London: Adding half a cup of walnuts to your daily diet can lower your cholesterol levels by around 8.5 percent and reduce the risk of heart disease, a study has found. Researchers from the Hospital Clínic de Barcelona recruited 628 adults and put half of them on a diet that included daily walnut consumption. After two years, the team found the walnut eaters also had modest reductions in their so-called LDL cholesterol levels.
High levels of LDL — sometimes dubbed the ‘bad cholesterol’ — is linked to an increased risk of heart disease and stroke. Study participants who ate walnuts daily saw a reduction in both the total number of LDL particles in their blood and, in particular, the number of small LDL particles.
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According to the American Heart Association, walnuts are high in omega 3 fatty acids — the heart-healthy fat famously found in oily fish. ‘Prior studies have shown that nuts in general, and walnuts in particular, are associated with lower rates of heart disease and stroke,’ said paper author and nutrition expert Emilio Ros of the Hospital Clínic de Barcelona, in Spain.
‘One of the reasons is that they lower LDL-cholesterol levels, and now we have another reason: they improve the quality of LDL particles. ‘LDL particles come in various sizes. Research has shown that small, dense LDL particles are more often associated with atherosclerosis, the plaque or fatty deposits that build up in the arteries.
‘Our study goes beyond LDL cholesterol levels to get a complete picture of all of the lipoproteins and the impact of eating walnuts daily on their potential to improve cardiovascular risk.’ In their investigation, Dr. Ros and colleagues analyzed data on 628 healthy adults — each aged 63–79 — who resided in either Barcelona, Spain, or Loma Linda, California.
Participants were divided into two groups, with the first adding half a cup of walnuts to their daily diet, while the other abstained from eating any of the nuts. After two years, the team tested each participant’s cholesterol levels, alongside analyzing the concentrations and sizes of their lipoproteins to look for features known to be associated with an increased risk of cardiovascular disease.
The researchers found the participants in the walnut-eating group ended up with lower LDL cholesterol levels at the end of the study period — by an average of 4.3 mg/dL. At the same time, their total cholesterol was lowered by an average of 8.5 mg/dL.
Habitual walnut consumption was found to be associated with a 4.3 percent reduction in the total number of LDL particles and small LDL particles by 6.1 percent — both changes are known to be linked to a lower risk of cardiovascular disease.
Furthermore, the team found that Intermediate Density Lipoprotein, or ‘IDL’ cholesterol — which is a precursor to LDL — also decreased in the walnut group. (In the last decade, medical experts have pointed to IDL cholesterol as a relevant lipid cardiovascular risk factor independent of LDL cholesterol.)
The researchers noted that — for reasons that are not yet clear — LDL cholesterol changes in the walnut group differed by s-e-x. In men, the average reduction was 7.9 percent, while it was 2.6 percent in women. ‘While this is not a tremendous decrease in LDL cholesterol, it’s important to note that at the start of the study all our participants were quite healthy, free of major non-communicable diseases,’ said Dr. Ros.
‘However, as expected in an elderly population, close to 50 percent of participants were being treated for both high blood pressure and hypercholesterolemia. ‘Thanks in part to statin treatment in 32 percent, the average cholesterol levels of all the people in our study were normal.
‘For individuals with high blood cholesterol levels, the LDL cholesterol reduction after a nut-enriched diet may be much greater. ‘Eating a handful of walnuts every day is a simple way to promote cardiovascular health,’ the researcher continued.
The researchers cautioned that their study was limited by the fact that both they and the participants knew whom among the latter was eating walnuts. However, they added, the study did involve two different cohorts with distinct diets.
‘The outcomes were similar in both groups, so we can safely apply the results of this study to other populations,’ Dr. Ros said, noting that further research will be needed to clarify the differences in LDL results between men and women. The full findings of the study — which was funded by the California Walnut Commission — were published in the journal Circulation.