Research

Daily consumption of walnuts reduces “bad" cholesterol and improves the quality of low-density lipoprotein (LDL)

The Hospital Clínic-IDIBAPS is carrying out a trial to explore the effects of a diet enriched with walnuts for two years on healthy ageing in individuals over 63 years of age. It shows a reduction in the levels of “bad” or LDL cholesterol, and an improvement in the LDL particles, which are less likely to build up plaque in the arteries.  

A handful of walnuts every day (45 grams, 6-8 walnuts) provides an energy increase of 15%. Nuts lower the levels of LDL cholesterol, known as “bad” cholesterol”, and improve the quality of these particles.

This study, developed by Dr. Emili Ros, former director of the Endocrinology and Nutrition Service Lipids Unit at the Hospital Clínic de Barcelona, and emeritus researcher in the IDIBAPS ‘Cardiovascular risk, nutrition and ageing’ research group, determined that frequent walnut consumption favours the metabolism of cholesterol and the lowering of LDL levels. Using nuclear magnetic resonance spectroscopy, a complete analysis was carried out of the lipoproteins that transport cholesterol in the blood, and the changes that daily walnut consumption leads to in these particles. A reduction was observed in the number of LDL particles in circulation and their capacity for being deposited in the arteries.  The results show that the regular consumption of nuts in general, and walnuts in particular, is associated with a 15% reduction in the risk of suffering cardiovascular disease and a 23% reduction in mortality from this pathology. 

The two-year trial recorded a reduction in “bad” or LDL (low-density lipoprotein) cholesterol, a predictor of the risk of developing heart disease.  These data were used to determine that walnuts also contribute to healthy ageing in adults over the age of 63.

A handful of walnuts every day (45 grams, 6-8 walnuts) provides an energy increase of 15%, unsaturated fat, fibre, and healthy antioxidants and minerals.  Walnuts are an excellent source of omega-3 fatty acids (alpha-linolenic acid, ALA), a type of fatty acid that has been shown to have a beneficial effect on cardiovascular health, and is the plant equivalent of the omega-3 fatty acids that are found in large quantities in oily fish and some types of shellfish.  “Nuts in general, and walnuts in particular, lower the levels of LDL cholesterol, known as “bad” cholesterol”, and improve the quality of these particles. There is a reduction in the quantity of LDL particles in circulation and in that of the smaller and denser LDL particles, which are associated with atherosclerosis plaques, the fatty deposits that build up in the arteries," explains Dr. Ros.

In order to carry out this analysis, data were collected from over 600 participants aged between 63 and 70, 68% of whom were women.  The participants were divided into two groups: those who added walnuts to their usual diet, and the control group with no dietary changes. After two years, the participants’ cholesterol levels were analysed, and the concentration and size of the lipoproteins measured.

In the group of participants that ate walnuts, there was a 3.6% reduction in LDL cholesterol levels, a 4.3% reduction in the number of LDL particles in circulation, and a 6.1% reduction in the smaller and denser LDL particles.  Differences by sex were observed in the reduction in cholesterol levels. In men, LDL cholesterol fell by 7.9%, and in women by 2.6%. The experts indicate that more research is needed to find an explanation for this difference. Anthropometric measurements were also taken, and it was found that the daily consumption of walnuts did not cause participants to gain weight.

It is hoped that the simple change of adding walnuts to the diet will improve the metabolism of cholesterol in many people.  Moreover, prior studies showed that walnuts have other beneficial effects. The consumption of walnuts improves cognition in individuals with a high risk of cognitive decline. It also lowers blood pressure and decreases the number of circulating inflammatory molecules. All this contributes to healthy ageing, the overall objective of the study.

Author: Dr. Emilio Ros, former director of the Endocrinology and Nutrition Service Lipids Unit at the Hospital Clínic de Barcelona and emeritus researcher of the IDIBAPS ‘Cardiovascular risk, nutrition and ageing’ research group.