Researchers have questioned the practice of replacing saturated fats with polyunsaturated fats, claiming that there is ‘much evidence’ that doing the opposite is more relevant.
Writing in Mayo Clinic Proceedings , a team of international researchers noted that the main argument for reducing saturated fats in the diet has been that it lowers the concentration of cholesterol in the blood and therefore prevents cardiovascular disease (CVD).
“For many years we have been told that to prevent cardiovascular disease (CVD), we must lower our intake of saturated fatty acids (SFAs) and instead eat more carbohydrates and polyunsaturated fatty acids (PUFAs),” said the authors – led by Danish researcher Uffe Ravnskov.
“There is in fact much evidence that doing the opposite is more relevant.”
The team said that the diet-heart recommendations of the American Heart Association, published in 1982 - based mainly on recommendations by Keys et al - were already questioned a year later, and that since then, many more objections have been presented.
“The dietary recommendations, according to which SFAs should be exchanged with carbohydrates, were introduced more than 30 years ago for the US population and have been followed in many countries,” said the team. “In retrospect, the current epidemics of obesity, metabolic syndrome, and type 2 diabetes that started shortly afterward may be an effect of this diet.”
The experts cited a wide range of evidence that goes against the recommendations to slash saturated fats, adding that many studies which rely on diet data are based on interviews “are of course inaccurate.”
“A more reliable way is to analyse the concentration of short-chain SFAs (12:0–15:0) in fat cells because their concentrations reflect the intake of saturated fat during the past weeks or months.”
“In 3 case-control studies of patients with myocardial infarction and healthy control individuals, no difference was found with regard to the content of short-chain SFAs; in 2 studies, it was even significantly lower in the patients.”
“These facts have had no effect on the official guidelines,” said the team. “Although the authors of the recent World Health Organization/Food and Agriculture Organization of the United Nations guidelines stated that ‘the available evidence from cohort and randomised controlled trials is unsatisfactory and unreliable to make judgement about and substantiate the effects of dietary fat on risk of CHD,’ they found no reason to change the advice regarding the intake of SFAs.”
The team concluded that the supposed benefits of replacing SFAs with PUFAs “are questionable.”
“There is no evidence that a lower intake of SFA can prevent CVD and a high intake of PUFAs without specification may result in a high intake of omega-6, which is associated with many adverse health effects,” they warned.
In fact, according to Ravnskov and his colleaguses, the team warned that because there is ‘much evidence’ that saturated fat may even be beneficial, “we urge the American Heart Association, the American Diabetes Association, and the National Institute of Clinical Excellence to consider the aforementioned evidence when updating their future guidelines.”
Source: Mayo Clinic Proceedings
Volume 89, Issue 4, April 2014, Pages 451–453, doi: 10.1016/j.mayocp.2013.11.006
“The Questionable Benefits of Exchanging Saturated Fat With Polyunsaturated Fat”
Authors: Uffe Ravnskov, James J. DiNicolantonio et al