Is a healthy diet that includes lots of fruits and vegetables more effective than drugs in lowering the risk of heart disease?
“Yes,” says a recent article in the journal Circulation, which shows compelling evidence to prove this point.
Scientists at Hamilton's McMaster University in Canada analyzed data of dietary patterns in more than 16,000 people from 52 countries as part of the INTERHEART study, and showed that an unhealthy diet increases the risk of heart attacks globally by about 30% compared to what the risk would be had the diet been healthier.
A few words about how this study was performed:
This study looks at food, unlike other studies that focus on nutrients, such as saturated fats, sugars, vitamins etc,
INTERHEART is unique in its global reach throughout Africa, Asia, Australia, Europe, the Middle East, and North and South America (most studies are done on populations of European origin, and in the developed world, and sets out to investigate whether the same risk factors for heart disease are applicable in other parts of the world, where heart disease is prevalent and still on the rise).
The population of the study consisted of almost 6,000 patients with their first heart attack, and of almost 11,000 control subjects, who were free of heart disease. This is a case-control study that compares subjects who have a medical condition (in this case, myocardial infarction) with participants who do not have the condition but are otherwise similar.
Data collected included demographics, socioeconomic factors, risk factors (such as smoking, stress, alcohol use) measurements (height, weight, hip and waist circumferences, blood lipids, blood pressure), and detailed food frequency input. The results of food questionnaires were classified into 19 food categories, such as green leafy vegetables, tofu, fish, dairy and so on.
Using statistical methods the researchers found that the eating habits of the participants fell into three main types: Oriental (high intake of tofu, plus soy and other sauces); Western (high intake of fried foods, salty snacks, eggs and meat); and prudent (high intake of fruit and vegetables). After adjusting for potential influencers and risk factors such as age, sex, physical activity, smoking and obesity analysis revealed that the more that a diet resembled the prudent diet (rich in fruits and vegetables), the lower the risk of heart attack, and the more it resembled a Western diet (higher regular intake of fried and salty foods, meat and eggs) the higher the risk.
In fact, the risk of having a heart attack was 30 per cent higher when the diet was closer to the Western style compared to the prudent style. The Oriental diet appeared to have no effect on heart attack risk.
The authors led by Salim Yusuf, write (all writing in parenthesis is mine):
“Our finding of a protective role of the prudent diet against AMI (acute myocardial infarction—heart attack) is similar to other reports indicating that such a dietary pattern protects against diabetes mellitus, CVD (cardiovascular disease), cancer, and mortality…
INTERHEART shows that unhealthy dietary intake, as assessed by a simple DRS (dietary risk score), increases the risk of AMI significantly, whereas consumption of a prudent diet is associated with a lower risk. The PAR (population-attributable risk—the reduction in incidence that would be observed if the population were entirely unexposed, compared with its current (actual) exposure pattern) for AMI worldwide associated with poor dietary intake is substantial. The present work suggests that increased consumption of fruits and vegetables and reduced intake of fried foods, probably related to the type of fat used for frying and salty snacks, is likely to reduce the risk of AMI in all regions of the world.”
I’m sure that you’ve heard, and read on my previous posts that case-control studies —even large population size ones like this one—are not the strongest medical evidence, and although very useful in providing rapid results at relatively low cost, should always be confirmed by other, more robust evidence, the gold standard of which would be a double blind placebo controlled prospective study.
In this case, the protective effects of fruits and vegetables has been confirmed already by so many studies—it is indeed one of the consensus points all nutrition experts agree on—that this study only strengthens what we already know, and extends beyond the Western countries to other parts of the world including developing countries.
Another thing I think is interesting about this study is its analysis of food groups, as opposed to nutrients. One can argue about what’s in fruits and vegetables that's beneficial to heart health: Is it the fiber? The vitamins? The antioxidants and phytochemicals? Or is it all of them acting in concert?
The intake of isolated nutrients has not shown to be beneficial the way the whole plant is. In the same way we can hypothesize that the offensive nutrients in the Western diet foods could be the saturated fats, the overload of salt and refined sugar or the cholesterol. But from a study about food, comes practical advice about food: eat a more prudent diet.
The conclusion of this paper is to eat more fruits and vegetables and less fried foods and meats to reduce the risk of heart disease, not look at labels of highly processed foods, to see how much saturated and trans fats are present. This is a simple, strait-forward and practical recommendation.
It’s upsetting to think that while in nutrition class our kids learn the importance of eating fruits and vegetables (“five-a-day”), the school cafeteria lunch will typically consist of chicken nuggets and French fries.
There’s more about the importance of eating fruits and vegetables in my blog post here.