Ultra-processed foods include packaged baked goods and snacks, fizzy drinks, sugary cereals, ready meals and reconstituted meat products - often containing high levels of sugar, fat, and salt, but lacking in vitamins and fibre. They are thought to account for up to 50 per cent of total daily energy intake in several developed countries.
A few studies have linked ultra-processed foods to higher risks of obesity, high blood pressure and cholesterol levels. But firm evidence linking intake to risk of disease is still scarce.
However, a team of researchers based in France and Brazil, set out to evaluate potential associations between ultra-processed food intake and risk of overall cancer, as well as that of breast, prostate, and bowel (colorectal) cancers.
Their findings are based on 104,980 healthy French adults (22 per cent men; 78 per cent women) with an average age of 43 years who completed at least two 24-hour online dietary questionnaires, designed to measure usual intake of 3,300 different food items (NutriNet-Santé cohort study).
Foods were grouped according to degree of processing and cases of cancer were identified from participants’ declarations validated by medical records and national databases over an average of five years.
Several well known risk factors for cancer, such as age, sex, educational level, family history of cancer, smoking status and physical activity levels, were taken into account.
The results show that a 10 per cent increase in the proportion of ultra-processed foods in the diet was associated with increases of 12 per cent in the risk of overall cancer and 1 1per cent in the risk of breast cancer.
No significant association was found for prostate and colorectal cancers.
Further testing found no significant association between less processed foods (such as canned vegetables, cheeses and freshly made unpackaged bread) and risk of cancer, while consumption of fresh or minimally processed foods (fruits, vegetables, pulses, rice, pasta, eggs, meat, fish and milk) was associated with lower risks of overall cancer and breast cancer.
Plans are being drawn up to restrict price promotions on foods by the Scottish Government and a new poll by Cancer Research UK has also found 62 per cent of people back the move.
The survey also found that two-thirds of Scots are worried about their weight or the weight of a family member, while 82 per cent believe multi-buy deals encourage people to buy unhealthy food.
Professor Linda Bauld, Cancer Research UK’s prevention expert based at the University of Stirling called on the Scottish Government to take action to regulate price promotions like those favoured by the supermarket giants.
She said: “This study suggests that eating more processed foods like fizzy drinks, crisps and biscuits could increase your overall risk of cancer. It’s already known that eating a lot of these foods can lead to weight gain, and being overweight or obese can also increase your risk of cancer, so it’s hard to disentangle the effects of diet and weight.
“People shouldn’t worry about eating a bit of processed food here and there based on this study.
“There is good evidence that too little fruit, vegetables and fibre and too much processed and red meat in our diets can contribute to the development of some types of cancer.”
She added: “We know people are often nudged into eating more foods that are high in fat, sugar and salt by enticing price promotions, and we’re calling for the Scottish Government to take action to regulate these.
“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.”
A Scottish Government spokesperson said: “Improving the food environment is the single biggest change we want to see in terms of public health and we recognise the link between lifestyle factors, such as diet, and the prevalence of cancer.
“That is why our diet and healthy weight strategy includes world leading proposals to restrict the marketing of foods high in fat, salt and sugar and our national cancer strategy places an important emphasis on prevention.”
In a linked editorial, Martin Lajous and Adriana Monge based at the National Institute of Public Health in Mexico, say this study provides “an initial insight into a possible link between ultra processed foods and cancer” but “we are a long way from understanding the full implications of food processing for health and wellbeing.”
They point to several challenges, such as identifying the precise elements in ultra-processed foods that could lead to cancer, and the potential impact of other unmeasured factors on the results.