November 23, 2016

expert reaction to study looking at saturated fats and coronary heart disease risk

Scientists publishing in the British Medical Journal have reported a high intake of saturated fats could be linked to increased coronary heart disease risk.

Dr Nita Forouhi, Programme Leader, MRC Epidemiology Unit, University of Cambridge, said:

“Despite the usual caveats of observational studies and limitations of dietary measurement which the authors clearly acknowledge, this is an important contribution from the US-based study among nurses and doctors.

“The study findings provide clear support for dietary guidelines that advocate the benefits of replacing dietary energy from saturated fats with that from polyunsaturated fats, as well as from whole grain carbohydrates and plant source proteins.

“The authors included fat intake made up of even-chained fatty acids, which are major contributors to total fat intake, but a particular omission that is of great interest is the role of odd-chain fatty acids with 15 and 17 carbon atoms that derive largely from dairy products.

“Research from us and others has shown that some dairy products (such as yoghurt) and odd-chain fatty acids circulating in the blood seem to have health benefits rather than health harms, and this requires further study.

“While it is crucial to firm up the evidence for nutrients like different types of fats, the quality of carbohydrates and protein, which this article does, the editorial from the Canadian authors helpfully makes the highly important point that it is foods and overall dietary patterns that should be the focus rather than nutrients themselves.”

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

“This is an important and timely study that provides further detail on an earlier publication by the same group which showed that replacing saturated with unsaturated fats, whole grain carbohydrates or plant proteins is associated with a lower risk of death from cardiovascular disease as well as all-cause mortality. The detail provided in this new study is on the effects of individual saturated fatty acids.

“Raised low density lipoprotein (LDL) cholesterol is an important factor contributing to the risk of heart disease. It is well established that saturated fatty acids with chain lengths between 12-16 carbons raise LDL cholesterol, but shorter or longer chain fatty acids do not have this effect. This has resulted in some countries such as France not including stearic acid (C18) or short chain saturated fatty acids (C4-C10) in their dietary recommendations to reduce saturated fats in their cardiovascular disease prevention guidelines; butter fat is a major source of those fatty acids and the French consume more butter and cheese than other European countries.

“As expected, in this study C12-16 fatty acids were associated with increased risk of heart disease, but so was stearic acid (C18).  However, stearic acid is also found in high amounts in beef fat and hydrogenated soybean oil which is widely used in the USA.  This might explain some of the differences between the USA and Europe.

“Most saturated fat in the diet comes from meat and meat products.  The other important category is dairy, and then compound foods such as cakes, biscuits and pastries, which tend to use high melting point fats such as lard or vegetable shortening which are high in saturated fatty acids. The sources of saturated fat may be important, with meat fat being more harmful than dairy. There is growing evidence from other research that dairy foods such as milk, yoghurt and cheese are not associated with increased risk of cardiovascular disease and may be protective. This might explain why the Dutch study referred to in the Editorial found different effects; the Dutch are big consumers of milk and cheese.

“One limitation of this study is that it did not consider the association of C15 and C17 saturated fatty acids – which are markers of dairy fat intake – with risk. A previous meta-analysis has found these fatty acids to be associated with lower rather than higher risk.

“This study found that replacing saturated fats with either unsaturated fats, whole grain carbohydrates or plant proteins was beneficial – there are no significant differences between the different types of substitution in terms of which of these three it’s better to replace the saturated fat with.

“In my opinion, the bottom line of this study is that it is important to focus replacing saturated fatty acids with healthier unsaturated fats or unrefined carbohydrates, which is in line with current dietary guidelines.  So, choose lean cuts of meat, chicken, fish and vegetable protein alternatives (nuts and beans), where possible use reduced-fat dairy, restrict the intake of cakes, biscuits and pastries, and use oils high in unsaturated fatty acids such olive or rapeseed oil for cooking or in salad dressings, and spreads with a reduced saturated fatty acid and a higher polyunsaturated fatty acid content, rather than butter.”

Dr Amelia Lake, state registered dietitian and registered nutritionist, and Lecturer in Knowledge Exchange in Public Health, Durham University, said:

“This large study emphasises the need to swap the less healthy fats (saturated fats) from our diet and replace them with healthier fats – think Mediterranean diet.

“This research is from a high quality large study with a long follow up and repeated measures.  The study is not without some limitations, but that is the nature of this work.

“We need to think about foods and focus less on nutrients.  We don’t eat nutrients, we eat food and we need to eat food with a healthy nutrient profile.

“The key message is to eat less saturated fat (hard fats like lard, butter, fats on meat, and fats found in fatty meat products, pastries, cakes, biscuits, full fat dairy foods and less healthy take-away foods, palm oil, coconut oil and cream) and to eat more polyunsaturated fat (plant based oils like sunflower oils, rapeseed oil, oily fish), and whole grain carbohydrates (brown rice, oats, whole wheat and whole wheat flour, whole rye and whole rye flour).”

‘Intake of individual saturated fatty acids and risk of coronary heart disease in US men and women: two prospective longitudinal cohort studies’ by Geng Zong et al. published in the BMJ on Wednesday 23 November 2016.

Declared interests

Dr Nita Forouhi: “No COI.”

Prof. Tom Sanders: “Prof Tom Sanders is a Scientific Governor of the charity British Nutrition Foundation, member of the scientific advisory committee of the Natural Hydration Council (which promotes the drinking of water), and honorary Nutritional Director of the charity HEART UK.

Prof Tom Sanders 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.”

Dr Amelia Lake: “No conflicts of interest.  Grant funding from NIHR.  Member of British Nutrition Foundation scientific committee.”