Fat, one of the most important sources of energy with a gram providing around 9 kcal, is an essential component of our diet. But like everything, it can be detrimental to our health if the wrong types of fats are consumed in excess.
Fats are made up of fatty acids classified as saturated, monounsaturated or polyunsaturated depending on their chemical structure. Too much of any one type of fat can lead to weight gain and – over time and if not checked – can result in obesity, which increases the risk of developing conditions such as heart disease, type 2 diabetes and even certain cancers.
So how much fat do we need each day?
According to experts, fat intake shouldn’t exceed 35 per cent of our total daily energy intake from food and saturated fat shouldn’t exceed 11 per cent of total energy intake from food. As a broad guideline, men should consume less than 30g of saturated fat a day and women 20g.
But which are the fats to go heavy on – and the ones to go easy on?
Eating vegetable oils instead of animal fats such as butter does not lower the risk of heart disease, according to a new study that challenges official dietary guidelines that recommend ditching saturated fat. So, with expert opinion appearing to flip-flop on the issue, how are we to know which fats are healthy and which ones to avoid?
Found in Meat, dairy, processed cakes, biscuits
The low-down Trans fats are found naturally in low levels in foods like meat and dairy. However, artificial trans fats – formed when oil goes through a process called hydrogenation – are problematic.
They are used in some processed cakes and biscuits to give them a longer shelf life. The general consensus is that diets high in trans fats can cause heart disease, heart attack and stroke.
The bottom line Avoid anything with ‘hydrogenated vegetable oil’ on the label.
Found in Meat, butter, cheese, coconut oil
The low-down For decades, animal fat has been a dietary bogeyman, ablamed for boosting the artery-clogging ‘bad’ cholesterol thought to be linked to heart disease and stroke.
The new study by the US National Institutes of Health challenges that thinking. Researchers reanalysed data gathered from 9,500 people in a 1970s study and found that switching from saturated fats to unsaturated omega-6 fats did lower blood cholesterol – but did not lead to a reduction in death from heart disease. In fact, some participants who had the greatest reduction in blood cholesterol had the higher risk of death.
There is other emerging evidence to suggest that saturated fat might not be the dietary villain it was once considered to be. For example, some studies indicate not all saturated fats are the same and that certain types – like those found in some dairy products – might reduce the risk of diabetes and heart disease. But further research is needed on this.
The bottom line Expert opinion is changing, but many researchers stress there is not yet any scientific green light to eat unlimited amounts of saturated fat. More important, they say, is to consume enough healthy fat.
Found in Oily fish, vegetable oils
The low-down There are two types of polyunsaturated fat: omega-3 and omega-6. These are technically known as essential fatty acids as they cannot be made by the body and must be included in our diet. Omega-6 fats are found in vegetable oils such as rapeseed, corn, sunflower and some nuts. Omega-3 fats are found in oily fish such as mackerel, kippers, herring, trout, sardines, salmon and fresh tuna.
According to the NHS Choices website, most of us get sufficient omega-6 in our diet, mostly from cooking oil, but we are advised to consume more omega-3 by eating at least two portions of fish, ideally oily, each week.
Some doctors, such as Dr Aseem Malhotra, London-based cardiologist and adviser to the National Obesity Forum, points to emerging evidence that not all polyunsaturated fats are good for us.
He believes too much omega-6, also known as linoleic acid, from vegetable oils, might not be good for heart health. There is also some evidence that consumption of omega-6 and omega-3 fats needs to be well-balanced to ensure optimum health.
The bottom line Eat plenty of oily fish.
Found in Olive oil, rapeseed oil, avocados and nuts including almonds, brazils and peanuts
The low-down Monounsaturated fats help protect our hearts by maintaining levels of ‘good’ HDL cholesterol while reducing levels of ‘bad’ LDL cholesterol.
Dr Malhotra regards olive oil as a ‘medicine’ and recommends consuming several tablespoons a day, along with a handful of nuts to reduce the risk of heart disease, stroke, dementia and cancer.
The bottom line Include in your daily diet.