A new longitudinal cohort study published by UK medical journal The Lancet could help raise the profile of saturated fats such as coconut oil, butter and olive oil. The study found that a high carbohydrate intake was associated with a higher rate of mortality and moderate fat intake was associated with lower mortality, has received mixed reactions from researchers in the UK and Australia.
The study, published late August, followed 135,000 people aged 35 to 70 years from 18 lower-income, middle-income and high-income countries across five continents for seven years, was led by researchers from McMaster University, Ontario, and Hamilton Health Sciences, Hamilton, Canada.
The study, Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): a prospective cohort study, found that people who get more than three-quarters of their total calories from diets high in carbohydrates have a 28 percent higher risk of death, compared to those who get around half of their calories from low carbohydrate diets.
Diets with a high total fat intake were associated with a 23 percent lower risk of death, compared to those with a low-fat intake. However, there was no risk difference of having major cardiovascular disease in both diets.
And the researchers conclude that intake of saturated fat had an association with a lower risk of stroke.
"Total fat and types of fat were not associated with cardiovascular disease, myocardial infarction, or cardiovascular disease mortality, whereas saturated fat had an inverse association with stroke. Global dietary guidelines should be reconsidered in light of these findings," the authors concluded.
However, researchers from the UK's Behind The Headlines - Health News from NHS Choices, said that the study mainly looked at people in lower- and middle-income countries, where diets are very different, so the results may not be relevant to the UK, where headlines suggested, " Eating a low-fat diet 'increases your risk of dying young by 25%".
"Many previous studies linking high levels of saturated fat to heart disease and early death were carried out in high-income countries, such as the UK and US, where heart disease and consumption of saturated fats are both relatively high.
"The resulting recommendations that people avoid a high-fat diet may not be very relevant in countries such as Bangladesh and Zimbabwe, where eating enough may be a more pressing concern than weight gain. That's why this latest study focused on lower- and middle-income countries," Behind The Headlines said.
"However, people from lower- and middle-income countries are more dependent on refined carbohydrates, such as white rice. These are known to be less healthy than unrefined sources, such as brown rice and wholemeal bread, which are more readily available in the UK."
The researchers say their results suggest global dietary guidelines should be revised. However, their recommendations – that carbohydrates should provide 50 to 55 percent of energy intake and fat around 35 percent – are in line with existing UK dietary guidelines.
"The whole 'fats vs carbs' debate is arguably a bit of a sideshow: the truth is that, based on the latest UK obesity statistics, many of us simply eat too much," they said.
The current guidelines recommend that 50-65 percent of a person's daily calories come from carbohydrates and less than 10 percent from saturated fats. The study found the average global diet consisted of at least 60 percent carbohydrate.
Lead author Dr Mahshid Dehghan at McMaster University, Canada would like the carbohydrate recommendation reduced.
"The current focus on promoting low-fat diets ignores the fact that most people's diets in low and middle-income countries are very high in carbohydrates, which seem to be linked to worse health outcomes," Dr Dehghan said.
The study conclusions received a mixed reaction from Australian health experts. Professor Amanda Lee - a nutritionist and senior advisor at The Australian Prevention Partnership Centre - says a major limitation of the study is that it does not mention what foods the macronutrients came from.
Professor Lee suggested that it's carbohydrate from added sugars and refined grains that is "problematic" and said the findings may not translate in Australia. "The upper levels of intakes of carbohydrate reported in the study are much higher and the lower intakes of fats are very much lower than consumed here," Professor Lee said.
Professor John Funder at the Hudson Institute of Medical Research said what the study shows is that fats - saturated, mono-unsaturated and polyunsaturated - are not the "no-no" most people have been brought up to believe.
Go for dairy, olive oil and even the occasional wagyu beef burger, have lots of grains, fruit and vegetables, and lay off the sweet stuff, especially sugar-sweetened soft drinks, Professor Funder said.