December 15, 2025

expert reaction to systematic review study looking at saturated fat intake and cardiovascular disease events

A systematic review published in Annals of Internal Medicine looks at saturated fat intake and cardiovascular events. 

Prof Nita Forouhi, Professor of Population Health and Nutrition, MRC Epidemiology Unit, University of Cambridge, said:

“The authors acknowledged several prior systematic reviews of saturated fat and cardiovascular disease or mortality, but justified their current analysis based on making methodological improvements, which, I agree, is true for some issues and a positive step.  However, they also introduced some new methodological challenges that limit interpretation.

“They differentiated between individuals with low vs. high baseline CVD risk and evaluated the absolute risk reduction for CVD or mortality outcomes at 5 years.  They did not consider any systematic differences by baseline risk groups nor what may happen over a longer time horizon of 10 years, which is out of step with typical CVD risk prediction algorithms that are used in clinical practice.  A sensitivity analysis with comparative results at 10 years is important to inform this gap as 5 years may be too short to capture meaningful differences in CVD events or mortality especially in low- risk individuals.

“The inclusion criteria for individual RCTs were much more permissive in this meta-analysis than some other meta-analyses that included, for instance, only four RCTs as eligible core trials.  Their current approach increases sample size and the range of intervention criteria and trial designs, but this comes at the cost of including, for instance, the Women’s Health Initiative (WHI) study (the biggest study that they included by several fold), which is not a trial of saturated fat.  In the WHI study the goal was to reduce total fat, and as the authors acknowledge, the “low-fat” intervention diet reduced SFA intakes modestly but also reduced the “beneficial” MUFA and PUFA to a similar or greater degree.  Moreover, in the WHI study the replacement nutrient when reducing SFA was not PUFA – the current public health recommendation – but carbohydrates.

“For these methodological reasons it is premature to consider any change to the existing dietary guidelines that recommend saturated fat reduction to under 10% of energy intake in the UK.  Importantly, there is increasing knowledge from our own research and that of others that saturated fat is a complex entity, and it is not all the same – its health effects vary by saturated fat sub-types and its food sources.  For example, saturated fat in red or processed meat vs that in fermented dairy (yoghurt, cheese) exerts different health effects.  The focus needs to shift from the nutrient as the sole consideration to the foods that the nutrient comes from.”

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

“This study is a re-analysis of randomized controlled trials of saturated fat reduction on cardiovascular mortality.  Overall, there was a trend for a reduction in risk with decreasing saturated fatty acid intake, but it did not achieve statistical significance.  However, in subjects judged at high-risk, there was a statistically significant benefit of replacing saturated fatty acids with polyunsaturated fatty acids.  No effect in low-risk individuals could be detected.

“The limitations of the review are as follows:

“1. Most of the studies were conducted in the 1960-1970s in USA, Europe and Australia when intakes of saturated fat were much higher (e.g. 18-20% food energy compared to 11-13% nowadays).  Most of these studies had fewer than 1000 participants and these were mainly in people with pre-existing cardiovascular disease who are at much greater risk of events or death from cardiovascular disease.

“2. A much large number of participants is required to demonstrate a benefit in people of average risk.  The Women’s Health Initiative (29,294 women) was the only study with sufficient statistical power to detect an effect.  This study showed no benefit on cardiovascular disease mortality.  However, it was a trial of a low-fat diet (not saturated fatty acid reduction) to prevent breast cancer not cardiovascular disease.  There are no comparable studies in men.

“3. The definition of high risk used in this study was used to describe participants who had already cardiovascular disease rather than one of the algorithms currently used such as QRISK-3.  This is important because individuals can be at high risk if they have not had a cardiovascular event and absolute risk increases greatly with age.

“Interpretation:

“Population dietary advice is aimed at lowering the average cholesterol level (or more specifically non-HDL cholesterol) because it decreases the progression of atherosclerosis and population risk of cardiovascular disease.  Saturated fatty acid reduction in many countries has contributed to the fall in non-HDL cholesterol over the past 50 year.  In the UK saturated fat intakes fell from 20% energy in 1970s to 13% energy nowadays.  The population average cholesterol and non-HDL cholesterol has also fallen and much of the fall occurred before statins started to be prescribed.  This reduction can be attributed to the reduction in saturated fatty acid intake.  For individuals at high risk of cardiovascular disease, statins are far more effective at lowering non-HDL cholesterol than diet.  However, maintaining a lower saturated fat intake is beneficial in terms of cardiovascular disease prevention not just for those at high risk but for the whole population.”

‘Effect of Interventions Aimed at Reducing or Modifying Saturated Fat Intake on Cholesterol, Mortality, and Major Cardiovascular Events: A Risk Stratified Systematic Review of Randomized Trials’ by Jeremy P. Steen et al. was published in the Annals of Internal Medicine at 22:00 UK time on Monday 15 December 2025. 

DOI: 10.7326/ANNALS-25-02229

Declared interests

Prof Nita Forouhi: “I have no conflicts of interest to declare.”

Prof Tom Sanders: “Relevant conflicts of interest are HEART UK and Malaysian Palm Oil Board.

Full list:

I have received grant funding for research on vegans in the past.  I have been retired for 10 years but during my career at King’s College London, I formerly acted as consultant for companies that made artificial sweeteners and sugar substitutes.

I am a member of the Programme Advisory Committee of the Malaysia Palm Oil Board which involves the review of research projects proposed by the Malaysia government.

I also used to be a member of the Scientific Advisory Committee of the Global Dairy Platform up until 2015.

I did do some consultancy work on GRAS affirmation of high oleic palm oil for Archer Daniel Midland more than ten years ago.

My research group received oils and fats free of charge from Unilever and Archer Daniel Midland for our Food Standards Agency Research.

I was a member of the FAO/WHO Joint Expert Committee that recommended that trans fatty acids be removed from the human food chain.

Member of the Science Committee British Nutrition Foundation.  Honorary Nutritional Director HEART UK.

Before my retirement from King’s College London in 2014, I acted as a consultant to many companies and organisations involved in the manufacture of what are now designated ultraprocessed foods.

I used to be a consultant to the Breakfast Cereals Advisory Board of the Food and Drink Federation.

I used to be a consultant for aspartame more than a decade ago.

When I was doing research at King’ 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.”