Hazelnuts: a small cholesterol effect and a real allergy

A meta-analysis of 3 randomized trials found that 1 to 2.4 oz (29 to 69 g) of hazelnuts a day for 4 to 12 weeks lowered LDL cholesterol by 5.8 mg/dL (0.15 mmol/L), with an interval running from 0.31 down to 0.003, which nearly touches zero. That is a small drop, and three trials is a thin base. In a meta-analysis of 15 trials in 667 adults with type 2 diabetes, hazelnuts lowered fasting glucose by 16 mg/dL (0.90 mmol/L) at three months or earlier, a subgroup figure the authors themselves call not clinically significant. Across randomized trials pooled in a network meta-analysis, nut diets did not change body weight or BMI against control diets, though almond diets did shrink the waist more than hazelnut diets. The clearest harm on this page is allergy. Hazelnut is the most common tree nut allergy in Europe.

The numbers, per 3.5 oz (100 g)

As people eat it, per 3.5 oz (100 g)

How much is actually in it

• Across 8 USDA samples of raw hazelnuts, manganese ranged sixfold from 2.3 to 14 mg per 3.5 oz (100 g) and calcium from 91 to 152 mg, while fat stayed between 45 and 58 g. — Nuts, hazelnuts or filberts, raw, USDA Foundation Foods, 8 analyzed samples; UK CoFID 14-874 Hazelnuts, kernel only for comparison (n = 8 samples) Evidence E source
  Manganese mean 6.06 mg (2.26 to 14.0); calcium 134.7 mg (90.6 to 152.0); magnesium 155.8 mg (136 to 186); fat 53.49 g (45.35 to 57.5); CoFID gives fat 63.5 g, magnesium 160 mg, vitamin E 24.98 mg, energy 650 calories per 3.5 oz (100 g)

What a real portion looks like

• The US dietary survey counts one hazelnut as 2 g and an unspecified serving as 28 g, which at the UK table value of 650 calories per 3.5 oz (100 g) is about 180 calories. — household measures for Hazelnuts in the USDA food and nutrient database for dietary studies (n = 4 household measures for FNDDS code 42107000) Evidence E source
  1 nut 2 g; quantity not specified 28 g; 1 package 50 g; 1 cup 135 g; 28 g x 650 calories per 3.5 oz (100 g) = about 182 calories

What your body absorbs

• In iron absorption tests in 137 Indian women, adding nuts including hazelnuts to a bread meal cut iron absorption from 6.6% to 1.8%, and all the nuts contained phytates and polyphenols. — 137 Indian women, single test meals of bread alone or bread with walnuts, almonds, peanuts or hazelnuts (n = 137) Evidence C source
  Geometric mean iron absorption 1.8% with nut meals vs 6.6% with bread alone (p < 0.0005); 50 mg ascorbic acid overcame the effect for Brazil nuts and peanuts

What cooking and storage change

• Roasting hazelnuts at 140 C for 40 minutes lowered their allergenic activity, yet 5 of 17 birch pollen allergic patients still reacted to the roasted nuts in blinded challenges. — 17 birch pollen allergic patients with challenge-confirmed allergy to raw hazelnut (n = 17) Evidence C source
  5 of 17 positive to roasted hazelnuts, symptoms mostly mild oral allergy syndrome; skin prick, histamine release and specific IgE all reduced by roasting
• In a 3-phase randomized crossover trial in 48 people with mildly high cholesterol, 1.1 oz (30 g) of hazelnuts a day for 4 weeks improved blood lipids equally whether ground, sliced or whole. — 48 mildly hypercholesterolemic adults, 30 g ground, sliced or whole hazelnuts for 4 weeks in each phase (n = 48) Evidence B source
  No difference between forms (all P >= 0.159); vs baseline lower total and LDL cholesterol (P < 0.001), higher HDL (P = 0.023) and alpha-tocopherol (P = 0.005), body weight unchanged (P = 0.813)

What it does to your health

• A meta-analysis of 3 randomized trials found that 1 to 2.4 oz (29 to 69 g) of hazelnuts a day for 4 to 12 weeks lowered LDL cholesterol by 5.8 mg/dL (0.15 mmol/L). — 9 trials with 425 adults, 3 randomized trials pooled, hazelnut-enriched vs control diet for 28 to 84 days (n = 425) Evidence A source
  LDL -5.8 mg/dL (-0.150 mmol/L) (95% HPD -0.308 to -0.003); total cholesterol -0.127 (-0.284 to 0.014); BMI +0.062 kg/m2 (-0.293 to 0.469)
• A meta-analysis of 15 trials in 667 adults with type 2 diabetes found hazelnuts lowered fasting glucose by 16 mg/dL (0.90 mmol/L) at 3 months or less, a subgroup result the authors call not clinically significant. — 15 randomized trials, 667 adults with type 2 diabetes, tree nuts vs placebo or other interventions (n = 667) Evidence A source
  Fasting blood glucose MD -16 mg/dL (-0.90 mmol/L) with hazelnuts (subgroup); all tree nuts -4.7 mg/dL (-0.26 mmol/L) fasting glucose and -0.11% HbA1c
• A network meta-analysis of 105 randomized trials found no nut raised body weight or BMI, and almond diets gave a smaller waist than hazelnut diets by a standardized difference of 0.30. — 105 RCTs in adults, body weight n = 6768, waist circumference n = 5045 (n = 105 RCTs) Evidence A source
  Nut diets did not modify body weight or BMI vs control; waist circumference SMD 0.30 (95% CI 0.02 to 0.59) favoring almond over hazelnut diets

Safety, limits and interactions

• In blinded challenges in 31 hazelnut allergic patients, half are expected to react to 6 mg of hazelnut protein. — 31 patients with hazelnut allergy history and positive skin test or specific IgE, 7 rising doses from 1 mg to 1 g hazelnut protein (n = 31) Evidence C source
  29 of 31 reacted; subjective thresholds 1 to 100 mg hazelnut protein; ED50 6 mg (95% CI 2 to 11 mg)
• In 310 food challenges in 211 young children, a hazelnut challenge had about 11 times the odds of ending in a reaction. — 211 children (median age 21 months) at a tertiary pediatric allergy center, 310 oral food challenges in 2023 (n = 211) Evidence C source
  Hazelnut OR 11.286 (95% CI 3.858 to 33.017) for a positive challenge; anaphylaxis in 5 of 38 positive challenges across all foods
• Observational data from 36 studies put challenge-confirmed tree nut allergy below 2%, and hazelnut is the most common tree nut allergy in Europe. — 36 population prevalence studies, mostly in children and from Europe, 1996 to 2014 (n = 36 studies) Evidence C source
  Challenge-confirmed prevalence under 2%; probable tree nut allergy 0.05 to 4.9%; 8 to 11.4% when oral allergy syndrome is included
• The CDC lists whole or chopped nuts among potential choking hazards for young children. — Infants and young children (n = -) Evidence E source
  Listed as food to avoid for young children (choking risk)

What people believe that the data does not support

• The EU refused to authorize the claim that eating 1.1 oz (30 g) of nuts a day, hazelnuts included, helps maintain heart health, and US 21 CFR has no health claim naming hazelnuts. — EU Register on nutrition and health claims, substance peanuts and tree nuts including hazelnuts (n = 1 claim, status non-authorized) Evidence E source
  Heart health claim for 1.1 oz (30 g) of nuts a day is non-authorized in the EU; no authorized claim for hazelnuts

The bottom line

A handful is small in weight and large in energy. The US dietary survey counts one hazelnut as 2 g and an unspecified serving as 28 g, about 182 calories by the UK table value of 650 calories per 3.5 oz (100 g). For young children a whole nut is also a choking risk. The CDC lists whole or chopped nuts among potential choking hazards for them, and its list gives no age cut-off. The two tables disagree on fat by about 10 g per 3.5 oz (100 g), 63.5 g in the UK against 53.5 g in the US average. Across 8 US samples manganese varied sixfold, from 2.3 to 14 mg per 3.5 oz (100 g). Form does not matter much for the cholesterol effect. In a randomized crossover trial in 48 adults with mildly high cholesterol, 30 g a day for 4 weeks worked the same ground, sliced or whole, and body weight did not change. The abstract compares each phase with baseline and gives no sizes. Nuts can lower the iron you take from a meal. In test meals in 137 Indian women in 1988, adding walnuts, almonds, peanuts or hazelnuts to bread cut iron absorption from 6.6% to 1.8%, with all the nuts pooled together and no separate figure for hazelnut. For people with hazelnut allergy, very small amounts count. In blinded challenges in 31 allergic patients, half are expected to react to 6 mg of hazelnut protein (95% CI 2 to 11 mg), mostly with subjective mouth symptoms. In 211 young children at one specialist allergy center, a hazelnut challenge had about 11 times the odds of ending in a reaction (95% CI 3.9 to 33), and these are odds, not risk. Across 36 prevalence studies, mostly in European children, challenge-confirmed tree nut allergy stayed under 2%, with only 7 studies using a challenge. Roasting at 140 C for 40 minutes weakened the allergen, yet 5 of 17 birch pollen allergic patients still reacted to roasted nuts. That test covered pollen-linked allergy only, so roasted hazelnut is not a safe swap for anyone allergic. We found no data on hazelnuts in pregnancy, in kidney disease or with medicines. The EU refused a claim that 1.1 oz (30 g) of nuts a day, hazelnuts included, helps maintain heart health. The refusal means the evidence fell short at the time of review, and the modest LDL drop above fits that picture.

Sources

1. hzn-daily-r7-01 · reference dataset
   Nuts, hazelnuts or filberts, raw (Foundation, 8 samples) - Manganese 6.059 MG range 2.26-14.0 - Calcium 134.7 MG range 90.6-152.0 - Magnesium 155.8 MG range 136.0-186.0 - Total lipid (fat) 53.49 G range 45.35-57.5 | CoFID 14-874 Hazelnuts, kernel only - Fat 63.5 G - Magnesium 160 MG - Vitamin E 24.98 MG - Energy 650 KCAL
   USDA FoodData Central, Foundation Foods release 2026-04-30, Nuts, hazelnuts or filberts, raw, with UK CoFID 2021 (Public Health England, OGL v3.0) · checked 2026-09-29
2. hzn-daily-r7-02 · reference dataset
   Hazelnuts (FNDDS 42107000, fdc_id 2707502) - 1 nut 2 g - 1 cup 135 g - 1 package 50 g - Quantity not specified 28 g
   USDA FNDDS (FoodData Central, Survey), food code 42107000, fdc_id 2707502 · checked 2026-09-29
3. hzn-daily-r7-03 · controlled absorption study
   When the absorption from bread and nut meals (walnuts, almonds, peanuts, and hazelnuts) was compared with that from bread meals, the overall geometric mean absorption from the nut meals (1.8%) was significantly less than from the bread meals alone (6.6%, t = 9.8, p less than 0.0005). ... All the nuts tested contained significant amounts of two known inhibitors of Fe absorption (phytates and polyphenols)
   Am J Clin Nutr, 1988 · checked 2026-09-29
4. hzn-daily-r7-04 · food challenge study
   Double-blind, placebo-controlled food challenges (DBPCFC) with roasted hazelnuts (140 degrees C, 40 min) were performed in 17 birch pollen allergic patients with DBPCFC-confirmed food allergy to raw hazelnuts. ... RESULTS: In 5/17 patients the DBPCFC with the roasted nuts were positive.
   Allergy, 2003 · checked 2026-09-29
5. hzn-daily-r7-09 · randomized crossover trial
   In a randomized crossover study with three phases, 48 mildly hypercholesterolemic participants were asked to consume 30 g of ground, sliced or whole hazelnuts for 4 weeks. ... RESULTS: There were no significant differences in any outcome variable between the different forms of nuts (all P ≥ 0.159).
   Eur J Clin Nutr, 2011 · checked 2026-09-29
6. hzn-daily-r7-08 · meta-analysis
   Nine studies representing 425 participants were included in the analysis. The intervention diet lasted 28-84 days with a dosage of hazelnuts ranging from 29 to 69 g/day. Out of nine studies, three randomized studies have been meta-analyzed showing a significant reduction in low-density lipoprotein (LDL) cholesterol (pooled MDΔ = -0.150 mmol/L; 95% highest posterior density interval (95%HPD) = -0.308; -0.003) in favor of a hazelnut-enriched diet.
   Nutrients, 2016 · checked 2026-09-29
7. hzn-daily-r7-10 · meta-analysis
   Fifteen trials were included with a total sample size of 667. ... The subgroup analysis demonstrated MD of -0.45, -0.16, and -0.90 mmol/L in fasting blood glucose following ingestion of walnuts, almonds, and hazelnuts, respectively, and -0.17% in glycated hemoglobin following ingestion of walnuts at three month or earlier follow-up. Although not clinically significant, these figures give an indication that further research with larger sample sizes and longer follow-up may show encouraging results.
   JBI Evid Synth, 2021 · checked 2026-09-29
8. hzn-daily-r7-11 · network meta-analysis
   Body weight Table 1 shows the comparisons in which nut-enriched diets did not modify BW compared to control diets. Body mass index Similarly, nut-enriched diets did not modify BMI compared to control diets (Table 2). ... Moreover, almond-enriched diets achieved significant reductions in WC compared with pistachio- (SMD: 0.30; 95% CI 0.04 to 0.55), mixed nuts- (SMD: 0.28; 95% CI 0.01 to 0.54), and hazelnut-enriched diets (SMD: 0.30; 95% CI 0.02 to 0.59) (Table 3).
   Nutrients, 2021 · checked 2026-09-29
9. hzn-daily-r7-05 · food challenge study
   Threshold doses for eliciting subjective reactions varied from a dose of 1 mg up to 100 mg hazelnut protein (equivalent to 6.4-640 mg hazelnut meal). Extrapolation of the dose-response curve showed that 50% of our hazelnut-allergic population will suffer from an allergic reaction after ingestion of 6 mg (95% CI, 2-11 mg) of hazelnut protein.
   Clin Exp Allergy, 2002 · checked 2026-09-29
10. hzn-daily-r7-06 · retrospective cohort
    Multivariate logistic regression identified milk or dairy products (OR: 3.326, 95% CI: 1.437-7.702, P = 0.005), sesame (OR: 7.022, 95% CI: 1.194-41.311, P = 0.031), and hazelnut (OR: 11.286, 95% CI: 3.858-33.017, P < 0.001) as independent predictors of OFC positivity.
    Allergol Immunopathol (Madr), 2026 · checked 2026-09-29
11. hzn-daily-r7-07 · systematic review
    Challenge-confirmed IgE-mediated tree nut allergy prevalence was less than 2 % (although only seven studies used this gold standard) while probable tree nut allergy prevalence ranged from 0.05 to 4.9 %. ... Prevalence of individual tree nut allergies varied significantly by region with hazelnut the most common tree nut allergy in Europe
    Curr Allergy Asthma Rep, 2015 · checked 2026-09-29
12. sf-choke-r2-10 · agency advice
    Whole or chopped nuts and seeds.
    CDC, Infant and Toddler Nutrition: Choking Hazards · checked 2026-10-08
13. hzn-daily-r7-12 · regulatory decision
    POL-HC-7666 Nuts - peanuts and tree nuts (almonds, hazelnuts, pecans, pistachios and walnuts), excluding brazil, macadamia and cashew nuts Eating 30g of nuts per day as part of a balanced diet helps maintain heart health. Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-7666, snapshot 2026-09-21 · checked 2026-09-29