**1. Introduction**

Oily dried fruit is a different food from dried fruit (figs, apricots, plums, and raisins) because the latter has a high sugar content and is therefore particularly suitable for the beginning of the day because it provides a load of immediately available energy. Dried fruit, such as nuts and various seeds, is the vehicle for the reproduction of vegetables; within them is the potential of the entire plant. The term "walnut" commonly indicates the seed of a tree enclosed in a woody casing, but many seeds that we consider "nuts," such as peanuts, do not correspond to the strict definition of pure walnut.

There are more than 300 types of walnut, and all of their plants produce seeds, but only a few are very important as a product for food and human health

In terms of world production, coconut is the most widely grown and used, followed by peanuts; both account for about 94% of world walnut production. The main reason is that both coconut and peanuts provide oils that are among the essential ingredients of cooking oils, margarine, and cooking fats at a low price. For example, peanuts are the most known nut in the United States, and the harvest exceeds 70% of the annual nut production, followed by almonds, walnuts, and pecans.

Unfortunately, nuts are usually eaten after being fried in fat and salted or as an ingredient in sweets and packaged and ultra-processed foods. Today, many people are trying to orient themselves to healthier foods, and the consumption of nuts and oil seeds is growing dramatically!

It is worth mentioning that oily fruit contains essential nutrients and substances defined as "anti-nutrients" but always to a lesser extent than healthy ones, which are fibrous compounds, protease inhibitors, ellagic acid, and other polyphenols. Since nuts and seeds contain a large amount of oil, one might think that eating nuts frequently would increase the rate of obesity. Still, worldwide epidemiology shows us, on the contrary, that obesity is less common among nut eaters, and one of the positives is thought to come from a greater sense of satiety and appetite satisfaction. In general, nuts and oil seeds, due to their high oil content, should be purchased and stored still in the shell because it is a natural protector against free radical damage caused by light and air. It is discouraged to eat moldy nuts and seeds and use them for cooking because they pose a health risk, just as the use of chewy, dark, or wilted nuts is similarly not recommended. Instead, it is advisable to store nuts and oilseeds in their shells in a cold, dry environment, and if by chance you are forced to buy them unshelled, be sure to seal them in airtight containers in the refrigerator or freezer. Chopped or sliced walnuts, in general, are rancid, and it is preferable to prepare them at home, using whole walnuts.

The nutritional characteristics of the two types of fruit are a high sugar content for dried fruit and a high quantity of calories for dried fruit. The high-calorie intake is due to its high fat content, especially polyunsaturated fatty acids, such as alphalinolenic acid (ALA). Another type of fat found in this food is eicosapentaenoic acid (EPA). These two types of fats are an excellent source for people who do not eat fish.

Oily dried fruit is a large family, including hazelnut, with high fat content. It is a food that is present in diets because its characteristic aroma makes it versatile in the combination of other flavors, and it is a widely used ingredient in commercial confectionery products. During the second world war, cocoa was challenging to find, and hazelnut was used to prepare products that resembled chocolate. After the war, when the cocoa supply returned to normal, confectionery producers found that the public's taste remained oriented toward specialties in which the hazelnut aroma sweetened the cocoa aroma's sourness. Consumers' preferences are generally oriented toward large, somewhat round, well-colored, and hard-shelled hazelnuts. Hazelnuts contain omega-3 and omega-6 unsaturated fatty acids and are rich in fibers that facilitate intestinal transit and, in turn, make you absorb less sugar and less fat.

Walnuts contain the kernel, the part eaten with a pleasant flavor and with a delicate taste. Walnut is very nutritious and has a high calorific value, as it includes a characteristic oil in a percentage that varies, depending on the variety, from 55% to 65%. The high-calorie nature of walnuts makes them undesirable for those who want to lose weight, as they provide many calories.

Walnut oil contains alpha-linolenic acid (ALA), a precursor of omega-3 fatty acid, called EPA. The intake of four walnuts per day leads to the presence of EPA in the body, similar to that obtained from eating fish. The nut is appreciated as a dessert and is sought after as a delicacy at the end of a meal, as it stimulates the taste of drinking.

From a nutritional point of view, almonds are similar to walnuts. They, too, contain an oil with a high percentage of omega-3 and omega-6 and a minimum amount of water; almond is, therefore, a high-calorie food. It is an essential source of mineral salts such as phosphorus, calcium, iron, copper, and magnesium. Almonds are often eaten dry and can be distinguished as dry and bitter. They can hardly be digestible due to their high oil content.

Almond oil is extracted by applying pressure to a sweet variant. When it is emulsified with water and sugar, a natural laxative is obtained that can also be given to

children. If you add a small dose of bitter almond oil to this preparation and dilute it, it becomes the basis for preparing barley.

For many years, numerous scientific studies have confirmed that a balanced diet, such as the Mediterranean diet, allows you to prevent numerous chronic diseases and that, in pathological conditions, diet is an integral part of medical therapy. Diet plays a crucial role in the etiology of numerous chronic diseases, thus contributing to significant geographic variations in chronic disease morbidity and mortality rates in different countries and populations worldwide [1].

The daily eating style, in addition to having an essential role in prevention, can be one of the causes of some metabolic diseases if you follow an unbalanced diet. It has also been found that it significantly influences the composition of the intestinal microbiota [2], where we can distinguish about 1014 commensal bacteria [3] grouped into seven different divisions: the most numerous are those of the Bacterioidetes families (in particular, Bacteroides and Prevotella) and Firmicutes, which are more than 90% of the total population [4], and in the remaining 10%, we find archaea, viruses, parasites, and fungi [5].

The microbiological families make up the microbiota and feed on the fermentation of non-digestible food carbohydrates [6], producing gas, some organic acids, and short-chain fatty acids (SCFA) [4, 6, 7]. The latter are acetate, propionate, and butyrate and have a crucial role in human health [7]. Butyrate acts on the intestinal mucosa by activating the synthesis of mucin and favoring the formation of tight junctions [8], essential for maintaining intestinal permeability.

SCFA, as confirmed by the scientific literature, plays a role in the modulation of the immune system [9, 10] by regulating the production of pro-inflammatory cytokines and chemokines [9, 11] and the function of T lymphocytes [10].

#### **2. What is a dried fruit?**

When we talk about taking dried fruit in the daily diet, we refer to nuts, including oily achenes.

Walnut is one of the many names used to refer to the oily achenes produced by different plant species. These include walnuts, hazelnuts, almonds, pistachios, pine nuts, peanuts, Brazil nuts, pecans, cashews, and macadamias. Generally rich in protein and exceptionally energizing, the above-mentioned oily nuts represent an essential natural nutritional choice in vegetarian and sports nutrition. Thanks to their richness in fiber and excellent content of mono- and polyunsaturated fatty acids (especially walnuts), they exert a protective action against the so-called wellness diseases, such as diabetes, hypercholesterolemia, and obesity.

For these assumptions to be valid, dried fruit must be consumed sparingly, replacing (never adding to) other less-healthy lipid sources (such as animal fats). Given its high caloric value and great fat richness, dried fruit should be eaten away from main meals, contextualized in snacks, perhaps in combination with fresh fruit (e.g., an apple and some almonds or a kiwi or some walnuts).

A reasonable serving shouldn't exceed 30 g, however. If associated with fresh fruit, it represents an excellent snack and a good ally for our health and daily well-being. The dried fruit marketed with its shell does not guarantee the quality of the product, but it is healthier than a chopped or shelled one. The latter category of food, even if packaged in sealed containers, requires the addition of artificial antioxidants, necessary to avoid the rancidity of fats and extend storage time.

The scientific communities have conducted and are conducting scientific studies for a healthy diet, where the daily intake of dried fruit is recommended. In one of the most significant studies on the Mediterranean diet PREDIMED enrolled in 2003 and 2011, over 7000 people were at high risk of cardiovascular events. The trial divided the participants into three groups: a Mediterranean diet supplemented with extra virgin olive oil, a Mediterranean diet enriched with dried fruit (walnuts, hazelnuts, and almonds), and a low-fat isocaloric diet (animal and vegetable). The two groups assigned the Mediterranean diet adhered well to the dietary regimen and improved clinical analyses. The study showed that for patients with high CVD risk, the Mediterranean diet with extra virgin olive oil or dried fruit intake reduces the incidence of cardiovascular disease [12].

For some time now, clinical studies have focused on the beneficial properties of dried fruit as cardiovascular prevention, especially for coronary heart disease, and then extended to other pathologies [13].

Among the epidemiological studies carried out over the years, it has been found that a regular intake of dried fruit reduces the risk of death from CVD and a reduction in the risk of developing cardiovascular disease [14].

The benefit of dried fruit is the cholesterol-lowering effect, which explains its role in cardiovascular prevention. One of the most prominent large-scale cohort studies of 2005 showed a significant inverse association between the frequency of nut consumption and inflammatory markers (c-reactive protein, IL-6, and fibrinogen) [15].

Nutrition experts in dietary prescriptions recommend replacing ultra-processed foods that exceed in fat, sugar, and salt with nuts as snacks. This substitution helps lower the diet's glycemic load and therefore reduces the risk of developing cardiovascular disease. Among the various benefits of consuming nuts is the satiating power. The consumed fibers fill and quench hunger, making the next meal less excessive.

Having a low glycemic index, walnut, and other types of nuts, combined with a good amount of fat, reduce the total glycemic load of the meal.

The particles produced contain intact plant cells that derive from their fibrous and indigestible wall during chewing. The plant cell wall reduces the entry of digestive enzymes, slowing digestion and absorption of about 25% of the fats. The abrasive consistency of oily fruits allows these foods to be natural exfoliants, removing plaque and stains from tooth enamel. Once in the stomach, they manage to activate the satiating power. In the intestine, soluble fibers such as inulin help reduce the gases produced physiologically by the intestinal microbiota.
