Study Links Cooking Methods and Health

New research pub­lished in Nature Scientific Reports has iden­ti­fied some of the impacts of dif­fer­ent cook­ing meth­ods on meta­bolic health and inflam­ma­tion.

The team of Spanish researchers stud­ied how eat­ing food raw com­pared with boil­ing, roast­ing, pan-fry­ing, fry­ing, toast­ing, sautéing and stew­ing food affects renal func­tion, inflam­ma­tion or alters other rel­e­vant bio­mark­ers.

Investigating how food prepa­ra­tion influ­ences its nutri­tional value has become an increas­ingly com­mon field of study as con­sumers become more aware of what and how they eat.

“Classical nutri­tional epi­demi­ol­ogy has focused on an approach based on indi­vid­ual foods, exam­in­ing the role of cer­tain foods or food groups on health,” Montserrat Rodríguez-Ayala and Pilar Guallar-Castillón, researchers at the Autonomous University of Madrid and co-authors of the study, told Olive Oil Times.

“However, cook­ing meth­ods have hardly been explored using pop­u­la­tion data,” they added. ​“Cooking meth­ods have mostly been addressed when study­ing their effects on physic­o­chem­i­cal char­ac­ter­is­tics of foods or bioavail­abil­ity of nutri­ents.”

The cross-sec­tional study con­ducted on almost 2,500 Spanish res­i­dents over 65 years of age showed trends, such as bet­ter health out­comes from eat­ing larger quan­ti­ties of raw or pan-fried food.

The researchers also stressed the dis­ad­van­tages of cook­ing with veg­etable oils – though notably not olive oil – at high tem­per­a­tures.

In their study, researchers found that four dif­fer­ent cook­ing meth­ods – raw, boil­ing, pan-fry­ing and toast­ing – cor­re­sponded with ben­e­fi­cial effects on sev­eral inflam­ma­tory mark­ers, as well as improved kid­ney func­tion, thy­roid hor­mone bal­ances and vit­a­min D lev­els.

None of the cook­ing meth­ods, includ­ing fry­ing food, showed sig­nif­i­cant detri­men­tal asso­ci­a­tions for the inflam­ma­tory and meta­bolic bio­mark­ers the researchers assessed.

“Our study is a first approach to the effect of cook­ing meth­ods on health,” Rodríguez-Ayala and Guallar-Castillón said. ​“Therefore, with the cur­rently avail­able infor­ma­tion, rec­om­men­da­tions to avoid cer­tain cook­ing meth­ods can­not be made. However, cook­ing meth­ods that do not include adding oils heated to high tem­per­a­tures are safe and can poten­tially be asso­ci­ated with health ben­e­fits.”

Many dietary guide­lines sug­gest that raw and boiled foods pro­vide more health ben­e­fits than fried foods, the con­sump­tion of which should be lim­ited.

“Our results agree with this rec­om­men­da­tion for the con­sump­tion of raw and boiled foods,” Rodríguez-Ayala and Guallar-Castillón said. ​“However, in our pop­u­la­tion, no harm­ful effect of fried food con­sump­tion was observed, pos­si­bly because olive oil is the main source of fat for fry­ing in Spain.”

“Olive oil is con­sid­ered very sta­ble when heated at high tem­per­a­tures and is also rich in antiox­i­dants and flavonoids,” they added. ​“Other added oils or fats have not shown these prop­er­ties. Therefore, the results could vary in pop­u­la­tions using other oils or fats for cook­ing.”

“In Spain, olive oil con­sump­tion might exert a pos­i­tive influ­ence on health, which could influ­ence to some degree the effect on the health­i­ness of dif­fer­ent cook­ing meth­ods,” the researchers con­tin­ued. ​“The role of olive oil as a cook­ing fat could be very impor­tant, but it has not yet been quan­ti­fied.”

Additionally, Rodríguez-Ayala and Guallar-Castillón noted that the study, com­prised of 53 per­cent female vol­un­teers and an aver­age age of 71, was not rep­re­sen­ta­tive of the Spanish pop­u­la­tion.

They sug­gested peo­ple in this demo­graphic might eat health­ier food com­pared to younger gen­er­a­tions, which could sug­gest dif­fer­ent results even when cook­ing meth­ods are con­sid­ered.

“So far, no sim­i­lar study has been con­ducted in younger pop­u­la­tions, and it is to be expected that the results could vary to some degree,” Rodríguez-Ayala and Guallar-Castillón said. ​“Diet qual­ity is lower among younger peo­ple because adher­ence to the Mediterranean dietary pat­tern has decreased among younger peo­ple and also because the con­sump­tion of ultra-processed foods has increased.”

“Therefore, we start from a more dis­ad­van­taged meta­bolic sit­u­a­tion,” they added. ​“However, we believe that the gen­eral rule of avoid­ing cook­ing meth­ods with added oils at high tem­per­a­tures would also be ben­e­fi­cial for younger peo­ple.”

The same researchers were also involved in a sep­a­rate study that found olive oil con­sump­tion to be asso­ci­ated with lower risks of car­dio­vas­cu­lar dis­ease and stroke. The higher the qual­ity of the olive oil, the bet­ter the out­come.

“Our research group has shown that olive oil con­sump­tion did not increase coro­nary risk nor the risk of stroke, despite being an energy-rich food,” Rodríguez-Ayala and Guallar-Castillón said. ​“Recently, we have also shown that vir­gin olive oil con­sump­tion was asso­ci­ated with less ath­er­o­scle­ro­sis in carotid arter­ies and femoral arter­ies as well as a decrease in coro­nary cal­cium.”

The researchers added that fur­ther lon­gi­tu­di­nal and long-term stud­ies must be done to expand the cur­rent knowl­edge about cook­ing meth­ods and estab­lish more robust asso­ci­a­tions.

They explained that those meth­ods should be explored for the role they can play in dif­fer­ent pop­u­la­tions, such as non-Mediterranean, and dif­fer­ent age groups.

“Our results are a first step in the process of estab­lish­ing the role of cook­ing meth­ods on health,” Rodríguez-Ayala and Guallar-Castillón said. ​“However, more basic and pop­u­la­tion-based research is needed before estab­lish­ing final con­clu­sions.”

“Undoubtedly, know­ing what cook­ing meth­ods could be included as healthy eat­ing habits is an essen­tial part of the pre­ven­tion and man­age­ment of chronic con­di­tions that are related to diet,” they con­cluded. ​“A new field of dietary pre­ven­tion has been opened up.”