Time to stop talking about saturated fat?
Different foods, different effects
The scientific evidence indicates that the general advice of the World Health Organization (WHO) draft guidelines to reduce saturated fat will weaken the impact of diet recommendations on chronic disease incidence and mortality. A food-based translation of the recommendations for saturated fat intake is essential to avoid unnecessary reduction or exclusion of foods that are key sources of important nutrients. The analysis is published in the international scientific journal British Medical Journal (BMJ).
The WHO draft guidelines single out saturated fatty acids and trans-fatty acids to be of particular importance when it comes to cardiovascular diseases and related mortality. The WHO ‘draft guidelines’ on dietary saturated fatty acids and trans-fatty acids for adults and children were published for consultation in May 2018. The guidelines recommend reducing intake of total saturated fat to less than 10% of total energy intake, and replacing it with polyunsaturated fat and monounsaturated fat.
Unfortunately, the recommendation fails to take into account considerable evidence that the health effects of saturated fat vary for different types of fatty acids, and that the composition of the food in which the saturated fat is found crucial important:
“The composition of food and the food source has a substantial impact on the digestion, absorption and metabolism of lipids in the blood, which are an independent cardiovascular disease risk factor. Recent evidence shows that some foods with high content of saturated fat actually lower cardiovascular risk due to effects other than those on blood cholesterol,” says professor MD DMSC Arne Astrup, Department of Nutrition, Exercise and Sports from University of Copenhagen.
He continues: “Findings suggest very clearly that a food-based translation of the recommendations for saturated fat intake is essential in order to avoid unnecessary reduction or exclusion of foods that are key sources of important nutrients.”
Different foods contain saturated fat in a diversity of compositions
Saturated fat is found mainly in animal fats, such as meat, butter, cheese and milk, whilst unsaturated fat can be found in foods as fatty fish, plant oils and nuts. Many ready-prepared foods, such as pizza, dairy desserts, and sausages, have a high content of saturated fat.
However, different foods contain saturated fat in a wide diversity of compositions, with completely different physiological effects. Foods from animal sources – like meat and dairy - have a wide range of compositions and structures, with essential differences between unprocessed meat and processed meat, and where full-fat milk differs from butter, which differs from yogurt, which differs from cheese – and cheese is a complex story in itself. See more information on these differences below.
The WHO guidelines should consider different types of saturated fat
Arne Astrup and co-authors of the article in BMJ find that the WHO recommendations are not evidence-based, and that they could distract from other more effective food-based recommendations. The recommendations may actually cause a reduction in the intake of nutrient-dense foods that are important for preventing disease and improving health:
“We’re concerned that, based on several decades of experience, a focus on total saturated fat may have the unintended consequence of misleading governments, consumers, and industry toward promoting foods low in saturated fat but rich in refined starch and sugar. The WHO saturated fat guidelines should consider different types of fatty acids and, more importantly, the diversity of foods containing saturated fat that may be harmful, neutral, or even beneficial in relation to major health outcomes,” concludes professor Arne Astrup. He strongly recommends a food-based translation of how to achieve a healthy diet and reconsideration of the draft guidelines on reduction in total saturated fat.
The analysis is published in the article The WHO draft guidelines on dietary saturated and trans-fatty acids: time for a new approach? in British Medical Journal. The press release from British Medical Journal can be read here.
Arne Astrup has received financial support from Danish Dairy Foundation, Global Dairy Platform, Arla Foods Amba, Denmark, and European Milk Foundation for projects conducted at the University of Copenhagen exploring the effects of dairy fats and cheese consumption on human health. The European Milk Foundation sponsored the Expert Symposium on the Dairy Matrix 2016, organised by Arne Astrup. Furthermore Arne Astrup has received travel expenses and honorariums in connection with meetings and lectures from Danone, Arla Foods, and Global Dairy Platform.
For more information about effects of saturated fatty acids
Professor Arne Astrup, MD, DMSc
Head of Department of Nutrition, Exercise and Sports, University of Copenhagen
Telephone: + 45 2143 3302
Kristian Levring Madsen
Department of Nutrition, Exercise and Sports, University of Copenhagen
Telephone: +45 4048 1684
The diversity of the saturated fatty acids in foods
Saturated fatty acid-rich vegetable oils such as palm oil and coconut oil are 100% lipids.
Animal fats, such as lard and tallow, are 100% lipids. In unprocessed meat, lipids are mostly present within adipocytes and intracellular lipid droplets of muscle. Processed meats can contain fat inclusions in a gelled protein matrix, free fat domains, and remnant adipocytes, according to processing. Egg yolk contains lipids structured as lipoproteins of both low and high density.
In dairy products, full-fat milk is a natural emulsion of fat globules enclosed in milk fat globule membrane, but when milk is homogenized the droplets are much smaller and covered with proteins. Butter is a water-in-oil emulsion. Yogurt is a fermented food containing live cultures, in which milk fat globules are dispersed in the gelled milk protein matrix. Cheese is one of the most complex dairy matrices. It is a fermented food containing live cultures, where fat is present within milk fat globules, and sometimes as free fat inclusions in a solid matrix rich in milk proteins, calcium, and milk fat globule membrane. Ice cream contains a combination of crystallized fat globules around air bubbles, and ice crystals in a liquid syrup phase.
In processed foods such as pastries and cookies, the fat inclusions (composed of palm oil, butter etc.) are embedded within a more or less solid, often sugar-rich, carbohydrate matrix. Chocolate is composed of particles (e.g. sugar), and fermentation products from cocoa bean embedded in solid fat.