The prevalence of metabolic syndrome was reduced by 13.7 per cent when the diet was supplemented with nuts, by 6.7 per cent when supplemented with olive oil, and by only 2 per cent in the control group, according to findings published in the Archives of Internal Medicine.
The Med diet, rich in cereals, wine, fruits, nuts, legumes and whole grains, fish and olive oil, and low in dairy, meat, junk food and fat , has been linked to longer life, less heart disease, and protection against some cancers. The diet's main nutritional components include beta-carotene, vitamin C, tocopherols, polyphenols, and essential minerals.
"Traditionally, dietary patterns recommended for health have been low-fat, high-carbohydrate diets, which generally are not palatable," wrote the authors, led by Jordi Salas-Salvado from the University of Rovira i Virgili, Spain.
"The results of the present study show that a non–energy-restricted traditional Mediterranean diet enriched with nuts, which is high in fat, high in unsaturated fat and palatable, is a useful tool in managing the metabolic syndrome."
Metabolic syndrome (MetS) is a condition characterised by central obesity, hypertension, and disturbed glucose and insulin metabolism. The syndrome has been linked to increased risks of both type 2 diabetes and CVD.
"Development of the metabolic syndrome depends on a complex interaction between still largely unknown genetic determinants and environmental factors, including dietary patterns," explained the authors.
Salas-Salvado and his co-workers in the PREDIMED (Prevencion con Dieta Mediterranea) study assessed 1,224 participants at high risk for cardiovascular disease aged between 55 and 80. The subjects were randomly assigned to one of three groups: one group received advice on a low-fat diet while two received advice on the Mediterranean diet. One of the Mediterranean diet groups was provided with one litre per week of virgin olive oil and the other received 30 grams per day of mixed nuts.
After one year, the researchers evaluated the 409 participants in the Med diet plus olive oil group, 411 in the Med diet plus nuts group and 404 in the control group. While no changes in the body weight of the participants were recorded, the number of individuals with large waist circumference, high triglycerides or high blood pressure was found to have significantly decreased in the Med diet plus nuts group compared with the control group, said the researchers.
“The novelty of our findings is that a positive effect on MetS was achieved by diet alone, in the absence of weight loss or increased energy expenditure in physical activity,” they wrote.
The benefits of the Med diet, particularly in the nut group, were linked to macro- and micronutrients such as unsaturated fatty acids, fibre, arginine, potassium, calcium and magnesium.
“The decreased oxidative stress promoted by the MedDiet concurs with the reduction in inflammatory markers, as previously shown in the PREDIMED study,” said the researchers.
“Reversion of abdominal obesity in the Med diet plus nuts group is plausible, given that consumption of nuts has been associated with satiety, increased thermogenesis, fat malabsorbtion, and lower adiposity, and could further reduce inflammation.
“Therefore, a reduced inflammatory state might account for an important part of the beneficial effect of the Med diet plus nuts on MetS status,” they added.
The researchers noted that the nutritional education for the low-fat diet group was less intense than the education received by participants in the Med diet groups. Moreover, 61.4 per cent of the subjects had MetS and 45 per cent had diabetes, meaning that the results are not applicable to the general population.
Source: Archive of Internal MedicineVolume 168, Issue 22, Pages 2449-2458“Effect of a Mediterranean Diet Supplemented With Nuts on Metabolic Syndrome Status: One-Year Results of the PREDIMED Randomized Trial”Authors: J. Salas-Salvado, J. Fernandez-Ballart, E. Ros, M.-A. Martinez-Gonzalez, M. Fito, R. Estruch, D. Corella, M. Fiol, E. Gomez-Gracia, F. Aros, G. Flores, J. Lapetra, R. Lamuela-Raventos, V. Ruiz-Gutierrez, M. Bullo, J. Basora, M.-I. Covas, for the PREDIMED Study Investigators