Neither exercise nor omega-3 supplements has a protective effect on the brains of older adults, according to the results of two large randomized controlled studies published Tuesday in JAMA.
The results from the omega-3 study aren’t that surprising, given the growing number of clinical trials that have failed to find any kind of health benefit, including protection against heart disease, for such supplements.
But the findings regarding exercise and cognitive skills in the aging brain are somewhat unexpected. Exercise’s health benefits elsewhere in the body — such as on the cardiovascular system — are well documented. And a meta-analysis published last year found that one of the strongest predictors of dementia was decreased physical activity.
For the new omega-3 study, Dr. Emily Chew and her colleagues at the National Eye Institute (NEI) followed the cognitive function of about 3,500 older people (average age: 72 years) over a period of five years. All were participating in a larger study that was testing the possible effects of various nutrient supplements, including those containing omega-3, on age-related macular degeneration (AMD), a progressive eye disease that is a leading cause of vision loss among people aged 50 and older.
Half of the participants were given supplements with omega-3, a fatty acid found most abundantly in fish, but also in flaxseed, walnuts, soy products and a few other plant sources. The other half took a placebo. All had their cognitive skills tested before the study started and then twice more, at two-year intervals.
At the end of five years, no difference in cognitive abilities was found between the groups.
“The bottom line is that supplements are not the fast cure,” Chew told Time magazine reporter Alice Park. “You are what you eat, and you’ve got to eat well. Maybe it was too late for some of the people in our study.”
The exercise study
For the exercise study, Dr. Kaycee Sink of the Wake Forest School of Medicine and colleagues randomly assigned 1,635 sedentary older people to either a structured, 24-month physical activity program (involving walking, resistance training and flexibility exercises) or a health education program. All the participants, aged 70 to 89, were at risk of losing their physical mobility but able to walk at least a quarter of a mile.
After two years, the participants’ cognitive function was assessed through a series of tests. No significant differences in scores were found between the two groups.
“Cognitive function remained stable over 2 years for all participants,” Sink and her co-authors write. “We cannot rule out that both interventions were successful at maintaining cognitive function.”
The researchers did find, however, that the structured exercise program tended to help two subgroups of people retain better executive function skills (the ones we use to do such “high-level” tasks as planning, organizing, problem-solving, and reasoning). Those subgroups were people aged 80 and older and those who had started the study with poorer overall cognitive abilities.
“This finding is important because executive function is the most sensitive cognitive domain to exercise interventions, and preserving it is required for independence in instrumental activities of daily living,” the researchers write. “Future physical activity interventions, particularly in vulnerable older groups (e.g., ≥80 yrs of age and those with especially diminished physical functioning levels), may be warranted.”
Lifestyle still important
Do these results mean that exercising and eating nutrient-rich healthful foods (not supplements) is a waste of time and effort for older adults?
Absolutely not, as the authors of a JAMA editorial that accompanies the studies stress.
While these two studies “failed to demonstrate significant cognitive benefits, these results should not lead to nihilism involving lifestyle factors in older adults,” they write.
“There is clear evidence that physical activity and a healthy diet contribute to improvements in a wide variety of health outcomes,” they add. “These interventions are safe and widely available, but to be effective will require sustained efforts from older individuals and encouragement from their physicians.”
You’ll find abstracts of the studies on JAMA’s website.