Hazel
Scientific Name(s): Corylus americana Walter (American hazel)., Corylus avellana L. (common hazel)., Corylus colurna L. (Turkish hazel).
Common Name(s): Dukkah, Filbert, Hazelnut
Medically reviewed by Drugs.com. Last updated on Mar 21, 2022.
Clinical Overview
Use
Hazelnuts (raw, roasted, or ground into a paste) are used as a dietary source of protein and minerals. They are a source of vitamin E, unsaturated fatty acids, and linolenic acid. Hazelnut oil also is used in the cosmetic industry as well as in confectionery.
Dosing
There are inadequate data to support dosing for therapeutic effect. Approximately 100 g of nuts delivers 15 mg of vitamin E.
Contraindications
Allergy to tree nuts or their products. Use caution in patients with known allergy to peanuts.
Pregnancy/Lactation
Information regarding safety and efficacy during pregnancy and lactation is lacking. Consumption of hazelnuts is generally recognized as safe when used as a food. No teratogenicity studies specific to hazelnut have been found.
Interactions
None well documented.
Adverse Reactions
Cross-reactivity with other tree nuts and co-allergy with peanuts have been described.
Toxicology
A review by the Cosmetic Ingredient Review Expert Panel concluded there are insufficient data to support the safety of hazelnut oil in cosmetic products. Carcinogenic aflatoxins are possible contaminants of hazelnuts.
Scientific Family
- Betulaceae (birch)
Botany
The genus Corylus includes at least 11 species of hazel trees and hybrids also exist.1 The trees grow from 3 to 8 m in height and were probably introduced into North America from Europe. Turkey is the leading producer of hazelnuts in the world.2 The deciduous trees bear large (6 to 12 cm) rounded leaves with soft hairs on both surfaces and a doubly serrate margin. The tree flowers in early spring before the leaves develop, and the nuts hang in clusters of 1 to 5. A "husk" encloses 75% of the yellow-brown, spherical/oval nut, leaving a scar at the base of the hazelnut kernel.1
History
In addition to consumption of the nuts as a source of protein, the leaves of the hazel tree have been used in folk medicine to relieve hemorrhoidal symptoms and varicose veins caused by purported vasoconstrictor properties.3
Chemistry
The minerals of the nut include calcium, copper, iron, magnesium, manganese, phosphorus, selenium, and zinc; vitamins include alpha-tocopherol, ascorbic acid, folates, niacin, riboflavin, thiamin, and vitamin K as phylloquinone; fatty and amino acids include alanine, arginine, aspartic acid, glutamic acid, and leucine.2, 4, 5
Tocopherol composition remains fairly consistent across geographic distribution and harvesting period.6 The hazelnut is the best dietary nut source of alpha-tocopherol, containing 2 to 3 times more than olive oil.7
The kernels contain about 60% seed oil2, 7 which is derived by cold pressing. The oil contains saturated fatty acids (7%), mono- (78%) and polyunsaturated fatty acids (10%), and phytosterols (0.1%).5, 8 Composition of the oil varies with geographic origin8; however, roasting the nuts prior to compressing appears to have little or no effect on oil composition.2,
