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Why You Shouldn't Eat 5 Portions
Part 2: So what is the evidence for '5 portions' a day?
This was a question I had hoped that Jane could answer because I had been unable to find any such evidence: There simply didn't seem to be any evidence — at least there wasn't when the recommendations were first drawn up.
But there is now.
And it doesn't support the recommendations.
But first things first: If there really is a dose-response whereby four portions, say, isn't good enough, then surely the size of the portion and the number of portions would be important. It is odd, therefore, that portion numbers and quantity don't seem to matter all that much.
Other scientists must have thought so as well, because over the last few years several studies into the 5-a-day claim have been conducted to test the advice — with disappointing results.
The prestigious CARDIO2000 study published its results in 2003.[3] This study was looking at intakes of fruit and vegetables specifically in relation to acute heart disease. They found that vegetables did reduce the risk of heart disease. But, significantly, it needed a lot less than '5 portions a day' for the maximum effect. In their conclusions the researchers say:
'Our findings support that even low consumption of fruits and vegetables (1–2 servings per week) is associated with about 45% lower coronary risk. Consumption of 2 or more servings per week is associated with about 70% reduction in relative risk.'
The Daily Mail picked this story up and, as part of its article, the Mail interviewed Professor Sir Charles George, medical director of the British Heart Foundation, about the obvious conflict with the '5-a-day' guidelines. Sir Charles told the Mail 'There is some argument about how much you need — I think five may be an arbitrary figure'[4] — and, by so doing, admitted that this was another example of dietary advice which was based on nothing more than wishful thinking.
So we don't need to eat anything like 5 a day to derive benefits in terms of heart disease. But is there a benefit in terms of other chronic diseases such as cancer? This was considered in another study published in 2004. And again the answer was: No!
This study of over 100,000 people, conducted by the Harvard School of Public Health, showed that, 'Increased fruit and vegetable consumption was associated with a modest although not statistically significant reduction in the development of major chronic disease' [emphasis added]. It continued: 'The benefits appeared to be primarily for cardiovascular disease and not for cancer.'[5] Their conclusions state:
'Consumption of five or more servings of fruits and vegetables has been recommended . . . but the protective effect of fruit and vegetable intake may have been overstated.'
And in 2010, the enormous EPIC study, which involved half a million men and women in ten European countries, pretty much wrapped it up.[6] Although EPIC did find a 'very weak' reduction in cancers over the nine years of the study, that reduction was limited. 'High intake of vegetables, and fruits and vegetables combined, was associated with a small reduction in overall cancer risk. The association was stronger in heavy alcohol drinkers but was restricted to cancers caused by smoking and drinking.' There was no appreciable reduction in cancers seen from eating fruit. They conclude: 'A very small inverse association between intake of total fruits and vegetables and cancer risk was observed in this study. Given the small magnitude of the observed associations, caution should be applied in their interpretation.' and under 'Limitations' they say 'The inverse association between overall cancer risk and high intake of fruits and vegetables was weak. Errors inherent to self-reported dietary habits may have resulted in bias.'
Whenever studies such as these are reported, the diet police repeat their dogma that eating the recommended number of fruit and vegetables has numerous health benefits. But they never seem able to quote any evidence to support those assertions or to specify exactly what the benefits are. In view of the above evidence, that will probably come as no real surprise.
Dr Barnett Kramer, of the National Institutes of Health in the US, said of the healthy eating message: 'A lot of the public is completely unaware that the strength of the message is not matched by the strength of the evidence.' That we are kept unaware of it demonstrates just how strong is the influence the diet dictocrats on our minds and the news media.
Last updated 7 April 2010
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