Mild cognitive impairment is an intermediate stage between the normal cognitive deficits commonly associated with aging and dementia. Many adults with mild cognitive impairment progress to having Alzheimer’s disease; however, interventions that increase dietary antioxidant content may improve cognitive function and prevent further decline. A recent study showed that olive oil consumption improves cognition in adults with mild cognitive impairment.

Olive oil contains monounsaturated fatty acids as well as a number of phenolic compounds that act as antioxidants, protecting the body from oxidative stress and inflammation. A growing number of studies demonstrate that olive oil may provide protection against cognitive decline.

The authors of the study recruited 50 adults who had mild cognitive impairment. They assigned participants to consume 50 milliliters of high-phenolic extra virgin olive oil (EVOO) daily, 50 milliliters of moderate phenolic EVOO daily, or to adhere to a Mediterranean dietary pattern (which is rich in olive oil, plants, and whole grains) for the duration of the study. The participants completed cognitive tests at baseline and after one year of following their diet intervention. Some participants also consented to have their DNA sequenced for the presence of the APOE4 gene. Having one copy of the APOE4 gene increases Alzheimer’s disease risk as much as threefold; carrying two APOE4 copies increases risk as much as fifteenfold.

Participants in all three groups experienced improvement in cognitive performance after one year. Participants in both of the groups that consumed olive oil demonstrated additional improvements in global cognition, letter fluency, and stability of impairment. The effects of the olive oil treatments were especially strong in participants carrying at least one copy of the APOE4 gene. The authors did not find significant differences between the olive oil types.

The authors cautioned that their small sample size may have limited their findings. They noted that both olive oils used in the study have phenol concentrations that meet the European Commission’s standard for quality olive oil, making differences in their effects harder to detect. They suggested that future studies should collect biomarkers, use PET scans to measure disease progression, and include larger sample sizes.

• Link to full study.