Adherence to Mediterranean Diet Alleviates PTSD Symptoms, Study Suggests

A study con­ducted by researchers from Brigham and Women’s Hospital and the Harvard T.H. Chan School of Public Health has shed new light on the intri­cate rela­tion­ship between post-trau­matic stress dis­or­der (PTSD), dietary pat­terns and the gut micro­biome.

The study, pub­lished in Nature Mental Health, uncov­ered a notable con­nec­tion between adher­ence to a Mediterranean diet and a reduc­tion in PTSD symp­toms.

PTSD is a fear-based men­tal health con­di­tion that can develop in indi­vid­u­als exposed to dis­tress­ing and trau­matic sit­u­a­tions, includ­ing severe injury, the threat of death or acts of vio­lence.

Individuals who have PTSD not only con­tend with its imme­di­ate psy­cho­log­i­cal effects but also face an increased risk of chronic health con­di­tions such as coro­nary heart dis­ease, stroke, dia­betes, autoim­mune dis­or­ders and even pre­ma­ture death.

Recognizing the role of diet and the gut micro­biome in the con­text of PTSD has the poten­tial to yield rec­om­men­da­tions and out­comes that ben­e­fit those affected by the dis­or­der.

Co-author Yang-Yu Liu, from the Channing Division of Network Medicine at Brigham and Women’s Hospital, high­lighted the intrigu­ing rela­tion­ship between the human gut micro­biome and the brain.

“Through our study, we exam­ined how fac­tors like diet are asso­ci­ated with PTSD symp­toms,” she said. ​“While fur­ther research is needed, we are closer to being able to pro­vide dietary rec­om­men­da­tions for PTSD pre­ven­tion or ame­lio­ra­tion.”

The human gut micro­biome is an active hub of meta­bolic activ­ity. Within the colon, bac­te­ria play a piv­otal role in fer­ment­ing and digest­ing var­i­ous com­po­nents, includ­ing car­bo­hy­drates, pro­tein and lipids from the host and the diet. These processes gen­er­ate metabo­lites that can have either ben­e­fi­cial or detri­men­tal effects on health.

For exam­ple, the fer­men­ta­tion of car­bo­hy­drates pro­duces short-chain fatty acids, mainly acetate, pro­pi­onate, and butyrate.

These com­pounds offer numer­ous health ben­e­fits, such as pro­vid­ing energy for colon cells, enhanc­ing ion absorp­tion, pos­sess­ing anti-inflam­ma­tory prop­er­ties and reg­u­lat­ing sero­tonin pro­duc­tion while influ­enc­ing the num­ber of ente­rochro­maf­fin cells.

Remarkably, butyrate has exhib­ited anti­de­pres­sant-like effects in mice, sur­pass­ing the effects of flu­ox­e­tine, a com­mon ingre­di­ent in many anti­de­pres­sants.

Furthermore, com­men­sal bac­te­ria can pro­duce neu­ro­trans­mit­ters with neu­roac­tive prop­er­ties, includ­ing GABA, sero­tonin and dopamine. These neu­ro­trans­mit­ters can­not cross the blood-brain bar­rier but may stim­u­late intesti­nal epithe­lial cells to release mol­e­cules that, in turn, mod­u­late neural sig­nal­ing. This com­plex inter­play can influ­ence brain func­tions and behav­ior.

Although exten­sive research has high­lighted the gut micro­bio­me’s influ­ence on emo­tional devel­op­ment and response, the link between the micro­biome and post-trau­matic stress dis­or­der was largely unex­plored.

The researchers under­scored the sig­nif­i­cance of explor­ing the gut-brain axis, as it pro­vides insights into the inter­de­pen­dence of men­tal and phys­i­cal health.

Their find­ings sug­gest that the rela­tion­ship between PTSD and the human gut micro­biome presents a promis­ing avenue for research, offer­ing the poten­tial for rec­om­men­da­tions to alle­vi­ate the down­stream neg­a­tive health con­se­quences of PTSD.

To inves­ti­gate this rela­tion­ship, the team col­lected data from 191 par­tic­i­pants in sub-stud­ies of the Nurses’ Health Study-II, which encom­passed the Mind-Body Study and the PTSD sub-study.

Participants were cat­e­go­rized into three groups: those with prob­a­ble PTSD, those who had expe­ri­enced trauma with­out devel­op­ing PTSD and those with no his­tory of trauma expo­sure.

Each par­tic­i­pant pro­vided two sets of four stool sam­ples: one at the study’s com­mence­ment and another six months later. This approach enabled the col­lec­tion of micro­bial DNA data and con­fir­ma­tion of the sta­bil­ity of each par­tic­i­pan­t’s gut micro­biome through­out the six months.

The researchers then ana­lyzed the asso­ci­a­tions between the micro­bio­me’s over­all struc­ture and var­i­ous host fac­tors. These fac­tors included PTSD symp­toms, age, body mass index (BMI), and dietary infor­ma­tion.

Through this eval­u­a­tion, the researchers iden­ti­fied sev­eral host fac­tors linked to the micro­biome struc­ture, such as BMI, depres­sion and the use of anti­de­pres­sants.

Subsequently, the team explored the con­nec­tion between avail­able dietary infor­ma­tion and PTSD symp­toms. Their find­ings revealed that par­tic­i­pants adher­ing to a Mediterranean diet expe­ri­enced fewer PTSD symp­toms.

Notably, the con­sump­tion of red and processed meats, mostly absent from the Mediterranean diet, exhib­ited a pos­i­tive asso­ci­a­tion with the sever­ity of PTSD symp­toms. In con­trast, the con­sump­tion of plant-based foods neg­a­tively cor­re­lated with these symp­toms.

The researchers exam­ined the link between PTSD symp­toms and gut micro­biome sig­na­tures to iden­tify poten­tial species that could pro­tect against PTSD. Eubacterium eli­gens emerged as the most likely pro­tec­tive species for the dis­or­der.

They con­cluded that E. eli­gens was pos­i­tively asso­ci­ated with com­po­nents of the Mediterranean diet, such as veg­eta­bles, fruits, and fish while dis­play­ing a neg­a­tive asso­ci­a­tion with red and processed meat con­sump­tion. E. eli­gens has pre­vi­ously been linked to nut con­sump­tion and veg­e­tar­ian diets.

While the study offers valu­able insights, the authors acknowl­edge cer­tain lim­i­ta­tions, such as the use of a short screen­ing scale for PTSD instead of a for­mal clin­i­cal diag­no­sis. Nevertheless, the results pro­vide a foun­da­tion for future research endeav­ors.

These include inves­ti­ga­tions into other men­tal health dis­or­ders and dietary inter­ven­tions, intend­ing to enhance rec­om­men­da­tions for alle­vi­at­ing or pre­vent­ing symp­toms asso­ci­ated with these con­di­tions.

• Harvard School of Public Health
• Can J Psychiatry