Fat

Looking at fats and oils in the diet and how they our affect health

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The science of fat

Key points

  • Dietary fats provide essential fatty acids that the body cannot make itself; these become important components of cell membranes, including those in the brain and nervous system.
  • Fat also carries the fat-soluble vitamins A, D, E and K.
  • Fats are a major and concentrated source of dietary energy, providing 9 kcal/37 kJ of energy per gram, compared with 17 kJ (4 kcal) per gram for carbohydrates and for proteins.
  • Although fats are often described as a single entity, there are different types of fats and each of these can have a different effect on our health.
  • Fatty acids are usually classified as saturated, monounsaturated or polyunsaturated, depending on their chemical structure. Among the polyunsaturated fatty acids, there are further structural differences which determine whether the fatty acid is known as a n-3 (omega-3) or n-6 (omega-6) fatty acid.
  • The structural differences of fatty acids directly influence their health effects. Substituting saturated fats with unsaturated fats (polyunsaturated and monounsaturated fats) lowers serum LDL cholesterol, which is a risk factor in the development of cardiovascular disease.
  • Unsaturated fats are often considered to be healthy fats Trans fats are a particular type of fatty acid. High intake of trans fats produced industrially (as partially hydrogenated oils) is widely recognised as having adverse effects on heart health.
  • In the UK, saturated fats currently contribute 12.8% of food energy in adults (excluding energy intake from alcohol), which is above the recommendation of 11%, whereas average total fat intake is close to the maximum 35% of food energy recommended for the population.
  • Intake of trans fatty acids is now well below the population recommendation of no more than 2% of food energy, at 0.5%.
  • In the UK, we typically eat enough n-6 fats, but intake of n-3 fats (e.g. from oily fish) is low.

Summary

Dietary fats are one of the three macronutrients in our food, and are a major source of dietary energy, providing more energy per gram (9 kcal/g) than protein or carbohydrates. For most people, fats are the largest store of energy in the body.

Dietary fats and oils typically contain a mixture of saturated and unsaturated fatty acids, and so we usually describe a food as being high in saturated or unsaturated fat depending on the balance of fatty acids they contain. Saturated fats are typically solid at room temperature and tend to be from animal sources (e.g. butter, ghee, lard), as well as some from plant sources (mainly as tropical fats, e.g. coconut and palm oil). Unsaturated fats are usually liquid at room temperature and come from plant sources (olive, rapeseed, sunflower, corn oils).

The relationship between saturated fat intake and health was reviewed by the UK Scientific Advisory Committee on Nutrition (SACN) in a report published in 2019. In its report, SACN concluded that higher saturated fat consumption is linked to raised blood cholesterol and an increased risk of heart disease. 

No change to existing advice that saturated fats should be swapped with unsaturated fats was recommended. Evidence from clinical trials shows that replacing saturated fats with unsaturated (especially polyunsaturated) fats can have a beneficial effect on blood cholesterol levels, one of a number of ‘classical’ modifiable risk factors for cardiovascular disease (CVD), and also appears to benefit other ‘emerging’ risk factors for CVD (e.g. inflammation, endothelial dysfunction).

There are 2 main types of polyunsaturated fats: n-3 and n-6 fatty acids (also called omega-3 and omega-6), and we need to include both types in our diets. Linoleic acid (n-6) and alpha-linolenic acid (n-3) are known as essential fatty acids, as they cannot be synthesised in the body. Vegetable oils are a rich source of linoleic acid, and linseed/flaxseed oil, rapeseed oil, walnuts and walnut oil are all a rich source of alpha-linolenic acid (ALA). The long-chain n-3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are important for heart health. While our bodies can make EPA and DHA from ALA, the conversion rate is thought to be quite low. EPA and DHA can also be obtained preformed from the diet from oily fish (e.g. salmon, mackerel, sardines), and it is recommended that we consume at least one oily fish portion (140 g) per week.

Average intakes of total fat among UK adults (aged 19-64 years) are close to the recommended amount (35% of food energy), but intakes of saturated fats are above the recommended amount (11% of food energy) for all age groups.

It is a legal requirement to declare the amount of total and saturated fats on nutrition labels. This can be supplemented with the amount of monounsaturated and polyunsaturated fats, although it is not mandatory. A number of nutrition (e.g. ‘low in saturated fat’) and health claims (e.g.,‘EPA and DHA contribute to the normal function of the heart’) have been authorised for use in Great Britain, providing they meet the conditions of use. Voluntary front-of-pack nutrition labels (‘Traffic Light’ Labelling) can help consumers to identify products high in fat and saturated fat more easily, and so allow them to choose products that are lower in fat or saturated fat when shopping.

There are a number of ways in which consumers can reduce their saturated fat intake, including:

  • Eating foods such as cakes, biscuits, chocolate, pastries, butter, cream, ice cream and deep-fried foods less often and in small amounts,(if at all).Choosing meats low in fat, such as chicken (without skin) and lean cuts of red meat.
  • Removing visible fat and skin where possible.
  • Choosing lower fat versions of dairy products where possible.
  • Grilling, steaming or baking foods, or roasting foods using small amounts of unsaturated oils (e.g. sprinkle olive or rapeseed oil on vegetables)

People can also replace saturated with unsaturated fats by swapping butter, ghee or coconut oil for unsaturated oils such as olive, rapeseed, or sunflower oils or spreads for cooking and preparing foods.

Functions of fats

Fat has a number of important functions as a nutrient. Fat is the carrier for fat-soluble vitamins (A, D, E and K), and is also the source of the essential fatty acids linoleic acid (n-6) and alpha-linolenic acid (n-3). Dietary essential fatty acids and fatty acids made from them are incorporated into phospholipids in cell membranes and are therefore critical components of new cell membranes.

Dietary fats are a rich source of energy, supplying 9 kcal per gram, more than double that provided by either protein or carbohydrate that both provide 4 kcal per gram, with alcohol providing 7 kcal per gram.

The chemical structure of dietary fats

The majority of fats we eat in our diet have a similar chemical structure and are made up of three fatty acids attached to a molecule of glycerol as a ‘backbone’, known as triglyceride or triacylglycerol. Individual fatty acids can be classified according to the number of double bonds they contain:

  • saturated fatty acids (SFA): 0 double bonds (also known as ‘saturated fat’ or ‘saturates’)
  • monounsaturated fatty acids; (MUFA): 1 double bond (also known as ‘monounsaturated fat’ or ‘monounsaturates’)
  • polyunsaturated fatty acids (PUFA): more than 1 double bond (also known as ‘polyunsaturated fat’ or ‘polyunsaturates’)

SFA, MUFA and PUFA are associated with different health effects, but individual fatty acids within each broad category can also have distinct biological properties. For example, while all saturated fatty acids have similarities in their chemical structure (i.e. no double bonds),  it is increasingly recognised that individual saturated fatty acids with different carbon chain lengths have distinct biological effects, and therefore not all saturated fats will have the same effects on health. The most commonly consumed SFA in our diet are 12-18 carbon atoms long. This includes lauric (12 carbons), myristic (14 carbons), palmitic (16 carbons) and stearic acids (18 carbons). A higher intake of lauric, myristic and palmitic SFA has been shown to increase total, LDL and HDL cholesterol levels, but stearic acid is reported to have a neutral effect on blood cholesterol. However, as the fats within our diet typically contain a mixture of these SFA, it is recommended that we should reduce our saturated fat consumption overall to reduce the risk of CVD.

Similarly, for unsaturated fatty acids (MUFA and PUFA) there are distinct fatty acids with different chain lengths that may have different effects on health and are found in particular types of food. For example:

  • Oleic acid (MUFA) found in olive and rapeseed oils.
  • Linoleic acid (PUFA, n-6) found in rapeseed and sunflower oils.
  • Alpha-linolenic acid (PUFA, n-3) found in linseeds and walnuts.
  • Eicosapentaenoic acid (PUFA, n-3) found in oily fish and eggs.

Most naturally occurring PUFA are in the ‘cis’ chemical configuration but ‘trans’ fatty acids can occur naturally in meat and dairy products from ruminants and as a product of industrial partial hydrogenation. These are discussed further below.

Dietary oils and fats generally contain a range of different fatty acids, both saturated and unsaturated, but are described as a ‘saturated fat’ or ‘unsaturated fat’ according to the proportions of fatty acids present. For example, butter is often described as a ‘saturated fat’ because it has more SFA than unsaturated fatty acids, while most vegetable oils are described as ‘unsaturated fats’ as they have more unsaturated fatty acids (MUFA and PUFA) than SFA.

Generally, saturated fats are solid at room temperature and tend to be derived from animal sources (meat and dairy), and unsaturated fats are liquid at room temperature and are usually derived from plants. But there are exceptions, for example palm oil and coconut oil are plant-derived oils which contain a high percentage of SFA.

Trans fats

The most common configuration of unsaturated fatty acids in nature is the ‘cis’ configuration (see below), but those with at least one double bond in the ‘trans’ configuration are referred to as trans fatty acids (TFA). This altered double bond configuration has an impact on the properties of these fatty acids, but importantly has consequences for health.

An example of the chemical structure of a cis and a trans fatty acid is shown right.

Trans fatty acids are naturally occurring at low levels in dairy products and meats from ruminant animals, where they are produced in the rumen (largest stomach chamber) of cows and sheep. They may also be produced by the industrial hydrogenation of plant-derived oils to produce the semi-solid and solid fats that were historically used in food manufacture (e.g. margarines).

Industrial TFA have largely been removed from UK food chain. The majority of trans fat in UK diets now comes from natural sources in meat and milk.  Average intake in UK adults is now thought to be about 0.5% of total energy intake (and so below the UK target of <2% of energy intake). This has largely come about by the use of alternative methods to process oils to make spreads and cooking fats, including the use of ‘interesterification’ (see below for more information).

An EU regulation limiting the amount of industrially produced trans fat in all foods sold to EU consumers came into effect in April 2021, which sets a maximum limit of 2 grams of industrially produced trans fats per 100 grams of fat in food. In many foods, the level is below 0.5 grams trans fats per 100 grams of fat or trans fats cannot be found at all. However, globally, some products remain on the market which have high levels of TFA, and the World Health Organisation (WHO) has set goal of global elimination of industrially produced TFA from the entire global food supply by 2023.

Essential fatty acids

The body can typically make the different types of fatty acids it needs from fat consumed in the diet except for two, known as alpha linolenic acid (ALA, n-3) and linoleic acid (LA, n-6), which are termed essential fatty acids and must be supplied by the diet. Vegetable oils are a rich source of linoleic acid, and linseed/flaxseed oil, rapeseed oil, walnuts and walnut oil are a rich source of alpha-linolenic acid (ALA). The essential fatty acids are important for helping the body function normally, and act as the precursors to other longer-chain fatty acids that have important functions in our body for growth, development and health.

The most important long-chain n-3 fatty acids that can be synthesised from ALA are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). However, this pathway does not appear to be very efficient in humans although seems to be greater in women than men. We can also get EPA and DHA pre-formed from the diet. Oily fish such as salmon, mackerel and sardines are rich sources of EPA and DHA and they are also found at lower levels in eggs. They are also present in the meat or eggs of animals fed n-3 fatty acid-enriched diets. Foods produced in this way could be considered alternative sources to oily fish, although the amounts of EPA and DHA present are typically much less than in oily fish. Other alternatives to oily fish are being explored as a potential source of EPA and DHA in the diet, including oils derived from genetically modified plants (e.g. Camelina sativa), although there are regulatory restrictions that may prevent the commercial cultivation of these plants at present. Arachidonic acid is a long-chain n-6 fatty acid that can be synthesised from linoleic acid and is found in small amounts in meat, especially pork and the dark meat from chicken and turkey and in oily fish.

Essential fatty acids, and the longer-chain fatty acids synthesised from them, are important components of cell membranes, particularly in the brain and nervous system. Arachidonic acids and EPA are substrates for important signalling molecules, such as eicosanoids, which control many important functions at a cellular level, including inflammatory responses.

Fats in the diet (intakes and recommendations) 

The main sources of total fat and saturated fats in the average UK adult (aged 19-64 years) diet can be seen in the table below, in descending order of their relative contribution. 

Type of fat

Source

Total fat

Meat & meat products (22%)
Cereals & cereal products (incl. cakes and biscuits) (21%)
Milk & milk products (13%)
Fried potatoes & savoury snacks (7%)

Fat spreads (9%)
Eggs & eggs dishes (5%)

Fish and fish dishes (5%)

Saturated fats

Meat & meat products (21%)
Milk & milk products (21%)
Cereals & cereal products (incl. cakes and biscuits) (21%)
Fat spreads (10%)
Fried potatoes & savoury snacks (3%)
Eggs & egg dishes (5%)

Source: National Diet and Nutrition Survey (NDNS) rolling programme, Years 9 to 11 (2016/2017 to 2018/2019).

Dietary recommendations for saturated fat

Current government advice for saturated fat is to choose lean meats, and less processed meat and lower fat dairy products, to help reduce population saturated fat intakes. This advice reflects the recommendation to reduce population saturated fatty acid intakes in the UK to no more than 10% of total dietary energy, first made in 1994 by COMA (Committee on Medical Aspects of Food Policy),  and which remained unchanged following a review of the scientific evidence published by the independent Scientific Advisory Committee on Nutrition (SACN) in 2019. SACN reviewed the totality of available evidence on saturated fats and health outcomes (more information on the report findings is provided below) and recommended that:

  • The population dietary reference value (DRV) for saturated fats should remain unchanged from the previous recommendations made in 1994.
  • The population average contribution of saturated fatty acids to total dietary energy (including energy from alcohol) be reduced to no more than about 10%.
  • Saturated fats are substituted with unsaturated fats in the diet (mono- or polyunsaturated fats). More evidence was available supporting substitution with PUFA than substitution with MUFA.
  • This recommendation applies to UK adults and children aged 5 years and is made in the context of existing UK Government recommendations for macronutrients and energy.
  • SACN recommended that the government gives consideration to strategies to reduce the population average contribution of saturated fatty acids to total dietary energy (including energy from alcohol) to no more than about 10%.
  • It was also recommended that risk managers should be mindful of the available evidence in relation to substitution of saturated fats with different types of unsaturated fats and ensure that strategies are consistent with wider dietary recommendations, including trans

These recommendations for saturated fat are consistent with international recommendations, including those made in the US and Australia, and by the World Health Organisation and European Food Safety Authority.

Dietary reference values for fat (as population averages) were set by COMA in 1991 and are shown in the table below, with relevant intake data for UK adults (aged 19-64 years) from the National Diet and Nutrition survey rolling programme.

 

 

 

Dietary Reference Value (population average unless otherwise indicated)*

Current average intake in adults (19-64 years)

Total fat

35% of food energy (i.e., excluding alcohol)

35.2% in men

35.7% in women

Saturated fats

11% of food energy

12.7% in men

12.9 % in women

Trans fatty acids

Below 2% of food energy

0.5% in men and women

Total Cis polyunsaturated fats

6.5% of food energy

ND

Cis n-3 polyunsaturated fats

Minimum intake for individuals, ≥0.2% of total energy from alpha linolenic acid.

1.0% in men

1.1% in women

Cis n-6 polyunsaturated fats

Minimum intake for individuals, ≥1% of total energy from linoleic acid.

5.2% in men

5.3% in women

EPA + DHA

450 mg/day

ND

Monounsaturated fats

13% of food energy

13.1% in men

13.2% in women

Sources: National Diet and Nutrition Survey (NDNS) rolling programme Years 9 to 11 (2016/2017 to 2018/2019); COMA (Committee on Medical Aspects of Food Policy) Dietary Reference Values for Food Energy and Nutrients for the United Kingdom report (1991). *Note that ‘food energy’ excludes energy intake from alcohol, whereas ‘total energy’ includes energy from alcohol; ** The COMA (Committee on Medical Aspects of Food Policy) Dietary Reference Values for Food Energy and Nutrients for the United Kingdom report (1991) recommended that cis-MUFA (principally oleic acid) should continue to provide on average 12% of dietary (food) energy for the population. ND, no data available from NDNS.

Current intakes of saturated fats

Although intake of saturated fats has fallen over the past 30 years, UK intakes remain above the recommended level of no more than 10% of total dietary energy (11% of food energy) for all population groups (see table below).

Saturated fat intakes (% total energy) for different age groups in the UK population.

 

Age group 

 

4-10 years 

11-18 years 

19-64 years 

65-74 years 

75+ years 

Total saturated fat intake (% total energy) 

13.1 

12.6 

12.3 

12.8 

14.1 

Source: National Diet and Nutrition Survey (NDNS) rolling programme Years 9 to 11 (2016/2017 to 2018/2019).

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 vegetarian and Mediterranean-style diets, which have been shown in many studies to reduce cardiovascular disease risk. More information about a healthy diet and lifestyle to reduce risk of cardiovascular disease is available here [LINK TO HEART HEALTH PAGE].

The evidence on dietary fats and heart health

Saturated fats

The evidence as a whole suggests that reducing saturated fat in the diet and replacing it with unsaturated fats improves blood lipid profiles (e.g. lower LDL cholesterol), and reduces the risk of cardiovascular disease and coronary events (e.g. heart attack). Importantly, the evidence suggests that reducing saturated fat intake is unlikely to have adverse effects on health.

The totality of available evidence supports and strengthens current recommendations that saturated fatty acids should make up no more than 10% of total dietary energy, and that saturated fats are substituted in the diet with unsaturated fats (poly- or monounsaturated fats). Although there is less evidence available for the beneficial effects of replacing saturated fats with monounsaturated fats, there is a suggestion of beneficial effects on blood lipids. The Mediterranean dietary pattern is lower in saturated fat and higher in monounsaturated fats and is a diet that has been associated with cardiovascular health benefits. For example, in the well-known PREDIMED trial (conducted in Spain), there was a lower incidence of major cardiovascular events among participants who followed a Mediterranean diet supplemented with either extra-virgin olive oil or nuts, compared to those assigned to a low-fat diet.

n-3 fatty acids 

Since it was first suggested that the abundance of n-3 fatty acids in the diet of the Greenland Inuit people was responsible for their low mortality from heart disease (Bang 1972; Bang 1976), there has been considerable interest in the potential protective role of the long-chain n-3 fatty acids found in oily fish on heart health.

In the UK, government advice to consume at least two portions of fish per week (140g each), one of which should be an oily fish, has been in place since a review of the evidence in 1994 by COMA (Committee on Medical Aspects of Food Policy) concluded that this would likely benefit heart health of the UK population by reducing cases of coronary heart disease (CHD). A recent systematic review of trials (published in 2020) in which people increased their long-chain n-3 fatty acid intake (for at least 12 months), it was concluded that there was limited evidence to suggest a benefit in terms of lowering the risk of cardiovascular events or cardiovascular mortality. However, the authors’ conclusions were based mainly on trials in which people consumed EPA and DHA as fish oil supplements, and they noted that there was little evidence available on the effects of eating fish. It was also acknowledged that oily fish are nutrient-dense foods, which provide other important nutrients in the diet (e.g. vitamin D, calcium [when eaten with bones], iodine and selenium).  

The interest in the potential heart health benefits of n-3 fats has spread to encompass plant seeds and oils rich in ALA, including chia seed, flaxseed and rapeseed oils, and nuts (especially walnuts). One of the proposed mechanisms for the protective role of n-3 fats against cardiovascular diseases is via their ability to lower blood triglyceride concentration. However, in the same extensive systematic review of the evidence on long-chain n-3 fats, the authors also concluded that eating more short-chain ALA (e.g. as walnuts or enriched margarine) probably makes little or no difference to all‐cause, cardiovascular or coronary deaths, or coronary events.

Dietary fats as part of healthier dietary patterns

It is important to remember that we consume a variety of foods in our diets that provide a range of nutrients, and not just single nutrients like saturated fatty acids. Therefore, a ‘whole diet’ approach is important when considering the impacts of diet on long-term health. This focusses on the balance of foods consumed within the context of the overall dietary pattern, rather than individual foods, food constituents or single nutrients. Healthier dietary patterns that are associated with lower risk of chronic diseases, including heart disease have been explored in the scientific literature. Such diets are consistently rich in vegetables and fruits, nuts, wholegrains, and include some unsaturated fats and oils, as well as a variety of protein foods, including nuts and pulses, seafood, eggs, lean meats and poultry, and some lower-fat dairy products (or dairy alternatives). They are also characterised by lower intakes of fatty/processed meats, refined grains, sugar-sweetened foods and beverages, lower salt, and lower saturated fat content. Alongside dietary patterns, there are other aspects of a healthier lifestyle, including regular exercise, adequate sleep, maintaining a healthy weight, and not smoking, which are also associated with lower risk of chronic diseases, and should also be considered alongside dietary factors.

SACN Saturated fats and health report

The Scientific Advisory Committee on Nutrition Saturated fats and health report (2019) reviewed the evidence on saturated fats and health outcomes, including cardiovascular disease (CVD) mortality and events (such as coronary heart diseases [CHD], stroke, peripheral vascular disease), type 2 diabetes, selected common cancers, cognitive impairment and dementias. SACN also looked at evidence for the association between saturated fats and risk factors such as blood lipids, blood pressure, bodyweight and cognitive function. In summary, 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.

SACN’s 2019 review of the evidence for saturated fat intake on health outcomes included systematic reviews, meta-analyses and pooled analyses of either randomised controlled trials (RCTs) or prospective cohort studies that met the Committee’s inclusion criteria and evidence was graded as adequate, moderate, limited, inconsistent, or insufficient. 

Only evidence graded as adequate or moderate was used to inform the recommendations. In total 47 systematic reviews and meta-analyses were included. Based on the evidence from RCTs (unless specified otherwise) and findings based on either adequate or moderate evidence as described in the report, SACN concluded that:

Reducing intake of saturates 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 triacylglycerol).

There was 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 saturates with polyunsaturates 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 (a marker of average blood glucose levels) and insulin resistance.

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

Substituting saturates with monounsaturates 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).

There was 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

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

SACN concluded from its report that the findings support and strengthen the evidence to reduce our consumption of saturated fats and replace foods rich in saturated fats with those with a higher proportion of unsaturated fats. Importantly, the report also found that reducing saturated fat intake was unlikely to increase health risks for the UK population. SACN recommended that the dietary recommendation that saturated fatty acids should make up no more than 10% of total dietary energy (11% of food energy) is upheld and that the advice for the public should remain as saturated fats should be substituted with small amounts of unsaturated fats (PUFA or MUFA).

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  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 fats had a beneficial effect, demonstrating that the type of fat in the diet is not only important in relation to blood cholesterol.

Fats and overweight and obesity

Fat is the richest source of energy available in the diet and so can readily contribute to weight gain. As fat may also have a less satiating (filling) effect than some other food components (e.g., protein and fibre) it may be easier to consume an excess of energy when eating a diet with lots of foods high in fat. If energy intake and expenditure are unbalanced then any excess energy is stored in the body as fat, which may over time result in an individual becoming overweight or obese.

Low-fat diets (containing between 10 and 30% dietary energy from fat) compared to usual diets have been shown to have benefits for weight loss. Caloric restriction is the fundamental premise of a successful weight loss strategy, and evidence suggests that individuals can lose body weight and improve their health status on a wide range of energy (calorie) restricted dietary patterns with varying proportions of macronutrients. Whether weight loss is achieved by lowering the proportion of calories from fat or carbohydrate, restricting energy intake during certain days/period of time, or using low energy meal replacements, optimizing adherence may be the most important factor for weight loss success in the long term.

Nutrition labelling of fats

The labelling of total and saturated fats in pre-packed foods is mandatory under Regulation (EU) 1169/2011 on food information to consumers (FIC), a version of which has been retained and continues to apply to businesses in Great Britain following the UK’s departure from the EU. The amount of monounsaturated and polyunsaturated fats in the food may also be included on nutrition labels if desired. Labelling of the trans fats content of pre-packed foods is not permitted, but partially or fully hydrogenated oils can be included in the ingredients list. However, a recently adopted EU regulation has set a maximum limit for trans fats (other than those naturally occurring of animal origin) of 2g per 100g of fat in all food products sold to EU consumers, which businesses have been obliged to comply with as of April 2021.

Nutrition and health claims on fats and oils

A number of nutrition claims are permitted for fats on food packaging. Some examples of these can be seen in the table below. A list of authorised health claims for use on products in Great Britain (England, Wales and Scotland) can be found on the Great Britain nutrition and health claims (NHC) register

Nutrition claim

Definition

Fat-free

The product contains no more than 0.5 g of fat per 100 g or 100 ml

Low fat

The product contains no more than 3 g of fat per 100 g for solids or 1.5 g of fat per 100 ml for liquids (1.8 g of fat per 100 ml for semi-skimmed milk)

Low saturated fat

The product does not contain more than 1.5 g per 100 g of saturated fatty acids and trans fatty acids for solids, or 0.75 g per 100 ml for liquids. In either case, the sum of saturated fatty acids and trans fatty acids must not provide more than 10% energy.

Saturated fat-free

The sum of saturated fat and trans-fatty acids in the product does not exceed 0.1 g of saturated fat per 100 g or 100 ml.

 

Source of omega-3 fatty acids

The product contains at least 0.3 g ALA per 100 g and per 100 kcal, or at least 40 mg of EPA + DHA per 100 g and per 100 kcal

High in omega-3 fatty acids

The product contains at least 0.6 g of ALA per 100 g and per 100 kcal, or at least 80 mg of EPA+DHA per 100 g and per 100 kcal

Source: Regulation (EU) 1924/2006

Health claims that are authorised for different types of fatty acids are:

Nutrient

Claim

Alpha-linolenic acid (ALA)

ALA contributes to the maintenance of normal blood cholesterol levels

 

Alpha-linolenic acid (ALA) & linoleic acid (LA), essential fatty acids

Essential fatty acids are needed for normal growth and development of children.

 

Docosahexaenoic acid (DHA)

 

DHA contributes to the maintenance of normal blood triglyceride levels

DHA contributes to the maintenance of normal vision

DHA contributes to maintenance of normal brain function

DHA maternal intake contributes to the normal brain development of the foetus and breastfed infants.

DHA intake contributes to the normal visual development of infants up to 12 months of age.

DHA maternal intake contributes to the normal development of the eye of the foetus and breastfed infants.

 

Eicosapentaenoic acid and docosahexaenoic acid (EPA/DHA)

 

EPA and DHA contribute to the normal function of the heart

DHA and EPA contribute to the maintenance of normal blood pressure

DHA and EPA contribute to the maintenance of normal blood triglyceride levels

Foods with a low or reduced content of saturated fatty acids

 

Reducing consumption of saturated fat contributes to the maintenance of normal blood cholesterol levels

 

Unsaturated fats

 

Replacing saturated fats with unsaturated fats in the diet contributes to the maintenance of normal blood cholesterol levels 

Replacing saturated fats with unsaturated fats in the diet has been shown to lower/reduce blood cholesterol. High cholesterol is a risk factor in the development of coronary heart disease

 

Practical ways to help meet recommendations for fats intakes

Although progress has been made in recent years towards reaching population goals for intakes of some nutrients in the UK (e.g. free sugars), intakes of saturated fats remain above the recommended 10% of total dietary energy, and analysis of NDNS data indicates that average intakes have not decreased significantly during over the 11 years of the survey (from 2008/09 to 2018/2019).

The UK government’s Eatwell Guide recommends that foods high in fat, salt and/or sugar (HFSS), if included in the diet, should be consumed less often and in smaller amounts.

Examples of swaps that can be made to reduce saturated fat include:

  • Cooking sparingly with oils richer in monounsaturated fats (g. olive and rapeseed oil) or polyunsaturated fats (e.g. sunflower or corn oil), instead of butter, palm or coconut oil
  • Using a lower fat spread instead of butter
  • Choosing lean meat or poultry without the skin, or oily fish, instead of red or fatty meat.
  • Remove visible fat before cooking where possible
  • Grilling or baking foods, instead of frying and roasting using small amounts of unsaturated oils, e.g. olive, sunflower or rapeseed oils
  • Switching to semi-skimmed, 1% or skimmed milk instead of whole milk
  • Choosing low-fat, no added sugar yogurt instead of cream for desserts
  • Having a piece of fruit as a mid-morning or afternoon snack, instead of cake or biscuits
  • When using cheese to flavour a dish or sauce, use smaller amounts of strong-tasting cheese, such mature cheddar, or use reduced-fat versions,

Emerging research in dietary fats

 

Dairy, saturated fat and health

Dairy foods are an important food group as part of a healthy, balanced diet. Food-based dietary guidelines such as the UK’s Eatwell Guide recommend that dairy foods (or fortified dairy alternatives) should make up approximately 8% of the food we consume by volume and it is recommended that we choose lower fat dairy foods where possible, such as semi-skimmed, 1% and skimmed milk, reduced fat cheeses and low-fat yogurt. However, some evidence has shown that milk and dairy foods have neutral or protective effects on cardiovascular disease, type 2 diabetes and other metabolic diseases, despite some products being higher in saturated fats. For example, whole yogurt and whole milk do not seem to increase the risk of heart disease in the way that would be predicted from their saturated fat content, and cheese consumption has been shown to not raise LDL-cholesterol compared to the same amount of fat from butter. Overall, dairy food consumption is associated with reduced risk of cardiovascular disease and type 2 diabetes, positive effects on bone health, weight management and managing blood lipid levels and blood pressure.

The explanation behind this apparent contradiction has been suggested to be that the food matrix in dairy foods changes how saturated fat impacts on health. Dairy foods are made up of complex matrices of nutrients, bioactives and other components, such as calcium and bioactive peptides which interact with each other when consumed. Additionally, the fat in dairy foods is found within a biological membrane called the milk fat globule membrane, which may have an influence on the amount of fat that is absorbed from dairy foods in the small intestine during digestion.

More research into the dairy food matrix will help us understand fully how the structure of dairy foods and the mixture of nutrients they contain may bring health benefits. For more information, you can read a review on saturated fats, dairy foods and health in our peer-reviewed journal, Nutrition Bulletin.

Reformulation to reduce saturated fats in foods

 

Interesterified fats

A process called ‘interesterification’ is increasingly being used by the food industry to produce modified fats with different compositions and desirable functional and physical properties that can be used when reformulating food products. Interesterification uses chemicals or enzymes to rearrange the fatty acids in a triglyceride molecule, in either a random or specific way, to produce an interesterified (IE) fat with different functional characteristics, such as a higher melting point, which might be useful in certain food products. Using modified fats, such as IE fats, has helped food producers to remove trans fats from food products without losing important aspects of functionality. More recently, it has also been used as a means of reducing the saturated fat content of food products, by providing fats and oils with similar properties but a lower saturated fatty acid content.

In the UK, IE fats are typically used in the manufacture of fat spreads, bakery products, biscuits, dairy cream alternatives and confectionery, but could be used to reformulate more products in the future to help reduce population intakes of saturated fats. Research is limited on the health effects of consuming IE fats but suggests no adverse effects on cardiovascular health. However, there are gaps in the research that require further investigation. To learn more about how fats are used in the foods we eat, watch our Fats Forward webinar to hear from experts in this area. A briefing report from a Roundtable event on the subject of interesterified fats in foods is available open access through our peer-reviewed journal, Nutrition Bulletin.

Oleogels

Emerging research is investigating the potential of using edible oleogels in food manufacture as a way to remove saturated fats to develop healthier food products. Edible oleogels are liquid oils that are trapped in a 3D solid network, and therefore have more solid-like properties. Though this technology isn’t currently being used to produce foods that are on our supermarket shelves, in the future edible oleogels could be used as a replacement for solid fats containing high levels of saturated fats in food products such as chocolate, dough and pastry, fat spreads, processed meat products and ice cream.

 

Key references

EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA); Scientific Opinion on Dietary Reference Values for fats, including saturated fatty acids, polyunsaturated fatty acids, monounsaturated fatty acids, trans fatty acids, and cholesterol. EFSA Journal2010; 8( 3):1461. [107 pp.]. doi:2903/j.efsa.2010.1461.

FAO (2010) Food and Agriculture Organization of the United Nations, Fats and fatty acids in human nutrition. Report on an expert consultation. Available at: http://www.fao.org/3/i1953e/i1953e00.pdf

Bates B, Collins D, Jones K et al. (2020) National Diet and Nutrition Survey. Results from Years 9 to 11 of the Rolling Programme (2016/2017 to 2018/2019). Available at:

Department of Health (1991) Dietary Reference Values, A Guide. HMSO, London. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/743790/Dietary_Reference_Values_-_A_Guide__1991_.pdf

Department of Health (1994) Report on Health and Social Subjects No. 46. Nutritional Aspects of Cardiovascular Disease. Report of the Cardiovascular Review Group Committee on Medical Aspects of Food and Nutrition Policy. HMSO, London. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/743527/Nutritional_Aspects_of_Cardiovascular_Disease__1994_.pdf

SACN (2019) Saturated Fats and Health. Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/814995/SACN_report_on_saturated_fat_and_health.pdf

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