Findings from the influential Moli-Sani study conclude that inequalities in diet-related behaviours and nutrient intake persist amongst individuals of high and low income.
Additionally, these cardiovascular advantages directly correlate to those who entered higher education.
“Our study has revealed that the socioeconomic position is able to modulate the health advantages linked to the Mediterranean diet,” said lead study author Dr Marialaura Bonaccio, researcher at the Department of Epidemiology and Prevention at The Institute for Research, Hospitalization and Health Care (I.R.C.C.S.) Neuromed in Pozzilli, Italy.
“In other words, a person from low socioeconomic status who struggles to follow a Mediterranean model is unlikely to get the same advantages of a person with higher income, despite the fact that they both similarly adhere to the same healthy diet".
While the benefits of a Mediterranean diet are not in question, the study raises concerns as to the choices available to low-income individuals as well as the quality and diversity of food.
Whilst fruit and vegetables are a main ‘Mediterranean’ dietary component, the researchers found those earning more or went to school for longer had greater access to a richer diversity of fruit and vegetables.
This may explain why they tended to consume products richer in antioxidants and polyphenols, as well as foods rich in fatty acids, micronutrients, organic vegetables and whole grain bread consumption.
Interestingly, the team also found differences in the preferred cooking methods. The higher income and education group veered towards healthier methods of vegetable preparation such as boiling and stewing.
However, this group also tended to use more hazardous methods, such as frying, roasting and grilling, for cooking beef.
“Med diet shift”
"Our results should promote a serious consideration of socioeconomic scenario of health,” said Giovanni de Gaetano, director of the department of epidemiology and prevention at I.R.C.C.S.
“Socioeconomic disparities in health are growing also in access to healthy diets. During the very last years, we documented a rapid shifting from the Mediterranean diet in the whole population, but it might also be that the weakest citizens tend to buy 'Mediterranean' food with lower nutritional value.
“We can’t keep on saying that the Mediterranean diet is good for health if we are not able to guarantee an equal access to it," he added.
The Moli-Sani study recruited over 18,000 men and women aged above 35 years of age.
Adherence to the diet was assessed by the Mediterranean diet score (MDS) assigning values to fruits and nuts, vegetables, legumes, cereals, fish, fats, meat, dairy products consumed as well as alcohol intake.
Household income (euros/year) and educational level were also used as indicators of socioeconomic status.
Variety of fruit and/or vegetable intake was assessed by four (fruit, vegetables, vegetables subgroups and fruit/vegetable combined) different diet diversity scores.
Diversity was calculated as the total number of individual vegetable/fruit products eaten at least once in 2 weeks.
Data on cooking procedures were collected for vegetables, meat and fish. A score was assigned to differentiate healthy and hazardous cooking methods, the healthier the procedure, the higher the score.
Organic food intake was limited to organic vegetables and categorised as ‘yes’ or ‘no.’ Whole-grain products consumption was restricted to whole-grain bread intake (yes/no).
Over 4.3 years of follow-up, 252 cardiovascular disease (CVD) events occurred. Overall, a two-point increase in MDS was associated with 15% reduced CVD risk.
Such association was evident in highly but not in less educated subjects.
Similarly, CVD advantages associated with the MD were confined to the high household income group.
In a subgroup of individuals of different socioeconomic status but sharing similar MDS, diet-related disparities were found as different nutritional intakes were noted.
“Holistic and societal view needed”
“These substantial differences in consuming products belonging to Mediterranean diet lead us to think that quality of foods may be as important for health as quantity and frequency of intake", said Licia Lacoviello, head of the Laboratory of Nutritional and Molecular Epidemiology at I.R.C.C.S and study author.
Dr Amitava Banerjee, senior clinical lecturer in Clinical Data Science and honorary consultant cardiologist, Farr Institute of Health Informatics Research at University College London (UCL), recognised the study as a first in recognising an “attenuation of the benefit of a Mediterranean diet in lower income individuals.”
“We need a holistic and societal view of heart disease and stroke, recognising the role of poverty reduction and reducing social gradients. Moreover, the Mediterranean diet is neither accessible to all nor works the same in all.”
Dr Tim Chico, reader in Cardiovascular Medicine at the University of Sheffield, commented that the study confirmed a well-known but depressing fact.
“People of lower education or income have almost double the risk of heart disease compared with those who are better off”.
“(The findings) are likely due to other differences between low and high income groups, rather than the diet not being effective.
“The authors suggest that there are some elements of the Mediterranean diet that are eaten more often by high rather than low income groups, but there are other possible explanations for these findings”
Source: International Journal of Epidemiology
Published online ahead of print: doi.org/10.1093/ije/dyx145
“High adherence to the Mediterranean diet is associated with cardiovascular protection in higher but not in lower socioeconomic groups: prospective findings from the Moli-sani study.”
Authors: Marialaura Bonaccio, Augusto Di Castelnuovo, George Pounis, Simona Costanzo Mariarosaria Persichillo, Chiara Cerletti, Maria Benedetta Donati Giovanni de Gaetano Licia Iacoviello