The BMJ has questioned the WHO’s advice on replacing saturated fat with unsaturated fat
Advice to reduce intake of total saturated fat and replace it with unsaturated fat to curb levels of chronic disease and prevent deaths, set out in draft World Health Organization (WHO) guidance, has been called into question by experts in The BMJ.
Arne Astrup at the University of Copenhagen and colleagues look at the evidence linking saturated fat intake and cardiovascular risk, and say the recommendations “fail to take into account considerable evidence that the health effects of saturated fat varies depending on the specific fatty acid and on the specific food source.”
They also warn that these recommendations might cause a reduction in the intake of nutrient-dense foods that are important for preventing disease and improving health.
The WHO draft guidelines were published for consultation in May 2018. They recommend reducing intake of saturated fatty acids (found in foods such as hard cheese, whole milk and butter) and replacing it with polyunsaturated and monounsaturated fatty acids (found in oily fish, vegetable oils, nuts and seeds) to reduce rates of chronic disease and related deaths.
Many governments consider WHO dietary guidelines to be state of the art scientific evidence, translating them into regional and national dietary recommendations, so the consistency of the science behind such recommendations and the validity of the conclusions are crucial, write the authors.
But while consensus exists on the health benefits of eliminating industrially produced trans fatty acids, the evidence linking saturated fat to cardiovascular disease and death is less clear, they say.
They point out that the draft guidance relies heavily on a meta-analysis of 84 randomised controlled trials (RCTs) that tested the effect of altering saturated fat intake on blood cholesterol levels.
But this approach – which focuses on total saturated fatty acids, ignores food sources, and uses indirect (‘surrogate’) measures – is problematic for several reasons, they say.
For example, not all saturated fatty acids are equal and cannot be viewed as one homogeneous group with regard to effects of diet on disease risk.
What’s more, the food matrix (compounds like fibre and minerals in whole foods) in which the fatty acids exist might be more important for the effect on cardiovascular disease risk than the saturated fat content, they add.
They point to other studies that show why a broader view of biomarkers of cardiovascular disease is needed to inform guidelines.
“We think that recommendations to reduce intake of total saturated fat without considering specific fatty acids and food sources are not based on evidence and will distract from other, more effective, food based recommendations,” the researchers argue.
“We’re concerned that, based on several decades of experience, a focus on total saturated fat might have the unintended consequence of misleading governments, consumers, and industry towards promoting foods low in saturated fat but rich in refined starch and sugar,” they add.
“We strongly recommend a more food based translation of how to achieve a healthy diet and reconsideration of the draft guidelines on reduction in total saturated fatty acids,” they conclude.