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expert reaction to opinion piece questioning WHO draft guidance on saturated fat

An opinion piece published in The BMJ argues that WHO recommendations might reduce intake of important foods for preventing disease and improving health.

 

Prof Judith Buttriss, Director General, British Nutrition Foundation, said:

“This opinion piece by Astrup et al. highlights the complexity of providing dietary recommendations based on nutrients as we never eat nutrients alone but foods that are a complex mixture of different components.  This is why countries produce food-based dietary advice based on nutrient guidelines to communicate with the general public.

“The authors rightly point out that different saturated fatty acids have different health effects – not all saturated fatty acids raise blood cholesterol levels – and also that the food matrix is important in terms of overall effects on health.  For example, whole yogurt and whole milk don’t seem to increase the risk of heart disease in the way that would be predicted from their saturated fat content.  Research to better understand such anomalies is certainly warranted and may assist in fine tuning dietary recommendations in the future.  However, when it comes to giving practical advice, it’s very difficult to give simple guidance on the specific fatty acids we consume.  This is because all fat-containing foods contain mixtures of different fatty acids that are individually recognised as having differing effects on risk factors such as blood cholesterol.

“The authors recommend food-based guidance and most countries do already have some kind of food-guide to provide healthy eating advice.  In the UK, the Eatwell Guide encourages us to eat a healthy, varied diet including wholegrains, fish and plenty of fruit and vegetables, some dairy products (mostly lower fat options) and small amounts of unsaturated oils and spreads.  The Guide suggests limiting red and processed meat, choosing leaner cuts of meat and avoiding sugary foods and drinks.  This type of healthy dietary pattern has been shown to help reduce the risk of chronic disease.

“The opinion piece suggests that the link between saturated fat, blood cholesterol and cardiovascular disease may apply to some saturated fatty acids and sources of saturated fats but not others.  Nevertheless, while there can always be inconsistencies between studies of different designs, clinical trials have shown that the partial replacement of dietary saturated fatty acids with unsaturated fatty acids can be beneficial for lowering blood cholesterol and cardiovascular disease risk.  A dietary pattern approach to reducing disease risk and promoting health is becoming more popular.  However, we do need more research on the specific effects of changing dietary patterns on health as this is a very complex area to investigate in studies, not least because we need a multitude of different essential nutrients regularly from the food we consume.

“It is worth noting that saturated fat may do more than simply adversely affect blood cholesterol.  In a Task Force report on emerging risk factors for cardiovascular disease, recently published by the British Nutrition Foundation, it was found that saturated fatty acids not only had a detrimental effect on blood cholesterol but also on other risk factors such as inflammation, endothelial function and platelet activity.

“The opinion piece in the BMJ suggests that advice to reduce saturated fat might lead people to exclude foods that are rich in nutrients.  But this is not encouraged in the UK’s Eatwell Guide, which is based on the long-standing recommendation to replace saturated with unsaturated fat, in the context of a diet that embraces other important nutritional considerations, such as the need for many people to increase their fibre intakes and for diets to provide sufficient vitamin and minerals.  The Eatwell Guide recommends choosing lower fat versions of dairy foods most of the time (due to the high prevalence of overweight/obesity); it does not suggest that dairy foods be excluded.”

 

Prof Nita Forouhi, MRC Epidemiology Unit, University of Cambridge, said:

“The authors’ argument that WHO guidelines on dietary fat should consider the different types of saturated fatty acids and the diverse foods that contain them, is consistent with our own EU-funded research in people in 8 European countries showing the varying effects of different types of blood saturated fatty acids on the risk of type 2 diabetes.

“A call to distinguish between different food sources of saturated fats, not focus on the nutrient alone, is in line with the recent progress in nutrition science, but we must be mindful to not pre-judge the final report that is yet to be released by the WHO following the public consultation period that ended in June 2018.

“The WHO provided an open opportunity for anyone globally to provide online comments to the public consultation on the draft report between 4th May till 1st of June 2018, and also sent the report for external peer review.  The final report is not yet released, and it is not yet known how much it will differ from the draft report, so it is important to wait for the final report.  Guidelines to maintain saturated fat intakes to under 10% of energy intake and to replace excess saturated fat with polyunsaturated fat are currently in place in many regions of the world.  Linking the nutrient (saturated fat) to its diverse food sources will be important for the real-world translation of guidelines into public action.”

 

Prof Tom Sanders, Professor emeritus of Nutrition and Dietetics, King’s College London, said:

“This opinion piece raises some valid questions regarding dietary guidelines concerning saturated fatty acids, but it in no way suggests we got it wrong on saturated fats.  It does raise the important issue about labelling all foods that are high in saturated fatty acids (including dairy, oily fish and nuts) as unhealthy, because evidence has emerged from prospective cohort studies suggesting that liquid milk and yoghurt (but not butter), oily fish and nuts are associated with a lower risk of cardiovascular disease (CVD).  However, red meat and meat products, which are major sources of saturated fatty acids, are consistently linked to a greater risk of CVD.  So this is not the green light for saturated fats.

“A number of clinical trials were conducted in the 1960s-1970s to test whether decreasing saturated fatty acid intake lowered the risk of cardiovascular disease.  These indicated a possible benefit for replacing saturated with polyunsaturated fatty acids (e.g. using vegetable oils instead of lard and using margarine low in saturated fatty acids instead of butter) on coronary heart disease events such as heart attacks, but not on death.  The resurrection by this opinion piece of the Minnesota Coronary Survey trial to suggest that serum cholesterol is not a reliable surrogate marker for risk of coronary disease is surprising as this was a flawed trial, in only patients with mental illness, had a short duration, a large percentage of withdrawals from the study, and intermittent treatment, as well as the use of lightly hydrogenated corn oil margarine in the polyunsaturated fat diet containing trans linoleic acid (the type of trans fatty acid most strongly associated with coronary heart disease).  A meta-analysis of all the saturated fatty acid reduction trials shows the results to be unclear.  Further trials are unlikely to happen owing to the enormous cost of recruiting over 100,000 participants and maintaining them on their respective diets for several years.

“Saturated fatty acids are normal products of metabolism and most are stored in the body as palmitic acid.  Even breastmilk contains 25-30% palmitic acid.  In the 1950s-1970s, North America and Northern Europe were in the midst of an epidemic of coronary heart disease – this was blamed on cigarette smoking and a diet high in saturated fatty acids and cholesterol, derived mainly from meat and milk from ruminants, and low in polyunsaturated fatty acids.  Nowadays, the intake of saturated fatty acids is about 8% lower (as a percentage of energy intake) than in the past, and the intake of polyunsaturated fatty acids is about 2% higher.  For the past thirty years, vegetable oil has replaced much of the animal fats used in cooking and as spreads, and in the UK partially hydrogenated fats were phased out 20 years ago.  Although the intake of whole milk has fallen and been partially replaced by skimmed and semi-skimmed milk, the butter fat still remains in the food chain in compound foods such as cakes and pastries.  Premature deaths from coronary heart disease have fallen by more than 60% over this time, but the reasons for the formerly high rates of CHD in the UK and other countries remain hotly debated.

“There is no doubt from scientific evidence that certain saturated fatty acids raise blood cholesterol, and that each 1 mmol/L increase in blood cholesterol raises the relative risk of cardiovascular death by about 10%.  Some short-chain fatty acids found in butter and stearic acid have no effect on blood cholesterol, but others do.  Despite this, butter raise blood cholesterol even more than vegetable oils including coconut oil1.  French dietary guidelines make allowances for these non-cholesterol-raising fatty acids, which is ironic for a country that consumes the most cheese and butter in Europe!  Current intakes of saturated fatty acids in the UK are around 12% of energy, and recommended intake is no more than 10% of energy – a reduction from 12% to 10% would be predicted to lower cholesterol by about 0.12 mmol/l, which would translate as a 1.2% reduction in cardiovascular disease risk, whereas increasing saturated fatty acid intake back to the levels prevalent in the 1970s would increase risk by 5%.  There is an analogy here with salt, blood pressure and risk of stroke.  Salt raises blood pressure, and raised blood pressure increases stroke, but the relationship between stroke and salt intake is only seen when the intake is very high.  So, it would seem sensible to continue to recommend an intake of saturated fatty acids close to 10% energy – this can be easily achieved without causing dietary distortions of the overall nutrient balance by opting for dairy products with a reduced fat content.  It is still sensible to hold back on the butter and cream, but we shouldn’t demonise all dairy products.”

1 Khaw KT, Sharp SJ, Finikarides L, Afzal I, Lentjes M, Luben R, Forouhi NG. Randomised trial of coconut oil, olive oil or butter on blood lipids and other cardiovascular risk factors in healthy men and women. BMJ Open. 2018 Mar 6;8(3):e020167.

 

Prof Tim Chico, Professor of Cardiovascular Medicine and Honorary Consultant Cardiologist, University of Sheffield, said:

“The World Heath Organisation has suggested that people eat less than 10% of their calories from saturated fats.  This is because we know from many studies that higher saturated fat intake is associated with higher cholesterol and higher rate of heart disease.  The authors of this opinion piece point out that recent studies have shown not all saturated fats are as harmful as others.  For example, the saturated fat derived from dairy products and dark chocolate may be beneficial, while saturated fat from processed meat is almost definitely harmful and transfats (which are now banned in many countries) are very harmful.

“The new article calls for dietary guidelines to be more specific about what foods are beneficial rather than focusing on single nutrients (such as saturated fat).  This is reasonable but it is simply a difference in emphasis and communication, and the WHO report was not intended as a broad dietary recommendation and only discussed saturated and transfats.  In my view current UK government dietary recommendations are sensible and if followed would improve population health.

“It is challenging to prove scientifically what exact diet is best to reduce heart disease.  However we should be encouraged that our understanding is improving all the time, which will allow future dietary recommendations to be more specific.  I advise people to be reassured about what we already know with great confidence; that a diet high in vegetables, fruit, nuts, seeds, olive oil, and low in processed food, cakes, biscuits, snacks, etc. coupled with regular physical activity slashes the risk of heart disease.”

 

Prof Naveed Sattar, Professor of Metabolic Medicine, University of Glasgow, said:

“Whilst this opinion piece was written by nutritional experts, and some historical points are well made, the overall message is somewhat confusing and contains some areas of inaccuracy.  If people interpret this as meaning ‘no need to reduce saturated fat’ I would worry that could have adverse consequences for public health.  For example, despite what the authors state, that saturated fat intake in excess increases bad LDL-cholesterol levels is not in doubt, and neither is the link between high LDL-c and cardiovascular disease.  We also know LDL-cholesterol is harmful from numerous trials of cholesterol lowering drugs and genetic studies of people with high cholesterol.  Also, the best trials do show lower heart disease with less saturated fats and all other bad heart-relate outcomes appear to be reduced even if the power in some of the analyses were limited.  The authors also state evidence from a mix of selected nutritional trials and observational studies and so it is not easy to assess the objectivity of their points.

“That said, whether some type of saturated fat are not so bad as others needs to be need to be proven by randomised trials using robust markers such as LDL-cholesterol as outcomes.  Without such evidence, no robust conclusions can be made and we will continue to speculate, as this article does.  For the time being, the general advice of cutting saturated fat in diets remains strong and this opinion piece does not change my mind.  Neither does it change my mind on current healthy dietary advice, including diets richer in poly and monounsaturated fatty acids, more fruit and vegetables and cutting down on refined sugars and saturated fats.”

 

Prof Margaret Rayman, Surrey Distinguished Chair and Professor of Nutritional Medicine, University of Surrey, said:

“I think this article is very timely and clearly shows why all saturated fats are not equal.  Although I am not an expert in fats, I am an academic nutritionist and have listened to lectures and read a number of articles (e.g. 1-4), some from authors of this piece, explaining why saturated fats have to be considered against the background of the food matrix in which they occur.  For instance, the calcium in dairy products can form a soap with the fatty acids, increasing faecal fat excretion and reducing absorption.  This is not a new concept – there are papers from the 1930s explaining this fact (5) – though it may have been forgotten from time to time.

“As asserted by the authors whose eminence in this field is well recognised, it is time for us to pay more consideration to foods and less to nutrients.  Indeed, there are many examples of nutrients having a different effect when consumed in whole foods rather than as supplements.”

1 Astrup A, Dyerberg J, Elwood P et al. The role of reducing intakes of saturated fat in the prevention of cardiovascular disease: where does the evidence stand in 2010? Am J Clin Nutr. 2011 Apr;93(4):684-8. doi: 10.3945/ajcn.110.004622. Epub 2011 Jan 26.

2 Soerensen KV, Thorning TK, Astrup A et al. Effect of dairy calcium from cheese and milk on fecal fat excretion, blood lipids, and appetite in young men. Am J Clin Nutr. 2014 May;99(5):984-91. doi: 10.3945/ajcn.113.077735. Epub 2014 Mar 12.

3 Thorning TK, Bertram HC, Bonjour JP et al. Whole dairy matrix or single nutrients in assessment of health effects: current evidence and knowledge gaps. Am J Clin Nutr. 2017 May;105(5):1033-1045. doi: 10.3945/ajcn.116.151548. Epub 2017 Apr 12.

4 Guo J, Givens DI, Astrup A et al. The Impact of Dairy Products in the Development of Type 2 Diabetes: Where Does the Evidence Stand in 2019? Adv Nutr. 2019 May 24. pii: nmz050. doi: 10.1093/advances/nmz050. [Epub ahead of print]

5 Boyd, O.F., Crum, C.L., and Lyman, J.F. (1932). The absorption of calcium soaps and the relation of dietary fat to calcium utilization in the white rat. J. Bioi. Chern. 95: 29-41.

 

* ‘WHO draft guidelines on dietary saturated and trans fatty acids: time for a new approach?’ by Arne Astrup et al. will be published in The BMJ at 23:30 UK time on Wednesday 3 July 2019, which is also when the embargo will lift. 

DOI: 10.1136/bmj.l4137

 

Declared interests

Prof Judith Buttriss: “Professor Buttriss has been a member of UK government expert/advisory committees considering topics such as nutrient profiling, food based dietary guidelines and dietary surveys.  As Director General of the British Nutrition Foundation (BNF – a UK charity that engages with healthcare professionals, academics, schools, government, the food industry and the media), she provides advice on a variety of nutrition and food related matters to stakeholders across the nutrition sector, including a range of food/beverage companies (all fees are paid directly to BNF).  BNF’s funding comes from a variety of sources including EU projects; contracts with national government departments and agencies; conferences, publications and training; membership subscriptions; donations and project grants from food producers and manufacturers, retailers and food service companies; and funding from grant providing bodies, trusts and other charities.  BNF is not a lobbying organisation nor does it endorse any products or engage in food advertising campaigns.  More details about BNF’s work, funding and governance can be found at www.nutrition.org.uk/aboutbnf.”

Prof Nita Forouhi: “Member of ILSI-Europe Expert Group on a one-off review on an update on the health effects of different saturated fats.  This is an invited, unpaid, expert scientific role with no payments made for time, travel or personally.”

Prof Tom Sanders: “Honorary Nutritional Director of HEART UK.  Scientific Governor of the British Nutrition Foundation.  He is now emeritus but when he was doing research at King’s College London, the following applied: Tom does not hold any grants or have any consultancies with companies involved in the production or marketing of sugar-sweetened drinks.  In reference to previous funding to Tom’s institution: £4.5 million was donated to King’s College London by Tate & Lyle in 2006; this funding finished in 2011.  This money was given to the College and was in recognition of the discovery of the artificial sweetener sucralose by Prof Hough at the Queen Elizabeth College (QEC), which merged with King’s College London.  The Tate & Lyle grant paid for the Clinical Research Centre at St Thomas’ that is run by the Guy’s & St Thomas’ Trust, it was not used to fund research on sugar.  Tate & Lyle sold their sugar interests to American Sugar so the brand Tate & Lyle still exists but it is no longer linked to the company Tate & Lyle PLC, which gave the money to King’s College London in 2006.  Tom also used to work for Ajinomoto on aspartame about 8 years ago.  Tom was a member of the FAO/WHO Joint Expert Committee that recommended that trans fatty acids be removed from the human food chain.  Tom has previously acted as a member of the Global Dairy Platform Scientific Advisory Panel and Tom is a member of the Programme Advisory Committee of the Malaysian Palm Oil Board.  In the past Tom has acted as a consultant to Archer Daniel Midland Company and received honoraria for meetings sponsored by Unilever PLC.  Tom’s research on fats was funded by Public Health England/Food Standards Agency.”

Prof Tim Chico: “No conflicts.”

Prof Naveed Sattar: “No COI.”

Prof Margaret Rayman: “I have no competing interests.”

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