Contrary evidence: Mediterranean diet may not influence cholesterol levels, study suggests

In a recent study published in Nutrients, researchers evaluated the association between Mediterranean diet (MD) adherence and lipid profiles among disease-free community residents who participated in the Colaus|PsyCoLaus study.

Study: Impact of Mediterranean Diet on Lipid Composition in the Colaus-PsyColaus Study. Image Credit: AntoninaVlasova/Shutterstock.com

Background

MD, enriched with vital micronutrients, fiber, and antioxidants, has been demonstrated to considerably improve cardiovascular health and prevent atherosclerotic cardiovascular disease (CVD).

Low-density lipoprotein (LDL) cholesterol and triglyceride (TG) levels must be reduced to promote cardiovascular health. MD is characterized by an increased intake of plant-origin foods, a moderate to low intake of dairy products, fish, and wine, and a low intake of red meat and sweets.

The link between MD and lipids has been determined to be weak to moderate, owing to confounding factors such as healthy practices and small sample sizes. To further understand the link between MD and lipid profile, prospective studies with greater levels of evidence are necessary.

About the study

In the present study, researchers investigated whether adherence to MD significantly altered lipid composition/incident dyslipidemia among Colaus|PsyCoLaus participants.

Three studies with cross-sectional designs were conducted analyzing data from the initial follow-up (FU1, between April 2009 and September 2012), the second follow-up (FU2, between May 2014 and April 2017), and the third follow-up (FU3, April between 2018 and May 2021) of the population-based CoLaus|PsyCoLaus study (n=19,830), undertaken in Lausanne, Switzerland, including Caucasian individuals aged 35 to 75 years.

Only individuals who completed the first and either the second or third follow-up were included. Individuals with missing data on covariates and variables necessary for dietary evaluation or lipid composition assessment were excluded.

Multivariate modeling and logistic regressions were performed. Food intake in the previous four weeks was evaluated using food frequency questionnaires (FFQs).

Two Mediterranean diet scores (Vormund and Trichopoulou) were computed, and the total cholesterol, HDL and LDL cholesterol, and triglyceride levels were monitored. New-onset dyslipidemia was described as hypolipidemic therapy initiation at the second or third follow-up.

The study participants were subjected to similar interventions at study initiation and follow-ups, including interviews, clinical assessments, serum and urine sample collection, and lifestyle and health questionnaires.

The study objectives were to determine the link between the Mediterranean diet scores at FU1 and (i) lipid levels/hypolipidemic therapy at the initial follow-up, (ii) new-onset dyslipidemia among untreated individuals at the initial follow-up, and (iii) alterations in total, HDL, and LDL cholesterol between the initial and the subsequent follow-ups among individuals with and without statin treatments at follow-up.

Results

Of 5,064 individuals from FU1, 815 were eliminated, and the remaining 4,249 individuals (84%) were analyzed. Among the study participants, 54% were women, with a mean age of 58 years and scores of 4.0 and 7.0 for Trichopoulou and Vormund assessments, respectively.

The sample population included more Swiss-born, better-educated, non-smoking individuals residing with others and had higher MD scores with a lower likelihood of being diabetic, hypertensive, or obese.

None of the Mediterranean diet scores showed significant associations with lipid profiles, and comparable findings were reported stratifying by hypolipidemic status. Of 3,092 untreated FU1 individuals with complete follow-up information, 11% (n=349) received dyslipidemia diagnosis by the second or third follow-up. Individuals who received treatment for incident dyslipidemia were of advanced age, smokers, less educated, overweight, diabetic, and hypertensive.

Non-significant differences in the Mediterranean diet scores were reported between individuals who were diagnosed with incident dyslipidemia compared to those who were not (4.8 versus 4.8 and 4.1 versus 4.0 for Vormund and Trichopoulou, respectively). In addition, non-significant associations were reported between the MD scores and lipid alterations at five (FU2) or ten years (FU3).

Concerning incident dyslipidemia as the study outcome, the adjusted odds ratios for a one-unit elevation in the Vormund and Trichopoulou scores were 1.1 and 1.1, respectively. Contrasting previous studies, Mediterranean dietary adherence at study initiation showed a non-significant impact on the composition of lipids and new-onset dyslipidemia development among Colaus|PsyCoLaus trial participants.

The Mediterranean diet scores were positively related to HDL and negatively linked to TG levels among individuals who did not receive dyslipidemia treatment. In contrast, non-significant associations were reported for total and LDL cholesterol.

Among individuals prescribed hypolipidemic drugs, negative relationships were observed between the Vormund MD score and LDL and TC levels. The multivariate analyses yielded similar findings.

Conclusions

Overall, the study findings showed no significant relationship between MD and lipid indicators adherence and no effect on dyslipidemia development or lipid alterations over five to ten years of follow-up.

In addition, the findings showed no evidence of a link between MD dietary adherence and dyslipidemia or changes in lipid levels.

According to the study, adherence to MD, as determined by the Trichopoulou or Vormund score, offers minimal protection against dyslipidemia. However, further research is required to explore long-term diet treatments across communities and to call the one-diet-fits-all strategy into question.

Written by

Pooja Toshniwal Paharia

Dr. based clinical-radiological diagnosis and management of oral lesions and conditions and associated maxillofacial disorders.