The impact of dietary factors on indices of chronic disease in older people: a systematic review

Objectives: There has been little evaluation of the evidence relating dietary factors to functional capacity in older adults. The aims were to i) conduct a systematic review of studies assessing dietary factors in relation to six key functional indicators which impact on quality of life in adults ≥65 yrs: non-fatal cardiovascular events, cognition, mental health, falls and fractures, physical health (muscle mass, strength) and frailty; and ii) assess if there was sufficient evidence to devise food-based dietary recommendations. Design: Systematic review. Participants: Cross-sectional and prospective cohort studies were included together with intervention studies that evaluated food/drink interventions (excluding supplements). Evidence base statements were determined according to the GRADE (Grades of Recommendation, Assessment, Development and Evaluation) levels of evidence criteria (Grades (A-excellent; B-good; C-satisfactory; D-poor). Results: There was good evidence that the Mediterranean type diet (MD) reduced the risk of non-fatal cardiovascular events (Grade B) and reduced cognitive decline (Grade B). There was some evidence indicating that a MD decreases the likelihood of frailty (Grade C), consistent but weaker evidence that ≥3 servings/d of vegetables is associated with reduced cognitive decline (Grade D), a modest increase in protein may be associated with improved cognition (Grade C) and decreased frailty (Grade C), and that protein plus resistance exercise training in frail elderly may enhance physical strength (Grade C). Conclusion: It is recommended that older adults adopt the characteristics of a Mediterranean type diet such as including olive oil and eating ≥3 servings/d of vegetables to reduce their risk of chronic disease, impaired cognition and frailty. Consumption of dietary protein above the current dietary requirements would be recommended to reduce risk of frailty and impaired cognition. A modest increase in dietary protein when combined with resistance exercise would be recommended to help maintain muscle mass and strength and to enhance functional capacity.