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An editorial published in the journal Open Heart has argued for the importance of balancing omega-6 (such as from cooking oils or eggs) and omega-3 (such as from oily fish) fatty acids in the prevention and management of obesity.
Dr Nita Forouhi, Programme Leader, MRC Epidemiology Unit, University of Cambridge, said:
“The authors’ attempt to combine a review of history and biology is commendable but their inclusion of prior research seems selective, not systematic, and this can be misleading. I agree with the authors when they make a valid point about the importance of including information from blood circulating fatty acids, so that both dietary intake and the body’s metabolic processes can be taken into account. But, they don’t then go on to discuss the studies that have done so, and have in fact found results that are at variance with their central points.
“In our 8-country study with the world’s largest resource of type 2 diabetes, we found that higher circulating blood levels of linoleic acid (the most abundant omega-6 fatty acid) were related with lower risk of future diabetes. In our study, arachidonic acid (another omega-6 fatty acid) was not related with diabetes risk, but in other research that was a pooling of all available studies, higher arachidonic acid levels were related with lower future heart disease risk.
“For sure more research is still needed, but there is no convincing reason to go against the current advice about the potential benefits of polyunsaturated fatty acids, both omega-3 and omega-6 types.”
Prof. Naveed Sattar, Professor of Metabolic Medicine, University of Glasgow, said:
“Sadly, there is no easy cure to the obesity epidemic and whilst this editorial tries to place the blame on overeating one type of polyunsaturated fat versus oily fish-based fats, it does so on very weak scientific evidence.
“Strong evidence, however, shows us a calorie is a calorie and obesity stems from the overconsumption of calories, so we can become overweight by eating or drinking a wide range of foods in excess of the calories we burn. For most folk, excess intakes stem from excess intake of fats in general.
“We need as a society to stop looking for miracles cures for the obesity epidemic and face the fact that there are simply too many cheap and tasty products – fatty, or sweet, or both – widely available to all in society. Only a radical shift away from unhealthy to healthier food products, and differential pricing (making healthy food cheaper and making unhealthy food more expensive) will make any big inroads to obesity levels. Everything else is a distraction.”
Dr Ian Johnson, Nutrition researcher and Emeritus Fellow, Institute of Food Research, said:
“In their opinion piece, Simopoulos and DiNicolantonio call upon public health bodies to establish nutrition policies based on science, but they justify their criticisms by advancing an unproven hypothesis on the adverse effects of omega-6 polyunsaturated fatty acids, derived largely from theoretical arguments and animal studies, as if it were established fact. The work by Wang and co-workers that Simopoulos and DiNicolantonio place at the heart of their argument in fact showed only relatively weak associations between red cell polyunsaturated fatty acid levels and weight gain in humans, and the findings were described by the study’s authors as only ‘suggestive’. Meanwhile other recent human studies suggesting beneficial effects of omega-6 polyunsaturated fatty acids on health are ignored in this editorial.
“A case can be made for further research on this issue but it is highly unlikely that the huge and complex problem of obesity in the modern world can be solved by focusing on polyunsaturated fatty acids, or indeed any other single dietary component.”
Dr Gunter Kuhnle, Associate Professor in Nutrition and Health, University of Reading, said:
“An editorial should be seen as what it is: an opinion piece by experts in the field which comments on current issues. Editorials are often biased and strongly opinionated, rather than a balanced overview of the evidence – and this is of course no exception.
“It is part of the normal scientific process to question long-held beliefs – and editorials are an ideal way to move this process forward. Dietary recommendations are of course no exception and it is right to question whether they’re still up-to-date – but this must be done with data, evidence and analysis; not just with opinion.
“The authors are of course correct if they demand that governments base their dietary recommendations and nutritional policies on science: but this is exactly what is happening. In the UK, Public Health England conducts reviews of the data available and bases recommendations on those – in a very transparent process.”
Prof. Tom Sanders, Professor emeritus of Nutrition and Dietetics, King’s College London, said:
“This article attributes the obesity epidemic to the increased use of high linoleic (omega-6) vegetable oils such as corn, safflower, soybean and sunflower seed oils, which they claim cause an imbalance in the ratio of omega-6 to omega-3 fatty acids in the diet – the omega-3 fatty acids being derived mainly from fish oil but also from some vegetable oils. Surprisingly, the article fails to mention palm oil, which is not high in linoleic acid, but accounts for 55% of world vegetable oil production and has seen the biggest increase in production over the last twenty years.
“However, only about 20% of dietary fat is derived from vegetable oils and most of the fat in the Western diet is still derived from food of animal origin, especially meat and dairy (butter fat removed from skimming milk re-enters the food supply in cakes, biscuits and pastry). If vegetable oils were such an important contributor to obesity, one would expect that vegetarians and vegans would be fatter (they have high ratios of omega-6: omega-3 fatty acids in their diets) whereas in fact they are leaner than meat-eaters.
“The article wrongly suggests that the increase in the ratio of omega-6: omega-3 fatty acids in human diets coincides with the obesity epidemic. The ratio increased in the 1970-1980s but has been either been relatively stable or more likely has fallen over the past two decades, during which obesity has rocketed. Indeed, food manufacturers have actively sought to lower the ratio mainly because of emerging evidence regarding the health benefits of omega-3 fatty acids with regard to cardiovascular disease and visual function. This is very evident from the composition of high in polyunsaturated fatty acid margarine in the 1980s compared to nowadays, where the ratio has dropped from 131:1 to 4:1. There has also been increased use of new high oleic varieties of sunflower oil and soybean oil for deep fried foods as well as increased usage of rapeseed oil (Canola), which has a relative low ratio. The phasing out of partial hydrogenation of vegetable oils would also have lowered the ratio.
“The article claims that lowering the omega-6: omega-3 ratio would increase sensitivity to insulin and leptin which in turn contributes to regulating appetite and increasing energy expenditure. However, the evidence cited is all based on mice fed extreme diets containing large amounts of fish oil. We conducted a six month long randomized controlled trial in 258 older men and women and found no effect of lowering the ratio of omega-6 to omega-3 fatty acids on insulin sensitivity or body weight1. A Food Standards Agency review of this study and other similar studies concluded that focusing on ratio was of little value2.
“Obesity only results when more food energy is consumed than is expended, which the authors resolutely seem to deny. In my opinion, the ratio of omega-6 to omega-3 fatty has little relevance to the modern obesity epidemic but has far more to do with the way that people live and eat in metropolitan areas.”
1: Griffin MD, Sanders TA, Davies IG, Morgan LM, Millward DJ, Lewis F, Slaughter S, Cooper JA, Miller GJ, Griffin BA. Effects of altering the ratio of dietary n-6 to n-3 fatty acids on insulin sensitivity, lipoprotein size, and postprandial lipemia in men and postmenopausal women aged 45-70 y: the OPTILIP Study. Am J Clin Nutr. 2006 Dec;84(6):1290-8.
2: Stanley JC, Elsom RL, Calder PC, Griffin BA, Harris WS, Jebb SA, Lovegrove JA, Moore CS, Riemersma RA, Sanders TA. UK Food Standards Agency Workshop Report: the effects of the dietary n-6:n-3 fatty acid ratio on cardiovascular health. Br J Nutr. 2007 Dec;98(6):1305-10.
‘The importance of a balanced ω-6 to ω-3 ratio in the prevention and management of obesity’ by Artemis P Simopoulos and James J DiNicolantonio published in Open Heart on Monday 24 October 2016.
Declared interests
Dr Nita Forouhi: “No conflict of interest.”
Prof. Naveed Sattar: “No COI.”
Dr Ian Johnson: “No conflict of interests to declare.”
Dr Gunter Kuhnle: “Associate Professor at the University of Reading.
Grant funding: Investigation of links between polyphenol intake and health – EU, Mars, Horizon.
Appointments: EFSA Working group – risk assessment of soy isoflavones.
Memberships: British Mass Spectrometry Society, British Nutrition Society, Registered Nutritionist (Reg. Nr. 8236); 2011 to 2012 member of ‘Biomarker group’ at ILSI Europe.
Other financial interests: Vineyard owned by family.”
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.”