The Effect of the Mediterranean Diet on Mortality in Patients With Metabolic Syndrome

The Mediterranean diet can decrease risk of all-cause and cardiovascular mortality in patients with metabolic syndrome, according to research published in Diabetology and Metabolic syndrome.

The Mediterranean diet, defined as a diet rich in vegetables, fruits, fish, grains, legumes, and olive oil, has been shown to be associated with improvement in insulin resistance in patients with obesity. Additionally, it is beneficial in primary prevention of atherosclerotic cardiovascular disease (ASCVD).  As these ailments coincide in those with metabolic syndrome (MetS), researchers aimed to investigate the effects of the Mediterranean diet adherence on all-cause and cardiovascular mortality in patients with MetS. Additionally, researchers evaluated the joint effects of the Mediterranean diet, sedentary behavior, and depression on all-cause and cardiovascular mortality in people with MetS.

A prospective cohort study was conducted using data from The National Health and Nutrition Examination Survey (NHANES) from 2007 to 2018, which is representative of the American population. MetS was characterized according to the International Diabetes Federation.

Adherence to Mediterranean diet was calculated using the alternative Mediterranean diet index (aMED); overall intakes of fruits, vegetables, grains, fish, red and processed meat, ratio of monounsaturated to saturated fat, and alcohol content were assessed to calculate adherence. The aMED score, indicating how closely a person adhered to the diet was scaled with a range of 0 to 9 (below median, aMED scores of 0 to 3; median, aMED score of 4; above median, aMED scores to 5 to 9). The Global Physical Activity Questionnaire (GPAQ) was utilized for participants to report their physical activity; the physical health questionnaire (PHQ-9) was given to assess for depressive symptoms, rated in quintiles on a scale of 1 to 27.

A total of 8301 subjects were included in the final analysis, with a median follow-up time of 6.3 years. Participants with an above median aMed score were older, had a significantly smaller waist circumference, and had higher high-density lipoprotein cholesterol levels. Additionally, their diets were lower in meat consumption and higher in vegetables, fruits, whole grains, nuts and seafood. A lower percentage of depressive symptoms were also found in this group.

Cox regression analysis for all-cause and cardiovascular mortality in MetS participants found that median and above median aMED score, physical activity, treatment for hypertension, and treatment for diabetes were all significantly associated with a lower risk of all-cause mortality. Depression, smoking, and sedentary behavior were all associated with a higher risk of for all-cause mortality.

Stratifying participants according to aMED score and physical behavior, participants with a below median aMED score with sedentary behavior had the highest risk of all-cause mortality (hazard ratio [HR], 2.45; 95% CI, 1.90-3.17; P=.00). No difference in HR was found between groups that were nonsedentary within all tertiles of aMED scores. Individuals with a low aMED score who were sedentary had the highest risk of cardiovascular mortality (HR, 2.91; 95% CI, 1.77-4.79; P =.00). A lower amend score was found to be an independent risk factor for all-cause mortality (HR, 1.27; 95% CI, 1.00-1.60; P=.05), demonstrating a high-quality Mediterranean diet may attenuate all-cause mortality in Met’s patients without sedentary behavior.

Regression analysis for all-cause and cardiovascular mortality in different dietary classes with and without depression found that patients with a lower armed diet score without depression had an increased HR for all-cause mortality (HR, 1.27; 95% CI, 1.04-1.55; P=.02) compared with individuals with a higher amend score without depression, signifying that a lower-quality Mediterranean diet in those without depression increases all-cause mortality. Similarly, those with depression with lower armed scores had the highest risk of all-cause mortality (HR, 1.97; 95% CI, 1.45-1.269; P =.00).

Examining components of the Mediterranean diet and their contribution to all-cause and cardiovascular mortality, eating more vegetables, legumes, nuts, and foods with a high monounsaturated fatty acid to saturated fatty acid ratio was associated with a lower all-cause mortality, after adjusting for age, sex, race, education, smoking, and cardiovascular disease. A higher vegetable intake was found to be significantly associated with a lower cardiovascular mortality as well.

Limitations of the study include the collection of covariates from NHANES questionnaires, in which some variables are missing and can lead to a reduction of the included population. Additionally, as dietary data was collected by questionnaire, there may have been discrepancies between dietary data between participants and NHANES interviewers.

 “…high-quality or moderate-quality Mediterranean diet could attenuate, even reverse the adverse effects of sedentary behavior and depression on all-cause and cardiovascular mortality in participants with meets,” the study authors wrote.