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Publishing in the European Heart Journal, a group of researchers have examined the effect of diet on patients with coronary heart disease and report that greater consumption of healthy foods (such as in a typical Mediterranean diet) may be more important than avoidance of unhealthy foods (such as in a typical Western diet) for prevention of further instances of heart disease.
Dr Nita Forouhi, Programme Leader, MRC Epidemiology Unit, University of Cambridge, said:
“It is good news for people with existing heart disease that this study provides evidence that a healthy ‘Mediterranean diet’ is associated with lower future cardiovascular disease risk, and that this applies across many countries and world regions, not just in the Mediterranean region.
“If we take the microscope to how the Mediterranean diet was estimated, we can take issue with some limitations. The study considered only frequency of consumption not amount of intake, nor did it account for total calories. Nuts and olive oil were not included in the definition though the PREDIMED trial specifically reported on the benefits of adding these to the diet intervention. Dairy foods were left out, though close to 40% of the sample consumed 1 or more dairy servings per day.
“But, if we take away the overall message that benefits come from generally healthy “Mediterranean type” diets which include more frequent consumption of fruit and vegetables, this certainly gives a great public health message that among people with heart disease a healthy diet can be an effective part of management in reducing further cardiovascular events.
“On the surface it is an attractive message that greater emphasis should be on encouraging healthy foods rather than avoiding unhealthy foods, but such a conclusion is premature. The study finding that the unhealthier ‘Western’ type diet is not associated with an increased cardiovascular risk is inconclusive, given that the methods used in this study were limited and crude. The proportion reporting frequent consumption of one or more servings per day of the ‘unhealthy’ foods was very low – for instance only about 2% reported daily (one or more serving/day) consumption of deep fried foods and about 10% of consuming sugar-sweetened beverages, in contrast to about 45% reporting at least daily consumption of fruits and vegetables. This is not surprising, given that these participants had known heart disease as well as other risk factors, and they have been part of a drug trial, and are likely to make an effort to lead healthier lifestyles. Also some important unhealthy food/nutrient items such as processed meats and salt intake were not included in the definition. It is too early without further research to conclude convincingly about the lack of harm of unhealthy foods.”
Victoria Taylor, Senior Dietitian at the British Heart Foundation said:
“The study reinforces existing research we have on the Mediterranean style diet that links it to a range of health benefits including a lower risk of cardiovascular disease. But we should be cautious about the suggestion from the study that greater consumption of refined carbohydrates, deep fried foods, sugars and desserts, which are more typical of Western diets, are not associated with an increase in heart attack, stroke or death.
“Limitations in this study, including the use of self-reported data that did not assess habitual intake or define portion size means the researchers could be underestimating the strength of the association between the seemingly unhealthy diet and an increased risk of heart attack or stroke.
“Despite its limitations, the study reminds us that healthy eating is about a whole diet. We should aim to eat more fruits and vegetables, pulses, whole grains, fish and switch from saturated to unsaturated fats. This is reflected in the new Eatwell guide published by Public Health England – a reminder of the importance of putting dietary guidelines into practice to reduce our risk of dying from cardiovascular disease.”
Dr Ian Johnson, nutrition researcher and Emeritus Fellow, Institute of Food Research (IFR), said:
“This interesting study suggests that a prudent diet, high in fruits, vegetables, whole-grain carbohydrates and fish, but relatively low in meat, is associated with a reduced risk of heart attacks and stroke, even in patients with established heart disease. These observations are certainly consistent with dietary guidelines for the prevention of cardiovascular disease in the general population, but they also imply that even for those known to be at high risk, it is never too late to benefit from relatively simple dietary advice, such as closer adherence to the “5-a-day” message.”
Dr Tim Chico, Reader in Cardiovascular Medicine / consultant cardiologist, University of Sheffield, said:
“This study attempts to answer an interesting two-part question; is it what you eat, or what you don’t eat, that most determines your risk of heart disease? It has probably been more successful in answering the first part.
“It is very difficult to scientifically determine the diet most likely to reduce the risk of heart disease. Showing a certain diet is (or is not) associated with a difference in risk (as in this study) is not the same as proving what foods are healthiest. This study used a single questionnaire to assess what people reported they generally ate, then observed them to see whether they suffered a heart attack, stroke, or died. It was not possible to check the accuracy of the reported diet, or whether this changed over time. This is more likely to lead to not observing a link between someone’s true diet and their risk of heart disease, which is why the lack of a link between a Western diet and future risk does not mean such a link does not exist.
“However, this study does add to the already substantial evidence that a so-called Mediterranean diet (high in vegetables, fish, fruit, nuts, seeds and olive oil, while low in red and processed meat) is the diet that most reduces risk of heart disease, as far as we can currently tell. I say so-called as only 20-30% of participants in Mediterranean countries ate a Mediterranean diet in this study. More people in Australia and New Zealand ate a Mediterranean diet, so we may need to start talking about an Antipodean diet.
“This study only examined people who already had heart disease. This is very important; most people are interested in not getting heart disease in the first place. This may explain why a “Western” diet did not seem to increase risk as all participants already had established heart disease. It is equally possible a Western diet does increase the risk of future heart problems, but the study design was unable to detect this effect. These results do not show that a Western diet does not increase the risk of developing heart disease in the first place.”
Prof. Tom Sanders, Professor emeritus of Nutrition and Dietetics, King’s College London, said:
“This study was in older men and women who had stable coronary heart disease (CHD) who had participated in a 3.7 year randomised controlled trial of a drug (darapladib). Although the drug tested showed no benefit, those who reported a higher adherence to a Mediterranean dietary pattern at baseline had a slightly lower incidence of subsequent major cardiovascular events including heart attacks and strokes.
“The study found no relationship between deep-fried foods, refined carbohydrates and sugar sweetened beverages (characteristic of a Western dietary pattern) and risk; this is of note given the recent furore over sugar but is hardly surprising as older people are not major consumers of pop!
“The decision to categorise participants as having a Mediterranean diet or Western type of diet was rather arbitrary as the study included Asians, Eastern and Western Europeans and North and South Americans who have diversely different dietary patterns. Ironically the Mediterranean diet score was higher in Asian and Western Europeans from the north than in those from Mediterranean countries!
“This study does have limitations – it is an observational study and not a trial. The study did not record the types of fats eaten (i.e. olive oil and other vegetable oil vs animal fats), and the consumption of dairy products and eggs was not included in the score. Also, health conscious individuals are more likely to report eating more fruit and vegetables. The participants were also receiving a cocktail of other drugs including aspirin as well as those to lower blood pressure, cholesterol and control diabetes, which limits how generalisable the findings are to the population at large.
“The authors do comment that eating more fish and soya foods were the only food items associated with lower risk, which is consistent with current dietary advice for heart health.”
‘Dietary patterns and the risk of major adverse cardiovascular events in a global study of high-risk patients with stable coronary heart disease’ by Ralph A. H. Stewart et al. published in the European Heart Journal on Monday 25 April 2016.
Declared interests
Dr Nita Forouhi: “No conflict of interest.”
Victoria Taylor: “No declarations of interest.”
Dr Ian Johnson: “Ian Johnson is an emeritus fellow at the Institute of Food Research, and was an external member of the SACN working group on Carbohydrates and Health. He currently holds no research grants and has no commercial affiliations.”
Dr Tim Chico: “I am a committee member and Treasurer of the British Atherosclerosis Society, a charity established in 1999 to promote UK atherosclerosis research.”
Prof. Tom Sanders: “Prof Tom Sanders is a Scientific Governor of the charity British Nutrition Foundation, member of the scientific advisory committee of the Natural Hydration Council (which promotes the drinking of water), and honorary Nutritional Director of the charity HEART UK. Prof. Tom Sanders is now emeritus but when he was doing research at King’s College London, the following applied: Tom does not hold any grants or have any consultancies with companies involved in the production or marketing of sugar-sweetened drinks. In reference to previous funding to Tom’s institution: £4.5 million was donated to King’s College London by Tate & Lyle in 2006; this funding finished in 2011. This money was given to the College and was in recognition of the discovery of the artificial sweetener sucralose by Prof. Hough at the Queen Elizabeth College (QEC), which merged with King’s College London. The Tate & Lyle grant paid for the Clinical Research Centre at St Thomas’ that is run by the Guy’s & St Thomas’ Trust, it was not used to fund research on sugar. Tate & Lyle sold their sugar interests to American Sugar so the brand Tate & Lyle still exists but it is no longer linked to the company Tate & Lyle PLC, which gave the money to King’s College London in 2006. Tom also used to work for Ajinomoto on aspartame about 8 years ago. Tom was a member of the FAO/WHO Joint Expert Committee that recommended that trans fatty acids be removed from the human food chain. Tom has previously acted as a member of the Global Dairy Platform Scientific Advisory Panel and Tom is a member of the Programme Advisory Committee of the Malaysian Palm Oil Board. In the past Tom has acted as a consultant to Archer Daniel Midland Company and received honoraria for meetings sponsored by Unilever PLC. Tom’s research on fats was funded by Public Health England/Food Standards Agency.”