Our advice on fats

12 August 2015        

A picture of some foods that are high in saturated fat including cheese and milk.

Conflicting advice on what to eat and what not to eat regularly hits the headlines. This can be confusing. Our healthy eating guidance is based on decades of evidence from research. Here our Senior Dietitian Victoria Taylor helps to explain it and what the latest news means.

Trying to eat a healthy diet can be difficult when newspaper headlines are telling us certain foods or types of nutrient are bad for us one day and good for us the next. The latest headlines are about fats after a new study published in the BMJ found there to be no association between saturated fat and cardiovascular disease. It also, more importantly, reminds us of the risks associated with trans fats.

Although the study may be new, the findings are not. Last year research we helped to fund suggested there wasn’t enough evidence to support current guidelines on which types of fat to eat. While both studies don't show saturated fat is associated with cardiovascular disease, they also don’t show that eating more of it is better for your heart health. So the news is not an excuse to binge on butter and bacon.

Is saturated fat bad for our heart health or not?

Well the first point to acknowledge is that it’s very difficult for scientists to understand the relationship between our diets and our health. That’s because, unlike a clinical trial to assess a medicine, studies on diet and disease are very difficult to conduct. This is because, unlike regulating whether a person takes a tablet every day, it is incredibly difficult to carefully control the diets of thousands of people over many years.

In June research from the University of Reading was published that involved giving people at moderate risk of heart disease one of three different types of diet and monitoring its impact of four months. That study involved less than 200 people but was the largest of its kind showing how difficult it is to do studies like this. The researchers found that replacing saturated fats with unsaturated ones reduced the participant's cholesterol and blood pressure. These are two important risk factors for heart and circulatory disease.

At the crux of this debate is the role of different types of fat in our diet. Diets that are high in saturated fat have been shown, for example in the Reading study, to increase cholesterol. A high cholesterol level is linked to an increased risk of cardiovascular disease, so that’s why current recommendations emphasise the importance of reducing the saturated fat in our diets. 

Replacing saturated fat

A picture showing sources of polyunsaturated fats such as vegetable oil and nuts.

Where the issue becomes complicated is what you fill that ‘saturated fat gap’ with.

Contrary to some of the reporting on this issue, cutting saturated fat doesn’t necessarily mean lowering all fat. We all need some fats in our diet and, over time, the very low fat diets recommended in the past have been put to one side as our understanding of the effect of this nutrient has developed. So, current guidance tells us to switch from saturated to unsaturated fats rather than cutting the fat completely.

However, it is still important to talk about processed foods and what is in them. A lot of the food we eat is pre-prepared, and while sometimes the processing is as simple as canning tomatoes, processed foods also include foods like ready meals, sweet treats or processed meats where food manufacturers can alter the amounts of different fats, salt or sugar.

As with our diets, when one thing goes out, something else will take its place. The concern is what saturated fat is replaced with when it is removed.  Replacing saturated fat with refined carbohydrates, like sugary foods, or trans fats won’t improve our health, but replacing them with unsaturated fats seems to have a positive benefit. 

We also know that we are already eating too much salt and sugar on average so, while we welcome changes to reduce saturated fat in our everyday products, we also want manufacturers to be mindful of what they replace it with. As consumers, we still need to keep an eye on food labels to understand what is in the foods we are buying and make the best choices for ourselves, too.

What about trans fats?

A picture showing possible sources of trans fats including fast food and cake.This new study is reminder that trans fats should be avoided wherever possible. We are fortunate in the UK that trans fats are very rarely included in foods. Trans fats are not likely to be found in UK margarine for example.

So if you want to reduce the amount of saturated fat in your diet by switching from butter to a margarine spread, you should not be worried about trans fats and this is something we recommend.

Look at the big picture

All this is a good reminder that individual changes to one nutrient can have a knock-on effect on another. Eating well isn’t just about making single changes to a food or food group. When we are making adjustments to our diets we need to think about the overall balance of the food and nutrients that we are eating.

The answer to a healthy diet isn’t only about whether you eat more or less sugar and fat. We need to consider our whole diet and the amount of salt we eat, how many portions of fruit and vegetables we include and the variety of foods in our diets are all important to make sure we get the right balance.

So, rather than arguing over which is the worst dietary offender, perhaps it’s more helpful to focus on the foods that we want to include more of in our diets. Eating a diet rich in fruit and vegetables, pulses, beans, whole grains, unsaturated oils and fish means there is less room for the foods high in saturated fat and salt like fatty or processed meats and sweet treats.

Lots of research studies have shown that people who follow this type of Mediterranean-style diet have a lower rate of heart disease as well as maintaining a healthy weight and better quality of life and even though there are still unanswered questions about why this diet is so much better for us, this does seem to be one area where there is agreement.

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