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Can a High-Carb Diet Shorten Your Life?

Sep 21, 2017

Research on more than 135,000 people across five continents found that eating moderate amounts of fat plus moderate helpings of fruits and vegetables, while limiting overall carbohydrate intake, was associated with lower risk of death. Mahshid Dehghan, PhD, and other researchers found that the lowest risk of death was in people who consumed three to four servings (or a total of 375–500 grams) of fruits, vegetables and legumes a day, with little additional benefit from more.

The researchers also discovered that, contrary to popular belief, consuming a higher amount of fat (about 35% of energy) was associated with a lower risk of death compared with lower fat intakes. A diet high in carbohydrates (more than 60% of energy) was related to higher mortality, although not with the risk of cardiovascular disease.

These were the top messages of two reports published in the August 29 issue of The Lancet. Both were 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, Ontario.

The data are from the Prospective Urban Rural Epidemiology (PURE) study that 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 7.5 years.

The research on dietary fats found that they were not associated with major cardiovascular disease, and higher fat consumption (about 35% of energy, as noted above) was associated with lower mortality; this was seen for all major types of fats (saturated fats, polyunsaturated fats and mono unsaturated fats), with saturated fats 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 pointed out that, while these findings may surprise some people, the new results are consistent with several observational studies and randomized controlled trials 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, says Dehghan, 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, in a Newswise press release from McMaster University.

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 was based on the idea that reducing saturated fat should reduce the risk of cardiovascular disease, but did not take into account how saturated fat was replaced 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% or 45% of caloric intake and saturated fat intakes were more than 20%. These levels are now much lower in North America and Europe (31% and 11%, respectively).

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