- Switch from animal fats to unsaturated vegetable oils e.g., rapeseed, sunflower or olive oil and spreads made from them
- Avoid coconut and palm fat - these are exceptionally high in saturated fat
- Reduce red meat and avoid processed meats - fully or partly replaces with beans, nuts, seeds
- Switch to lower fat dairy options or fortified plant-based alternatives.
- For individuals with FH or at high risk of CVD, dietary cholesterol intakes should be limited to no more than 300mg/day.
Reducing saturated fats and replacing them with unsaturated fats
Dietary fat recommendations for heart health have been reviewed by a number of expert bodies and professional organisations 1-6 with consistent findings:
- Saturated Fatty Acids (SFA) are the dietary factor with the greatest impact on Low Density Lipoprotein Cholesterol (LDL-C).
- SFA should be substituted with unsaturated fatty acids (UFA) – polyunsaturated (PUFA) and monounsaturated (MUFA).
- Reducing SFA per se, or substituting with PUFA, MUFA, or a mixture of the two reduces total and LDL-C.
- Substituting SFA with UFA has no adverse effect on HDL, but simply reducing SFA or substituting with carbohydrate, reduces High Density Lipoprotein Cholesterol (HDL-C).
- Trans fatty acids (TFA) have a similar effect on LDL-C, however, while SFA increase HDL-C), TFA decreases it.
- TFA can be produced industrially by the partial hydrogenation of vegetable and fish oils, but also occur naturally in meat and dairy products from ruminant animals (e.g. cattle, sheep, goats, camels). Industrially-produced TFA can be found in baked and fried foods, pre-packaged snacks and food. TFA from ruminant animals are considered to be of less concern at the typical levels consumed in the diet 7,8 .
- In the UK, voluntary measures by the food industry have resulted in mean TFA intakes in adults and children significantly decreasing. Current intake at 0.5% 9 of food energy is below the recommended maximum for both the UK ( 10 and internationally ( 11 .
In the 2019 review of the evidence examining the impact of saturated fat on health, the Scientific Advisory Committee on Nutrition (SACN) concluded that reducing saturated fat lowers the risk of cardiovascular disease (CVD) and coronary heart disease (CHD), lowers total, LDL-C and HDL-C and improves indicators of glycaemic control. Reducing population averages of SFA from current intake to no more than about 10% of total dietary energy would result in health benefits to the population 3 . Mechanism of action
Research suggests that eating too much SFA impacts the LDL receptors, preventing them from taking up LDL-C from the blood and into the liver to be broken down. The resulting effect is a build-up of LDL-C in the blood 12 .
Why the confusion?
Despite the universal consensus, the question of fat around CVD risk is hotly debated with claims suggesting dietary recommendations to reduce SFA intake have been over exaggerated. Are fats the villains, neutral or the heroes? And which fats have different effects?
The recent controversy has arisen following a couple of recent analyses failing to find an association between SFA and CHD risk 13,14 . However, these findings can be explained by:
- A lack of control over the replacement calories. When saturated fat is reduced, it’s important to consider the substitute nutrient. A Cochrane systematic review of 15 randomised controlled trials, involving almost 60 000 participants, found greater reductions (27%) in CVD events in studies that replaced SFA with PUFA than in studies where SFA was replaced with carbohydrate or protein, where there was little evidence of any effect 4 . Replacing SFA with UFA, and especially PUFA, leads to a reduction in serum LDL-C levels 15 .
- The inclusion of older studies using spreads with higher TFA content. Other limitations of these types of meta-analyses include the use of cohort studies (which show associations but not cause and effect); the differing effects of individual SFA on LDL-C; and the effects of SFA from different foods - the food matrix and nutrients may interact with SFA resulting in different outcomes.
Individual SFAs & their impact on blood lipids
Not all SFA raise cholesterol – Lauric (12:0), Myristic (14:0) and Palmitic (16:0) Acids raise total, LDL-C and HDL-C, while stearic acid (18:0) is considered to have a neutral affect. However replacing stearic acid with unsaturated fat lowers LDL-C. Read the WHO's detailed overview of the impacts of different SFA on cholesterol 4 .
Foods containing SFA usually comprise a combination of SFA (see right), and so their individual differences on serum cholesterol should not affect dietary recommendations to lower overall saturated fat intake and replace with unsaturated fat.
Omega-3 fats
PUFA exist in the n-3 or n-6 isomeric configuration. Both isomers are essential nutrients and have different biological effects. α-Linolenic acid, a dietary n-3 PUFA, is present in soybean and rapeseed oil, walnuts and in very small amounts in some green vegetables. Fish oil contains the very-long-chain n-3 PUFA, eicosapentaenoic acid and docosahexaenoic acid.
Observational evidence indicates that consumption of fish (at least twice a week) and vegetable foods rich in n-3 fatty acids is associated with lower risk of CVD death and stroke but has no major effects on plasma lipoprotein metabolism at this intake 5,16 . However high-dose prescription n-3 supplemental forms may be used to treat hypertriglyceridaemia.
Public health guidance is to eat two portion of fish a week, one of which should be oily, to achieve the SACN recommendations of 0.45g of long chain Omega 3 fatty acids a day 16 . While a recent Cochrane review has questioned the heart health benefits of fish oil supplements 17 , the dietary advice for fish consumption remains.
Dietary cholesterol
Although there is a positive dose-dependent relationship between the intake of dietary cholesterol with blood LDL-C concentrations, the main dietary determinant of blood LDL-C concentrations is SFA intake. As such, public health recommendations do not provide guidance on dietary cholesterol intakes. A good overview on the effects of dietary cholesterol on lipids can be found here.
NICE guidance for both ‘Familial Hypercholesterolaemia management’ and for ‘Cardiovascular disease: risk assessment and reduction, including lipid modification’, do provide advice for high risk individuals, recommending an intake of dietary cholesterol less than 300 mg/day. As a nation our average intake of dietary cholesterol is below this threshold 18 .
All animal foods contain some cholesterol, so by cutting down on animal foods high in saturated fat, cholesterol intakes will also be reduced.
In 2019, the American Heart Association 19 reviewed the evidence examining the relationship between dietary cholesterol and blood lipids, lipoproteins and cardiovascular disease risk. Meta-analyses of intervention studies generally find associations between cholesterol intakes that exceed current average levels with elevated total and LDL-C. However, the available evidence suggests that, within the context of healthy eating patterns, replacing SFA with UFA is expected to produce greater reductions in LDL-C than reducing dietary cholesterol alone. Rather than provide a specific dietary cholesterol target, it is recommended to promote healthy eating patterns which emphasise fruit and vegetables, whole grains, low fat dairy foods, lean protein sources, nuts, seeds and liquid vegetable oils. These eating patterns are inherently low in cholesterol. 