New Research Finds No Link Between Diet and Reduced Dementia Risk

The study found no link between adherence to a modified Mediterranean diet and lower dementia incidence. Still, researchers indicated that diet likely remains one factor among many.
By Paolo DeAndreis
Oct. 31, 2022 15:30 UTC

A large-scale, long-term study has found no link between Mediterranean-like diet adher­ence and reduced demen­tia risk.

The study, pub­lished in Neurology, fol­lowed nearly 30,000 peo­ple for about 20 years. The researchers’ goal at the out­set was to deter­mine whether diet could reduce the risk of devel­op­ing a range of cog­ni­tive dis­or­ders.

One chal­lenge for such a long study inter­val is that dietary habits could not be fol­lowed lon­gi­tu­di­nally over the period to assess poten­tial changes in dietary habits. Thus, the results are chal­lenged by poten­tial con­founders.- Nils Peters, neu­rol­o­gist, Klinik Hirslanden

The study found that fol­low­ing con­ven­tional dietary rec­om­men­da­tions or a mod­i­fied Mediterranean diet (where dietary fat com­prised olive oil and veg­etable oil due to low con­sump­tion of the for­mer in Sweden) was not sig­nif­i­cantly asso­ci­ated with a reduced risk of devel­op­ing all-cause demen­tia, Alzheimer’s dis­ease or vas­cu­lar demen­tia.

The researchers added that the results were sim­i­lar when exclud­ing par­tic­i­pants who devel­oped demen­tia within five years and those with dia­betes.

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Dementia cases are expected to triple dur­ing the next 30 years, high­light­ing the impor­tance of find­ing mod­i­fi­able risk fac­tors for demen­tia,” the researchers wrote.

The sci­en­tists based their results on the dietary habits of more than 28,000 res­i­dents in the Swedish city of Malmö who were born between 1923 and 1950 and had par­tic­i­pated in the prospec­tive Swedish pop­u­la­tion-based Malmö Diet and Cancer Study” between 1991 and 1996, with a fol­low-up for inci­dent demen­tia until 2014.

During that period, nearly 7 per­cent of the par­tic­i­pants devel­oped dif­fer­ent types of demen­tia. No spe­cific diet was asso­ci­ated with the pres­ence of Alzheimer’s dis­ease mark­ers in affected patients.

Dietary habits were assessed with a seven-day food diary, detailed food fre­quency ques­tion­naire and one-hour inter­view,” the researchers wrote.

Previous stud­ies have demon­strated the ben­e­fit of fol­low­ing the Mediterranean diet on cog­ni­tion and brain func­tion, espe­cially in older adults.

A 2021 study pub­lished in Clinical Nutrition found that par­tic­i­pants expe­ri­enced small-to-mod­er­ate” improve­ments in sev­eral cog­ni­tive domains after fol­low­ing the Mediterranean diet for three years com­pared with a con­trol group. Improvements included spa­tial, visual and ver­bal mem­ory improve­ments and atten­tion span.

In another 2022 study from Harvard University, researchers found that fol­low­ing a green Mediterranean diet low in red meat intake pro­tected the brain from atten­u­ated age-related brain atro­phy.

Still, the new Swedish research con­firmed find­ings from two stud­ies con­ducted by the American Medical Association in 2019, which included thou­sands of indi­vid­u­als but had found no evi­dence that diet, includ­ing the Mediterranean diet, affects the risk of devel­op­ing demen­tia.

Commenting on the Swedish study, Nils Peters, a neu­rol­o­gist at the Klinik Hirslanden in Switzerland, and Benedetta Nacmias, an asso­ciate pro­fes­sor of neu­rol­ogy at the University of Florence, Italy, observed that diet as a sin­gu­lar fac­tor may not have a strong enough effect on cog­ni­tion, but is more likely to be con­sid­ered as one fac­tor embed­ded with var­i­ous oth­ers, the sum of which may influ­ence the course of cog­ni­tive func­tion.”

Other fac­tors include reg­u­lar exer­cise, smok­ing, alco­hol con­sump­tion and stress.

One chal­lenge for such a long study inter­val is that dietary habits could not be fol­lowed lon­gi­tu­di­nally over the period to assess poten­tial changes in dietary habits,” Peters told Live Science.

Thus, the results are chal­lenged by poten­tial con­founders, such as changes of dietary habits, lifestyle changes or newly co-occur­ring med­ical con­di­tions over time,” he con­cluded.


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