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.