SACN report on saturated fats and health published today

Following a consultation on a draft report, which came out in 2018, the final report on saturated fats and health from the Scientific Advisory Committee on Nutrition (SACN) has been published today.

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SACN report on saturated fats and health published today

Following a consultation on a draft report, which came out in 2018, the final report on saturated fats and health from the Scientific Advisory Committee on Nutrition (SACN) has been published today. The report looks at the effect of saturated fat, and replacement of saturated fat with different nutrients on a number of health outcomes.

Based on 47 systematic reviews and meta-analyses SACN concluded that:

  • higher saturated fat consumption is linked to raised blood cholesterol
  • higher intakes of saturated fat are associated with increased risk of heart disease
  • saturated fats should be swapped with unsaturated fats
  • there is no need to change current advice that saturated fat should not exceed around 11% of food energy.

Based on the findings, the report supports and strengthens the current recommendation that foods high in saturated fat should be eaten less often and in smaller amounts and that we should swap to unsaturated fats as part of a healthy balanced diet.

The effect of saturated fat on health has been hotly debated in recent years (see here for further details) and the relationship between saturated fat and cardiovascular disease (CVD) has been called into question. As the SACN report highlights, we have evidence from clinical trials that replacing saturated fat with unsaturated fats (especially polyunsaturated fats) can have a beneficial effect on blood cholesterol levels and CVD risk.

However, whilst blood cholesterol, along with other ‘classical’ modifiable CVD risk factors such as smoking, blood pressure and obesity, remain influential, they are not the whole story when it comes to determining our risk of CVD. The more emerging risk factors that are also understood to play a role in heart disease and stroke were reviewed in the recently published BNF Task Force report Cardiovascular Disease: Diet, Nutrition and Emerging Risk Factors. The report explores areas including inflammation, endothelial function and platelet activity and for each of these, replacing saturated with unsaturated fat had a beneficial effect, demonstrating that the type of fat in the diet is not only important in relation to blood cholesterol.

According to the most recent NDNS data, although intake of saturated fat has fallen over the past 30 years UK intakes remain above recommended levels for all population groups. So the report published today suggests that public health advice should continue to promote cutting back on key contributors to saturated fat in the diet such as fatty meats, pastry, higher fat dairy products, cakes and biscuits. It’s important to remember that we consume foods and drinks, not single nutrients like saturated fat. In order to reduce our risk of cardiovascular disease as well as other chronic diseases, it’s important to eat a healthy dietary pattern. The UK Eatwell Guide provides guidance on the proportions of different food groups that make up a healthy diet and this can be applied to suit different dietary patterns including the plant-based and Mediterranean diets, which have been shown in many studies to reduce CVD risk. More information about a healthy diet and lifestyle to reduce risk of CVD available here.

Details from the SACN report

The terms of reference for this report were for SACN to:

  • Review the evidence for the relationship between saturated fats and health and make recommendations
  • Review the evidence for the association between saturated fats and key risk factors and health outcomes at different life stages for the general UK population.

The health outcomes reviewed were:

  • Cardiovascular mortality
  • Cardiovascular events (coronary heart disease (CHD), stroke, peripheral vascular disease)
  • Type 2 diabetes
  • Selected common cancers (colorectal, pancreatic, lung, breast and prostate cancers)
  • Cognitive impairment and dementias (including Alzheimer’s disease).

Intermediate markers and risk factors reviewed were:

  • Blood lipids (total cholesterol, LDL-cholesterol, HDL-cholesterol, total:HDL cholesterol and triacylglycerol.
  • Blood pressure (systolic and diastolic).
  • Markers of glycaemic control (fasting blood glucose, fasting insulin, glycated haemoglobin (HbA1c), glucose tolerance and insulin resistance (assessed by HOMA or infusion tests).
  • Anthropometric measures such as weight change, Body Mass Index (BMI), waist circumference, and gestational weight gain.
  • Cognitive function (cognitive decline, mild cognitive impairment).

Systematic reviews, meta-analyses and pooled analyses of either randomized controlled trials (RCTs) or prospective cohort studies that met the Committee’s inclusion criteria were considered and evidence was graded as adequate, moderate, limited, inconsistent, or insufficient. Only evidence graded as adequate or moderate was used to inform the recommendations.

The key findings are summarised below, based on the evidence from RCTs unless specified otherwise. Only findings based on either adequate or moderate evidence as described in the report are included below. Further details on the level of evidence and considerations in each case are available in the SACN report.

Reducing intake of saturated fat may:

  • Reduce the risk of CVD and CHD events (RCTs did not find an effect on mortality, however follow up in the studies may have been too short to detect this).
  • Reduce total cholesterol and LDL cholesterol and also (in adults) HDL cholesterol (no effect on triacyglycerol).
  • No clear evidence for an effect on blood pressure, stroke, type 2 diabetes, measures of glycaemic control, anthropometric measures, the cancer types considered or cognitive outcomes.

 

Replacing saturated fats with polyunsaturated fats may:

  • Reduce risk of CVD and CHD events (but not mortality – see comment above).
  • Reduce total cholesterol and LDL cholesterol (no effect on HDL cholesterol).
  • Reduce fasting glucose, HbA1c and insulin resistance.

No clear evidence for an effect on blood pressure, stroke, type 2 diabetes, anthropometric measures, the cancer types considered or cognitive outcomes.

 

Substituting saturated fats with monounsaturated fats may:

  • Reduce total cholesterol and LDL cholesterol (no effect on HDL cholesterol).
  • Reduce HbA1c and insulin resistance but also associated with an increase in fasting insulin.

No clear evidence for a reduction in CVD, CHD or stroke mortality or events (there were fewer studies available on monounsaturated fats compared with polyunsaturated fats) or for an effect on blood pressure, stroke, type 2 diabetes, anthropometric measures, the cancer types considered or cognitive outcomes.

Substituting saturated fats with carbohydrates may:

  • Increase the risk of CHD events based on some evidence from prospective cohort studies (but not based on evidence from RCTs see further comments below).
  • Reduce total and LDL cholesterol but also HDL cholesterol.
  • Increase triacylglycerol
  • Increase fasting insulin.

No clear evidence for reduction in CVD , CHD or stroke mortality or events and no effect on blood pressure, type 2 diabetes or other measures of glycaemic control, stroke, anthropometric measures, the cancer types included or cognitive outcomes.

Substituting saturated fats with protein (see further comments below)

SACN found no evidence for an effect of substituting saturated fats with protein on outcomes reviewed.

Abbreviations: CVD – cardiovascular disease, CHD – coronary heart disease, LDL – low density lipoprotein, HDL – high density lipoprotein, HbA1c – refers to glycated haemoglobin

Recommendations

The report highlights that the evidence base on saturated fats and health has increased considerably since 1994, when previous recommendations were published. There is now a significant body of research on the effect of different fatty acids on blood lipid profiles as well as other intermediate factors, risk markers and health outcomes.

These findings support and strengthen the evidence for current public health nutrition advice to reduce our consumption of saturated fat and replace foods rich in saturated with those with a higher proportion of unsaturated fat. Importantly, the report also found that reducing saturated fat intake was unlikely to increase health risks for the UK population.  The report found evidence that reducing saturated fat and replacing it with polyunsaturated fats improved blood lipid profiles and reduced the risk of CVD and CHD events. In the case of replacing saturated fats with polyunsaturated fats, there was also some evidence that this could improve some aspects of glycaemic control. There was less evidence for beneficial effects of replacing saturated fats with monounsaturated fats although there did appear to be beneficial effects on blood lipids.

The report concludes that the current recommendation that saturated fatty acids should make up no more than 10% of total dietary energy (11% of energy from food and drink, excluding alcohol) should be upheld and that saturated fats are substituted with unsaturated fats (poly or monounsaturated fats). While the report did not look specifically at older adults or children under 5 years they state that there’s no reason to assume that these recommendations cannot apply and therefore they apply to the population as a whole. As all age groups are currently consuming more than 10% of total energy from saturated fats, this means that strategies to reduce our intakes are recommended.

In relation to replacing saturated fats with carbohydrate, the report generally did not find evidence that this was beneficial on any of the outcomes in question and even found a potential increased risk of heart disease events. This was based on evidence from a pooled analysis of prospective cohort studies (Jakobsen  et al. 2009). It should be noted, however, that this study did not look at the impact of different types of carbohydrate or carbohydrate-rich foods or drinks, but only total carbohydrate. Looking at the impact of replacing saturated fats with different types or sources of carbohydrate was not within the scope of this report. There have been some studies however, that have found that replacing SFA with wholegrains reduced CVD risk (see Briggs et al 2017 for a review). It is also worth noting that in its report on carbohydrates and health, SACN found evidence that both dietary fibre and wholegrains were associated with a lower risk of CVD as well as having beneficial effects on a number of other health outcomes.  

While SACN found no evidence for a significant effect of replacing saturated fats with protein, again this may depend on the source of protein (plant vs animal), which was outside the scope of the report. While some studies indicate that replacing saturated fats with animal protein may increase risk of CVD (Briggs et al. 2017), one study, using two large cohorts has suggested that replacing saturated fats with plant protein may reduce risk of CHD (Zong et al. 2016).

For replacement of saturated fats with both carbohydrates and protein, more research is needed to help us understand the potential impact of replacement with different types and food sources on health.

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