Cashews: Heart Health, Copper, and Everyday Minerals

Evidence Review

Lipid effects

The most cited cashew study for lipid outcomes is Mah et al. (2017), a randomised, isocaloric, crossover controlled-feeding trial in 51 mildly hypercholesterolaemic adults aged 21–73 [1]. Participants consumed either 28–64 g/day of cashews or an equal-calorie amount of potato chips for 28 days, with a two-week washout between arms. The cashew arm produced significant reductions in total cholesterol (−3.9%) and LDL cholesterol (−4.9%) and a non-significant improvement in the TC/HDL ratio. The comparison to a refined-carbohydrate snack is important context: the benefit may partly reflect displacement of an unhealthy food rather than a specific cashew property.

A 2019 trial by O'Neil et al. (PMID 30753323) reached a different conclusion: consumption of 1.5 servings of cashews per day for six weeks did not significantly change blood lipids or other cardiovascular risk markers compared to a control snack. The discrepancy between studies is likely explained by differences in the control condition, baseline cholesterol levels, and dietary substitution effects.

A 2024 review of lipid meta-analyses and a growing body of tree nut data suggest that cashews — like most tree nuts — improve the overall lipid profile modestly when they replace less healthy snacks, but the effect is not as pronounced as for walnuts or almonds.

Blood pressure and HDL in type 2 diabetes

Mohan et al. (2018) is among the largest and most methodologically rigorous cashew-specific trials [2]. The 12-week randomised controlled trial enrolled 300 Asian Indians with type 2 diabetes, randomising them to a cashew-supplemented diet (30 g/day of unsalted cashews replacing refined carbohydrates) or a control diet. At 12 weeks, the cashew group showed:

• HDL cholesterol increase: +1.7 ± 5.6 mg/dL vs. +0.1 ± 4.6 mg/dL (p = 0.01)
• Systolic BP reduction: −4.9 ± 13.7 mmHg vs. −1.7 ± 11.6 mmHg (p = 0.04)

No significant differences were seen in fasting glucose, HbA1c, total cholesterol, or LDL, which the authors attributed to cashews' relatively high carbohydrate content compared to other nuts. The blood pressure result is clinically meaningful — a 3–5 mmHg reduction in systolic pressure is associated with meaningful reductions in cardiovascular event risk at a population level.

Insulin sensitivity and oxidative stress

Darvish Damavandi et al. (2019) conducted an 8-week randomised isocaloric controlled-feeding trial in 50 patients with type 2 diabetes [3]. The cashew group consumed 10% of total daily calories from cashews; the control group ate a standard diet without nuts. At 8 weeks, the cashew group showed:

• Significant reduction in serum insulin (p < 0.05)
• Significant reduction in LDL/HDL ratio (p < 0.05)
• Trend toward improved oxidative stress markers

The reduction in fasting insulin without significant change in fasting glucose suggests a shift in insulin sensitivity rather than a simple glucose-lowering effect. However, sample size (50 participants) limits generalisability, and the 10% calorie substitution is higher than typical dietary consumption.

Cardiovascular risk factors during weight loss

The Brazilian Nuts Study (Meneguelli et al., 2024) enrolled adults undergoing an energy-restricted weight-loss intervention and randomised them to receive cashew nuts, cashew nut oil, or neither over 8 weeks [4]. Both cashew-supplemented groups showed greater reductions in apolipoprotein B (a direct measure of atherogenic lipoprotein particles) and liver function biomarkers (ALT and GGT) compared to the control group. Neck circumference, a marker of visceral fat distribution, also decreased more in the cashew nut group. This study is notable for isolating cashew-specific effects within a broader weight-loss context.

Copper and antioxidant enzymes

Dias et al. (2025) conducted a 12-week randomised trial in 81 adolescents with obesity, comparing 30 g/day of roasted cashews plus nutritional counselling against nutritional counselling alone [5]. The cashew group showed a significant increase in superoxide dismutase (SOD) activity (p = 0.030) and a decrease in plasma copper (p = 0.004) — the latter interpreted as increased copper incorporation into metalloenzymes like SOD rather than copper depletion. The copper-to-zinc ratio improved in both groups, with a more pronounced shift in the cashew group.

Overall evidence assessment

The cashew evidence base is moderately strong for specific endpoints: HDL improvement and blood pressure reduction in people with type 2 diabetes (one large, well-designed trial [2]) and LDL reduction when substituted for refined-carbohydrate snacks [1]. The copper-related antioxidant enzyme data are early-stage but mechanistically plausible.

The evidence is weaker or inconsistent for: fasting glucose and glycaemic indices (a 2021 meta-analysis of six trials found no significant overall effect on fasting blood sugar, insulin, or HOMA-IR), body weight, and LDL reduction outside a refined-carb comparison context.

As with most tree nut research, funding by industry groups (nut boards, trade associations) is common in this literature and should be factored into interpretation. The mechanistic case for cashews rests on well-established properties — copper's roles in SOD and collagen synthesis, oleic acid's cardiovascular effects, magnesium's metabolic functions — rather than any single large cashew-specific trial.