Pacific walnut/Dracontomelon dao, the New Guinea walnut, Pacific walnut, or Paldao, is a tropical canopy tree distinguished mostly by its height (reaching up to about 45 metres or 148 feet), for its greyish-brown trunk which is branchless up to about 20 m (66 ft), and for its narrow buttresses which can reach up its trunk up to 6 m (20 ft) high.[rx] The species name is taken from the tree’s name in Filipino.
D. dao is found in the tropical forests of: peninsular Malaysia (Kedah, Kelantan, Trengganu, Penang Isl., Perak, Pahan, Selangor, Negeri Sembilan), Borneo, Sumatra, Philippines (Luzon, Mindoro, Tablas, Negros, Leyte, Samar, Basilan, Mindanao, Palawan), Lesser Sunda Isl., Java, Sulawesi, Moluccas, New Guinea, Solomons, Andamans (South Andamans), Nicobars (Car Nicobar Island), E-India, Myanmar [Burma] (Kachin, Rakhine, Sagaing, Taninthayi, Mandalay, Yangon), Cambodia, Laos, Thailand and Vietnam.[rx]
Walnuts are round, single-seeded stone fruits that grow from the walnut tree. They are a good source of healthful fats, protein, and fiber. They may enhance heart and bone health and help in weight management, among other benefits.
Walnut trees are native to eastern North America but are now commonly grown in China, Iran, and within the United States in California and Arizona.
Beneath the husk of the walnut fruit is a wrinkly, globe-shaped nut. The walnut is split into two flat segments to be sold commercially.
| Pacific Walnut Quick Facts | |
|---|---|
| Name: | Pacific Walnut |
| Scientific Name: | Dracontomelon dao |
| Origin | Eastern India, Andaman Islands, South China, Myanmar, Indochina, Thailand |
| Colors | Green turning yellow when ripe |
| Shapes | Drupe, globose, 5-celled, or seemingly 1-celled by abortion |
Dracontomelon dao also known as New Guinea walnut, Pacific walnut, or Paldao, is actually a tropical canopy tree well-known mostly by its height for its greyish-brown trunk which is branchless up to about 20 m (66 ft.). The plant belongs to Anacardiaceae (Sumac family) and is native to eastern India, Andaman Islands, South China, Myanmar, Indochina, Thailand, Peninsular Malaysia, Indonesia, Philippines, New Guinea, and the Solomon Islands. The species name is taken from the tree’s name in Filipino. Other popular common names of the fruit are Argus pheasant tree, Mon fruit, New Guinea walnut, Papua New Guinea walnut, pheasant tree, Papuan Walnut, Asam Kuang, Sengkang, Sekuan, and Kueh. Genus epithet ‘Dracontomelon’ is derived from Greek terms for dragon (Draco) and melon, a reference to the fruits. Species epithet ‘day is derived from the vernacular name for this tree in the Philippines.
Plant Description
Pacific Walnut is a large, tall, erect, deciduous tree that grows about 36 m high with a large trunk of 70–100 cm diameter. The plant is found growing in undisturbed primary or secondary, evergreen, or semi-deciduous (monsoon) forest in tropical areas and especially along riverbanks and in swampy sites, occasionally flooded for short periods. The plant is found scattered on well-drained to poorly-drained, clayey to stony soils, organosols, gley humus soils, or red-yellow podsolic soil, on alluvial flats and in swampy areas and along river banks. The trunk is straight and cylindrical, unbranched to 15m height, with a root buttress at the base. The outer bark is greyish-brown and the inner bark is pink. Wounded bark exudes slightly sticky colorless resin which turns pale golden upon exposure to air.
Leaves
Leaves are arranged spirally, crowded towards the ends of branchlets, large, imparipinnate with 6–44 cm long leaf rachis and 4–9 pairs of leaflets. Leaflets are alternate to opposite, chartaceous, sub coriaceous, elliptic-oblong, oblong, ovate-oblong to lanceolate, 4.5–27 cm × 2–10.5 cm, glabrous or sometimes pubescent below, lower surface pale green, upper surface dark green with 3–10 pairs of nerves. Young leaves are brownish-yellow in color.
Flower & Fruit
Flowers are bisexual, stalked, actinomorphic, 5-merous, slightly fragrant, white to greenish-white, 7–10 mm long, in panicles of up to 50 cm long; petals are oblanceolate and valvate but imbricate at the apical part, puberulous outside or on both surfaces, or glabrous. Stamens are in 2 whorls, filaments are glabrous, and anthers are dorsifixed, disk intrastaminal, puberulous or glabrous. The pistil is composed of 5 carpels which are free but connate at base and apically. The ovary is superior, 5-celled with a single ovule in each cell, styles 5, stigma is capitate. Fruit is a drupe, globose, 5-celled, or seemingly 1-celled by abortion, each cell with a distinct operculum, endocarp lentiform, woody and hard, and with 5 oval markings on the upper side of the fruit. Fruits are green when young turning yellow when ripe.
Health Benefits
Nutritional breakdown
According to the U.S. Department of Agriculture (USDA) National Nutrient Database, 1 cup of unbranded, organic walnuts (30 grams) contains[rx]:
- Energy: 200 calories
- Carbohydrate 3.89 grams (g)
- Sugar: 1 g
- Fiber: 2 g
- Protein: 5 g
- Fat: 20 g
- Calcium: 20 milligrams (mg)
- Iron: 0.72 mg
- Sodium: 0 mg
Walnuts are also a good source of:
- manganese
- copper
- magnesium
- phosphorus
- vitamin B6
- iron
They are high in monounsaturated and polyunsaturated fats and omega-3 fatty acids. They are also a good source of protein.
Nuts have a reputation for being a high-calorie and high-fat food. However, they are dense in nutrients and provide heart-healthy fats.
The combination of healthy fats, protein, and fiber in walnuts helps to increase satisfaction and fullness. This makes them more healthful as a snack, compared with chips, crackers, and other simple carbohydrate foods.
Heart health
The monounsaturated and polyunsaturated fatty acids found in walnuts have been shown to decrease LDL (harmful) cholesterol and triglyceride levels.
This, in turn, reduces the risk of cardiovascular disease, stroke, and heart attack.
A study published in the British Journal of Nutrition showed that the risk of coronary heart disease is 37 percent lowerTrusted Source for those consuming nuts more than four times per week, compared to those who never or rarely consumed nuts.
In 2013, scientists published findings of a small study which indicated that:
- walnut oil can benefit endothelial function
- whole walnuts can enhance the process of eliminating “bad” LDL cholesterol
Results of a meta-analysis published in 2009 suggested that a diet that is high in walnuts is linked to improved lipid and cholesterol profiles. The researchers also concluded that walnuts may also help reduce oxidative stress and inflammation.
In 2003, the U.S. Food and Drug Administration (FDA) approved the claim for food labels on a variety of nuts, including walnuts, that:
“Eating 1.5 ounces per day of most nuts as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease.”
FDA
However, they note that while scientific evidence suggests that this is true, it does not prove it. The statement also refers to whole or chopped nuts, and not products that contain nuts.
Weight management
According to research published in the Asia Pacific Journal of Clinical Nutrition, routine nut consumption is associated with higher levels of energy use while resting. In trials that compared weight loss using diets that include or exclude nuts, the diets that included nuts in moderation showed greater weight loss. A study published in the American Journal of Clinical Nutrition also found that women who reported rarely eating nuts had a greater incidence[rx] of weight gain over an 8-year period than those who consumed nuts two times a week or more.
Gallstone disease
According to another study in the American Journal of Clinical Nutrition, frequent nut consumption is associated with a reduced risk of cholecystectomy, an operation to remove the gallbladder. In over a million people documented over 20 years, women who consumed more than 5 ounces of nuts a week had a significantly lower risk of cholecystectomy than women who ate less than 1 ounce of nuts each week.
Bone health
Walnuts are a good source of mineral copper. Severe copper deficiency is associated with lower bone mineral density and an increased risk of osteoporosis.
Osteoporosis is a condition where bones become thinner and less dense, making them easier to fracture and break. More research is needed on the effects of marginal copper deficiency and on the potential benefits of copper supplements to prevent and manage osteoporosis. Copper also plays an important role in the maintenance of collagen and elastin, major structural components of the body.
Without sufficient copper, the body cannot replace damaged connective tissue or the collagen that makes up the building blocks for bone. This can lead to a range of issues including joint dysfunction. Walnuts contain a high amount of manganese. Manganese has been shown to prevent osteoporosis in combination with the minerals calcium and copper.
Magnesium, another mineral in walnuts, is important for bone formation as it helps with the absorption of calcium into the bone. While manganese and copper supplements may provide quantities of minerals that can be harmful, getting these minerals through the diet is thought to be good for bone health.
Epilepsy
Rats with manganese deficiency have been shown to be more susceptible to seizures. People with epilepsy have also been found to have lower whole blood manganese levels than those without epilepsy, although a manganese deficiency is not thought to cause epilepsy. More research is needed into whether manganese supplementation would benefit people with epilepsy.
Walnuts in the diet
Nuts have a high-fat content, and so they are prone to becoming rancid. Rancid nuts are not unsafe but have a sharp flavor that people may find unpleasant.
Keeping walnuts in their shells in a cool, dark, and dry place can improve their shelf life.
Kept in a refrigerator below 40 degrees Fahrenheit or in a freezer below 0 degrees Fahrenheit, they can be stored for over a year.
If you want to store them at room temperature, freeze them first at 0 degrees Fahrenheit or less for 48 hours to kill any pests.
Quick tips:
Here are some easy and delicious ways to get more walnuts into the diet:
- Top salads with chopped walnuts
- Make homemade granola with a mixture of nuts, seeds, and dried fruit, using walnuts
- Make a pesto sauce using walnuts and use with pasta or flatbread
- Top yogurt with chopped walnuts and fruit
Try these healthy and delicious recipes developed by registered dietitians:
- Cinnamon-roasted brussels sprouts with walnuts
- Whole-grain gnocchi alfredo with spinach and walnuts
- Apricot and walnut trail mix
- Walnut bread
Risks
Some researchers have concludedTrusted Source that consuming walnuts does not lead to weight gain.
However, walnuts are dense in calories, and people are advised to consume them in moderation to reduce this risk.
A high consumption of walnuts has also been linked to diarrhea.
This could be after a person eats a large quantity of walnuts, because of the high oil or fiber content, or because they have a sensitivity, for example, in people with irritable bowel syndrome (IBS).
A 1-ounce serving of walnuts contains about 14 half-walnut pieces.
People who are allergic to nuts should not eat walnuts. If the person develops a rash or hives or difficulty breathing after eating walnuts, medical attention should be sought.
Children should not consume pieces of nut, or they should be supervised while doing so, as this can lead to choking.
Walnuts can be a healthful addition to the diet. A diet that is balanced overall and followed alongside an exercise regime is best for health.
Traditional uses and benefits of Pacific Walnut
- In china, fruits are used to cool and relieve itchiness, cure internal ulceration, and as an antidote for poisoning in China.
- Bark can be used for dysentery.
- Fruits can be used to soothe sore throat and inflammation of the skin.
- Indonesians drink a decoction of bark to expel the membrane enveloping the fetus in the womb.
- The bark is used in traditional medicine to provoke an abortion.
- Leaves and flowers are used in traditional medicine.
- Fruit is depurative and is used in the treatment of dermatitis.
- Mature fruits are used in dentistry.
- Leaves were found to possess antiseptic properties against a broad spectrum of bacteria.
- Fruits reportedly have cooling properties and are used to treat sore throat, skin inflammation, itch, internal ulcers, as well as an antidote for poisoning.
Culinary Uses
- Young fruits are used to flavor curry, and the edible flesh covering the seed is sweet-sourish and eaten in Thailand.
- Fruit is used as a sour relish with fish in Malaysia.
- The seed kernel is also edible.
- Flowers, fruits, and young leaves are eaten cooked as vegetables e.g. in Vietnam, Thailand, East Malaysia, and Papua New Guinea.
- Flowers and leaves are used as spices for flavoring food in Maluku, Indonesia.
- Small, sourish-sweet fruit is cooked with soy sauce and eaten with rice, or used for flavoring curries.
- Flowers and leaves are cooked and eaten as a vegetable or used as a food flavoring.
- Fruits are edible, fresh, or stewed in honey.
- Kernels mixed with tea impart a fragrant and mucilaginous sweet taste.
Other Facts
- The tree is used for firewood and provides a source of commercial dao timber which is soft and light and not very durable.
- Usually, colorful timber is extensively used for furniture and interior finish, and also for joinery, cabinetwork, shop fittings, decorative (sliced) veneers, plywood, paneling, molding, flooring, light construction, fence posts, house posts, rafters, boat-building, shop fittings, cladding, lining, boxes, matches, turnery, carving and artifacts.
- Wood is also appreciated for joinery and turnery.
- The tree is planted as an ornamental in roadside plantings.
- Seeds are used by kids as toys.
- Trees are used as firewood.
- It is believed that holding a seed in the right hand on odd days and the left hand on even days will precipitate childbirth.
References
