A randomized controlled trial found that 30g daily of cashew nuts for 12 weeks reduced plasma copper levels in adolescents with obesity, while both intervention and control groups increased zinc levels through nutritional counseling . The clinical significance of these mineral shifts remains unclear.
Adolescents with obesity often have disrupted copper and zinc metabolism. Both minerals play central roles in antioxidant defense and immune function, and imbalances are associated with increased oxidative stress and inflammation. This 12-week randomized controlled trial tested whether adding cashew nuts to the diet could shift these mineral biomarkers in a healthier direction.
The study enrolled 81 adolescents with obesity across two groups: 54 received 30 grams of roasted cashew nuts daily alongside nutritional counseling, while 27 received only the nutritional counseling. Researchers measured plasma copper and zinc, along with superoxide dismutase (SOD), an antioxidant enzyme that depends on both minerals as cofactors. The groups were assessed at baseline and again after 12 weeks.
The cashew nut group showed a meaningful decrease in plasma copper (p = 0.004) compared to the control group. Within the cashew nut group specifically, copper fell and superoxide dismutase activity increased (p = 0.030). Both groups showed increases in plasma zinc and decreases in the copper-to-zinc ratio, though the researchers attribute these improvements primarily to the nutritional counseling rather than the nuts themselves. The copper reduction in the cashew nut group was significant and distinct from the control group's response.
The finding that cashew nuts reduced copper is somewhat counterintuitive, since cashews are indeed a source of dietary copper. The mechanism behind this unexpected result remains unexplained in the paper. Possible explanations might involve interactions between cashew components and copper absorption, or changes in copper metabolism driven by other compounds in cashews, but the study provides no data to clarify this. The increase in SOD activity alongside lower copper suggests the mineral shift may have functional consequences, though whether this is beneficial requires further evidence.
This study is preliminary and focused on a specific biomarker pattern in a particular population. Here's what matters in practical terms:
For adolescents with obesity specifically: The results show measurable changes in mineral metabolism with cashew nut addition, but we lack data on whether these changes translate to clinical improvements in inflammation, oxidative stress markers, or health outcomes. A single 12-week trial with 54 participants in the intervention group is insufficient to establish long-term safety or efficacy. Cashew nuts are nutrient-dense and can fit into a healthy diet, but this study doesn't establish them as a targeted treatment for mineral status in obesity.
For the general population: This research doesn't apply beyond the studied group. Adolescents without obesity, or adults, may respond differently. The study also doesn't address whether copper reduction is desirable long-term or if it matters clinically.
On nutritional counseling: Both groups improved zinc status, attributed to the shared nutritional guidance component. This reinforces that dietary coaching matters for mineral balance independent of specific foods.
If you're managing adolescent obesity, work with a healthcare provider on comprehensive nutritional strategies rather than relying on single foods. Cashews can be part of a balanced diet due to their nutrient density, but this trial doesn't support them as a targeted intervention.
| Attribute | Details |
|---|---|
| Study Type | Randomized Controlled Trial |
| Sample Size | 81 completers (54 intervention, 27 control) |
| Duration | 12 weeks |
| Intervention | 30g roasted cashew nuts daily + nutritional counseling vs. nutritional counseling alone |
| Primary Outcomes | Plasma copper, zinc, superoxide dismutase activity |
| Key Finding | Cashew group showed decreased plasma copper (p = 0.004) vs. control; SOD increased in cashew group (p = 0.030) |
| Journal | Nutrients |
| Evidence Tier | B tier (small RCT, single intervention period, unclear clinical relevance of biomarker shifts) |
Pereira M, et al. Effect of Cashew Nut Consumption on Biomarkers of Copper and Zinc Status in Adolescents with Obesity: A Randomized Controlled Trial. *Nutrients*. 2024. PubMed ID: 39796597
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