Researchers have found that high-walnut-enriched diets significantly decreased total and LDL cholesterol for the duration of short-term trials.
Cholesterol can’t dissolve in the blood. It has to be transported to and from the cells by carriers called lipoproteins. LDL cholesterol is known as “bad” cholesterol and HDL cholesterol is known as “good” cholesterol.
When too much LDL cholesterol circulates in the blood, it can slowly build up in the inner walls of the arteries that feed the heart and brain.
Consumption of nuts has been associated with a decreased risk of cardiovascular disease events and death. Walnuts in particular have a unique profile: they are rich in polyunsaturated fatty acids, which may improve blood lipids and other cardiovascular disease risk factors.
The researchers conduct a literature review and a meta-analysis to combine the results from several trials and to estimate the effect of walnuts on blood lipids. Literature databases were searched for published trials that compared a specifically walnut-enhanced diet with a control diet.
They conducted a random-effects meta-analysis of weighted mean differences (WMDs) of lipid outcomes. Thirteen studies representing 365 participants were included in the analysis. Diets lasted 4-24 weeks with walnuts providing 10-24% of total calories.
When compared with control diets, diets supplemented with walnuts resulted in a significantly greater decrease in total cholesterol and in LDL cholesterol concentrations. HDL cholesterol and triglycerides were not significantly affected by walnut diets more than with control diets. Other results reported in the trials indicated that walnuts provided significant benefits for certain antioxidant capacity and inflammatory markers and had no adverse effects on body weight.
Larger and longer-term trials are needed to address the effects of walnut consumption on cardiovascular risk and body weight.
References:
1. Banel DK, Hu FB. Effects of walnut consumption on blood lipids and other cardiovascular risk factors: a meta-analysis and systematic review. Am J Clin Nutr. 2009 Jul;90(1):56-63. Epub 2009 May 20. PMID: 1945802.
2. American Heart Association.
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