The study, published in the British Medical Journal (BMJ), analysed data from more than 115,000 people in two long term cohort studies to investigate the potential associations between individual saturated fatty acids and the long-term risk of coronary heart disease.
Performed jointly by researchers from Harvard T.H. Chan School of Public Health (HSPH) in the USA and Unilever’s Research & Development group in the Netherlands, the analysis reiterates previously identified associations between an increased intake of saturated fats and increased risk of coronary heart disease.
However, it goes further than previous studies by identifying links between specific saturated fatty acids – including stearic acid, which some countries such as France do not currently include in saturated fat legislation.
“Owing to similar associations and high correlations among individual saturated fatty acids, dietary recommendations for the prevention of coronary heart disease should continue to focus on replacing total saturated fat with more healthy sources of energy,” said the team, led by senior author Dr Qi Sun from HSPH.
Commenting on the study findings, Professor Tom Sanders of King’s College London said the results are “important and timely” in that they provide further detail on earlier publications.
“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,” said Sanders – noting that butter fat is a major source of such fatty acids and that 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),” Sanders added.
In addition to outlining the risks from specific saturated fats, the Dutch-US research team also found that replacing just 1% of energy consumed in the form of saturated fats with polyunsaturated fats, monounsaturated fats, wholegrain carbohydrates or plant proteins, led to a 5-8% decreased risk of coronary heart disease.
“[The] risk of coronary heart disease is significantly lower when replacing the sum of these four major saturated fatty acids,” said the authors of the study – adding that current dietary recommendations and industry reformulation efforts should focus on replacing total saturated fat with unsaturated fats or whole grain carbohydrate as an effective approach towards preventing coronary heart disease.
“Collectively, our study supports current dietary guidelines that focus on reducing total saturated fat intake with unsaturated fats, which for example, can be achieved by replacing animal fats (eg, butter, lard) with vegetable oils high in unsaturated fat (eg, olive oil, canola oil),” Dr Qi Sun and colleagues commented.
They noted that certain snacks (such as crackers, chips, and popcorn) in addition to bakery products and table spread are also important dietary sources of saturated fatty acids, which should be a focus for reformulation.
“These foods are produced not only by food industry but also by small scale workshops (such as bakeries), restaurants, and home cooking,” they added.
What about dairy?
While the current study adds further weight to the links between longer chain saturated fatty acids —including lauric acid (12:0), myristic acid (14:0), palmitic acid (16:0), and stearic acid (18:0)— and coronary heart disease, both Professor Sanders and Dr Nita Forouhi from the MRC Epidemiology Unit at University of Cambridge note that the study fails to investigate the links between the saturated fats found in dairy – which have previously been linked to reductions in heart disease risk despite being classified as a saturated fat.
“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,” said Forouhi.
“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.”
Published online, Number 555, doi: 10.1136/bmj.i5796
“Intake of individual saturated fatty acids and risk of coronary heart disease in US men and women: two prospective longitudinal cohort studies”
Authors: Geng Zong, et al