Hazelnuts (Filberts): Nutrients, What Research Shows and Safety

The hazelnut, also called filbert, is the kernel inside the hard shell of the nut of Corylus avellana, a shrub or small tree in the birch family (Betulaceae). People eat the kernel raw, roasted or ground into spreads and baking flour, and many eat it for its fats, fiber, vitamin E and manganese. This page separates hazelnuts as a whole food from oils, extracts and supplements, and from hype, and it says plainly where the evidence is thin.

Read this first

• Hazelnuts are a tree nut, and tree nuts are a common food allergen. For trouble breathing, or swelling of the lips, mouth, throat or tongue, call 911 (999 in the UK). [10][11] See food allergy basics and emergency signs.
• If you have birch pollen hay fever, raw hazelnuts can make the mouth and throat itch. The NHS says this "pollen food syndrome" is usually not serious. [11][6]
• Whole nuts should not be given to children under 5 because they can choke on them. The NHS says crushed or ground nuts can be added to food from about 6 months, and nut butter should be spread thinly, not given on its own. [9]
• Honest summary: pooled trials found that hazelnut-rich diets lower LDL ("bad") cholesterol a little, and nut trials in general do not show weight gain. Claims that hazelnuts prevent disease rest mostly on observational studies, which cannot prove cause. [2][5][7]

What is in it (USDA values)

USDA data for raw hazelnuts (filberts). The USDA household portion is 1 ounce, about 21 whole kernels, which is 28.35 g. [1]

Source: USDA FoodData Central item 170581 (SR Legacy). [1] The per-serving column is the USDA per-100 g value scaled to 28.35 g. % Daily Value uses the FDA 2016 Daily Values; values vary with variety, growing place, roasting and storage. USDA lists no omega-3 (ALA) value for this item in our file.

Hazelnuts are mostly fat, and most of it is monounsaturated. [1][2] MedlinePlus names hazelnuts among the nuts that are food sources of vitamin E. [8] We did not read a source that measured the plant compounds (such as polyphenols) in hazelnuts in a way we can report, so we make no claim about them beyond the review statement that hazelnuts contain "antioxidant bioactive substances". [2]

What research says

Eaten as food vs taken as oil, extract or supplement. The trials above used whole hazelnuts as food. We did not read trials of hazelnut oil, skin extract or powders in people, so nothing here applies to those products. We did not check who paid for each review; many nut studies are funded by the nut industry, so check the funding statement when you read a study.

How much is a normal serving

The USDA household portions for hazelnuts are 1 ounce (28.35 g, 21 whole kernels), 10 nuts (14 g), and 1 cup whole (135 g). [1] One ounce has about 178 kcal. [1] The FDA's 2003 qualified health claim says "scientific evidence suggests but does not prove" that eating 1.5 ounces a day of most nuts, as part of a diet low in saturated fat and cholesterol, "may reduce the risk of heart disease"; hazelnuts were among the nuts the petition named, and the letter does not exclude them. [12] That is an official wording, not a prescription for you. Hazelnuts are energy dense, but weight-gain trials of nuts in general found no gain. [7]

Safety, allergy and medicines

• Allergy. The NHS lists hazelnuts with walnuts, almonds, cashews and Brazil nuts as tree nuts that can cause allergy, and lists peanuts separately. [11] In the US, tree nuts are one of the nine major allergens that must be declared on labels. [10] Call 911 (999 in the UK) for swelling of the lips, mouth, throat or tongue, fast breathing or difficulty breathing, a tight throat, or fainting. [11]
• Hazelnut allergy and birch pollen. In people with birch pollen allergy, immune responses to a hazelnut protein (Cor a 1) were found to cross-react with the main birch pollen protein in a laboratory study. [6] A meta-analysis of children found that blood tests for the hazelnut storage proteins Cor a 9 and Cor a 14 were more specific than tests for Cor a 1 or whole-hazelnut extract. [13] Testing and diagnosis belong to an allergist; we do not give advice on it.
• Cross-reactivity with other nuts. A small Spanish study of 7 people allergic to macadamia found that hazelnut extract blocked IgE binding to a macadamia protein, suggesting cross-reaction between those two nuts. [14] See macadamia nuts.
• Choking. The NHS says whole nuts should not be given to children under 5. [9] See foods for babies and toddlers.
• Mold and aflatoxin. WHO says aflatoxin-producing molds commonly affect tree nuts, and names hazelnuts as regularly contaminated. Aflatoxins can cause liver cancer in humans with long exposure. [15]
• Medicines. Proper evidence on hazelnuts changing how medicines work was not found in the sources we read. MedlinePlus warns about high-dose vitamin E supplements, which are not the same as eating nuts. [8] Ask a pharmacist about your own medicines.
• Kidney disease. We did not read a source on hazelnuts and kidney stones or kidney disease limits. If a clinician limits potassium or phosphorus for you, ask about nuts. See foods, kidney disease, potassium and oxalates.
• Calories. One ounce has about 178 kcal, according to USDA. [1]

Choosing, storing and food safety

• WHO advises inspecting nuts, including hazelnuts, and discarding any that look moldy, discolored or shriveled. [15]
• WHO also advises buying nuts as fresh as possible and storing them dry and not too warm, without keeping them a long time. [15]
• MedlinePlus (FDA information) says buying major brands of nuts and nut butters, and discarding moldy-looking nuts, can reduce aflatoxin intake. [16]
• For rancidity and storage details, see storing nuts and seeds.

Related pages

• Nuts and seeds for heart health: what trials found
• Nut and seed allergy basics
• Food allergy basics and emergency signs
• Foods for babies and toddlers: choking, honey and allergens
• Macadamia nuts
• Foods for cholesterol and heart health