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.

To be specific about moderate, the lowest risk of death was in those people who consume 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.

As well, contrary to popular belief, consuming a higher amount of fat (about 35 per cent of energy) is associated with a lower risk of death compared to lower intakes. However, a diet high in carbohydrates (of more than 60 per cent of energy) is related to higher mortality, although not with the risk of cardiovascular disease.

These are the top messages of two reports published Aug. 29 in The Lancet journal, both produced from a major global study led by researchers at the Population Health Research Institute (PHRI) of McMaster University and Hamilton Health Sciences. The reports were also presented at the Congress of the European Society of Cardiology.

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.

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 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 death due to cardiovascular disease.

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 per cent of daily caloric intake and saturated fat to below 10 per cent of caloric intake. But they 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.

"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.

Legumes include beans, black beans, lentils, peas, chickpeas and black–eyed peas and are frequently eaten as an alternative to meat or some grains and starches such as pasta and white bread.

In a third study, published concurrently by The Lancet Diabetes and Endocrinology journal, the same researchers looked at the impact of fats and carbohydrates on blood lipids and blood pressure.

They found that LDL is not reliable in predicting effects of saturated fat on future cardiovascular events. Instead, the ratio of Apolipoprotein B (ApoB) and Apolipoprotein A1 (ApoA1), or organizing proteins in the blood, give the best indication of the impact of saturated fat on cardiovascular risk.