According to new research, low-fat diets could raise your risk of early death by almost a quarter.
The study of more than 135,000 people across five continents has shown that a diet that includes a moderate intake of fat, alongside fruits and vegetables and avoidance of high carbohydrates, is associated with lower risk of death.
And contrary to popular belief, consuming a higher amount of fat (about 35% of energy) was found to be associated with a lower risk of death compared to lower intakes.
However, a diet high in carbohydrates (of more than 60% of energy) is related to higher mortality, according to the findings.
The results are taken from two reports published in The Lancet, both produced from a major global study led by researchers at the Population Health Research Institute (PHRI) of McMaster University and Hamilton Health Sciences in Hamilton, Canada.
The study asked people about their diet and followed them for an average of seven and half years.
The research on dietary fats found that they are not associated with major cardiovascular disease, but higher fat consumption was associated with lower mortality.
This result was seen for all major types of fats (saturated fats, polyunsaturated fats and mono unsaturated fats), with saturated fats also being associated with lower stroke risk.
Total fat and individual types of fat were not associated with risk of heart attacks or death due to cardiovascular disease.
The researchers point out that, while this may appear surprising to some, these new results are consistent with several studies conducted in Western countries during the last two decades.
The large new study, when viewed in the context of most previous studies, questions the conventional beliefs about dietary fats and clinical outcomes, said Mahshid Dehghan, the lead author for the study and an investigator at PHRI.
“A decrease in fat intake automatically led to an increase in carbohydrate consumption and our findings may explain why certain populations such as South Asians, who do not consume much fat but consume a lot of carbohydrates, have higher mortality rates,” she said.
Dehghan pointed out that dietary guidelines have focused for decades on reducing total fat to below 30% of daily caloric intake and saturated fat to below 10% of caloric intake. This is based on the idea that reducing saturated fat should reduce the risk of heart disease, but did not take into account how saturated fat is replaced in the diet.
The second paper, from the PURE study, assessed fruit, vegetable and legume consumption and related them to deaths, heart disease and strokes.
The study found current fruit, vegetable and legume intake globally is between three to four servings per day, but most dietary guidelines recommend a minimum of five daily servings.
Given that fruits and vegetables are relatively expensive in most middle-income and low-income countries, this level of consumption is unaffordable for most people in many regions of the world such as South Asia, China, Southeast Asia and Africa, where the levels of their consumption is much lower than in Western countries, the researchers said.
“Our study found the lowest risk of death in those who consumed three to four servings or the equivalent to 375 to 500 grams of fruits, vegetables and legumes per day, with little additional benefit for intake beyond that range,” said Victoria Miller, a McMaster doctoral student and lead author of the paper.
“Additionally, fruit intake was more strongly associated with benefit than vegetables.
“The PURE study includes populations from geographic regions which have not been studied before, and the diversity of populations adds considerable strength that these foods reduce disease risk.”
According to the researchers, previous research has shown that eating fruits, vegetables and legumes decreases the risk of heart disease and deaths, but most studies were conducted mainly in North America and Europe, with a few from other parts of the world.
“Raw vegetable intake was more strongly associated with a lower risk of death compared to cooked vegetable intake, but raw vegetables are rarely eaten in South Asia, Africa and Southeast Asia,” Miller said.
“Dietary guidelines do not differentiate between the benefits of raw versus cooked vegetables ― our results indicate that recommendations should emphasise raw vegetable intake over cooked.”
Legumes include beans, black beans, lentils, peas, chickpeas and black-eyed peas and are frequently eaten as an alternative for meat or some grains and starches such as pasta and white bread.
“Legumes are commonly consumed by many populations in South Asia, Africa and Latin America. Eating even one serving per day decreases the risk of cardiovascular disease and death. Legumes are not commonly consumed outside these geographic regions, so increased consumption among populations in Europe or North America may be favourable,” said Miller.
But Salim Yusuf, principal investigator of the study and the director of the PHRI, has stressed the importance of moderation in diet.
“Moderation in most aspects of diet is to be preferred, as opposed to very low or very high intakes of most nutrients,” he said
The reports are due to be presented at the Congress of the European Society of Cardiology in Barcelona, Spain.