Hazelnuts and heart health in 22 studies
What it found
In people, eating hazelnuts improved some blood fat measures and did not change body weight, but study flaws make the results hard to interpret.
The authors say the evidence on other heart and blood sugar markers is mixed.
What they found
Studies in people
Blood fats
Of 16 studies, 9 found significantly lower total cholesterol and 10 found significantly lower LDL cholesterol with hazelnut consumption. Seven studies found significantly higher HDL cholesterol, 2 found lower triglycerides, and 1 found higher triglycerides.
Body weight
Across 17 studies, adding hazelnuts to the diet did not adversely affect body weight or composition. One small single-intervention study in older adults found a small but significant increase in body weight.
Blood pressure
Seven studies measured blood pressure. None found significant differences between hazelnut and control groups, and two single-intervention studies found no significant change. One single-intervention study reported a significant reduction in systolic blood pressure in the total cohort.
Blood sugar
One acute study found that bread containing hazelnuts led to a significantly lower blood glucose response over 2 hours than bread with no nuts. In longer studies, only 1 of 6 reported lower fasting blood glucose, and 3 studies found no significant reductions in insulin. One study in people with type 2 diabetes reported a reduction in HbA1c over 30 days.
Inflammation and oxidation
Six of seven studies found no improvement in inflammatory markers. Some studies reported increases in antioxidant markers, but results for oxidative stress markers were mixed.
Acceptance
Seven studies measured how much people liked hazelnuts over time. Ratings stayed stable for up to 12 weeks at doses of 30 to 42 g per day, but one study found that liking decreased over time at 60 g per day.
What the authors conclude
“However, there was consistent evidence that the inclusion of hazelnuts into the diet did not adversely affect body weight and composition.”
Also in their conclusions
- They say the findings show some improvements in cardiometabolic risk factors, but limitations in study design make interpretation difficult.
- They state that there was consistent evidence that including hazelnuts in the diet did not adversely affect body weight and composition, and that acceptance remained stable over time.
- They conclude that "the balance of the research suggests the benefits of hazelnut consumption outweigh any potential negative effects" and call for future studies with more robust designs.
How it was done
Hazelnuts have had less research attention than other nuts, and the authors wanted to update an older review and look at more outcomes, including blood pressure, blood sugar, and how well people accept hazelnuts.
They searched for human intervention studies that included hazelnuts and reported at least one heart or metabolic outcome. They found 22 studies (25 papers) from New Zealand, Italy, Turkey, Iran, and the USA, with sample sizes from 15 to 118 people and interventions lasting 2 to 16 weeks.
What it can’t tell you
- Many of the studies had flaws such as lack of randomisation, no control group, small samples, and short duration, so the results are hard to interpret.
- The studies used different designs, populations, and doses, making it difficult to draw firm conclusions about cause and effect.
- Most studies were in healthy people or those with specific conditions, so the findings may not apply to everyone.
Who paid
- Conflicts
- The authors declare no conflict of interest.
- Authors work at
- University of Otago, New Zealand
The paper
- Title
- Effects of Hazelnut Consumption on Cardiometabolic Risk Factors and Acceptance: A Systematic Review
- Type
- Systematic review
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Brown R, Ware L, Tey SL (2022). Effects of Hazelnut Consumption on Cardiometabolic Risk Factors and Acceptance: A Systematic Review. International journal of environmental research and public health. doi:10.3390/ijerph19052880Free full textPubMed 35270573DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error