Almost everybody knows that mass-produced ice cream, ham, crisps, cereal and bread, are less healthy than anything you can make in your own kitchen, but researchers have said the dangers may be even greater than thought previously as the chemicals used for ultra-processed foods may increase risk of cancer.

A study funded by Cancer Research United Kingdom and the World Cancer Research Fund suggests there may be some link between very processed foods and an increased risk of various types of cancer.

The Imperial College London team which led the study said the link could not be proven owing to the fact it is based on observations, where people remember what they eat.

However, they said people in the U.K. eat far too many ultra-processed foods – often called UPFs – and called for front-of-pack warning labels.

Ultra-processed foods usually contain ingredients that people would not add when they are cooking homemade food.

These additions may include chemicals, colourings, sweeteners and preservatives to extend shelf-life.

The most commonly eaten ultra-processed foods in the U.K. are shop-bought mass-produced bread, ready meals, various breakfast bowls of cereal, reconstituted meat products such as ham, sweets, and shop-bought biscuits, buns and cakes.

Not all processed food is bad. For example, the U.K.'s National Health Service (NHS) says some foods need processing to make them safe, such as milk, which needs to be pasteurised to remove bacteria.

Previous studies have suggested a link between ultra-processed foods and heart disease, as well as obesity and type 2 diabetes.

In the new study, published in eClinicalMedicine, the team used U.K. Biobank data to examine the diets of 197,426 people aged 40 to 69.

Their health was tracked over a decade and their risk of developing cancer or dying from it was also analyzed.

The study found that higher consumption of ultra-processed foods was associated with a greater risk of developing cancer overall, specifically ovarian and brain cancers.

It was also associated with an increased risk of dying from cancer, most notably ovarian and breast cancers.

The researchers found that for every 10% increase in ultra-processed food in a person’s diet, there was a 2% increased risk of cancer overall, and a 19% increased risk for ovarian cancer specifically.

So, as an example, if somebody had zero UPFs in their diet, their risk went up for every 10% increase.

Each 10% rise was also associated with a 6% increased risk of dying from cancer, with a 16% increased risk for breast cancer and a 30% increased risk of ovarian cancer.

These links held true even after adjusting for factors that may alter the results, such as exercise, body mass index (BMI) and deprivation.

The researchers also found that people who had the highest – typically 41% – UPF level in their diet had a 7% higher risk of cancer overall than those with the lowest intake of UPFs – 9%.

Dr. Eszter Vamos, the lead author of the study, said: "This study adds to the growing evidence that ultra-processed foods are likely to negatively impact our health including our risk for cancer.

"Given the high levels of consumption in U.K. adults and children, this has important implications for future health outcomes.

"Although our study cannot prove causation, other available evidence shows that reducing ultra-processed foods in our diet could provide important health benefits.

"Further research is needed to confirm these findings and understand the best public health strategies to reduce the widespread presence and harms of ultra-processed foods in our diet."

Dr. Kiara Chang, who also worked on the study, said: "The average person in the U.K. consumes more than half of their daily energy intake from ultra-processed foods.

"This is exceptionally high and concerning as ultra-processed foods are produced with industrially derived ingredients and often use food additives to adjust colour, flavour, consistency, texture, or extend shelf-life.

"Our bodies may not react the same way to these ultra-processed ingredients and additives as they do to fresh and nutritious minimally processed foods.

"However, ultra-processed foods are everywhere and highly marketed with cheap prices and attractive packaging to promote consumption.

"This shows our food environment needs urgent reform to protect the population from ultra-processed foods.

"We need clear front-of-pack warning labels for ultra-processed foods to aid consumer choices, and our sugar tax should be extended to cover ultra-processed fizzy drinks, fruit-based and milk-based drinks, as well as other ultra-processed products."

She said lower-income households are "particularly vulnerable" to cheap and unhealthy UPFs, saying minimally processed and freshly prepared meals should be subsidised.

Dr. Panagiota Mitrou, director of research and innovation at the World Cancer Research Fund, said: "The findings in this first U.K. study of its kind are significant as this is the most comprehensive assessment of ultra-processed foods and cancer risk. This adds to the growing evidence linking these foods to cancer and other health conditions."

Dr. Mitrou said people should limit the consumption of "fast foods" and other processed foods high in fat, starches or sugars, adding: "For maximum benefit, we also recommend that you make whole grains, vegetables, fruit and pulses a major part of your usual diet."

Cancer Research U.K.'s senior prevention policy manager, Malcolm Clark, said the jury on whether ultra-processed foods cause cancer was still out, but high-calorie and sugary food can cause weight gain.