Going nuts. critics have panned a document that questions whether the unsaturated fats, common in nuts, are healthier than saturated.
Wikimedia Commons / Sage Ross
When an article published on March 17 asked if the fats from fish oils or vegetables are healthier than meat or butter, he quickly made headlines around the world; after all, the study seemed to demystify the cornerstone of many dietary guidelines. But a new version of the publication was to be published shortly after his appearance on the site of Annals of Internal Medicine to correct several errors. And although the first author of the study held by the findings, a number of critical scientific paper and even calling the authors to retract.
"They have done a huge amount of damage," says Walter Willett, chairman of the nutrition department at the Harvard School of Public Health in Boston. "I think the withdrawal to promoting similar release should be considered. "
health officials have long argued that so-called saturated fats, found in butter, meat, chocolate and cheese, increase the risk of heart disease, and that people should instead eat more unsaturated fatty acids, the type that dominates in fish, nuts, and vegetable oils.
in the new study, a meta-analysis, scientists from Europe and the United States together 72 individual studies to assess how different fats influence the risk of heart attack or other cardiac events such as angina. These included trials in which participants were assigned randomly to different diets, as well as observational studies in which the consumption of fatty acids of participants was determined by asking them about their diet or measuring fatty acids circulating in the blood.
When the researchers compared those with the highest and the lowest saturated fat intake, they found no significant difference between the risk of heart disease or other cardiac events. Similarly, they found no significant difference between those who consume high or low amounts of supposedly healthy unsaturated fats. "Current data do not clearly taking guidelines that encourage high consumption of polyunsaturated fats and low intake of saturated total fat," the authors conclude.
But even before the document was published , other scientists began to report the errors, said first author Rajiv Chowdhury, an epidemiologist at the University of Cambridge in the UK. for example, the authors took a study on omega-3 fats, a type of unsaturated fats, to show a slightly negative effect, while in fact he showed a strong positive effect. the correction means that the meta-analysis now shows the people who report eating a lot of this particular fat have much less heart disease ; previously, he said there was no significant effect
critics have also pointed out two major studies on omega-6 fatty acids that the authors missed.. Errors "demonstrate research of poor quality and are wondering if there is more that has not been detected," wrote Jim Mann, a researcher at the University of Otago, Dunedin, New Zealand, writes in an e-mail. "had I been the referee I would have recommended rejection."
Mann and others say the paper has other problems, too. for example, it does not deal that people who reduced their consumption of saturated fats consumed instead. a 09 study concluded that replacing saturated fats with carbohydrates was no benefit, while replacing them with polyunsaturated fatty acids reduced the risk of heart disease. Many scientists say that should have been mentioned in the new document.
Chowdhury said the conclusions of the paper are valid, however, even after the corrections. randomized clinical trials are the "hard "such evidence, he says, and they do not show a significant effect of saturated and unsaturated fats. But even one of the authors of the article, Dariush Mozaffarian of Harvard School of Public Health, admits he is not happy with the main conclusion that the evidence does not benefit from polyunsaturated fats. "Personally, I think the results suggest that fish and vegetable oils should be encouraged," he said. But the document was drafted by a group of authors, he says. "And science is not a dictatorship . "
another study author, Emanuele Di Angelantonio from the University of Cambridge, said the main problem is that the paper was" misinterpreted by the media. "" We are not saying the guidelines are false and people can eat as much saturated fat as they want. We say that there is no strong support for the guidelines and we need more good tests. "
Willett said the correct paper is not enough." It is good that they set the record, but it has caused massive confusion and the public has not heard about the correction. "the paper should be removed, he said.
the controversy should serve as warning about the meta-analyzes, Willett says. These studies compile data from many individual studies to get a clear result. "it looks like a summary of scanning all the data it receives much attention," says Willett. "But these days meta-analyzes are often made by people who are not familiar with the field, who do not have primary data or do not make the effort to get it." And while the drug trials are often very similar in design, making it easy to combine their results, nutritional studies vary greatly in how they are implemented. "Often the strengths and weaknesses of the individual studies are lost," says Willett. "He is dangerous."
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