"The results show that a 10-percent increase in the proportion of ultra-processed foods in the diet was associated with increases of 12 percent in the risk of overall cancer and 11 percent in the risk of breast cancer", said a press statement from The BMJ which published the research.
They grouped foods according to how processed or unprocessed they were and compared the results to cases of cancer over an average of 5 years.
A new study suggests that the so-called ultra-processed foods can boost cancer risk by a significant amount.
It said ultra-processed foods with high levels of sugar, fat and salt were linked to the disease.
Carolyn Rogers, clinical nurse specialist at Breast Cancer Care, comments in an emailed statement: "Although this research is intriguing and will add to existing evidence on how diet may impact breast cancer risk, it's far from conclusive".
The study states, "Ultra-processed fats and sauces, sugary products and drinks were associated with an increased risk of overall cancer".
This includes convenience foods, such as mass-produced baked breads and buns, snacks and cookies - plus those staples of modern-day childhood, chicken nuggets and fish sticks, Srour said.
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"To our knowledge, this study is the first to investigate and highlight an increase in the risk of overall - and specifically breast cancer associated with ultra-processed food intake", said the team led by Bernard Srour from the French Institute of Health and Medical Research (Inserm) in Paris.
Researchers saw this new cancer link when they analyzed 24-hour dietary records of almost 105,000 adults in the NutriNet-Sante cohort, a general population group in France.
Researchers also took into consideration other risk factors such as age, gender, levels of education, whether the participant smoked and family history of cancer.
It comes after a Guardian report revealed how half of all food bought by United Kingdom families is now ultra-processed.
The researchers acknowledged that this is an observational study so no firm conclusions can be drawn about cause and effect, however they pointed out that the study sample was large and the research did take into account potentially influential risk factors.
Also, they are unable to say which part of the processing chain might be responsible for any increase in cancer risk.
"Eating a balanced diet, avoiding junk food and maintaining a healthy weight are things we can all do to help stack the odds in our favour". He said it chimed with the key concerns of his organisation's Real Bread Campaign and Sugar Smart initiative that "eating processed food may not be as good for you as eating unprocessed and minimally processed food".