In a recent study published in Preventive Medicine Reports
Journal, researchers performed a randomized clinical trial (RCT) to
investigate whether adhering to the Mediterranean diet (MedDiet) with or
without limiting calorie intake could improve cognition.
Study: Effect
of Mediterranean diet and Mediterranean diet plus calorie restriction
on cognition, lifestyle, and cardiometabolic health: A randomized
clinical trial. Image Credit: ElenaEryomenko/Shutterstock.com
Background
Obesity, lifestyle choices including diet and exercise, and
cardiometabolic comorbidities elevate the risk of cognitive decline. To
date, there are no efficient pharmaceutical therapeutics available to
prevent, retard, or manage cognitive deficits.
However, studies have shown that MedDiet and weight loss benefit
cognition, and combining the two may enhance cognitive function.
However, RCTs have shown inconsistent results, with either a favorable
or negligible impact of nutrition on cognition, warranting further
research.
About the study
In the present three-arm RCT, researchers evaluated the potential
cognitive benefit of adhering to MedDiet with or without limiting
calorie intake.
The Building Research in Diet and Cognition study was conducted
between January 2017 and October 2020, involving 185 residents of
Chicago, aged 55 to 85 years, largely female sex (86.0%), with obesity.
The participants were randomly allocated to the MedDiet with calorie
limitation (n=72, 25.0% kcal restriction for 5.0 to 7.0% loss of weight)
intervention group, MedDiet alone group (n=72), or control group
(n=36).
The period of the dietary interventions was eight months, including
26 sessions for the intervention groups and 25 sessions for the control
group, and follow-up assessments were performed over 14.0 months.
The primary study outcome was a change in the cognitive assessment
scores for attention, information, and processing (AIP); learning,
memory, and recognition (LMR); and executive function (EF).
Secondary
study outcomes were changes in body weight, cardiometabolic biomarkers,
and lifestyle. The team estimated habitual dietary consumption using
the Harvard food frequency questionnaires (HFFQS), and physical activity
was estimated using a triaxial accelerometer worn on the non-dominant
wrist for ≥4.0 days and ≥10.0 hours daily.
To assess cardiometabolic risk, blood pressure, serological levels of
low-density lipoprotein-cholesterol (LDL-C), high-density
lipoprotein-cholesterol (HDL-C), total cholesterol, triglycerides (TGs),
insulin, glycated hemoglobin (HbA1c), high sensitivity C-reactive
protein (hs-CRP), and glucose levels were measured in blood samples
provided by the patients.
Individuals were recruited via presentations in senior facilities and
advertisements in local neighborhoods, and they underwent telephonic
and physical screening before enrollment.
Individuals with body mass index (BMI) ranging from 30.0 to 50.0 kg/m2,
Mediterranean diet adherence screener score ≤6.0, Montreal Cognitive
Assessment (MoCA) scores ≥19.0, and those who could speak in English
were included in the analysis.
The team excluded individuals who could not exercise according to the
EASY physical activity screener, serological HbA1c values >9.0 at
screening, and significant comorbidities such as autoimmune disorders or
severe cardiovascular, pulmonary, renal, and hepatic diseases.
In addition, individuals using warfarin, suffering from severe
psychiatric conditions, individuals with a history of bariatric surgery,
individuals concurrently involved in formal bodyweight reduction
programs, and those who participated in cognition-associated research
activities in the previous 12.0 months were excluded from the analysis.
The MedDiet-adhering individuals received one oz of almonds and three
tablespoons of extra virgin olive oil daily.
The theories of social determination and social cognition were used
to guide adherence to the study interventions. In addition, participants
underwent hands-on (meal preparation) and didactic dietary training.
All individuals were advised to attain moderate-vigorous physical
activity levels at 150.0 minutes weekly. The control group participants
received general health newsletters weekly.
Results
The dietary interventions did not significantly impact the LMR, EF,
AIP, or MoCA scores. The mean increase in scores for adherence to the
MedDiet plus calorie limitation and MedDiet alone interventions were
6.30 points and 4.80 points, respectively, in relation to the control
group (+0.60 points).
The mean reductions in weight among individuals in the MedDiet plus
calorie limitation group, the MedDiet alone group, and the control group
were 4.60 kg, 2.60 kg, and 0.60 kg, respectively.
The dietary interventions showed no significant influence on the
physical exercise and cardiometabolic biomarker levels, although lower
fasting insulin levels and lower body weight values were observed in the
MedDiet plus calorie limitation group participants compared to the
other groups.
Particularly, a significant decrease in visceral adiposity was
observed; however, the percentage of total body fat did not differ
significantly among the groups post-intervention. Both intervention
group participants had similar attendance for group sessions, and 67.0%
of the study participants were hypertensive.
Conclusions
The study findings showed that MedDiet adherence with or without
calorie limitation had no significant influence on cognition. However,
the MedDiet interventions significantly reduced central obesity and body
weight and improved dietary quality.
The cognitive benefit of adherence to MedDiet with or without
limiting calorie intake could be associated with preventing or retarding
pathological cognitive aging instead of maintaining normal cognitive
aging.
Alternatively, the strength of the effect could have been lowered due
to the use of different cognitive assessment scores instead of one
composite score. Moreover, the limited sample size and short duration of
interventions could have lowered the impact of the dietary
interventions.
Further research must be conducted using objective dietary
evaluations, larger sample sizes, and longer intervention durations for
accounting for the alteration in the nutritional intake of processed
food items in MedDiet.