PURE study adds pieces to dietary puzzle
medwireNews: Two analyses of the Prospective Urban Rural Epidemiology (PURE) cohort associate low dietary fat and high carbohydrate intake with an atherogenic lipid profile and increased mortality.
However, a third analysis of the same cohort shows that high intake of carbohydrates in the form of fruit, vegetables, and legumes is associated with reduced mortality risk.
“This discrepancy suggests that processed carbohydrates, including added sugars and refined grains, are likely driving” the association between carbohydrates and mortality, say Christopher Ramsden and Anthony Domenichiello, from the National Institutes of Health in Baltimore, Maryland, USA, in a commentary in The Lancet accompanying the fat and carbohydrate analysis.
The fruit and vegetable analysis is also published in The Lancet and the lipid analysis appears in The Lancet Diabetes & Endocrinology. The PURE investigators presented all three analyses today at the European Society of Cardiology conference in Barcelona, Spain.
The PURE study involves over 150,000 people from 18 low-, middle-, and high-income countries. The participants were aged between 35 and 70 years at enrolment between 2003 and 2013, at which point they completed a food-frequency questionnaire. During a median follow-up of 7.4 years there were a total of 5796 deaths and 4784 major cardiovascular disease events.
Analysis of baseline data showed that higher intake of total and saturated, monounsaturated, and polyunsaturated fat was associated with higher levels of total and low-density lipoprotein (LDL) cholesterol, but also with higher levels of high-density lipoprotein (HDL) and apolipoprotein (apo)A1, and lower triglycerides and ratio of apoB to apoA-1, overall indicating a generally less atherogenic lipid profile.
By contrast, a higher carbohydrate intake was associated with a more atherogenic lipid profile. Simulations showed that replacing saturated fat with carbohydrates resulted in the largest shift toward an atherogenic lipid profile, whereas replacing it with unsaturated fats would only improve LDL cholesterol levels, while worsening HDL cholesterol and triglycerides.
In line with this, during follow-up, participants in the highest versus the lowest quintiles of total fat intake had a significant 23% reduction in the risk for death from any cause, and there were similar associations for each fat subtype, whereas those in the top versus bottom quintiles of carbohydrate intake had a 28% increased risk.
But consumption of carbohydrates in the form of fruit, vegetables, and legumes was protective, with participants who consumed eight or more portions per day being 42% less likely to die than those who had less than one portion per day, after accounting for age, gender, and study center. However, this reduction was markedly attenuated, to 19%, after further adjustment for factors including energy intake, smoking, diabetes, physical activity, and intake of white meat, red meat, breads, and cereals.
Furthermore, the lowest mortality risk after multivariable adjustment was seen for participants eating three to four portions per day, with no further reduction at higher amounts, all implying the greater importance of overall dietary pattern relative to individual nutrients, as discussed in a linked commentary by Estefania Toledo and Miguel Martínez-González, from the University of Navarra in Pamplona, Spain.
“[T]he relevant question is not whether to consume more plant-based foods or not, but to know which are the detrimental foods that should be replaced by fruits, vegetables, and legumes and in what amount,” they write.
The commentators stress that “a healthy diet rich in fruits and vegetables needs to be considered as part of a high-quality overall eating pattern, and this pattern should be based on country-specific dietary traditions to be fostered as an effective tool for prevention of cardiovascular disease and premature mortality.”
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