Linking Walnuts and Brain Health
Walnuts are certainly among the healthiest varieties of nuts, having impressive heart health benefits and the ability to lower cholesterol and inflammation levels in the body, both of which are known to be good for brain health as well. The nuts are also packed with healthy plant fats, such as omega-3 fats and alpha-linoleic acids, known to benefit memory and cognition, which made researchers question whether daily walnut consumption could have a beneficial effect on cognition.
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Since the early 2000s, test tube and animal studies have been conducted that strengthened the connection, with a 2014 study in mice with simulated Alzheimer's disease even establishing that a walnut rich diet can improve memory, learning, and even reduce anxiety levels in the mice with AD.
The first human study regarding the cognitive benefits of walnuts appeared in 2009, and it partly confirmed the hypothesis that walnuts benefit cognition. In the study, 64 college students were recruited and their memory, reasoning, and mood were measured over the course of 8 weeks, during which the participants were divided into 2 groups that were interchangeably given a daily portion of walnuts or a walnut-free diet.
As you can probably tell, the study was quite small and the period during which participants were followed was also short, but even in such as short time and limited sample size, a diet containing walnuts proved effective at improving the participants’ reasoning skills, which prompted new research in the field, with a very compelling and credible recent study finding a surprising link between walnuts and cognitive decline.
Can Walnuts Slow Down Cognitive Decline in Seniors?
The largest study to date investigating the cognitive benefits of walnuts in senior populations was conducted in California and Spain and was recently published in The American Journal of Clinical Nutrition. Known as The Walnuts and Healthy Aging Study, the study looked at the health effects of daily walnut consumption in 708 elders past the age of 60 in Loma Linda, California, United States, and in Barcelona, Catalonia, Spain.
For 2 years, half of the participants ate a fixed portion of walnuts every day, while the other half abstained from these nuts completely. After that period, the participants' memory was assessed, and a subsequent fMRI brain scan was conducted to check whether any reduction in cognitive decline was observed in the participants that showed the most improvement.
In healthy individuals who were at a lower risk of cognitive decline, researchers didn't observe any changes in memory performance, but the subgroup that was at a higher risk of cognitive problems, e.g. smokers, a diet rich in walnuts alone managed to slow down the progression of cognitive decline. Though these results may not seem stellar, they are still quite impressive, as the addition of just one food managed to reduce the progression of disease in the group that requires the extra boost the most.
The bottom line is that walnuts seem to benefit brain health, but at present, we can't reliably say if they have any cognitive boost for people who are healthy overall, at least not in the short term. At the same time, we think that you still add them to your diet for other reasons, such as cardiovascular and digestive health. If you are at a higher risk of cognitive decline, however, adding walnuts into your diet can also help your brain retain its cognitive capabilities for longer.