Mediterranean And 3 Other Diet Types May Lower Dementia Risk, Especially In Women

Written by Jessica Freeborn — Fact checked by Jill Seladi-Schulman, Ph.D.

Can what people eat affect their dementia risk? A new study suggests that this may likely be the case.

Researchers explored in depth how certain dietary habits are related to dementia risk.

Using data from the UK Biobank, the results confirm the benefits of dietary patterns like the Mediterranean diet and the MIND diet and suggest that inflammatory diets may increase someone’s chances of developing dementia.

The results also indicate that the impact of diet on dementia risk may be more significant for women and older adults.

This study examined diet and dementia risk while also considering the impact on people with certain characteristics, such as obesity or older age.

Researchers evaluated participants’ diets based on several scoring indices. One looked at adherence to the Mediterranean diet, and another at adherence to the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet. The MIND diet combines the DASH and Mediterranean diets and focuses on components like nuts, leafy vegetables, and berries.

Next was the Recommended Food Score, which helps evaluate diet quality based on how much people eat certain foods like lean meat, low-fat dairy, fruits, and vegetables. There was also the Alternative Healthy Eating Index-2010, which looks at how well someone is following American Dietary Guidelines.

Finally, researchers also used the Energy-adjusted Dietary Inflammatory Index (EDII) to look at how inflammatory diets were. This index considered components like some vitamins and minerals and components like alcohol and fat intake. Researchers then divided dietary index scores into four groups. They also considered covariates, including physical activity, smoking, and body mass index.

Researchers were able to analyze data from 131,209 participants, who did not all have a baseline dementia diagnosis. They then had exact matching in each of the five dietary categories for sex and age. Exact matching is a strategy used in cohort studies that can help with confounding.

At baseline, the average age of participants was age 56. The average follow-up time was 13.5 years, and throughout the follow-up, 1,453 participants developed dementia.

Overall, participants with the lowest scores for the Mediterranean diet, the MIND diet, and the Recommended Food Score experienced the “highest incidence of dementia.”

Researchers also observed that those with the lowest inflammatory diet scores and the highest Alternative Healthy Eating Index scores had “the lowest incidence of dementia after the follow-up period.” However, for these two groups, there were no quartile group differences that reached a significant level.

Researchers observed that higher scores for the Mediterranean diet, the MIND diet, the Recommended Food Score, and the Alternative Healthy Eating Index were all linked to decreased dementia risk. Following more of an inflammatory diet was linked to an increased dementia risk. They also found that higher scores for the MIND diet, the Recommended Food Score, and the Alternative Healthy Eating Index were all linked to a decreased risk for mild cognitive impairment.

Time was also an important factor. For example, at the less than five-year follow-up, only the MIND appeared to be associated with a decreased dementia risk. At the five to ten-year follow-up, more closely following the MIND diet, the Recommended Food Score, and the Alternative Healthy Eating Index appeared to decrease dementia risk.

At the ten-year or more mark, some associations remained significant, such as how greater following of the Mediterranean diet appeared to lower dementia risk by 24%.

Subgroup analyses looked at sex, age, and obesity. Researchers found that for participants ages 60 and older, more closely following the Mediterranean diet and the Alternative Healthy Eating Index reduced dementia risk, but this wasn’t the case for younger participants. The associations with other scoring indexes were still significant regardless of age.

For women, closer adherence to all healthy diets and lower inflammatory diet scores all appeared to lower dementia risk. For men, only the Recommended Food Score appeared to significantly decrease dementia risk, and the effects were still better for women.

Following the Mediterranean diet appeared to help with dementia risk regardless of weight. A greater inflammatory diet score was associated with an increased risk for dementia in participants with obesity. The other healthy dietary patterns besides the Mediterranean diet helped lower dementia risk for participants who did not have obesity.

Finally, researchers looked at how these diets impacted people with the ApoEε4 genotype, which can increase risk for Alzheimer’s disease. For non-ApoEε4 carriers, higher scores of all healthy diets helped to decrease dementia risk, and higher inflammatory diet scores increased risk. For ApoEε4 carriers, only adherence to the Recommended Food Score appeared to help decrease dementia risk.

Amarish Dave, DO, an osteopathic physician specializing in neurology, who was not involved in the study, commented with his thoughts on the findings:

“This study adds hard numbers to what we know intuitively, which is that healthy diets lower your dementia risk, and inflammatory foods raise it. It confirms that healthy eating patterns matter when it comes to reducing dementia risk. The size and quality of the data make these results hard to ignore.”

This study adds information regarding potential dietary interventions related to dementia. There are limitations, such as the study was only in participants in the U.K., and some information comes from participant reporting. There may be restrictions on generalizability to other groups, and future research can have more diversity. Any general limitations of the UK Biobank also apply to this study.

Researchers note that the self-reporting of food intake increases the risk of recall bias; people can make mistakes such as incorrectly estimating portions and nutrients. They also note the possibility of an underestimation of the association between diet and risk for dementia.

Participants were between ages 40 and 69 at baseline, and researchers only did follow-up for a certain timeframe. Researchers suggest that using other follow-up periods and working with diverse age groups could be helpful, as this could reveal variation.

Diet information was collected in a narrow window, and researchers did not take into account how participants’ diets could have changed during the follow-up. The researchers suggest that examining dietary changes could be helpful in truly looking at the potential long-term impact of diet on people’s chances of developing dementia.

Some dietary data was lacking. For example, researchers note that they lacked information on how much olive oil participants were consuming, so they weren’t able to include this in the scoring when considering the Mediterranean diet. Olive oil is a major component of the Mediterranean diet.

Researchers also lacked data from the original Dietary Inflammatory Index, so they only included some elements of this index.

The researchers acknowledge that the use of exact matching in this study was also limiting. They explain that “the estimated effect can only be generalized to a small population and lacks precision.”

Finally, there is the risk for residual confounding, which researchers acknowledge could impact “dietary choices and dementia risk.”

This study highlights the diet’s important role in possibly protecting against dementia. Alex Dimitriu, MD, double board certified in Psychiatry and Sleep Medicine and founder of Menlo Park Psychiatry & Sleep Medicine, who was also not involved in the study, noted the following clinical implications of the research:

“This study speaks to the importance of long-term adherence to diet and the benefits of this. It also demonstrates how diet may play a greater role for older women than for other groups. Also of interest, the study confirms prior findings that pro-inflammatory diets (high in saturated fats, and refined carbohydrates) can be a risk factor for dementia.”

The results also suggest the need for doctors to keep discussing diets with their clients. As noted by Dave:

“Doctors should be talking to patients about brain-healthy diets just like we talk about heart health. Eating less processed food and more whole, anti-inflammatory foods could be a powerful tool to prevent cognitive decline. These results show that food should be part of the prescription.”