Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): a prospective cohort study.

Key Findings

In one of the most comprehensive studies to date that examined how diet affects health and mortality, this study shows that rather than lowering fat, more people might benefit from lowering the amount of carbohydrates they eat. The data suggested that those who ate high quantities of carbohydrates, which are found in breads and rice, had a nearly 30% higher risk of dying during the study than people eating a low-carb diet. And people eating high-fat diets had a 23% lower chance of dying during the study’s seven years of follow-up compared to people who ate less fat. The results point to the fact that rather than focusing on fat, health experts should be advising people to lower the amount of carbohydrates they eat. In the study, which involved 135,000 people from 18 different countries, the average diet was made up of 61% carbohydrates, 23% fat and 15% protein. In some countries, like China, south Asia and Africa, however, the amount of carbohydrates in the diet was much higher, at 63% to 67%. More than half of the people in the study consumed high-carbohydrate diets. The initial studies linking fat to heart disease were conducted primarily in North America and Europe, which has the highest consumption of fat worldwide. In western cultures, where there is an excess of fat, reducing fat may play a role in lowering heart disease, as long as people aren’t replacing the fat with carbohydrates. In other parts of the world, where carbohydrates make up a large part of the diet, cutting back on carbs may make more sense than focusing on fat. Further research is required to determine optimal levels of fat and carbohydrates. The study did not compare, for example, people who ate low-fat diets to those who ate low-carb diets to see how their diets affected their mortality.

ABSTRACT:

Background: The relationship between macronutrients and cardiovascular disease and mortality is controversial. Most available data are from European and North American populations where nutrition excess is more likely, so their applicability to other populations is unclear. Methods: The Prospective Urban Rural Epidemiology (PURE) study is a large, epidemiological cohort study of individuals aged 35–70 years (enrolled between Jan 1, 2003, and March 31, 2013) in 18 countries with a median follow-up of 7·4 years (IQR 5·3–9·3). Dietary intake of 135 335 individuals was recorded using validated food frequency questionnaires. The primary outcomes were total mortality and major cardiovascular events (fatal cardiovascular disease, non-fatal myocardial infarction, stroke, and heart failure). Secondary outcomes were all myocardial infarctions, stroke, cardiovascular disease mortality, and non-cardiovascular disease mortality. Participants were categorised into quintiles of nutrient intake (carbohydrate, fats, and protein) based on percentage of energy provided by nutrients. We assessed the associations between consumption of carbohydrate, total fat, and each type of fat with cardiovascular disease and total mortality. We calculated hazard ratios (HRs) using a multivariable Cox frailty model with random intercepts to account for centre clustering.

Findings: During follow-up, we documented 5796 deaths and 4784 major cardiovascular disease events. Higher carbohydrate intake was associated with an increased risk of total mortality (highest [quintile 5] vs lowest quintile [quintile 1] category, HR 1·28 [95% CI 1·12–1·46], p_trend=0·0001) but not with the risk of cardiovascular disease or cardiovascular disease mortality. Intake of total fat and each type of fat was associated with lower risk of total mortality (quintile 5 vs quintile 1, total fat: HR 0·77 [95% CI 0·67–0·87], p_trend<0·0001; saturated fat, HR 0·86 [0·76–0·99], p_trend=0·0088; monounsaturated fat: HR 0·81 [0·71–0·92], p_trend<0·0001; and polyunsaturated fat: HR 0·80 [0·71–0·89], p_trend<0·0001). Higher saturated fat intake was associated with lower risk of stroke (quintile 5 vs quintile 1, HR 0·79 [95% CI 0·64–0·98], p_trend=0·0498). Total fat and saturated and unsaturated fats were not significantly associated with risk of myocardial infarction or cardiovascular disease mortality. Interpretation: High carbohydrate intake was associated with higher risk of total mortality, whereas total fat and individual types of fat were related to lower total mortality. Total fat and types of fat were not associated with cardiovascular disease, myocardial infarction, or cardiovascular disease mortality, whereas saturated fat had an inverse association with stroke. Global dietary guidelines should be reconsidered in light of these findings.