Foods proven to keep your brain young?
A polyphenol-rich diet is put to the test
As lifespan expands and many more people live into their 80s and 90s a big concern is cognitive decline later in life. Cognitive decline is related to several disease processes and the risk of intellectual deterioration has been associated with many lifestyle factors, including poor diet, obesity and sedentary lifestyle.
On the other hand, healthy diets such as the Mediterranean diet are associated with lower rates of Alzheimer's disease and cognitive decline. A plant-rich diet could affect brain health directly, as plant polyphenols do cross into the brain, where they can act as antioxidants and anti-inflammatory agents, reducing harmful processes that lead to brain cell dysfunction and loss.
These are consistent associations, but a new 18 month study reported in the American Journal of Clinical Nutrition, set out to test this link with an interventional clinical trial. The study was completed by 224 people who had either abdominal obesity (excess fat around the waistline) or abnormal lipid profiles (high cholesterol or triglycerides), and was conducted at a remote workplace, the nuclear facility in Dimona, Israel, in which lunch and exercise were provided and monitored onsite.
Mediterranean plus
The volunteers were randomly assigned to one of three calorie restricted diets: A healthy dietary guidelines group receiving standard nutrition counseling, a Mediterranean diet group advised to follow a diet rich in veggies, with chicken and fish replacing part of the red meat and supplanted with about an ounce of walnuts daily, and a Green Mediterranean diet group, that in addition to the Mediterranean diet instructions also were instructed to avoid processed and red meat, to eat more plant-based foods and to drink 3-4 cups of green tea and about 3 ounces of Mankai (Wolffia globosa, an aquatic plant rich in polyphenols, protein, iron and B12) as a dinner replacement. All three groups also had a free gym membership and received similar physical activity guidance.
Brain volume diminishes over time, a change apparent in brain imaging, and the brains of the participants were followed by MRIs before and after the intervention. One area of the brain is of special interest, the hippocampus, a brain area is involved with learning and memory. The hippocampus is located deep in the temporal lobe, and loss of volume there is considered a sensitive marker of brain decline, even before symptoms appear.
And the results: After 18 months brain atrophy was associated with the age of the participants, with atrophy accelerated among those over 50 years of age. The rate of atrophy was however attenuated in both of the Mediterranean diet groups, and especially in the Green Mediterranean diet group. The same protective effect was also seen in the younger volunteers.
Avoidance of red and processed meat, and consumption of walnuts and of “green” dietary components (Mankai and green tea) were associated with less loss of brain volume in the hippocampus. The researchers also saw that improvements in glucose tolerance, body weight and blood pressure with the ascribed diet correlated with less brain loss on MRIs. Moreover, urinary excretion of polyphenols, reflecting intake of plant foods, were also correlated with brain volume retention.
Do we have to eat walnuts?
This intervention – of 18 months – is shorter than a 4 year intervention study in 334 older people that showed improved cognition assessed by neuropsychological testing with a Mediterranean diet supplemented with olive oil and nuts. In this study, which showed a diet-brain volume correlation, neuropsychological testing didn’t measure differences between the three groups. These perhaps take more time to manifest.
Are these specific plant foods important? The walnuts and Mankai that were given to the participants were chosen because they’re rich in polyphenols, but they’re more an example of the type of food pattern that helps to maintain a healthy brain than an specific recipe: “we cannot claim an effect of specific foods or nutrients,” say the authors.
The list of polyphenol-rich foods is extensive, and includes berries, herbs and spices, vegetables such as broccoli, cocoa, coffee and tea. Most plant foods contain many types of polyphenols, and the level of content varies by the way the plant is grown, by the way the food is prepared, and many other factors. Polyphenol absorption also varies.
This is why sensible diet recommendations are to eat a varied diet centered on plant based foods. You don't need to hunt exotic superfoods as there are many nutritiously rich foods that grow locally and are commonly available.
These plant foods are important for cardiovascular health, for protection from inflammation, diabetes and cancer, and may also stave off brain decline.
Dr. Ayala