Intended for healthcare professionals

Observations From the Heart

Saturated fat is not the major issue

BMJ 2013; 347 doi: (Published 22 October 2013) Cite this as: BMJ 2013;347:f6340

Re: Saturated fat is not the major issue

It is well established that saturated fat increases LDL cholesterol. However in comparison to carbohydrates saturated fat also raises HDL cholesterol and reduces triglycerides with little effect on the total cholesterol :HDL ratio which is considered a better predictor of CHD events than total cholesterol alone. 1,2

The food source of saturated fat may have greater relevance. Most recently Otto et al revealed that a higher intake of dairy saturated fat was associated with a lower CVD risk but meat intake with an increased risk in the multi-ethnic study of atherosclerosis.3

Although there is evidence to support the replacement of saturated fat with polyunsaturated fat in reducing CHD events, this benefit may be more specific to omega 3, with higher omega 6 PUFA’s found commonly in industrialised vegetable oils implicated in pro-inflammatory, atherogenic oxidised LDL. This may explain why a re-analysis of unpublished data in the Sydney Heart study revealed that cardiac patients that replaced butter with omega 6 containing safflower oil and safflower oil containing margarine had increased all cause and cardiovascular mortality despite a 13% reduction in total cholesterol in this group.

Furthermore the exploitation of an unhelpful “low fat” mantra by the food industry has resulted in dietary prescriptions that have resulted in high refined carbohydrate diets, worsening obesity and fuelling atherogenic dyslipidaemia, a metabolic state defined by increased triglycerides, reduced HDL cholesterol and increased proportions of small dense LDL particles. A reduction in carbohydrate intake but not saturated fat appears to improve this dyslipidaemic profile.4

And two thirds of people admitted to hospital with acute myocardial infarction now qualify for a diagnosis of metabolic syndrome, with a 50% increased risk of mortality or rehospitalisation at one year.5

An over obsession with total calories consumed as opposed to the nutritional value of those calories has also proved be unhelpful and has been exploited by the food industry with the addition of cheap sugar to many processed foods. A 9 tea spoon sugared cola has less than 150 calories, but according to the EPIC study drinking just one can a day increased the risk of type 2 diabetes independent of BMI. Conversely the consumption of 4 table spoons of extra-virgin olive oil per day, approximating to 500 calories, as recommended in the PREDIMED study intervention arm significantly reduced heart attack and stroke risk. It’s perhaps instructive to note after a 2 year review of 16,000 studies Sweden has just become the first western nation to reject the “low fat” dietary dogma advocating a diet that is high fat and low in refined carbohydrates as the best for cholesterol profile and weight loss. Promoting a Mediterranean diet to reduce CVD risk and cognitive decline whilst simultaneously reducing population processed food and added sugar intake, which unlike fat and protein has no nutritional value, is the single dietary contributor to dental caries, and is driving the diseases of the metabolic syndrome may offer the best dietary solution to improving public health.

1. Mensink RP, Zock PL, Kester AD, Katan MB. Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials. Am J Clin Nutr 2003;77:1146–55.

2. Assmann G, Schulte H, von Eckardstein A, Huang Y. High-density lipoprotein cholesterol as a predictor of coronary heart disease risk. The PROCAM experience and pathophysiological implications for reverse cholesterol transport. Atherosclerosis 1996;124(suppl):S11–20.

3. de Oliveira Otto MC, Mozaffarian D, Kromhout D, Bertoni AG, Sibley CT, Jacobs DR Jr, Nettleton JA. Dietary intake of saturated fat by food source and incident cardiovascular disease: the Multi-Ethnic Study of Atherosclerosis.
Am J Clin Nutr. 2012 Aug;96(2):397-404. doi:10.3945/ajcn.112.037770.Epub 2012 Jul 3.

4. Krauss RM, Blanche PJ, Rawlings RS, Fernstrom HS, Williams PT Separate effects of reduced carbohydrate intake and weight loss on atherogenic dyslipidemia. Am J Clin Nutr 2006;83:1025–31,

5. Arnold SV, Lipska KJ, Li Y, Goyal A, Maddox TM, McGuire DK, et al.The accuracy and prognosis of in-hospital diagnosis of metabolic syndrome in patients with myocardial infarction. Prediabetes and the Metabolic Syndrome 2013 Congress, 20 April 2013.

Competing interests: No competing interests

14 November 2013
Aseem Malhotra
Cardiology Specialist Registrar
Croydon University Hospital