Effects of a Chilean Hazelnut-Supplemented Diet on Oxidative Stress and Cytokine Expression in PBMCs of Hypercholesterolemic Adults: A Randomized Controlled Trial.
González-Contreras C, Ramos-Pardo S, et al. • Nutrients • 2026
A Chilean diet supplemented with Chilean hazelnuts and a low-fat diet produced similar improvements in PBMC redox status in hypercholesterolemic adults, with no significant differences between groups, so the specific contribution of Chilean hazelnuts requires further investigation.
Key Findings
Results
Both the hazelnut-supplemented Chilean diet and the low-fat diet were associated with similar improvements in PBMC redox status over six months in hypercholesterolemic adults.
Randomized controlled trial with a 6-month nutritional intervention; 106 adults randomized, 81 completed.
Groups: Chilean diet supplemented with Gevuina avellana Molina (Chilean hazelnut) (n = 47) vs. low-fat diet (n = 34).
Improvements were characterized by reduced oxidative damage and enhanced antioxidant defence capacity.
Oxidative stress and inflammatory markers in PBMCs were secondary outcomes (ClinicalTrials.gov NCT07087704).
Results
Oxidative damage markers malondialdehyde (MDA) and protein carbonyls decreased in both dietary groups after the intervention.
MDA and carbonyl levels were measured in PBMCs.
The decrease occurred in both the hazelnut and low-fat groups.
Nitrotyrosine was also assessed as an oxidative damage marker.
Results
Antioxidant enzyme activities in PBMCs increased following the dietary interventions.
Activities of superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GRd) were analysed.
Enzymatic activities increased, consistent with enhanced antioxidant defence capacity.
Gene expression was assessed for SOD, CAT, GRd, IL-10, and TNF-α.
The discordance between CAT mRNA and activity suggests regulation not explained by transcription alone.
Results
No significant differences between the hazelnut-supplemented and low-fat groups were observed for oxidative stress, antioxidant, or inflammatory markers.
Between-group comparisons showed no significant differences in the assessed markers, including IL-10 and TNF-α expression.
Authors state the specific contribution of Chilean hazelnuts requires further investigation.
Conclusions
The authors interpret the findings as suggesting that improving dietary fat quality and increasing antioxidant-rich food intake may favourably alter cellular redox homeostasis.
Interpretation is based on similar improvements in both diet groups.
The study was conducted in a Chilean population using a native nut species, for which evidence was previously limited.
Methods
Study attrition and unequal group sizes: 81 of 106 randomized adults completed the study.
Completers: 47 in the hazelnut group and 34 in the low-fat group.
25 participants did not complete the 6-month intervention.
What This Means
This study tested whether adding Chilean hazelnuts (Gevuina avellana) to a Chilean-adapted Mediterranean-style diet would improve markers of cell stress and inflammation in adults with high cholesterol, compared with a standard low-fat diet. Of 106 people who started, 81 completed six months: 47 on the hazelnut diet and 34 on the low-fat diet. Researchers measured oxidative stress and inflammation-related markers in immune cells from blood.
Both diets were linked to similar improvements. Signs of oxidative damage (malondialdehyde and carbonyls) went down, and the activity of the body's antioxidant enzymes went up. Gene activity results were mixed: SOD gene expression rose, while catalase gene expression fell even though its enzyme activity increased. There were no significant differences between the two groups on any oxidative stress, antioxidant, or inflammatory marker.
This research suggests that improving the overall quality of the diet, such as better fats and more antioxidant-rich foods, may help cells handle oxidative stress, regardless of whether Chilean hazelnuts are included. The study could not show a specific added benefit from the hazelnuts, and the authors say more research is needed. The findings were also based on secondary outcomes and a group of participants that shrank over the six months.
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González-Contreras C, Ramos-Pardo S, Valdebenito E, Ramírez-Alarcón K, Zuniga F, Quetglas-Llabrés M, et al.. (2026). Effects of a Chilean Hazelnut-Supplemented Diet on Oxidative Stress and Cytokine Expression in PBMCs of Hypercholesterolemic Adults: A Randomized Controlled Trial.. Nutrients. https://doi.org/10.3390/nu18203400