Effect of including a dietary supplement of raisins, a food rich in polyphenols, on cognitive function in healthy older adults; a study protocol for a randomized clinical trial

Background Polyphenols have been shown to be effective against many chronic diseases, including neurodegenerative diseases. Specifically, the consumption of raisins, being a food rich in polyphenols, has been attributed with neuroprotective benefits. Therefore, our main objective is to evaluate the effect of including 50 g of raisins in the diet daily for 6 months, on the improvement of cognitive performance, cardiovascular risk factors and markers of inflammation in a population of older adults without cognitive impairment. Methods Design and intervention: This study will be a randomized controlled clinical trial of two parallel groups. Each subject included in the study will be randomly assigned to one of two study groups: control group (no supplement), intervention group (50 g of raisins daily during 6 months). Study population: The participants will be selected by consecutive sampling in the Primary Care consultations of urban health centers in Salamanca and Zamora (Spain), taking into account the selection criteria. Study variables: Two visits will be made, baseline and at 6 months. Cognitive performance will be evaluated (Mini-Mental State Examination test, Rey Auditory Verbal Learning Test, verbal fluency and montreal cognitive assessment (Moca)). It will also be analyzed the level of physical activity, quality of life, activities of daily living, energy and nutritional composition of the diet, body composition, blood pressure, heart rate, markers of inflammation and other laboratory tests of clinical relevance (glycaemia, total cholesterol, HDL cholesterol, LDL cholesterol and triglycerides). In addition, sociodemographic data, personal and family history, medication use and alcohol and tobacco consumption will be collected. Discussion In this project, it is intended to contribute to minimize the problems derived from cognitive deterioration in older people.