Research with more than 135,000 people across five continents has shown that a diet which includes a moderate intake of fat and fruits and vegetables, and avoidance of high carbohydrates, is associated with lower risk of death.
The research findings come from two published reports of 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 data are from the Prospective Urban Rural Epidemiology (PURE) study which followed more than 135,000 people from 18 low-income, middle-income and high-income countries. The study asked people about their diet and followed them for an average of seven and half years.
Higher fat intake linked to lower mortality risk, higher carb intake increased risk
Contrary to popular belief, consuming a higher amount of fat (about 35 percent of daily calories) was associated with a lower risk of death compared to lower fat intakes. However, a diet high in carbohydrates (of more than 60 percent of daily calories) was tied to higher mortality, although not with the risk of cardiovascular disease.
The research on dietary fats found that they were not associated with major cardiovascular disease, but higher fat consumption was associated with lower mortality, and this was seen for all major types of fats (saturated fats, polyunsaturated fats and monounsaturated fats), with saturated fats being associated with lower stroke risk.
Total fat and individual types of fat were not associated with risk of heart attack or death from cardiovascular disease.
The large new study, when viewed in the context of many previous studies, questions the conventional beliefs about dietary fats and health outcomes.
"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," one of the researchers said.
Dietary guidelines have focused for decades on reducing total fat to below 30 per cent of daily caloric intake and saturated fat to below 10 per cent of caloric intake. This is based on the idea that reducing saturated fat should reduce the risk of cardiovascular disease, but did not take into account what saturated fat is replaced with in the diet.
She added that the current guidelines were developed about four decades ago using data from some Western countries where fat was more than 40 per cent or 45 per cent of caloric intake and saturated fat intakes were more than 20 per cent. The consumption of these are now much lower in North America and Europe (31 per cent and 11 per cent respectively).
Link between fruit, vegetable, legume intake and mortality
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. The lowest risk of death was seen in people who consumed three to four servings (or a total of 375 to 500 grams) of fruits, vegetables and legumes a day, with little additional benefit from more.
Additionally, fruit intake was more strongly associated with benefit than vegetables.
Previous research has shown that eating fruits, vegetables and legumes decreases the risk of cardiovascular 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 vegetables. Dietary guidelines do not differentiate between the benefits of raw versus cooked vegetables; these results suggest that recommendations should emphasize 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 the researchers.
“The findings of these studies are robust, globally applicable and provide evidence to inform nutrition policies. This is relevant because in some parts of the world nutritional inadequacy is a problem, whereas in other parts of the world nutritional excesses may be the problem," said one of the study authors.
Another study author commented, "Moderation in most aspects of diet is to be preferred, as opposed to very low or very high intakes of most nutrients".
Source: The Lancet, August 29, 2017.
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