The fat of the land – research into the dietary intake of fats

The food and beverage industry is working harder than ever to keep up with consumer demands, while adhering to public-health guidelines and strict regulatory standards. From an industry and consumer point of view, changes to nutritional recommendations can cloud already muddy waters. Some recent research has cast possible doubts over current nutritional recommendations. However, the fundamental fact that we need to consume some fat as an essential part of a healthy, balanced diet, has not changed. Fats help us to absorb the fat-soluble vitamins A, D and E. Regardless of the type, fats are high in energy, providing 9kcal/g.

Frequently eating more calories than you need, however, whether it’s from fat, carbohydrate or protein, increases your risk of becoming overweight or obese, which may increase your blood cholesterol, a chemical building block found naturally within the cells in the body.

Cholesterol is needed to make steroid hormones and vitamin D, as well as bile acids, which help the gut digest and absorb dietary fat, but too much can be detrimental to our health.

Cholesterol is carried in the blood in two ways: as low-density lipoprotein (LDL) and high-density lipoprotein (HDL). LDL cholesterol is often referred to as ‘bad cholesterol’ as too much can lead to fatty deposits developing in the arteries, which can restrict the flow of blood to the heart and brain, increasing the risk of heart disease and stroke. HDL cholesterol is often referred to as ‘good cholesterol’ as it is protective, taking cholesterol from parts of the body where there is too much of it, to the liver, where it is disposed of.

Monounsaturated fats, found in olive and rapeseed oils and spreads, avocados, almonds, Brazil nuts and peanuts, maintain levels of ‘good cholesterol’ (HDL) while reducing levels of ‘bad cholesterol’ (LDL).

There are two types of polyunsaturated fats: omega-3 and omega-6, both of which can help lower levels of bad cholesterol. Omega-6 fats are found in vegetable oils (rapeseed, corn, sunflower) and some nuts, while omega-3 fats are found in oily fish (mackerel, kippers, herring, trout, sardines, salmon and fresh tuna). The majority of the UK population consumes sufficient omega-6, mostly from cooking oil, but many aren’t eating enough omega-3-containing food and we are advised to consume at least two portions of fish a week, one of which should be oily. Vegetable sources of omega-3 fats are not thought to have the same benefits to heart health as those found in fish.

Saturated fats are predominantly from animal sources, including meat and dairy products, as well as some plant foods such as palm oil. Most people are now aware of the types of foods considered high in saturated fats, including fatty cuts of meat, meat products (sausages and pies), butter, ghee and lard, cheese, ice cream, some savoury snacks (crisps), chocolate, biscuits, cakes and pastries, palm oil, coconut oil and cream. Based on UK-wide data-gathering studies, such as the National Diet and Nutrition Survey (NDNS), it is clear to see that people in the UK eat too many foods containing saturated fat. We are currently getting around 12.6% of our energy (calories) from saturated fats, which is above the 11.0% maximum recommended by the government.

Trans fats are found naturally at low levels in some foods, such as meat and dairy products, but they can also be found in hydrogenated vegetable oil. It is recommended that this type of fat, associated with high cholesterol, should make up no more than 2% of the energy we get from our diet. For adults, this is no more than about 5g a day. However, most of the supermarkets in the UK have removed hydrogenated vegetable oil from all their own-brand products and the majority of people consume less than half the recommended limit of trans fat.

Current public health guidelines

It is essential that we include some fat in our diet but, like all food groups, eating too much increases the risk of becoming overweight, which in turn increases our likelihood of developing health problems. One size doesn’t fit all, so there will be variation between individuals in terms of healthy intakes but it is recommended that no more than a third of our total fat intake should come from saturated fat. For men, this would be no more than 30g a day and 20g a day for women. Trans fats should make up no more than 2% of our total energy intake. Unsaturated fats (poly or mono) should provide the rest of our fat intake and this includes the omega-3 fats.

In order to be mindful about the amount of fat we are consuming, food labelling can be very helpful. You will now see many items with ‘reference intakes’ (RIs) for fats and calories, which (unless the label says otherwise) are based on an average-sized woman doing an average amount of physical activity. This is a guide and will vary from person to person, and from day to day.

Front-of-pack labelling (for example, the ‘traffic light system’) can also help consumers to distinguish those foods that are considered high in saturated fat (more than 5.0g of saturates per 100g), low in saturated fat (1.5g of saturates or less per 100g or 0.75g per 100ml for liquids) or saturated fat-free (0.1g of saturates per 100g or 100ml).

Should we review the guidelines regarding saturated fats?

When typing ‘saturated fat’ into a publications database, many of the 499,000 search results also contain the words ‘cardiovascular disease’, ‘cholesterol’ and/or ‘obesity’ in the title. Since the 1940–50s, a vast amount of research has been generated surrounding saturated fat and the many associated health conditions.

Recently, however, there has been talk of research that suggests saturated fat isn’t as bad as we first thought. Does this mean we should be consuming butter by the bucket load and start drinking bottles of ghee? No. While there may have been some research developments suggesting specific saturated fatty acids may have beneficial properties, this research is still in its infancy and the bottom line remains the same as it always has – too much of any food group, and, in particular, refined and processed foods, can lead to weight gain and associated diseases. The majority of guidelines recommend a reduction in saturated fats as being key to reducing incidence and mortality of cardiovascular disease.

Recent research has raised some doubts about the scientific substantiation for this advice, suggesting that a new approach to research is needed.

It is important to note, however, that while some results may be conflicting, a vast amount of evidence, past and present, supports the most current recommendations.

Fat facts

• Fat is made up of different types of fatty acids, some of which are essential for health in small amounts.
• Fatty acids are usually classified as saturated, monounsaturated or polyunsaturated, depending on their chemical structure.
• These structural differences directly influence health effects, with mono and polyunsaturates usually being associated with health benefits when consumed as part of a varied diet. The exception to this is trans fatty acids, which are unsaturated in terms of their structure but behave in the body like saturated fatty acids.
• Fat provides energy; 1g provides 37kJ (9kcal). Foods that contain a lot of fat provide a lot of energy. Fat is a carrier of fat-soluble vitamins and is necessary for their absorption.
• A high intake of saturated or trans fatty acids can have adverse effects on health.
• In the UK, saturates currently contribute 12.7% of food energy in adults, which is above the recommendation of 11.0%, whereas average total fat intake is close to the 35.0% of food energy recommended for the population.
• Intake of trans fatty acids is now well below the population recommendation of no more than 2.0% of food energy, at 0.7%.
• In the UK, intakes of omega-6 polyunsaturated (principally linoleic acid) are close to the recommendation of 6.5% of dietary energy, but intakes of the long-chain omega-3 fatty acids found in fish oils are low compared with recent recommendations.

The four pillars of fats

Fats can be broadly split into four groups:

• monounsaturated
• polyunsaturated
• saturated
• hydrogenated trans fat.