14/09/2015

Recent studies support the benefits of the Mediterranean diet for preventing retinopathy and breast cancer

The two recent studies were part of the PREDIMED (Prevenció amb Dieta Mediterrània) project. One of them, published in the journal Diabetis Care and coordinated by the URV, concludes that the Mediterranean diet supplemented with olive oil reduces the risk of diabetic patients suffering a retinopathy by 44%. The other study, published in the journal JAMA Internal Medicine, associates the Mediterranean diet with a reduction in the risk of suffering from breast cancer. This study was coordinated by the University of Navarre and the URV researchers who took part were led by Jordi Salas-Salvadó

The possibility of chronic complications is one of the concerns of people with diabetes, who know that any increase of sugar in the blood can block the blood vessels and, therefore, make it more difficult for the blood to reach certain organs. This can involve a loss of function.

Microvascular complications that affect the kidney and the eyes are the first to occur and can give rise to diabetic retinopathy – an eye disease that can lead to blindness – or diabetic nephropathies, which can give rise to renal insufficiency (that is to say, the kidneys stop functioning). To date no clinical studies have assessed the role of dietary patterns in microvascular diabetic complications. For this reason, the researchers from the project PREDIMED (Prevenció amb Dieta Mediterrània) have studied the effect of the Mediterranean diet on the reduction of these risks. And after monitoring a large population of diabetics for six years they have shown that the Mediterranean diet supplemented with olive oil can reduce the risk of suffering from a retinopathy by up to 44%.

A total of 3,614 men and women with diabetes type 2 between 55 and 80 years of age – with a mean age of 67 – volunteered to take part in the study. They had all been enrolled in PREDIMED, the multi-centre randomized nutritional study carried out in a population at high cardiovascular risk to evaluate the importance of the Mediterranean diet in cardiovascular prevention. The participants were divided into three groups and randomly assigned to one of the three dietary interventions: advice on following a Mediterranean diet supplemented with extra virgin olive oil, advice on following a Mediterranean diet supplemented with nuts and advice on following a diet low in animal and vegetable fat (control group).

During the six years that the participants were followed, 74 new cases of retinopathy and 168 of diabetic nephropathy were identified. As far as retinopathy was concerned, there were significant differences between the participants who had been on the Mediterranean diet and those who had not. So the results of the study confirmed that the Mediterranean diet (supplemented with olive oil) reduces the risk of diabetic patients suffering retinopathy, the main cause of blindness in these patients, by 44%. The participants who supplemented their diet with nuts had a non-significant reduction in risk of 37% compared to those participants on the reduced-fat diet.

The study was published on Monday 14 September in the scientific journal Diabetes Care and it was carried out by scientists (Andrés Díaz-López, Nancy Babio and Josep Basora) from the PREDIMED project led by Jordi Salas-Salvadó, head of the Human Nutrition Unit of the Universitat Rovira i Virgili, members of the Sant Joan University Hospital in Reus, the Pere Virgili Institute for Health Research and the Catalan Health Institutes.

Prevention of breast cancer

Another study published on the same day in the journal JAMA Internal Medicine concludes that the Mediterranean diet reduces the risk of developing breast cancer. This was demonstrated in a research project coordinated by the University of Navarre and the Spanish Biomedical Research Centre in the Physiopathology of Obesity and Nutrition (CIBERobn) in the framework of the multicentre clinical trial PREDIMED (Prevenció amb Dieta Mediterrània). Researchers from the Universitat Rovira i Virgili-Sant Joan University Hospital in Reus-Pere Virgili Institute for Health Research have also taken part under the leadership of Jordi Salas-Salvadó.

The researchers analysed the effects of two interventions with the Mediterranean diet (supplemented with 30 grams/day of extra virgin olive oil or 30 grams per day of mixed walnuts, hazelnuts and almonds) in comparison with a group of women who were advised to follow a diet low in fat.

Between 2003 and 2009, 4,282 women between 60 and 80 years old – with a mean of 67.7 years old – and a high risk of cardiovascular disease were recruited. They were randomly assigned either to the Mediterranean diet supplemented with extra virgin olive oil (1,476 women), to the Mediterranean diet supplemented with nuts (1,285 women) or the control diet with advice to reduce their dietary intake of fat (1,395 women).  For a mean follow up of almost five years, the authors identified 35 new cases of breast cancer. The authors conclude that women who follow a Mediterranean diet supplemented with olive oil had a 68% lower risk of malignant breast cancer than those assigned to the control diet. The women who followed a Mediterranean diet supplemented with nuts showed a non-significant reduction in risk in comparison with the women in the control group.

According to the authors, the assignation of the participants to the Mediterranean diet supplemented with virgin olive oil – which accounts for at least 15% of the energy intake – largely explains the protection provided against breast cancer. According to Doctor Jordi Salas-Salvadó, “breast cancer is a relatively common disease which affects women in particular and is a serious problem for public health because it reduces life expectancy.” And he adds that this study “suggests for the first time, and with a great deal of evidence, that the diet – in this case the Mediterranean diet – plays an important role in preventing this disease.”

Both studies were carried out in the framework of the PREDIMED (Prevenció amb Dieta Mediterrània) trial, which was designed to prove the effects of the Mediterranean diet in the primary prevention of cardiovascular disease. The PREDIMED project is a multicentre study carried out by a network of researchers from various universities and research institutions. At present, these centres are part of the CIBERobn of the Carlos III Health Institute.

References: Díaz-López A, et al. “Mediterranean Diet, Retinopathy, Nephropathy, and Microvascular Diabetes Complications: A Post Hoc Analysis of a Randomized Trial”. Diabetes Care 2015;38:1–8 | DOI: 10.2337/dc15-1117

Toledo E. et al. “Mediterranean Diet and Invasive Breast Cancer Risk Among Women at High Cardiovascular Risk in the PREDIMED Trial” JAMA Intern Med. Published online September 14, 2015. doi:10.1001/jamainternmed.2015.4838.


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