“The benefits within the new study’s three-year clinical trial weren’t as impressive as we’ve seen with the MIND diet observational studies in the past, but there were improvements in cognition in the short-term, consistent with the longer-term observational data,” said lead study author Lisa Barnes, Ph.D., associate director of the Alzheimer’s Disease Research Center at RUSH.
According to the researchers, within the 3-year period of this randomized Phase III clinical trial, there was no significant statistical difference in cognition for those in the MIND diet group compared to those in the control group consuming a usual diet, but there was a significant improvement during the first two years of the study. Both groups consisted of adults aged 65 years or older, and they were coached to reduce their calories by 250 kilocalories per day. Previous research indicated that there was a slower rate of decline among those eating specific foods.
“What we saw was improvement in cognition in both groups, but the MIND diet intervention group had a slightly better improvement in cognition, although not significantly better,” Barnes said. “Both groups lost approximately 5 kilograms over three years, suggesting that it could have been weight loss that benefited cognition in this trial.”
“There is established research that shows that a person’s diet affects health,” Barnes said. “The participants in this study had to have sub-optimal diets as determined by a score of 8 or less on a diet screening instrument before the study even began. It is reasonable to think that either they were going to maintain their cognition or decrease the rate of cognitive decline in the future.”
“It was exciting to see that there was improvement in cognition over the first year or so, but it could have been due to practice effects on the cognitive tests, and we saw it for the control diet as well, which focused on just caloric restriction, ” says Barnes.
In 2015, the late Martha Clare Morris, ScD, and colleagues from RUSH and Harvard University developed the MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diet based on compelling research on the foods and nutrients that affect brain health. The MIND diet combines the Mediterranean and DASH (Dietary Approaches to Stop Hypertension) diets which have both been shown to help reduce the risk of cardiovascular conditions. The MIND diet has 14 dietary components which include 9 brain-healthy food groups and 5 unhealthy groups. During their work in 2015, the researchers found that the MIND diet slows cognitive decline and significantly decreases the risk of developing Alzheimer’s disease even if the diet was not adhered to strictly.
This latest trial enrolled 604 participants who were overweight and had suboptimal diets and a family history of Alzheimer’s disease to compare two different dietary interventions that both included dietary counseling with mild caloric restriction of 250 calories/day for weight loss. Dietitians developed individual diet guidelines for the participants, and they all received regular consultations and group sessions during the study period. Additionally, the participants were seen 5 times during the 3 years to evaluate their mental abilities, diet, blood pressure, medication use, health conditions, and physical activity.
“Both groups of participants got a lot of support and accountability by trained registered dietitians,” said Jennifer Ventrelle, assistant professor in the Departments of Preventive Medicine and Clinical Nutrition and lead dietitian on the MIND diet trial at RUSH.
“The good news is that this helped all participants improve on average, but unfortunately hindered the ability to detect significant differences between the two groups in this relatively short period of time. Current and future research plans to look at people coached to follow the diet in this format compared to individuals following a usual diet in a format closer to usual care such as brief clinical encounters or a self-guided program with less support.”
“By the end of the study, the average weight loss was approximately 5.5% of initial body weight for all participants, exceeding the study target of 3%, the amount recognized as clinically significant to prevent or improve adverse health outcomes,” Ventrelle said.
“The average MIND score at the end of three years for the MIND group was 11.0 and 8.3 for the control group, placing both groups in a therapeutic range to slow cognitive decline and lower a risk for Alzheimer’s disease, according to previous studies. The significant weight loss and improved MIND scores suggest that the control group also improved their diet and may suggest that following the MIND diet at a score of at least 8.3, coupled with at least a 250-calorie reduction to produce weight loss, may improve cognition. More research is needed to confirm this.”
“Randomized trials are gold standards for establishing a cause-and-effect relationship between diet and incidence of Alzheimer’s disease,” Barnes said.
“These individuals were healthy at the start of the trial and had no cognitive impairment, and their cognition got slightly better over time,” Barnes said. “Why there was no difference between the two diet groups at the end of the trial could be a result of many factors including that the control group had a relatively healthy diet. Moving forward, we will look at specific food groups and their associations with biomarkers that were measured in the blood to see if certain nutrients and food groups are more important than others since the two groups were pretty healthy from a dietary perspective at the start.”
