Juglans regia

Juglans regia (the Common walnut, Persian walnut, or English walnut), is the original walnut tree of the Old World. It is native in a region stretching from the Balkans eastward to the Himalayas and southwest China. The largest forests are in Kyrgyzstan, where trees occur in extensive, nearly pure walnut forests at 1,000–2,000 m altitude (Hemery 1998)—notably at Arslanbob in Jalal-Abad Province.

Contents 1 Description 2 Taxonomy 3 Distribution and habitat 4 Ecology 5 Uses 5.1 Food 5.2 Medical potential 5.2.1 Oral Walnut Leaves and Diabetes Mellitus 5.2.2 Alcoholic Walnut extract and Alzheimer's 5.3 Nutriceutical 5.4 The health benefits of walnuts 5.4.1 Walnuts and Heart Disease 5.4.2 Walnuts and weight-control 5.4.3 Walnuts and Cognitive and Motor Function 5.4.4 Walnuts and Antioxidants 5.5 Walnuts in Chinese medicine 6 Culture 7 Notes 8 References 9 External links

Description

Juglans regia is a large deciduous tree attaining heights of 25–35 m, and a trunk up to 2 m diameter, commonly with a short trunk and broad crown, though taller and narrower in dense forest competition. It is a light-demanding species, requiring full sun to grow well.

The bark is smooth, olive-brown when young and silvery-grey on older branches, and features scattered broad fissures with a rougher texture. Like all walnuts, the pith of the twigs contains air spaces, and the chambered pith is brownish in colour. The leaves are alternately arranged, 25–40 cm long, odd-pinnate with 5–9 leaflets, paired alternately with one terminal leaflet. The largest leaflets the three at the apex, 10–18 cm long and 6–8 cm broad; the basal pair of leaflets much smaller, 5–8 cm long, the margins of the leaflets entire. The male flowers are in drooping catkins 5–10 cm long, and the female flowers terminal, in clusters of two to five, ripening in the autumn into a fruit with a green, semi-fleshy husk and a brown corrugated nut. The whole fruit, including the husk, falls in autumn; the seed is large, with a relatively thin shell, and edible, with a rich flavour.

Taxonomic keys	Male flower	Female flower	Fruit
Seed	Bark	Foliage	Habit
Walnuts from northern Poland

Taxonomy

The scientific name Juglans is from Latin Jupiter glans, "Jupiter's acorn", and regia, meaning "royal" in Latin. Its common name, Persian walnut, indicates its origins in Persia in southwest Asia; 'walnut' derives from the Germanic wal- for "foreign", recognizing that it is not a nut native to Great Britain. Synonyms include: Juglans duclouxiana Dode; J. fallax Dode; J. kamaonia (C. de Candolle) Dode; J. orientis Dode; J. regia var. sinensis C. de Candolle; J. sinensis (C. de Candolle) Dode.^[1]

Other names include Walnut (which does not distinguish the tree from other species of Juglans), Common Walnut and English Walnut, the latter name possibly because English sailors were prominent in Juglans regia nut distribution at one time.[2] Alternatively, Walter Fox Allen stated in his 1912 treatise What You Need to Know About Planting, Cultivating and Harvesting this Most Delicious of Nuts:^[2] "In America it has commonly been known as English Walnut to distinguish it from our native species."

In the Chinese language, the edible, cultivated walnut is called 胡桃 (hú táo in Mandarin), which means literally "Hu peach", suggesting that the ancient Chinese associated the introduction of the tree into East Asia with the Hu barbarians of the regions north and northwest of China. In Mexico, it is called nogal de Castilla^[3], suggesting that the Mexicans associate the introduction of the tree into Mexico with Spaniards from Castile.

Cultivars: Juglans regia 'Buccaneer' Produces an abundant crop of seeds. A self-fertile cultivar, it produces pollen over a long period and is thus a valuable pollinator for other cultivars. The tree is about the same size as a seedling walnut, it comes into leaf very late and so usually avoids damage by late frosts.

Distribution and habitat

Juglans regia is native to the mountain ranges of Central Asia, extending from Xinjiang province of western China, parts of Kazakhstan, Uzbekistan and southern Kirghizia and from mountains of Nepal, Tibet, northern India and Pakistan through Afghanistan, Turkmenistan and Iran to portions of Azerbaijan, Armenia, Georgia and eastern Turkey. In these countries, there is a great genetic variability in particular ancestral forms with lateral fruitfulness. During its migration to western Europe, English walnut lost this character by natural selection on account of competition with other vigorous forest species such as oaks. They became big trees with terminal fruitfulness. A small remnant population of these J. regia trees have survived the last glacial period in Southern Europe but the bulk of the wild germplasm in the Balkan peninsula and much of Turkey was most likely introduced from eastern Turkey by commerce and settlement several thousand years ago.

Four centuries BC, Alexander the Great introduced in Macedonia ancestral forms with lateral fruitfulness from Iran and Central Asia. They hybridized with terminal bearing forms to give lateral bearing trees. These lateral bearers were spread in southern Europe and northern Africa by Romans. Recent prospections in walnut populations of the Mediterrean Basin allowed to select interesting trees of this type. In the Middle Ages, the lateral bearing character was introduced again in southern Turkey by merchants travelling along the Silk Road. J. regia germplasm in China is thought to have been introduced from Central Asia about 2 000 years ago, and in some areas has become naturalized. Cultivated distribution now includes North and South America (Chile, Argentine), Australia, New Zealand, South Africa and Japan. So, the Persian walnut is grown from 30 to 50 degrees of latitude in the Northern hemisphere and from 30 to 40 degrees in the Southern hemisphere.

The walnut was introduced into western and northern Europe very early, by Roman times or earlier, and to the Americas by the 17th century, by English colonists. Important nut-growing regions include France, Serbia, Greece, Bulgaria, and Romania in Europe, China in Asia, California in North America, and Chile in South America. Lately the crop has spread to other regions: New Zealand and the southeast of Australia^[4]. It is cultivated extensively for its high-quality nuts, eaten both fresh and pressed for their richly flavoured oil; numerous cultivars have been selected for larger nuts with thinner shells.

Ecology

The Life Cycle:

Buds

Young tree

Fertilized flowers

Mature tree

Uses

The wood is of very high quality, and is used to make furniture and gunstocks. It has a density of 670 kg per cubic meter^[5]. Walnut ink, made by boiling the whole fruit or letting it oxidize, is dark brown in color and darkens as it oxidizes. It can also be used to stain wood. In China the tree is used horticulturally in classical garden design.

Food

Walnut, Common

Nutritional value per 100 g (3.5 oz)
Energy	2,738 kJ (654 kcal)
Carbohydrates	13.71 g
Sugars	2.61 g
Dietary fiber	6.7 g
Fat	65.21 g
Protein	15.23 g
Thiamine (Vit. B1)	0.341 mg (26%)
Riboflavin (Vit. B2)	0.150 mg (10%)
Niacin (Vit. B3)	1.125 mg (8%)
Pantothenic acid (B5)	0.570 mg (11%)
Vitamin B6	0.537 mg (41%)
Folate (Vit. B9)	98 μg (25%)
Vitamin C	1.3 mg (2%)
Calcium	98 mg (10%)
Iron	2.91 mg (23%)
Magnesium	158 mg (43%)
Phosphorus	346 mg (49%)
Potassium	441 mg (9%)
Zinc	3.09 mg (31%)
Manganese 3.414 mg
Selenium 4.9 mcg
Percentages are relative to US recommendations for adults. Source: USDA Nutrient database

100 g shelled walnuts provide:

• 15.2 g protein
• 65.2 g fat:
  • 6.1 g saturated fat
  • 8.9 g monounsaturated fat
  • 47.2 g polyunsaturated fat
• 13.7 g carbohydrates, including 6.7 g dietary fiber
• 0.34 mg Thiamin
• 0.54 mg Vitamin B₆
• 98 µg Folate
• 3.4 mg Manganese
• 1.6 mg Copper
• 158 mg Magnesium
• 346 mg Phosphorus
• 3.1 mg Zinc

A study of ten cultivars of J. regia in Turkey showed significant variations in fatty acid content:^[6]

• 62% - 71% fat
  • saturated fat (as a percentage of total fatty acid):
    • 5.2% - 7.3% palmitate
    • 2.6% - 3.7% stearate
  • unsaturated fat (as a percentage of total fatty acid):
    • 21.2% - 40.2% oleate (monounsaturated)
    • 43.9% - 60.1% linoleate (diunsaturated)
    • 6.9% - 11.5% linolenate (triunsaturated)

English walnuts feature a lower ratio between ω–6 and ω–3 fatty acids than many other nuts (even than the related nut, the black walnut). For example, according to the United States Department of Agriculture website, 100 g of walnuts has 47.14 g of polyunsaturated fatty acids, of which 38.093 g are linoleic acid (an ω–6 fatty acid) and 9.08 g are alpha-linolenic acid (an ω–3 fatty acid).

Medical potential

Oral Walnut Leaves and Diabetes Mellitus

One lone study has yielded the tantalizing result that feeding walnut leaves to diabetic rats with induced insulin-dependent diabetes mellitus had the effects of reducing fasting blood sugar and of regenerating beta cells.^[7] Because this suggestion of a possible means to cure for Type I diabetes mellitus in humans has not been supported by an actual case of such treatment curing a Type I diabetic human, a study in which such treatment caused regeneration of beta cells in some other species, a study in which such treatment caused regeneration of rat beta cells that were destroyed by a different means, or even a simple duplication of this study in another laboratory, this un-reproduced result remains merely tantalizing and not yet promising.

Alcoholic Walnut extract and Alzheimer's

A 2004 study by the NYS Institute for Basic Research in Developmental Disabilities (OMRDD) found that walnut extract was able to inhibit and defibrillize (break down) fibrillar amyloid beta protein - the principal component of amyloid plaques in the brains of patients with Alzheimer's. The study looked at the effect of walnut extract on amyloid beta protein fibrillization by Thioflavin T fluorescence spectroscopy and electron microscopy.^[8] Similarly, in a study done at Baldwin-Wallace College in Berea, Ohio it was found that two of its major components in walnuts, gallic and ellagic acid, act as "dual-inhibitors" of the enzyme acetylcholinesterase which, in association with amyloid-β, inhibits protein aggregation, and will also inhibit the site of acetylcholinesterase responsible for the breakdown of acetylcholine.^[9]

These results suggest that walnuts may reduce the risk or delay the onset of Alzheimer's disease by maintaining amyloid-β protein in the soluble form and prevent the breakdown of acetylcholine.^[8]

Nutriceutical

The walnut marketing industry has issued a press release interpreting a 2006 study published in the Journal of the American College of Cardiology to mean that eating walnuts after a meal high in saturated fats can reduce the damaging effects of such fats on blood vessels. Researchers from Barcelona's Hospital Clinic conducted a study on 24 adult participants, half of whom had normal cholesterol levels, and half of whom had moderately high levels of cholesterol. Each group was fed two high-fat meals of salami and cheese, eaten one week apart. During one meal, the researchers supplemented the food with five teaspoons of olive oil; the researchers added 40 g shelled walnuts to the other meal.

Tests after each meal showed that neither the olive oil nor the walnuts had any effect on inflammatory substances or lipid oxidation in the blood samples taken after the meals. However, the participants with moderately high cholesterol levels exhibited increased arterial wall movement after the meal containing walnuts and decreased movement after the meal containing olive oil. The participants who had normal cholesterol levels showed a much smaller effect on arterial movement.

Lead researcher Dr. Emilio Ros, who serves on the scientific advisory board of the California Walnut Commission^[10], speculated that walnuts' protective effects could be because the nuts are high in antioxidants and ALA, an omega-3 fatty acid. Dr. Emilio Ros also noted that walnuts also contain arginine, which is an amino acid that the body uses to produce nitric oxide, which he stated was necessary for keeping blood vessels flexible.^[11][12] Juglans regia is grown extensively for its nuts, as an ornamental tree, and for wood.

The health benefits of walnuts

In the last 20, years the scientific and public opinion concerning nuts consumption has changed dramatically. Once considered to be too fatty and unsuitable for daily consumption, we now know that nuts have an optimal lipid profile and contain many antioxidants and phytochemicals, which makes them a forefront food in the prevention against numerous chronic diseases.

Walnuts and Heart Disease

Several studies funded by The California Walnut Commission, Sacramento, CA (the marketing arm of the California Juglans regia growing industry) and authored by a member of the California Walnut Commission Scientific Advisory Committee, have concluded that daily consumption of walnuts instead of certain other un-named foods can reduce the risk of heart disease, and have beneficial effects on cholesterol levels. The studies did not compare walnut consumption with the consumption of any other nuts.

A study published in 1993 investigated the cholesterol lowering effects of walnuts. This study involved randomly placing 18 healthy men, ages 21 to 43, on two different diets, for four weeks each. One diet followed the guidelines for the National Cholesterol Education Program. In the second diet, 20% of the calories were derived from walnuts. The results from this study showed a 12.4% reduction of total cholesterol level, 16.3% reduction of LDL cholesterol and a 4.9% reduction in HDL cholesterol. The ratio of LDL cholesterol to HDL cholesterol was decreased by the walnut diet. Blood pressure was not affected. The authors concluded: "the results of this study indicate that a diet that includes moderate quantities of walnuts without an overall increase in total dietary fat and calories decreases serum cholesterol levels and favorably modifies the lipoprotein profile in normal men, an effect beyond that of the currently recommended diet for lowering cholesterol."^[13]

A study published in 2001 measured the effects of two diets, compared to a control, on serum lipoproteins. In this study, ten men with polygenic hypercholesterolemia (high cholesterol levels caused by their genes) followed a "Mediterranean-type cholesterol-lowering diet", a diet in which walnuts replaced approximately 35% of calories of the "Mediterranean" diet, and a control diet, for 6 weeks each. The total and LDL serum cholesterol fractions were reduced by a statistically insignificant amount on the "walnut" diet, compared to the control diet. The paper did not mention the results of the "Mediterranean" diet. A statistically significant effect was found in the association of LDL particles with certain liver cells during the "walnut" diet.^[14]

A study published in 2009 analyzed the effects of walnuts and fatty fish on serum lipid components. In a randomized feeding trial, 25 normal to mildly hyperlipidemic adults followed three different diets for four weeks each. The first diet contained no nuts or fish, the second diet included walnuts (42.5 g every day) as a substitute for some of the meat and dairy products, and the third diet included fatty fish (113g salmon, twice a week). The article did not state which species of walnut (Juglans sp.) was used. Fasting blood was drawn at the end of each diet period to analyze serum lipids. The walnut diet produced lower serum total cholesterol and LDL cholesterol concentrations than both the control and fish diets, both of which included more dietary cholesterol. The fish diet produced the lowest serum triglyceride and the highest serum HDL cholesterol and total cholesterol concentrations. The authors concluded "Including walnuts and fatty fish in a healthy diet lowered serum cholesterol and triglyceride concentrations, respectively, which affects CHD risk favorably."^[15]

Walnuts are also an excellent source of omega-3 fatty acids, and have been shown as helpful in lowering cholesterol.

Walnuts and weight-control

Many individuals are reluctant to consume walnuts daily because of the fear of weight gain. Several studies have shown that this isn’t necessarily true.

A study published in 2005, investigated whether regular walnuts consumption may lead to weight gain. Ninety participants (40 men and 50 women ages 32 to 72 years) in a 12-month randomized cross over trail were asked to eat every day 1.5 ounce (35 g) of walnuts or not to eat walnuts during the control diet. The walnuts supplemented diet resulted in daily energy increase of 557 kJ (133 kcal) and should theoretically have led to a weight gain of 3.1 kg (6.8 lb) over the 6-month period. However, the participants on walnut supplementation results showed only a very modest gain of only 0.4 kg (0.8 lb). After adjusting for energy differences between the control and walnut-supplemented diet, the observed difference in weight was not significant. Possible explanation for these results is that once participants started to eat walnuts they consumed less of other foods. Another possible explanation is that fat from walnuts is not absorbed. Researchers conclude that daily walnuts consumption poses no risk of significant weight gain.^[16]

The Nurses’ Health Study evaluated the dietary intake of nuts (peanuts and tree nuts) and weight changes from 1991 to 1999, in 51,188 women who ranged in age from 20 to 45 years of age. Those women who reported eating nuts more than 2 times per week, had slightly less weight gain than did women who rarely ate nuts. This study suggests there is no evidence of a positive association between nut consumption and weight gain.^[17]

In weight management, including walnuts or other nuts in the context of low caloric diets may actually enhance weight loss, and improve body composition. Eating four to six walnut halves before meals may decreases hunger and help consume less at meals.^[18]

Walnuts and Cognitive and Motor Function

Cognitive function “involves all aspects of perception, thinking, reasoning, and remembering.” ^[19] Motor functions are the “abilities to use and control muscles and movements.”^[20] Omega-3, which is a fatty acid that can be found in walnuts, may affect both cognitive and motor function. The type of omega-3 in walnuts is called alpha-linolenic acid, or ALA. There are 2.5 g of ALA in every 1.0 oz. of walnuts. A study published in 2009 looked at how walnuts in the diet affect motor and cognitive functions of rats. Groups of rats were given diets that included different amounts of walnuts. The rats then had to swim through a water maze to test their cognitive function. To test their motor function, they had to walk on a rod, hang on a wire with their paws, walk on a plank, walk on a screen that was tilted at an angle, and balance on a rod that was rotating. The researchers found that the rats who had walnuts in their diets did better on the motor tests than the rats with no walnuts in their diet. They also found that rats that ate walnuts were able to remember how to swim through the water maze better than the rats that did not eat walnuts.^[21] There is clearly more research needed to determine the effects of walnuts on human cognitive and motor function.

Transgenic Alzheimer's mice fed a diet containing 6 to 9 percent walnuts showed significant improvement in learning, memory, emotional regulation and motor coordination compared to similar transgenic mice that did not eat walnuts. ^[22]

Walnuts and Antioxidants

Antioxidants, which can be found in walnuts, are substances that can protect cells from being damaged. Walnuts contain at least 10 different antioxidants. In a 2006 study, 1,113 different commonly consumed foods were tested for content of redox-active compounds and walnuts ranked second after blackberries with an antioxidant content of 3.721 mmol/serving.^[23]

A study published in 2009 showed increased antioxidant levels in blood after walnuts and almonds consumption. Fourteen healthy subjects (7 men and 7 women ages 19–64) participated in this randomized crossover trail. Participants consumed either almonds or walnuts, blended into smoothies, or a control meal with no nuts. Each subject participated on three occasions, 1 week apart, consuming one of the smoothies each time. After consumption of the test meal, researcher collected blood samples every 30, 90, 150 and 210 minutes. The plasma polyphenol concentrations and total antioxidant capacity were measured. Within 30 min after the test meal for both walnuts and almonds the total antioxidant capacity levels increased, peaked at 150 minutes, and then started to decline at 210 min. There was a significant increase in plasma polyphenol concentration following both nut meals, with peak concentrations being achieved at 90 minutes, and with a walnut meal having a more sustained higher concentrations than the almond meal. The study provides evidence about the significant antioxidant protection offered by nuts.^[24]

Due to the high unsaturated fat content of the oil, English walnuts need to be kept dry and refrigerated to store well; in warm conditions they become rancid in a few weeks, particularly after shelling.

Walnuts in Chinese medicine

In Traditional Chinese Medicine, walnut seeds are primarily considered a kidney tonic. They are also considered beneficial to the brain, back, and skin, and to relieve constipation if it is caused by dehydration.^[25]

Culture

In Skopelos, a Greek island in the Aegean Sea, local legend suggests that whoever plants a walnut tree will die as soon as the tree can "see" the sea. This has not been proven as fact, however it might take some time to find a local arborist willing to take on the job of planting a walnut tree. Most planting is done by field rats (subfamily Murinae). In Flanders, a folk saying states: "By the time the tree is big, the planter sure will be dead" (Dutch: Boompje groot, plantertje dood). This saying refers to the relatively slow growth rate of the tree.

Notes

References

• Flora Europaea: Juglans regia
• Flora of Pakistan: Juglans regia
• Chauhan, N., Wang, K.C., Wegiel, J. and Malik, M.N. (2004) "Walnut Extract Inhibits the Fibrillization of Amyloid Beta-Protein, and also Defibrillizes its Preformed Fibrils", Current Alzheimer Research, 1 (3), p. 183–188
• Cortés, B., Núñez, I., Cofán, M., Gilabert, R., Pérez-Heras, A., Casals, E., Deulofeu, R. and Ros, E. (2006) "Acute Effects of High-Fat Meals Enriched With Walnuts or Olive Oil on Postprandial Endothelial Function", J. Am. Coll. Cardiol., 48 (October), p. 1666–1671, doi:10.1016/j.jacc.2006.06.057
• Hemery, G. E. (1998). Walnut seed-collecting expedition to Kyrgyzstan in Central Asia. Quarterly Journal of Forestry 92 (2): 153-157.
• Society for Neuroscience (2007). "News Release: Diet of walnuts, blueberries improve cognition; may help maintain brain function", Society for Neuroscience, 5 November 2007
• eFloras, Missouri Botanical Garden & Harvard University Herbaria (FOC Vol. 4 Page 282). "Juglans regia". http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200006112. Retrieved 2009. 

External links

External identifiers for Juglans regia
NCBI Taxonomy	51240
ITIS	503244
Encyclopedia of Life	487229
Also found in: Wikispecies