Hazelnuts

Hazelnuts

Hazelnuts are also called cobnuts or filberts (mainly in Britain), and their scientific name is Corylus avellana. In Hebrew they are called “אגוזי לוז”, and are also known as “אגוזי בונדוק”.

Hazelnuts suffer from the opposite image problem to other nuts: most people eat them almost exclusively in chocolate spread, and so think of them as a dessert ingredient rather than a food. Nutritionally this is a pity, because the nut itself has the healthiest fat profile of all the common nuts — closer to olive oil than to any other nut.

About 70% of world production comes from Turkey, mainly from the Black Sea region.

Nutrition facts

The fat profile — “the olive oil of nuts”

This is the most striking figure, and it deserves attention. About 75% of the fat in hazelnuts is monounsaturated, almost all of it oleic acid — exactly the same fatty acid that makes up most of olive oil.

This is the highest proportion among the common nuts:

Why does this matter? Monounsaturated fat is more resistant to oxidation than polyunsaturated fat, so hazelnuts go rancid more slowly than walnuts. In addition, replacing saturated fat with oleic acid is consistently linked in controlled trials to lower LDL without harming HDL.

Intervention studies that specifically tested a hazelnut-enriched diet found improvements in the blood lipid profile and in inflammatory markers — without weight gain, despite the added calories. This is a recurring finding across nut studies, attributed to satiety and to only partial absorption of the fat from the whole-nut matrix.

Manganese and copper — two minerals that are easy to overlook

• Manganese: 76% of the daily value in one handful. This is one of the densest dietary sources of this mineral. Manganese is a cofactor for the mitochondrial enzyme superoxide dismutase (MnSOD) — the main antioxidant defense system inside the mitochondria — and for enzymes involved in bone formation and carbohydrate metabolism.

• Copper: 53% in a handful. Needed for energy production, normal iron metabolism and the formation of collagen and elastin.

The brown skin — don’t remove it

This is a practical point that is almost unknown. About 80% of the polyphenols in hazelnuts are concentrated in the thin brown skin (the pellicle) that wraps the nut — not in the kernel itself.

The industrial process called blanching — a brief scalding that removes the skin to produce a pale, smooth nut — removes the vast majority of them. Skinned hazelnuts are a different product in terms of antioxidant content.

The skin is indeed slightly bitter and astringent, which is why it is removed in pastry making. But if the goal is nutritional, the whole nut with its skin is clearly better.

More benefits

• Vitamin E — 28% in a handful, in the form of alpha-tocopherol. Second only to sunflower seeds among the common seeds and nuts.

• Dietary fiber: 9.7 grams per 100 grams — a high amount that contributes to satiety and the microbiome.

• Folate: 113 mcg per 100 grams — one of the highest among nuts.

• Phytosterols: about 96 mg per 100 grams, which compete with cholesterol for absorption in the gut.

• Satiety and weight management: despite their calorie density, large cohort studies consistently find that regular nut eaters are not heavier — and sometimes the opposite. Some of the fat is not absorbed at all but leaves in the stool, because the cell walls of the whole nut are not fully broken down during digestion.

• Storage stability: thanks to their relatively high saturation with oleic acid (rather than more fragile polyunsaturated fats), they keep better than most nuts.

Downsides

• Allergy — the most significant downside, and in two completely different forms. This is the most important point on this page.

  True hazelnut allergy is one of the most common and serious tree nut allergies. It is mediated by stable storage proteins (Cor a 9, Cor a 14) that are not destroyed by heat or digestion, so it can cause a systemic reaction and even anaphylaxis. This allergy requires complete avoidance, including of products that contain traces.

  Oral allergy syndrome (OAS) is something else entirely, and much more common. People sensitive to birch pollen react to the Cor a 1 protein in hazelnut, which is structurally similar to the pollen allergen. The symptoms are local — itching or tingling in the mouth, lips and throat — and appear within minutes. This protein is heat-sensitive, so many people with OAS eat roasted hazelnuts without any problem, while raw ones irritate them.

  The distinction between the two is clinically important and not a matter for self-diagnosis — check with an allergist.

• Calorie density. 628 calories per 100 grams — among the highest of the nuts. A handful is 176 calories, which is perfectly fine; half a bag is not.

• The chocolate spread problem. This is the biggest practical point, because that is where most of the world’s hazelnuts are eaten. Commercial chocolate-hazelnut spreads usually contain only about 13% hazelnuts. The rest is sugar (the first ingredient on the list, about half the product), palm oil and cocoa powder. Per 100 grams: about 539 calories and about 56 grams of sugar.

  Chocolate-hazelnut spread is not “a way to eat hazelnuts” — it is a candy that contains a few nuts. None of the nut’s benefits described here carries over to it to any significant degree. There are pure hazelnut spreads (100% ground nuts) that are a completely different product.

• Phytic acid. Reduces absorption of zinc, iron and magnesium. Soaking partially reduces it.

• Excess manganese combined with supplements: the high manganese content is an advantage in a normal diet, but someone taking a manganese supplement alongside high intake of nuts and whole grains may exceed the limit. The safe upper limit for adults is 11 mg a day.

• Aflatoxins: as with other nuts, poor storage in humid conditions allows Aspergillus mold to develop. Avoid nuts that look moldy, have spots or smell musty.

• Roasting at high heat damages vitamin E and some of the polyphenols. Light roasting improves flavor and digestibility without significant damage.

Comparison: hazelnuts versus other nuts (per 28 grams)

Practical use

• How many a day: a handful, 28-30 grams — about 20 nuts. This is the serving studied in most nut research.
• With the brown skin. That is where about 80% of the polyphenols are. A pale, skinned nut is a poorer product.
• Raw or lightly roasted, not salted and not sugared.
• Pure hazelnut spread (100% nuts) instead of chocolate spread — a completely different product.
• In salads, in granola or with dark chocolate — a tasty combination that preserves the nutritional value.
• Store in an airtight container, preferably refrigerated. They are relatively stable, but not forever.
• For people allergic to birch pollen: roasted nuts may be tolerated while raw ones are not — check with an allergist and don’t experiment on your own.
• Roasting at home: 10-12 minutes at 150°C (300°F). Rubbing them in a towel afterward removes some of the skin — if you want that for pastry purposes.

Summary

Hazelnuts are the nut with the fat profile closest to olive oil — about 75% monounsaturated oleic acid, the highest proportion in the category — and alongside that an exceptional source of manganese (76% of the daily value in a handful), copper and vitamin E.

Two practical points matter more than everything else: don’t remove the brown skin, where about 80% of the antioxidants are concentrated, and keep the nut completely separate in your mind from chocolate spread — a product containing about 13% nuts and about 56% sugar, which carries almost none of the benefits described here. And finally, allergy: the serious kind requires complete avoidance, but the itchy mouth in people sensitive to birch pollen is a completely different phenomenon, which sometimes disappears with roasted nuts.