Eating over 60g of almonds a day may protect DNA and cut oxidative damage

By Hugo Francisco de SouzaReviewed by Susha Cheriyedath, M.Sc.Aug 14 2025

Scientists say high-dose almond intake could help shield your cells from oxidative harm while enhancing your body’s natural defense systems, but the benefits depend on the dose and how the nuts are prepared.

Study: The impact of almond supplementation on oxidative stress biomarkers: a systematic review and meta-analysis of randomized control trials. Image Credit: shine.graphics / Shutterstock

In a recent systematic review published in the journal Scientific Reports, researchers collated, synthesized, and meta-analyzed the results of eight clinical trials to validate and elucidate the impacts of almond supplementation in adults.

Review findings reveal a dose-dependent relationship wherein consuming over 60 grams (g) of almonds daily was observed to significantly reduce certain markers of cellular damage (notably MDA and 8-OHdG) and, in some analyses, improve the body's antioxidant enzymes (SOD overall, though not significantly in the >60 g/day subgroup).

These results support the role of almonds as a potential functional food for managing oxidative stress, though the authors emphasize that more standardized trials are needed before considering public health policy recommendations, particularly given the high variability in results and the influence of factors such as almond preparation, baseline oxidative stress status, and participant characteristics.

Background

Cells are under constant attack from reactive oxygen species (ROS), unstable molecules that are known to damage lipids, proteins, and even DNA, resulting in mutations and associated diseases. Oxidative stress is an imbalance between these damaging free radicals and the body's antioxidant defences, exacerbated by environmental pollution and poor behavioral choices (e.g., suboptimal diets and smoking).

Over time, this ROS-mediated cellular damage accumulates and has been identified as a leading cause of chronic conditions, including cardiovascular disease (CVD), diabetes, cancers, and neurodegenerative disorders.

Current oxidative stress investigations involve the estimation of biomarkers like malondialdehyde (MDA) for lipid damage, 8-hydroxy-2'-deoxyguanosine (8-OHdG) for DNA damage, and antioxidant enzymes like superoxide dismutase (SOD) as evidence for patient antioxidant performance. Despite these surveillance and diagnostic techniques, the global burden of oxidative stress continues to rise.

Almonds (specifically, the fruits of the Prunus amygdalus or Prunus dulcis tree) are rich in protective antioxidant compounds, including vitamin E, polyphenols, and healthy monounsaturated fats, making them a promising dietary tool to combat oxidative stress. While previous studies have been encouraging, their limited sample sizes made findings confounding and ungeneralizable, requiring a comprehensive analysis to consolidate their cumulative evidence.

About the review

The present systematic review addresses this knowledge gap by collating and reanalyzing data from several randomized controlled trials (RCTs) aimed at quantifying the effect of almond consumption on oxidative stress. The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

The comprehensive literature search comprised a custom keyword search of several online scientific repositories, including Scopus, PubMed/Medline, and the Web of Science from database initiation till January 2025. A two-phase screening process was employed to identify only publications examining adults (≥ 18 years), where almond supplementation of any form was the intervention, and outcomes were reported using oxidation status biomarkers. Any RCTs or crossover trials meeting these criteria were included in subsequent analyses.

Extracted data included estimates of key biomarkers, and analyses leveraged a random-effects model to pool the results and calculate the weighted mean difference (WMD; overall effect). Crucially, subgroup analysis was conducted to determine if the dose of almonds, specifically, less than or more than 60 grams daily, influenced observed outcomes.

Review findings

Title, abstract, and full text screening identified eight high-quality trials (five parallel RCTs and three crossover trials) that met inclusion criteria (n = 424 participants). Summary statistics revealed that the included study populations were diverse, including healthy individuals, smokers, and patients with chronic diseases. The almond interventions varied in dose, ranging from 5 to 168 grams daily, and lasted between four and 24 weeks.

Meta-analysis outcomes revealed that the antioxidant effects of almonds are partly dose dependent. While lower doses showed minimal impact, supplementation with 60 grams or more daily (~2 large handfuls) produced significant improvements in specific key biomarkers, particularly those indicative of cellular damage (MDA and 8-OHdG).

Levels of MDA, a product of lipid peroxidation, were reduced by a weighted mean difference of -0.46 (p = 0.002) in the high-dose subgroup, and 8-OHdG, a marker of oxidative DNA damage, was lowered by -5.83 (p < 0.001). In addition, the body's endogenous antioxidant defenses were observed to be improved overall, with SOD activity increasing by 2.02 (p = 0.008) in the pooled analysis, though the >60 g/day subgroup did not reach statistical significance.

Almond consumption also led to a small but significant reduction in uric acid levels (WMD = -0.64, p = 0.009), which the authors suggest may be related to inhibition of xanthine oxidase activity, a key source of uric acid and reactive oxygen species. Its impact on glutathione peroxidase (GPx) was not statistically significant. Notably, heterogeneity evaluations established a high degree of variability across the studies for some outcomes (I² > 90%), implying that differences in study design, almond preparation (raw vs. roasted, blanched vs. unblanched), loss of polyphenols from skin removal, potential genetic variability in antioxidant enzyme responses, and interactions between almond fiber and polyphenols influencing gut microbiota and systemic oxidative status likely contributed to inconsistent results.

Conclusions

This systematic review and meta-analysis provide evidence that almond supplementation can help manage oxidative stress, particularly for some biomarkers, and that benefits for MDA may be more evident at doses higher than 60 grams per day. Not all biomarkers responded in a dose-dependent manner, and SOD improvements were observed overall but not significantly in the high-dose subgroup.

These findings support the classification of almonds as a potential functional food. Still, the high variability between studies highlights a critical need for future research. The authors call for more standardized trials to pinpoint almonds' optimal dosage, duration, and form to maximize their antioxidant benefits, ideally using consistent almond preparation methods and stratifying participants by baseline oxidative stress levels to better target populations most likely to benefit.