Adding unhealthy foods to Mediterranean diet reduces cognitive benefits

The cognitive benefits associated with the Mediterranean diet may be diminished by eating unhealthy foods, according to research published in Alzheimer's & Dementia: The Journal of the Alzheimer's Association.

“Eating a diet that emphasizes vegetables, fruit, fish and whole grains may positively affect a person’s health,” Puja Agarwal, PhD, a nutritional epidemiologist and assistant professor in the department of internal medicine at Rush University Medical Center, said in a press release. “But when it is combined with fried food, sweets, refined grains, red meat and processed meat, we observed that the benefits of eating the Mediterranean part of the diet seems to be diminished.”

Agarwal and colleagues conducted an observational study of older adults who lived in Chicago. Every 3 years, the researchers interviewed each participant for 90 minutes at their home to assess their cognition and other characteristics.

The researchers assessed participants’ diet using a food frequency questionnaire that included 144 foods and questions on vitamins and minerals. They based Mediterranean diet scores on 11 food groups and Western diet factors on 40 food groups.

A total of 5,001 participants who completed food frequency questionnaires and underwent at least two cognitive assessments during follow-up were included in the analysis.

Agarwal and colleagues found that, overall, the Mediterranean diet was associated with slower cognitive decline. Additionally, they found that individuals with the highest Mediterranean diet scores had slower cognitive decline than those with the lowest Mediterranean diet scores. The difference in cognitive rates between those with the highest and lowest Mediterranean diet scores was nearly equivalent to being aged 3.9 years younger.

The researchers conducted an interaction analysis to determine whether the benefits associated with the Mediterranean diet were diminished by consuming unhealthy foods such as refined grains, fried foods and sweets in the Western diet.

They determined that the cognitive benefits associated with higher Mediterranean diet scores remained significant with low Western diet scores. However, in participants with high Western diet scores, the association between Mediterranean diet and cognitive decline was not significant.

Compared with those who had low adherence to the Mediterranean diet, the difference in cognitive decline was equivalent to being 5.8 years younger among those with high adherence to the Mediterranean diet and 3.7 years younger among those with moderate adherence to the Mediterranean diet.

The findings remained similar after adjusting for smoking status, BMI and cardiovascular conditions.

“The more we can incorporate green leafy vegetables, other vegetables, berries, olive oil and fish into our diets, the better it is for our aging brains and bodies,” Agarwal said in the press release. “Other studies show that red and processed meat, fried food and low whole grains intake are associated with higher inflammation and faster cognitive decline in older ages.”

Agarwal added that in order to “benefit from diets such as the Mediterranean diet, or MIND diet, we would have to limit our consumption of processed foods and other unhealthy foods such as fried foods and sweets.”

References:

Newswise. Including Unhealthy Foods May Diminish Positive Effects of an Otherwise Healthy Diet. https://www.newswise.com/articles/including-unhealthy-foods-may-diminish-positive-effects-of-an-otherwise-healthy-diet. Accessed January 15, 2021.

Agarwal P, et al. Alzheimers Dement. 2021;doi: 10.1002/alz.12277.