in bone development, protein construction, enzymatic actions, muscle contraction, dental health and the functioning of the immune system. It also plays a role in energy metabolism and in the transmission of nerve impulses.

 Iron . The nut is a source of iron for humans only. Each body cell contains iron. This mineral is essential for the transport of oxygen and the formation of red blood cells in the blood. It also plays a role in the production of new cells, hormones and neurotransmitters (messengers in nerve impulses). It should be noted that the iron contained in plants (for example in nuts) is less absorbed by the body than iron of animal origin. However, the absorption of iron from plants is favored if it is consumed with certain nutrients such as vitamin C.

 Zinc . The nut is a source of zinc. Zinc is involved in particular in immune reactions, in the production of genetic material, in the perception of taste, in the healing of wounds and in the development of the fetus. It also interacts with sex and thyroid hormones. In the pancreas, it collaborates in the synthesis (manufacture), the storage and the release of insulin.

 Copper . The nut is a source of copper. As a constituent of several enzymes, copper is necessary for the formation of hemoglobin and collagen (protein used for the structure and repair of tissues) in the body. Several copper-containing enzymes also help the body’s defense against free radicals.

 Vitamin B1 . The nut is a source of vitamin B1. Also called thiamine, vitamin B1 is part of a coenzyme necessary for the production of energy mainly from the carbohydrates that we eat. It also participates in the transmission of nerve impulses and promotes normal growth.

 Vitamin B6 . The nut is a source of vitamin B6. Vitamin B6, also called pyridoxine, is part of coenzymes that participate in the metabolism of proteins and fatty acids as well as in the synthesis (manufacture) of neurotransmitters (messengers in nerve impulses). It also contributes to the production of red blood cells and allows them to transport more oxygen. Pyridoxine is also necessary for the transformation of glycogen into glucose and it contributes to the proper functioning of the immune system. This vitamin finally plays a role in the formation of certain components of nerve cells and in the modulation of hormone receptors.

 Folate . The nut is a source of folate. Folate (vitamin B9) is involved in the production of all cells in the body, including red blood cells. This vitamin plays an essential role in the production of genetic material (DNA, RNA), in the functioning of the nervous system and the immune system, as well as in the healing of wounds and wounds. As it is necessary for the production of new cells, adequate consumption is essential during periods of growth and for the development of the fetus.

What is a “portion” of nuts worth?
Volume / weight Dehydrated and chopped nuts, 30 g / 60 ml
Calories 194
Protein 4.5g
Carbohydrates 4.1g
Fat 19.4g
saturated 1.8g
monounsaturated 2.7g
polyunsaturated 14.0 g
Omega 3* 2.7g
Cholesterol 0 mg
Dietary fiber 2.0 g

Source  : Health Canada. Canadian Nutrient File , version 2005.
* As alpha-linolenic acid.

If the nut is not considered a source of vitamin E , it is because gamma-tocopherol (the main form of vitamin E in the nut) is not used in the calculation of the nutritional intake recommended for this vitamin.

Vitamin E and nuts

The term vitamin E includes eight active compounds: four tocopherols and four tocotrienols. Of these compounds, alpha-tocopherol is the one with the greatest biological activity , the others not being used optimally by the body. In walnuts, alpha-tocopherol is present in small quantities compared to other shelled and oleaginous fruits (such as macadamia nuts, almonds and hazelnuts). Rather, it is gamma-tocopherol which is the main compound associated with vitamin E and even if it is less well used by the organism, certain studies show that it could have a higher antioxidant capacity than alpha-tocopherol 33 , 34. Interestingly, the vitamin E content of the nut would decrease by about 30% after three months of refrigeration 23 . It is therefore important to buy small quantities of nuts at a time and consume them within a reasonable time in order to make the most of their nutritional content.

Precautions

Allergy to shelled and oil seeds

In the list of the main allergens of the Canadian Food Inspection Agency (CFIA) 31 , we find “nuts”, which designate all the nuts and oilseeds. Some people, however, may be specifically allergic to nuts. In addition, one study found that walnuts, pecans and hazelnuts were a group whose allergies were strongly associated 32 : a person allergic to one of these foods is more likely to be allergic to the other two. In addition, it is usually recommended that people allergic to peanuts also refrain from consuming other nuts and oil seeds (including nuts), since they also have a high allergenic potential and are often handled and distributed. by companies specializing in peanuts. Symptoms of shellfish and oilseed allergy can be severe and lead to anaphylactic shock .

Urinary stones

Some people may be recommended to adopt a restricted diet of oxalates to prevent recurrences of kidney or urinary stones (also called urolithiasis). Oxalates are compounds that are found naturally in several foods, including shelled and oil seeds in general. It is therefore preferable that these people avoid consuming it.

The nut over time

The term ”  walnut  “, which appeared in the French language in 1155, comes from the Latin nüx , nucis . To clearly distinguish the whole nut from its flesh, we sometimes call the latter ”  kernel  “. The term “  brou  ” designates the pericarp which covers the shell; first green, it turns brown when the nut falls from the tree.

Depending on the location, the fruit of the walnut is designated by the terms “English walnut”, “Persian walnut” or “Italian walnut”. In Quebec, it is designated by the term “walnuts”, but the variety produced in the vicinity of Grenoble benefits from a controlled designation of origin and the expression can therefore only apply to fruits from this region.

The genus Juglans consists of around twenty species of walnut trees. These trees all bear edible fruit. The common walnut, or Juglans regia , is by far the most common species. Originating in a region which goes from the south-east of Europe to the Himalayan range, and whose heart could be China, the common walnut is sometimes called Persian walnut because it is in this country that we would have domesticated it or, at least, that we would have obtained the ancestors of our modern varieties. From there, he would have settled in Europe after having taken the old trade routes with the caravans. It then spread to temperate regions of North and South America, as well as to Australia.

A sought-after food

Long before being domesticated, the nut was collected in the wild. The oldest remains have been found in the Shanidar caves of Iraq, where 50,000 humans lived before our era. The domestication of the walnut tree probably started 12,000 years ago, at the end of the last glaciation. The wealthy Greeks and Romans looked for this nut, which they found to be much better than the acorns of oak, chestnuts and bees that made up the ordinary people.

Relatively unknown today except gourmets and chefs, walnut oil was commonly consumed in the Middle Ages and was an integral part of the cuisine of central France until the middle of the XIX th  century.

The nuts of other walnut species are of nutritional quality and flavor comparable to those of Juglans regia , but their husk is harder and their flesh less abundant. In North America, the black walnut , Juglans nigra , is harvested in particular . Consumed by the Amerindians, it was also appreciated by the colonists. But when the imported common walnut, which was easier to open, established itself on the market, the native walnut was somewhat forgotten. Fortunately, thanks to the creation of better harvesting and processing tools, we have started to harvest it again. Thus, in certain places, in Missouri in particular, millions of pounds are produced each year and the demand is such that the entire crop is sold locally.

Finally, butternut ( Juglans cinerara ), native to North America, gives a nut that some consider the best of all; it is not found on the market, but you can pick it yourself in the forest in autumn (September and October in southern Quebec).

Culinary uses

Choose well

Preferably, buy the nuts in their shell , because too often, those sold shelled have started to go rancid: these are the unsaturated fats of the nuts which transform quickly on contact with air.

Pickled nuts are found in delicatessens. These are young, still green and tender fruits marinated in vinegar and eaten like pickles.

Culinary dishes

To give nuts their full flavor, they can be roasted before serving or used in a recipe. It is simply a matter of placing the shelled nuts on a metal plate, in an oven set to 185 ºC (360 ° F). Cook for ten minutes until they are slightly browned and a pleasant aroma emerges.

They can also be roasted in their shell in an oven set to 190 ºC (375 ° F) for around twenty minutes. If desired, then make a nut butter by passing their flesh through a blender as long as it takes to obtain a good texture (four to six minutes).

In savory dishes

  • As an appetizer  : coat pieces of apples or seedless grapes with cream cheese (which you can add a little blue to enhance the taste), then roll in crushed nuts.
  • In salads , especially the classic Waldorf, with endives and apples. Or:
    – with lamb’s lettuce or other greens and diced beetroot;
    – with slices of kiwi, diced firm cheese and minced endives;
    – with spinach, bacon and pieces of citrus.
  • In pesto , you can very well replace the pine nuts with nuts.
  • Strain nuts, bread and coriander leaves in a blender to make breadcrumbs for breading fish fillets or cutlets.
  • To stuff a poultry  : mix bread crumbs, diced apples, nuts, shallots, an egg, thyme, salt and pepper. You can also include marinated nuts.

In Europe, a soup is prepared with a sliced ​​onion slightly browned in butter, nuts in a blender, diced potatoes and chicken broth. Add a little cream at the end of cooking to bind everything. A port fillet too, if desired.

In Italy, salsa di noci , or walnut sauce , accompanies pasta, stuffed or not. It consists of dipping bread in milk, then passing it through a blender with garlic and nuts; salt, add olive oil and serve with parmesan cheese and garnish with some roasted nuts. You can also make a spread or a dip sauce for vegetables. Various sauces can be thickened with ground nuts.

In sweet dishes

The walnut and maple syrup pie (real, of course) is a classic of Quebec cuisine.
  • In bread preparations, cakes, muffins, pie crusts, clafoutis, macaroons and other pastries . You can’t imagine banana bread without its nuts.
  • In bread pudding , with diced apples and raisins.
  • In peach, plum, pear or fig jams .
  • In mueslis, granolas and other cereal preparations .

Conservation

Keep the nuts in their shell at temperatures below 10 ºC (even in the refrigerator) and the walnut oil in the refrigerator.

Ideally, shelled nuts should be kept in the refrigerator at all times.

Organic gardening

You have to think twice before planting one or more walnut trees when you only have a small lot, because these are trees that reach impressive dimensions , and it takes at least nine meters between the trees, more for some varieties. In addition, their roots emit substances that inhibit the growth of many other plants, which can be a real disadvantage.

There are some cultivars of common walnut that can be grown in zone 5 by protecting them in winter, but it is a risky business, because if the tree can survive the cold, the flower buds are much more fragile and may be destroyed by April and May frosts. On the other hand, black walnut and butternut generally support the climate of southern Quebec well and can give excellent harvests. A few black walnut cultivars have been created that produce larger, easier-to-shell nuts than those grown in the wild.

Walnut trees require well-drained soil with a pH of 6 to 7, in a place without “jelly cuvée” (where pockets of cold air are frequent). The ideal is to plant on a gently sloping plot, facing north. A good hedge of conifers planted to the northwest of the hazelnut grove will create a microclimate favorable to the growth of young trees.

Ecology and environment

The walnut is a very useful tree that, in addition, the advantage of living to 250 years. Its majestic habit makes it a popular ornamental tree, while its precious wood is used in cabinetmaking and in the veneer industry. Its roots, which are sometimes called “walnut brambles”, are also sought after by cabinetmakers. The husk (shell of the shell) provides excellent dyes (brown, red or green, depending on the treatment) more stable than the majority of other plant products.

The leaves keep ants, flies and bedbugs away while kittens have been used in the past to make a so-called “catkin” wine. The hulls are used as fuel, in particular within the framework of a program of cogeneration of energy: they are burned at very high temperature in order to produce a vapor generating electricity. They are also used as an anti-slip agent in the manufacture of tires, as a blasting agent in the metallurgy industry, and they are used to manufacture activated carbon.

France and Canada are currently collaborating on a joint program for the development of hybrid walnut trees ( J. regia x J. nigra ). These fast-growing trees have great potential in the context of the development of land in Quebec that does not meet the requirements of modern agriculture. In France, the State subsidizes the establishment of agroforestry projects intended to promote agricultural production at the same time as the cultivation of walnut trees. This involves planting the latter at large spacings, which makes it possible to cultivate on the same land cereals or other plants with an annual yield.

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