Hazel

Generic name: Corylus Americana Walter (American Hazel)., Corylus Avellana L. (common Hazel)., Corylus Colurna L. (Turkish Hazel).
Brand names: Dukkah, Filbert, Hazelnut

Usage of Hazel

Hazelnuts are a dietary source of protein, unsaturated fats, minerals and micronutrients, phytochemicals, alpha-tocopherol, and fiber; they are considered a good source of tocopherol when used to meet the recommended daily allowance for vitamin E.(Alasalvar 2003, Alasalvar 2003, Durak 1999)

Cardiovascular risk

Animal data

Rabbits fed a high-cholesterol diet and concurrent hazelnut oil maintained their baseline lipid profiles. No effect of hazelnut oil on the lipid profile was found in the control rabbits fed a normal diet. Hazelnut oil was also protective against atherosclerotic plaque formation upon histological examination.(Balkan 2003)

Clinical data

Results from a small stud revealed that hazelnut supplementation of 1 g/kg body weight/day showed reduced low-density lipoprotein and total cholesterol and increased high-density lipoprotein and triglycerides.(Durak 1999) Researchers have demonstrated improved lipid profiles (increased HDL and decreased LDL-C and total-C:HDL-C ratio) with hazelnut supplementation.(Tey 2015, Tey 2011)

Trials and epidemiological studies have found the consumption of nuts to be protective against cardiac morbidity and mortality. The Physicians' Health Study, a large prospective cohort study of United States physicians, associated dietary nut intake with a reduced risk of sudden cardiac death (47% lower risk for those who consumed nuts 2 or more times a week) but did not find it protective against nonfatal myocardial infarction.(Albert 2002)

Assessment of data from 6,705 participants without baseline atrial fibrillation in the PREDIMED trial revealed a significant relevant reduction in risk of atrial fibrillation (38%) with the Mediterranean diet supplemented with extravirgin Olive Oil (50 g/day or more) but not with the Mediterranean diet supplemented with nuts (almonds, hazelnuts, walnuts).(Martinez-Gonzalez 2014)

As a component of medical nutrition therapy for patients with type 2 diabetes, the American Diabetes Association Standards of Care (2014) recommend higher quality dietary fat intake, as an alternative to decreased fat intake, by replacing saturated and/or trans fats with mono- and poly-unsaturated fatty acids in the diet. This Mediterranean-style approach to eating may improve glycemic control and cardiovascular disease risk factors (moderate-quality evidence).(ADA 2014)

Cataracts

Animal data

In doxorubicin-induced cataracts in rats, the administration of hazelnut was protective in lower-dose doxorubicin; hazelnut did not prevent cataracts at higher doses of doxorubicin. Because doxorubicin causes oxidative stress to cells, the anticataract effect is considered to be due to the antioxidant action of vitamin E and other elements found in the hazelnut (eg, copper, iron, Selenium, zinc).(Bayer 2005)

Cognitive effects

Animal data

Oral supplementation of hazelnuts (800 mg/kg/day) for 1 week in an Alzheimer rat model resulted in significant improvements in spatial working memory, memory impairment, and anxiety-like behavior. Increases in neuroinflammatory markers (ie, interleukin [IL}-1beta, cyclooxygenase [COX]-2, tumor necrosis factor [TNF]-alpha) induced in the untreated rat model were found to be reduced by at least 50% in animals supplemented with hazelnuts.(Bahaeddin 2017)

Obesity

In vitro data

Anti-obesity effects of a hazelnut extract (protein isolate) were identified in vitro with further purification of the peptide leading to a synthetic version that demonstrated significant inhibition of lipid accumulation and adipocyte differentiation.(Wang 2020)

Other uses

Antioxidant activity and radical scavenging properties of the kernel and green leaf/flower portions of the hazel tree have been demonstrated.(Alasalvar 2006)

An antiprostaglandin/anti-inflammatory action has been described.(Tunón 1995)

In vitro studies have demonstrated the ability of hazelnut oils to induce skeletal muscle cell differentiation and hypertrophy, which was not observed with olive oil.(Teruzzi 2018)

Hazel side effects

Allergies to nuts are common in the United States (estimated 1%)Enrique 2005; however, cross-Reactivity to the proteins from tree nuts (hazelnut) among people with peanut (legume) allergies is considered low. Rather, a co-allergy is probably the cause of allergic reactions among these atopic individuals. Cross-reactivity between hazelnut and Brazil nut has been documented; similar proteins are found in the nuts of these botanically distinct trees.Asero 2004, Sicherer 2000

Anaphylaxis, urticaria, vomiting, and wheezing have been reported in response to hazelnut consumption. Immunoglobulin E (mast cell) and T-cell (cytokine) responses are described. Because sensitization is required, the possibility of these responses occurring in utero or via breast milk has been postulated, but no high-quality studies exist to support this theory.Sicherer 2000 Oral desensitization to hazelnut may offer partial protection.Enrique 2005

The use of antiulcer drugs is another possible method of sensitization to hazelnut. Hazelnut allergens are not resistant to gastric and pancreatic acid digestion, and the use of famotidine, Omeprazole, ranitidine, and sucralfate in animal and human experiments displayed some evidence of this effect.Scholl 2005

Before taking Hazel

Information regarding safety and efficacy during pregnancy and lactation is lacking.

How to use Hazel

There are inadequate data to support dosing for therapeutic effect. One human trial used hazelnuts 1 g/kg body weight/day.Durak 1999 The recommended daily amount of 15 mg vitamin E would be contained in approximately 100 g of nuts.USDA 2005

A clinical study has demonstrated acceptability of 30g hazelnuts daily, but not 60g daily.Tey 2011, Tey 2013

Warnings

Placental transfer of fatty acids has been documented, but no teratogenicity studies specific to hazelnut have been found.Madhaven 2001

A review by the Cosmetic Ingredient Review Expert Panel concluded there are insufficient data to support safety of hazelnut oil in cosmetic products.Madhaven 2001

Aflatoxins are considered carcinogenic and are possible contaminants of hazelnuts.Madhaven 2001

What other drugs will affect Hazel

None documented.

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