Ultra-processed food (UPF), which includes packaged, instant and fast food items, now makes up a large part of the Western diet. It also includes commonly consumed food items, such as certain types of bread and cereals. This food is usually high in salt, sugar and saturated fats and is industrially manufactured to contain a range of additives and artificial flavouring to enhance their taste.

Although widely available, the food is associated with overall negative health impacts. Recent studies show their link with various diseases, including cancer, heart disease and type 2 diabetes. Here, we will define what UPF is, explore studies surrounding its adverse health effects and look at why it might be difficult to reduce UPF consumption.

What is ultra-processed food?

UPF can be defined by the NOVA classification system. This system organises food and drinks into the following groups:

1. Unprocessed food/minimally processed food: These are natural foods that have had little or no alterations with no additions such as salt, sugar, oils or fats to the additional food. This includes fresh fruit and vegetables, nuts, milk or meat.
2. Processed Ingredients: Processed foods are foods that have been modified from their original form to allow us to consume them safely and easily. This includes things like butter, sugar, and salt which can be used alongside natural, unprocessed foods used when cooking at home. It also includes food items such as pressing oils. According to the National Health Service (NHS) UK, most foods we eat are processed in some form. This is to ensure that the foods we consume are safe.
3. Processed food: This is a combination of natural, unprocessed food and processed ingredients such as salt. Processed food includes things like tinned vegetables, salted nuts, cured meat and cheese.
4. Ultra-processed food: UPF is food that has been industrially formulated on a mass scale. They are derived from different natural compounds and usually contain a large range of additives, flavour enhancers, emulsifiers and other ingredients that you wouldn’t use to cook food in your own home. It includes foods like cakes, biscuits, mass-produced bread, sausages, ice cream, soda, etc.

UPFs are formulated to be cheap and convenient whilst extremely palatable, meaning they are very appealing and can be difficult to resist. As mentioned, they usually contain high sugar, salt and saturated fat content but also have a low nutrient content. Research shows how diets primarily based on the consumption of UPFs are associated with negative health impacts.

We will explore some studies, including those published in the Open Access journal Nutrients, about the negative impacts of UPF consumption.

UPFs and inflammation

UPFs contain ingredients that enhance the flavours of food and have low nutrient content. These include emulsifiers, food colourants and artificial sweeteners, such as aspartame, which may trigger inflammatory responses in the body.

A review by Clemente-Suarez et al. discusses how the Western diet, which is high in saturated fats, sugar and salt, can cause inflammation and is associated with increased oxidative stress. Oxidative stress occurs when there are too many reactive oxygen species being produced in the body and not enough antioxidants to combat them. This imbalance leads to the release of pro-inflammatory components.

Another review provides evidence to suggest that UPF promotes systemic inflammation through the interaction of components with the gut microbiome. The review explains that changes in microbes in the gut can be due to a lack of things like fibre and nutrient-rich components otherwise found in unprocessed food. Hence, changes in the gut microbiome can also result in the release of pro-inflammatory components.

The presence of inflammatory molecules results in damage to cells, which may in turn, result in cell death. This damage triggers the inflammatory response even further. In this way, chronic and systemic inflammatory cycles can develop in the body.

The effect of inflammation in the body has been widely studied. Chronic inflammation has been associated with an increased risk of developing gut disease and cardiovascular disease, cancer, mental health disorders and non-alcoholic liver disease.

UPFs and cancer

Many studies have analysed the relationship between consumption of UPF and the risk of developing cancer. A study in Brazil shows that regularly consuming UPFs raises the risk of developing breast cancer by 2.35 times. Furthermore, for every 10% increase in UPF consumption, the risk of developing cancer rises by 12%. The development of cancer in regards to UPF consumption can be attributed to inflammation and the increase in oxidative stress, according to several studies seen in the review by Clemente-Suarez et al. The inflammatory components of UPFs may induce the activation of several oncogenes, also known as ‘cancer-causing genes’.

Furthermore, UPFs have an overall higher fat and sugar content compared to whole foods found in the Mediterranean diet. The review discusses the effect of consuming food with a high sugar content on cancer. The study suggests that a high consumption of refined sugar may be involved in the pathogenesis of certain cancers and lead to a ‘worse cancer prognosis’.

UPFs, mental health and sedentary behaviour

A meta-analysis by Pane et al. analyses shows how UPF consumption is linked to the risk of developing mental health disorders, such as depression and anxiety. The authors analysed data from 17 different observational studies, which included a total of 385,541 participants. It involved factors such as the high consumption of UPF as well as the sedentary behaviour of the participants.

Sedentary behaviours include little to no activity or movement and long periods of sitting or lying down when using the computer or watching TV. The World Health Organisation (WHO) recommends that adults need at least 150 minutes of physical activity a week. Leading a sedentary lifestyle alone has been previously associated with impacts on sleep duration and developing cardiovascular disease, cancer and type 2 diabetes.

The study found that high sedentary behaviour in combination with high UPF consumption showed an increase in anxiety-induced sleep disturbance. Furthermore, results from the systematic review showed the greater the intake of UPF, the greater the risk of developing depression and anxiety.

A simple solution would be to reduce the consumption of UPF, however, this may not be as simple as it sounds.

Why is it difficult to stop eating UPF?

Although production of UPFs has accelerated dramatically in the last forty years since their introduction to supermarket shelves, their health implications are only recently understood. But the combination of tailored marketing, easy access, affordability and convenience makes the issue surrounding excessive UPF consumption a complex one.

Another factor which may be taken into account is the social aspect of UFP consumption. Food is a big part of both culture and socializing, so people may feel they are ‘missing out’ when not participating in dinner plans involving UPF.

Furthermore, the use of flavour enhancers and artificial colourants to appeal to the population makes it immensely difficult for people to resist. The release of dopamine when consuming food that is rich in these components makes it difficult to stop eating and even creates cravings, making you come back for more. However, there is a light at the end of the tunnel.

There are many things you can do to cut down consumption of UPF, particularly junk food. This includes first and foremost breaking the habit of eating food rich in sugar and salt. It also includes the act of eating junk food mindfully and consuming irregularly. Focusing on food and appreciating each bite can help reduce the amount of food consumed in one sitting.

Shifting one’s diet towards a Mediterranean diet—a diet consisting of foods that are richer in nutrients and fibre—keeps one satisfied and full for longer. Mediterranean diets have been shown to reduce inflammation and the risk of many diseases such as cardiovascular disease and cancer.

From a public health standpoint, more frameworks and regulations should be put into place by governments regarding the availability and marketing of UPF in fast food and junk food. Research that illustrates the health impact of UPF is an important foundation for making changes at both an individual and national level.

Further research

If you would like to read more about research on diet and its impact on health, have a look at articles published in Nutrients, which are Open Access and free to read immediately. Click here if you would like to see a full list of MDPI’s Open journals, which includes new research across all disciplines of health science and biology.