A "Mediterranean" diet, high in fruit, vegetables, fish and unrefined foods, is linked to a lower risk of heart attack and stroke in people who already have heart disease, according to a study of over 15,000 people in 39 countries around the world. The research also showed that eating greater amounts of healthy food was more important for these people than avoiding unhealthy foods, such as refined grains, sweets, desserts, sugared drinks and deep-fried food -- a "Western" diet.
The study, which is published in the European Heart Journal, showed that for every 100 people eating the highest proportion of healthy "Mediterranean" foods, there were three fewer heart attacks, strokes or deaths compared to 100 people eating the least amount of healthy foods during nearly four years of follow-up from the time the participants joined the study.
The researchers asked 15,482 people with stable coronary artery disease and an average age of 67 to complete a lifestyle questionnaire when they joined the STABILITY trial, which was looking at whether a drug called darapladib 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 meat, fish, dairy foods, whole grains or refined grains, vegetables (excluding potatoes), 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 most amount of healthy 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 Ralph Stewart, from Auckland City Hospital, University of Auckland, New Zealand, who led the study, said: "After adjusting for other factors that might affect the results, we found that every one unit increase in the Mediterranean Diet Score was associated with a seven percent reduction In the risk of heart attacks, strokes or death from cardiovascular or other causes in patients with existing heart disease. In contrast, greater consumption of foods thought be less healthy and more typical of Western diets, was not associated with an increase in these adverse events, which we had not expected."
The findings were consistent across all the geographical regions involved in the study.
He continued: "The research suggests we should place more emphasis on encouraging people with heart disease to eat more healthy foods, and perhaps focus less on avoiding unhealthy foods."
However, he warned that this did not mean that people could eat unhealthy foods with impunity.
"The main message is that some foods -- and particularly fruit and vegetables -- seem to lower the risk of heart attacks and strokes, and this benefit is not explained by traditional risk factors such as good and bad cholesterol or blood pressure. If you eat more of these foods in preference to others, you may lower your risk. The study found no evidence of harm from modest consumption of foods such as refined carbohydrates, deep fried foods, sugars and deserts. However, because the assessments were relatively crude, some harm cannot be excluded. Also, the study did not assess the total intake of calories, which is a major determinant of obesity-related health problems, and we were unable to assess good fats and bad fats, so we can not comment of their importance to health."
The researchers did not specify what a "serving" of food might be and relied on people's interpretation of it; this usually meant that a serving might be an individual piece of fruit, a portion of meat, fish, vegetables or grains that would be enough for one person. This is a limitation of the study, but also a strength.
Prof Stewart said: "We did not specify what a serving meant because we needed to make the questionnaire very simple and intuitive, so that it would be easy and quick to complete. This is a limitation because the estimates of foods eaten are relatively crude and imprecise, but also a strength because we were able to show that even though diet is very complex, a few simple questions can identify a dietary pattern associated with a lower risk of recurrent heart attacks or strokes."
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Stewart, R. A., Wallentin, L., Benatar, J., Danchin, N., Hagström, E., Held, C., ... & Vedin, O. (2016). Dietary patterns and the risk of major adverse cardiovascular events in a global study of high-risk patients with stable coronary heart disease. European Heart Journal, ehw125.