Keeping Our Brains Sharp

What do you think are healthy behaviors when it comes to protecting your brain? Just a month ago, I’d have probably listed eating well, exercising, and meditating for stress reduction at the top of the list for primary prevention. Results from two new studies tell me I’d only be partly right. Turns out, one of these behaviors works, but the other two may not. So which would you put your money on?

Study 1: Mindfulness and Exercise

To look at the effects of mindfulness-based stress reduction (MBSR) training and exercise or their combination on the cognitive and executive function in older adults with subjective (but not objective) memory concerns, 585 adults, mean age 72 years, were randomized to one of four conditions: heath education, exercise, MBSR, or the combination of exercise and MBSR for 18 months. Cognitive function was measured over time using standardized neuropsychological tests.

The results were disappointing: There were no effects of mindfulness or exercise training on episodic memory or executive function (attention, working memory) at any time points compared to the control group.

Although people in the exercise group also had improved physical performance, aerobic fitness, strength, and sleep quality and quantity, MBSR didn’t affect any secondary variables either.

Authors were surprised by these results, since exercise and mindfulness have shown benefits in smaller studies. The study was well-designed, and there is no reason to think the interventions were deficient, so the authors surmised that one possible reason for no effects is that most participants were generally healthy and not excessively sedentary to start, and so there wasn’t much room for improvement. The other theory was that the “control” was too effective: In fact, cognitive function in all groups improved over the 18 months of the study.

Study 2: Ultra-Processed Food

The second study aimed to investigate the impact of ultra-processed (UPF) consumption on cognitive and executive function trajectories, just like the mindfulness and exercise study did. This study was done in Brazil, where UPF consumption is lower than in the U.S. (UPF accounts for 30 percent of total calorie intake in Brazil whereas it accounts for 58 percent of intake in the U.S.).

The Nova classification system was used to categorize foods into four groups, the top group being that of UPFs. According to this system, UPFs included sweet and savory snacks, cakes, crackers, cookies breakfast cereals, ice cream, sugar-sweetened beverages, processed meats, ready-to-eat frozen meals, and breads, just to name a few.

In this observational study of 10,775 people, average age 52 years, individuals in the top three quartiles of UP food consumption (calculated as percent of total calories from UPFs) had a 30 percent faster rate of global cognitive decline and a 25 percent faster rate of decline in executive function (attention, working memory, fluency) over a median of 8 years, compared to those in the lowest quartile, who ate less than 20 percent of their calories as UPF.

There was no association between UP food intake and memory score alone, however, and a subgroup analysis showed that people with a high healthy diet score (as determined by how well they adhered to the MIND diet, derived from the Mediterranean Diet and the DASH diet and comprised of green leafy vegetables, berries, nuts, olive oil, whole grains, fish, and poultry) were protected against UPF-related decline.

Although this was not a randomized controlled trial, the researchers controlled for numerous covariates that could have been driving the links between UPF intake and cognition, including body mass index (BMI), diabetes, hypertension, cardiovascular disease, depression, physical activity, smoking, alcohol, income, education, race and ethnicity. Those in the highest three UPF food consumption quartiles were more likely to be younger, women, Caucasian, have higher education and income, be nonsmokers, be alcohol consumers, have a higher total energy intake, and engage in lower physical activity. Interestingly BMIs were similar across groups.

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Authors posited that some potential mechanisms by which UPFs adversely affect brain function include direct effects on brain volume (grey matter, hippocampus) and systemic inflammation.

Conclusion

So what is our take-home message from these two fascinating studies?

Regarding the former study, does that mean it’s pointless to exercise or meditate if our main goal is to prevent cognitive decline? Possibly, yes. But it’s hard to say for sure.

First, the exercise intervention did improve sleep, and impaired sleep is a known predictor of cognitive impairment. Second, the exercise and meditation study was conducted in older adults, and outcomes only measured 18 months out, so it did not rule out the possibility that exercise and/or meditation might prevent cognitive decline in younger age groups or over a longer period of time. Third, Study 1 and Study 2 used different tests of executive function.

But the truth is, exercise and mindfulness might not give us as big a bang for our buck as we previously thought when it comes to cognitive function.

Do the results from Study 2 mean that we should do our best to reduce our percentage of daily calories consumed from UPFs to less than 20 percent? For this question, I would say, yes.

Although the UPF study was observational and not a randomized clinical trial, and therefore associations could have been driven by an unmeasured confounding variable, the results of this study are still compelling, because the researchers rigorously controlled for a number of important potential factors in their analyses. These results also build on the growing amount of evidence linking insulin resistance and Alzherimer’s (insulin resistance comes from high-carbohydrate, highly processed diets in many cases).

Eating primarily whole grains, fruits, veggies, healthy proteins, and fats—real food—and reducing UPFs to a minimal percentage of your diet seems like an excellent choice for the protection of brain health. It certainly can’t hurt.