The Effect of Walnut Intake on Lipids: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Abstract

Cardiovascular diseases (CVD) are the leading causes of death worldwide. Dyslipidemia is a cardiometabolic risk factor of CVD, yet it can be modifiable. Walnuts have been suggested as a dietary intervention to improve the lipid profile. Therefore, we reviewed the literature to assess the evidence linking walnut intake to the improvement of blood lipids, including total cholesterol (TC), low-density lipoprotein (LDL-C) cholesterol, high-density lipoprotein (HDL-C) cholesterol, and triglycerides (TG). PubMed and Embase databases were searched from 2010 up to March 2022. We limited our search to randomized controlled trials conducted on humans and published in English during the specified period. Cochrane’s risk of bias tool for interventional studies was used. A random-effects model was used for the meta-analysis, and weighted mean differences were obtained (WMD) Thirteen trials from the U.S., Europe, and Asia were included. Walnut intake was associated with significant reductions in TC (WMD: −8.58 mg/dL), LDL-C (WMD: −5.68 mg/dL), and TG (WMD: −10.94 mg/dL). Walnut consumption was not associated with HDL-C. Subgroup analysis showed that overweight/obese and those with comorbidities had more lipid improvement. A longer trial duration did result in further improvements. However, our results may be prone to bias due to extraneous confounding factors. Additionally, levels of heterogeneity were considerable for some outcomes of interest. Results from this meta-analysis provide evidence for the health benefits of walnuts on blood lipids. Walnuts possibly reduce the risk of CVD; thus, they can be successfully added to a dietary pattern to enhance health benefits.

Exploring the phenolic profile, antibacterial, and antioxidant properties of walnut leaves (Juglans regia L.)

“…The acquired results were also lower when compared to earlier studies examining the antioxidant activity of leaves, nuts, and walnut shells evaluated in the DPPH test (Pereira et al, 2007 , 2008 ). Natural antioxidants' primary function is to scavenge free radicals before they may trigger chain reactions in lipid‐rich matrices found in food, cosmetics, and pharmaceutical preparations, or in cell membranes (Alshahrani et al, 2022 ; Koşar et al, 2005 ).…”

“…Natural antioxidants' primary function is to scavenge free radicals before they may trigger chain reactions in lipid-rich matrices found in food, cosmetics, and pharmaceutical preparations, or in cell membranes (Alshahrani et al, 2022;Koşar et al, 2005).…”

Can daily consumption of enriched fatty acids diet be effective in improving metabolic syndrome? An attractive paradox for walnut kernel

“…( 2012 ) demonstrated a significant increase in apolipoprotein A ( p = .03). Additionally, a recent meta‐analysis of randomized controlled trials showed an improvement in lipid profile, especially in obese/overweight patients (TC: −8.58 mg/dL, LDL: −5.68 mg/dL, TG: −10.94 mg/dL) (Alshahrani et al., 2022 ).…”

‘Superfoods’: Reliability of the Information for Consumers Available on the Web

“…All these properties have been related to the high content in bioactive compounds, such as phenolic compounds (quercetin, ellagic acid, ellagitannins, cyanidin and proanthocyanidins), phytosterols, γ-tocopherol, dietary fiber, protein (high L-arginine content), phytomelatonin and α-linolenic fatty acid [69,71]. Walnuts consumption has been associated with significant decreases in triglyceride, total cholesterol and LDL cholesterol contents in middle-aged and older adults [72]; this improvement in lipid profiles is associated with the reduction of cardiovascular diseases risk [70,73].…”

“…Disease prevention and health promotion of walnuts intake in clinical trials seem to be prone to some bias, due to the wide dosage range, differences in diets among participants from different geographical regions and other defects in studies' design and methodology. For these reasons, including walnuts in one's diet probably has positive effects on health, although more investigations are needed [72,73].…”