Can Dietary Intervention Delay the Onset of Alzheimer’s Disease?
July 1, 2015 4 minutes read
By Richard S. Isaacson, MD
Associate Professor of Neurology (Education), Weill Cornell Medical College
Dr. Isaacson reports he is a consultant for Accera.
Synopsis: In a prospective study of an elderly population, moderate adherence to the MIND diet was associated with a 53% reduction in the development of Alzheimer’s disease.
Source: Morris MC, et al. MIND diet associated with reduced incidence of Alzheimer’s disease. Alzheimers Dement 2015; Feb 11. On-line at http://dx.doi.org/10.1016/j.jalz.2014.11.009. [Epub ahead of print].
There has been an explosion of recent evidence supporting the potential effect of nutrition on the development of cognitive decline and Alzheimer’s disease (AD). Many recent studies have looked into the effect of nutrition on a variety of conditions, such as mild cognitive impairment due to AD and AD dementia, age-related cognitive decline, and vascular cognitive impairment. This research has demonstrated that therapeutic effects of nutrition are not just limited to cognitive function, with improvements across the spectrum of cardiovascular risk reduction, weight loss, and insulin resistance, among many others. Nutritional interventions include two main types of categories: 1) dietary patterns and 2) single or multi-nutrients. A dietary pattern is a specific style of eating, commonly referred to most simply as a diet. The best example of this category is the Mediterranean-style diet, which has the largest volume of dietary pattern research for AD. Other studies have focused instead on an individual nutrient (e.g., the omega-3 fatty acid DHA) or multiple nutrients (e.g., vitamins B12, B6, and folic acid) in combination.
The Mediterranean diet (MeDi) includes plentiful amounts of plant-derived foods and fresh fruit (as the primary source of carbohydrates), olive oil (primary source of fat), fish and lean poultry (primary source of protein, in low to moderate amounts), red meat (in low amounts), low-fat yogurt and milk (in moderate amounts), and wine (in low to moderate amounts). Regular physical activity is also a part of this diet, which is representative of cultural patterns of eating in countries like Italy, Greece, Spain, and Morocco.
In part, because it has been shown to reduce inflammation, oxidative stress, and insulin levels, MeDi has long been known to help reduce the risk of heart disease, and has been associated with a decreased risk of AD as well. By one estimate, MeDi can decrease AD risk by as much as 40% in older patients. The more strictly the patients adhered to the diet, the more dramatically their risk was reduced. Another dietary pattern, called Dietary Approaches to Stop Hypertension (DASH), was shown to improve cognitive function in a group of hypertensive, overweight subjects when combined with exercise. Based on these data, Morris and colleagues from Rush University Medical Center devised the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND), which was initially shown to be more predictive of slower cognitive decline than MeDi or DASH. In the current study, Morris and colleagues aimed to shed more light on the effect of MIND adherence, more specifically on the development of AD rather than cognitive decline alone. The MIND diet is characterized by whole grains (> 28/week), green leafy vegetables (7+/week), berries (½ cup/day), regular cheese (≤ 1/day), butter (< 1 T/day), beans (3+/week), nuts (1/8 cup/day), lean red meats (< 4/week), fish (1+/week), poultry (2+/week), olive oil (> 1 T/d), and alcohol/wine (> 1/day). Key differentiating factors from MeDi and DASH include fewer grains/week, an emphasis on whole grains and berries, more red meat (but lean), less olive oil than MeDi, and unlike DASH, no specific percentage of total fat/saturated fat.
This study prospectively followed more than 900 people aged 58-98 years over 4.5 years and asked them to track their food patterns via food frequency questionnaires. Morris and colleagues found that moderate adherence to the MIND diet was associated with a 53% reduced risk of AD for those in the highest tertile of adherence (compared to a 35% risk reduction in the middle tertile). This effect was independent of other lifestyle conditions and cardiovascular-related conditions. When compared to adherence to MeDi and DASH, only those with the highest adherence to these dietary patterns showed an association with AD prevention.
Commentary
To reinforce these associations, two recent randomized, controlled trials (RCTs) have found additional support for the importance of nutritional interventions for AD. The Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) study1 was the first longitudinal RCT to prove that multimodal lifestyle intervention (nutrition, exercise, cognitive training) reduces the risk of cognitive decline. The second RCT by Ros and colleagues2 randomized subjects to three groups. Two of the groups followed the MeDi, also adding either 5 tablespoons of extra virgin olive oil each day or a handful of mixed nuts (30 grams of almonds, walnuts, or hazelnuts) each day. The third group followed a low-fat diet. Compared to the low-fat diet group, cognitive function in the areas of attention and executive function were higher in the MeDi plus olive oil group, and memory function was higher in the MeDi plus nuts group. Although further RCTs are warranted, from a practical clinical perspective, targeted nutritional interventions are an evidence-based and safe means of reducing the risk of AD and cognitive decline.
References
- Kivipelto M, et al. A 2 year multidomain intervention of diet, exercise, cognitive training, and vascular risk monitoring versus control to prevent cognitive decline in at-risk elderly people (FINGER): A randomized controlled trial. Lancet 2015;385:2255-2263.
- Ros E, et al. Mediterranean diet and age-related cognitive decline: A randomized clinical trial. JAMA Intern Med 2015; May 11 doi: 10.1001/jamainternmed.2015.1668. [Epub ahead of print].
In a prospective study of an elderly population, moderate adherence to the MIND diet was associated with a 53% reduction in the development of Alzheimer’s disease.
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