From The Lancet:
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.
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.
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.
Research in context
Evidence before this study
We did a systematic search in PubMed for relevant articles published between Jan 1, 1960, and May 1, 2017, restricted to the English language. Our search terms included “carbohydrate”, “total fat”, “saturated fatty acid”, “monounsaturated fatty acid”, “polyunsaturated fatty acid”, “total mortality”, and “cardiovascular disease”. We searched published articles by title and abstract to identify relevant studies. We also hand-searched reference lists of eligible studies. We considered studies if they evaluated association between macronutrient intake and total mortality or cardiovascular disease. The studies cited in this report are not an exhaustive list of existing research. Existing evidence on the associations of fats and carbohydrate intake with cardiovascular disease and mortality are mainly from North America and Europe.
Added value of this study
Current guidelines recommend a low fat diet (<30% of energy) and limiting saturated fatty acids to less than 10% of energy intake by replacing them with unsaturated fatty acids. The recommendation is based on findings from some North American and European countries where nutrition excess is of concern. It is not clear whether this can be extrapolated to other countries where undernutrition is common. Moreover, North American and European populations consume a lower carbohydrate diet than populations elsewhere where most people consume very high carbohydrate diets mainly from refined sources. Consistent with most data, but in contrast to dietary guidelines, we found fats, including saturated fatty acids, are not harmful and diets high in carbohydrate have adverse effects on total mortality. We did not observe any detrimental effect of higher fat intake on cardiovascular events. Our data across 18 countries adds to the large and growing body of evidence that increased fats are not associated with higher cardiovascular disease or mortality.
Implications of all the available evidence
Removing current restrictions on fat intake but limiting carbohydrate intake (when high) might improve health. Dietary guidelines might need to be reconsidered in light of consistent findings from the present study, especially in countries outside of Europe and North America.
The study appears mainly to have been funded by Canadian health organizations.