Common Walnut

In ancient times, when people were still eating acorns, the gods ate walnuts. According to legend, at least. The walnut's Latin classification, Juglans, roughly translated as Jupiter's fruit, reminds us that this food was dedicated to the gods of ancient Rome. The Greek name dios balanos, meaning "God's acorn" points to the nut's association with Zeus, king of the gods. In 1753 the Swedish natural scientist Carl von Linné ("Linnaeus") added regia, meaning "regal", to its Latin name.

In ancient times, the walnut was a symbol of fertility and a bringer of good luck. It was elemental to various folk customs and rituals. At weddings, walnuts were included in the marital chambre and distributed amongst the guests. Folklorists assume that the German word "Polterabend" for the raucous activities the night before a wedding refers to the thumping of the nuts on the ground. The walnut is also associated with the blessing of many children. Today in some rural areas it is still customary to plant a walnut tree after the birth of a couple's first son.

Where does the walnut come from, and what does it look like?

The tree first came to be around 2.6 to 65 million years ago in the Tertiary period, making it one of the oldest trees known to man. Archaeological research has found that the walnut was used as a food in Europe during the Stone Age. The tree's exact place of origin and distribution cannot be clearly determined. The range of walnut trees probably extended far into the north in the Tertiary period and died off in Northern Europe in the ice ages. However, the tree survived in the warmer regions of the eastern Mediterranean basin and was reintroduced to Europe by the Greeks and the Romans.

The walnut tree is a deciduous tree that is found all over the entire northern hemisphere. There are about 60 known different species of the plant genus Juglans, the most commonly cultivated being the common walnut (Juglans regia). Walnut trees can grow to a height of 30 metres and are not considered fully grown until they are 60 to 80 years old. They produce their first fruits between the ages of 10 and 20. In a good location, an adult tree can produce up to 55 kg of nuts annually.

Walnut trees are monoecious, with both male and female flowers. Flowering periods are from April to June, depending on location, whereby the male flowers, (also called catkins) usually appear first. Pollination occurs through the wind. Walnut trees can live to be 160 years old. They prefer climates with mild winters and can be found at elevations up to 2,000 m above sea level. Another special characteristic is that nothing else usually grows under a walnut tree. This is because the tree releases cinnamic acid, an inhibitor, into the soil from its leaves. This stops other higher plants, in competition for the nutrients in its environment, from thriving.

Interestingly, the walnut is not a nut. Its fruit is actually the green husk around the nut. From a botanical standpoint, the walnut is a drupe. The nut itself is only the seed of this fruit which is highly nutritious for us and useful for good health. Walnut wood is quite hard and considered one of the hardest woods in the world. Even walnut root wood is used in producing veneers in furniture making and in luxury cars because of its interesting grain. 

How are walnuts used?

The wood was used to make stocks for weapons in the Middle Ages. In Europe, thousands of trees were felled to make firearm butts to supply arms for the two world wars. This significantly decimated the wild-growing walnut population. Whilst walnut trees could once be found in almost every garden, the common walnut's population is endangered worldwide. Some regions, for example Iran, have almost completely lost their wild-growing populations. Only a few regions of Central Asia still have walnut forests that cover areas of up to 30,000 hectares.

The need for walnuts, and thus their cultivation, has risen sharply in recent years. Countries leading in walnut cultivation worldwide include China with about 2.5 million tonnes and the USA with about 600,000 tonnes. Other walnut-producing countries include Iran, Turkey, Mexico, and Ukraine. Within Europe, most walnut cultivation is in France. The total yield for all walnut-producing countries in 2019 was about 4.5 million tonnes. The largest exporter, the USA, celebrates National Nut Day on 22 October each year. This "holiday" was invented by the Liberation Foods Company as a way to create awareness about the economic necessity of fair trade in the nut industry. It also emphasises the health benefits of consuming nuts.

Walnuts are used in a variety of ways. In addition to the tree's wood, which is one of the most expensive woods in the world, walnuts leaves and fruits are also used widely. Walnut leaves were evaluated by the HMPC and the Commission E and are classified as traditional herbal medicinal products. They are amongst the classic tannin-containing medicines. They are used to make infusions for mild skin irritations as well as for excessive perspiration, for example in the hands and feet. Products to be taken internally include tablets or dragées and as alcoholic tinctures. In folk medicine, walnut leaves are used to treat non-specific diarrhoea and, as a bitters, to stimulate gastrointestinal function. Both the leaves and the green husks were also used for tanning leather and dying fabrics, due to their high tannin content.

In traditional Chinese medicine, the walnut is classified as an "earth" element. Foods of this element are sweet-tasting. They spread in all directions, nourish and moisturise. Walnut has a warming effect on the body. Its taste is categorised as bittersweet. Its effects are connected with the functions of the heart, kidneys, lungs and intestines.

Green walnuts are used to make schnapps and a variety of bitters. The famous black walnut is considered a culinary delicacy, notably as sweet pickled walnuts. The nuts are harvested, still green, in the second half of June, around the time of St. John's Day, and soaked in water. In the beginning this water must be changed frequently. Wearing gloves is recommended here, as the green nuts turn brown and contain many tannins that are flushed out in the water.

Cold-pressed walnut oil is often added to salads. Due to its low smoke point (130-160°C), walnut oil should not be used for frying or deep-frying. Walnut oil is viewed as a dietetic culinary oil because of its high amounts of oleic acid and linoleic acid. It has positive effects on cholesterol levels in the blood and lowers the risk of arteriosclerosis. Walnut oil also has strong fungicidal and disinfectant effects, making it ideal for use in healing ointments.

Walnut oil is used in cosmetics because of its high availability of fatty acids. It is quickly absorbed and is reputed to have a stabilising effect on cell walls. This helps to keep the skin well-nourished. It is quite fatty compared to other plant oils, and is often used as a base for ointments and creams. Its moisturising properties make it an ideal ingredient in lip balms, shampoos, and shower gels.

What are the active substances in walnuts?

Walnut leaves are high in tannins. They also contain flavonoids, phenolic acids, and naphthoquinones. The nuts are high in fat and protein. As a food, walnuts are used in the kitchen in many forms, such as in walnut breads, in cakes and various desserts, in mueslis, salads and, of course, in trail mixes. Of all nut types, walnuts contain the highest levels of linoleic acid, which is essential for the formation of the omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). They are also rich in tocopherols, zinc, potassium, magnesium, phosphorus, sulphur, iron, calcium, vitamins A, B1, B2, B3, C, and pantothenic acid. Walnuts are also said to help prevent high blood pressure, cardiovascular disease, and type 2 diabetes. The positive effects of walnut have been observed in numerous studies.

Walnut leaves are harvests between late spring and early summer, when the leaves are fresh, young, and green. Walnut fruits can be harvested twice a year. The green walnuts are harvested in June, around St. John's Day. This is when the core is still soft and the nuts can be easily cut and processed. During this time they are also especially high in vitamin C. The nut kernels are then harvested in autumn from September to November. The walnuts are freed from their soft outer shells and dried for storage. In their hard shells they keep well in dry and well-ventilated conditions and can be used throughout the year.

How is walnut used to treat illnesses in horses and dogs?

The anti-inflammatory effects of walnut leaves are beneficial to both humans and other animals. A decoction of walnut leaves can be applied externally for inflammations, mucous membrane inflammations, eczema, itching insect bites, and other skin irritations. The leaves can also be used for internally taken treatments for inflammations of the stomach and intestinal mucosa and for liver disorders, as well as for natural deworming. Horses can eat the leaves "as is". However, it should be noted that excess tannins and the cinnamic acid they contain can also irritate the stomach lining. Therefore, it is essential to adhere to the correct dosage. For this reason, ready-to-use supplements are recommended for horses and dogs.

Sources

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