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21st September 2021
Regular intake of nuts has been associated with a 15% lower risk of cardiovascular disease and a 23% lower risk of cardiovascular mortality. This reduction in risk is probably due to a reduction in low-density cholesterol (LDL-C) levels with one pooled analysis of 25 intervention trials finding that a mean daily intake of 67g of nuts produced a 7.4% mean reduction in LDL-C levels. However, none of the 25 trials lasted longer than 8 weeks and have not examined the effect of nuts on different LDL sub-fractions. In trying to establish the effect of both daily nut consumption and any differences in the effect on low-density lipoprotein levels, a team from the Lipid Clinic, Endocrinology and Nutrition Services, Villarroel, Barcelona, Spain, decided to explore these effects in a randomised trial. The team established the Walnuts and Healthy Aging (WAHA) trial which ran from 2012 to 2014 and was designed to examine the impact of bioactive compounds, such as n-3 fatty acids (found in walnuts) on both cognitive function and retinal health. Free-living participants were randomised to receive 30 – 60g/day of walnuts, which were delivered to the intervention group individuals, or to abstain from the nuts for the two years of the trial. One of the secondary outcomes of the original trial was changes in lipoprotein levels. Together with fasting glucose, lipoprotein levels were were measured at baseline at after 2 years. In addition, given that those eating walnuts were consuming more fat and thus likely to experience weight gain, this was also measured and compared with the baseline reading.
There were 636 participants with a mean age of 69 years (67% female) who completed the two-year trial. The mean baseline LDL-C and triglyceride levels were 117 and 105 mg/dL respectively. Among those taking walnuts, mean total cholesterol levels decreased by 4.4%
(-8.5 mg/dL, 95% CI -11.2 to -5.4), LDL-C by 3.6% (-4.3, 95% CI -6.6 to -1.6) and intermediate-density lipoprotein cholesterol by 16.8% (-1.3, 95% CI -1.50 to -1.0). Interestingly, levels of both triglycerides and high-density lipoprotein levels were unchanged. Weight changes in the walnut group were negligible at 0.06kg (95% CI -0.32 to 0.44). Furthermore, LDL-C reductions were higher for men than women (7.9% vs 2.6%, men vs women). In addition, there were also reductions in total LDL particles and small LDL particle number by 4.3% and 6.1% respectively.
The authors suggest that the reduction is LDL-C cholesterol at 4.3 mg/dL was modest and concluded that daily walnut intake may be useful way to improve cardiovascular risk.
Rajaram S et al. Effects of Walnut Consumption for 2 Years on Lipoprotein Subclasses Among Healthy Elders. Findings From the WAHA Randomized Controlled Trial. Circulation 2021.