“In a large geographically diverse cohort of high-risk patients with stable coronary heart disease, a diet containing more food groups included in the traditional Mediterranean diet […] was associated with a lower risk of major adverse cardiovascular events and all-cause death.
"In contrast, great consumption of foods thought to be less healthy and typical of Western diets was not associated with adverse CV [cardiovascular] events,” wrote the researchers in the European Heart Journal.
Previous studies have found a link between the Mediterranean diet, characterised by a high proportion of fruit, vegetables, legumes, whole grains and fish, moderate alcohol and little meat, and reduced incidences of heart attacks and strokes.
However, this global study, in which over 15,000 people from 39 countries participated, was one of the first large international studies to evaluate the relationship between dietary patterns and health in patients with stable coronary heart disease.
“Our study confirmed that a diet including the same broad food groups as the Mediterranean diet was beneficial in very diverse populations from different parts of the world, who would eat quite different foods,” professor Ralph Stewart, of the University of Auckland, told NutraIngredients.
No increased risk from ‘unhealthy’ foods
Surprisingly, the researchers also found that greater consumption of foods thought be less healthy and more typical of Western diets was not associated with an increase in heart attacks and strokes.
“There was no association between ‘Western diet score’ [for increased consumption of refined grains, sweets, desserts, sugared drinks and deep fried foods] and major adverse cardiovascular events,” wrote the researchers.
Asked why he thought this might be the case, professor Stewart said: “I think it is likely that there is a protective effect from healthy foods, and this is more important than the hazardous effect of ‘unhealthy' foods’.
"We do know this dietary pattern is associated with less inflammation, and this could be the mechanism. However we do not know the mechanisms for sure.”
A total of 15,482 people with stable coronary artery disease and an average age of 67 were asked to complete a lifestyle questionnaire when they joined the STABILITY trial, which was looking at whether a drug called darapladip reduced the risk of heart attacks, strokes and deaths.
The questionnaire included simple questions on diet: participants were asked how many times a week they consumed servings from food groups such as meat, fish, dairy foods, whole grains or refined grains, vegetables, fruit, desserts, sweets, sugary drinks, deep-fried foods and alcohol.
Depending on their answers, they were given a Mediterranean diet score (MDS) which assigned more points for increased consumption of healthy foods with a total range of 0-24. A Western diet score (WDS) assigned points for increased consumption of unhealthy foods.
After 3.7 years of follow-up, a major adverse cardiovascular event (MACE) – heart attack, stroke or death – had occurred in a total of 1588 (10.1%) of the study participants.
MACE occurred in 7.3% of the 2,885 people with an MDS score of 15 or over (who ate the healthiest foods), 10.5% of 4,018 people with an MDS of 13-14, and 10.8% of 8,579 people with an MDS of 12 or lower.
Professor Stewart described the findings as “strongly significant statistically”.
However, he said he could not exclude the possibility that a healthy diet reflected some other important factor, for example socio-economic status.
“This is a problem with most diet-health studies and is why we need clinical trials to be absolutely sure,” he said.
A change in focus
Clinical practice guidelines from the European Society of Cardiology recommend frequent consumption of fruit, vegetables, fish and other whole foods, alongside restrictions on sodium, sugar, saturated fats and refined carbohydrates.
In the light of these latest findings, the researchers suggested dietary guidelines for prevention of coronary heart disease should focus more on encouraging greater consumption of ‘healthy’ foods.
“I think this study is additional evidence to encourage people to choose a healthier dietary pattern. It is possible this advice will be strengthened in the guidelines,” said professor Stewart.
Source: European Heart Journal
“Dietary patterns and the risk of major adverse cardiovascular events in a global study of high-risk patients with stable coronary heart disease”
Authors: Ralph A.H. Stewart et al on behalf of the STABILITY investigators.