High Intake of Fruit and Vegetables Again Linked to Reduced Heart Disease Risk

Sue Hughes

Information fromanuary 21, 2011 (Oxford, United Kingdom) — The link between high intake of fruit and vegetables and a reduced risk of ischemic heart disease has been given more scientific weight by the latest results from the large-scale European Prospective Investigation into Cancer and Nutrition (EPIC)-Heart study [1].

In the study, published online January 19, 2011 in the European Heart Journal, people who ate at least eight portions of fruit and vegetables a day had a 22% lower risk of dying from heart disease than those who consumed fewer than three portions a day. A portion weighed 80 g, equal to a small banana, a medium apple, or a small carrot.
The authors, led by Dr Francesca Crowe (University of Oxford, UK), say that whether this association is causal and, if so, what the biological mechanism mediating the effect is, remain unclear.
They explain that previous observational studies have suggested that a high fruit and vegetable intake reduces the risk of coronary heart disease, but the presence of considerable between-study heterogeneity has led to uncertainty in the interpretation of this association.
The EPIC-Heart study followed 313 074 men and women without previous MI or stroke from eight European countries. After an average of 8.4 years of follow-up, there were 1636 deaths from ischemic heart disease. Results suggested that each one-portion increment in fruit and vegetable intake was associated with a 4% lower risk of fatal heart disease, after researchers controlled for established risk factors.
Is It the Micronutrients?
On the possible mechanism, the authors note that there is a long-standing hypothesis that various antioxidant micronutrients present in fruits and vegetables reduce atherosclerosis caused by oxidative damage, but this has not been supported by results from large randomized controlled trials of several antioxidant micronutrients. They add, however, that consuming antioxidant supplements is not the same as increasing the consumption of fruits and vegetables, because there are many other components in fruits and vegetables that may confer a cardioprotective effect.
In an accompanying editorial [2], Dr Michael Marmot (University College London, UK) points out that the main benefit of eating a diet high in fruit and vegetables has focused on cancer prevention, with evidence suggesting that fruit and vegetable consumption was "probably" protective for certain cancers. He adds that while obesity is convincingly related to several cancers, it has not been concluded that fruit and vegetables have a specific protective effect on weight gain. "Although, if it turns out that higher fruit and vegetable consumption goes along with lower intake of energy-dense or fast foods, there could be an indirect protective effect on obesity."
"Great Importance to Public Health"
Marmot says, therefore, that the potential protective effect of fruit and vegetables on cardiovascular disease is of great importance if advice on healthy eating is to be based on sound evidence, and the EPIC-Heartstudy is helpful, as "the numbers and logistics are truly impressive."
He points out that although the results have been adjusted for smoking, alcohol intake, body-mass index, physical activity, marital status, education, employment, hypertension, angina, diabetes, and total energy intake, there is always the worry about residual confounding, but the consistency of these results with those from other studies makes it more likely that the associations are causal.
Marmot further comments that: "A reduction of 22% is huge," but it comes with consumption of eight portions a day, and such a high consumption was found in only 18% of the population in this study. He points out that there would need to be a big shift in dietary patterns to achieve this healthy consumption, but it is worth trying to move in that direction. He concludes: "Reductions in cancers of several sites, in blood pressure, and stroke, would add to this reduction in fatal CHD. Moving to a diet that emphasizes fruit and vegetables is of great importance to public health."