Diet and Cognitive Function

The August 12, 2015 edition of Nutrients (open access) had an interesting review article on diet and cognitive deficits. Here are some of the points I found most interesting:

• Mid-life BMI could be more important in predicting a decline in cognitive functioning than late life BMI. Low BMI is often associated with illness, so it’s much harder to tease out the effect of BMI in late life. 
• Obesity is associated with systemic inflammation, metabolic syndrome, and reduced cardiovascular fitness. Any of these conditions affect cognition. 
• Some studies have shown that a diet high in fat and refined sugars is correlated with impaired hippocampal function and the associated impaired memory. Interestingly, this impairment also reduces sensitivity to internal signals of hunger, which in turn promotes overeating and obesity. 
• Other studies looked at the types of fats that people were eating. Some studies show that higher intake of saturated fatty acid is associated with impaired memory. Other studies show that a higher omega-3 to omega-6 polyunsaturated fat ratio was associated with a lower risk of cognitive decline. That would be a diet rich in fish and nuts and seeds and lower in meat and poultry. 
• High intake of simple sugar has also been associated with lower cognitive function. Sugar can increase inflammation in the body and brain. 
• Long chain polyunsaturated fatty acids such as docosahexaenoic acid (DHA) may help reduce the risk for cognitive decline. Studies have gone both ways, showing benefit and no benefit. When compared to animal studies, animals were supplemented for more than 10% of their (short) lifespan. For humans this would mean supplementing for more than 6-8 years for an effect to be noticed. So the time to start would be in midlife. 
• Curcumin, the active ingredient in turmeric, has also been shown to be helpful in preventing cognitive decline, although much more research in this area needs to be done. When buying curcumin, it is important to note that absorption can be an issue. There are now various products on the market that improve absorption.