Highly processed food may lead to greater cancer ‘burden’

Rising consumption of highly processed foods such as ready meals and fizzy drinks “may drive an increasing burden of cancer in the next decades”, a new study suggests.

The possible association between these foods and cancer was identified in the study, which examined the medical history of more than 100,000 people and was carried out by researchers based in France and Brazil.

However, the connection is not definitive and further exploration is needed, according to the research, published by the BMJ.

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.

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They are thought to account for over 40 per cent of total daily energy intake in many developed countries, including Ireland.

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, the authors acknowledge.

The 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 online dietary questionnaires, designed to measure intake of 3,300 different food items.

Risk factors

Foods were grouped according to the degree of processing and cases of cancer were identified from participants’ declarations – and validated by medical records and national databases.

Risk factors for cancer, such as age, sex, educational level, family history, smoking status and physical activity levels, were factored in. 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 11 per cent in the risk of breast cancer. No significant association was found for prostate and colorectal cancers.

Prof Donal O’Shea, consultant endocrinologist at St Vincent’s Hospital, Dublin, said the study provided “the clearest signal yet” that ultra-processed foods were linked to cancers, and were linked to common cancers in a young population. The connection with certain cancers but not all was also notable, he added.

The Irish Cancer Society (ICS) said the research findings are interesting but that as this is an "observational study" no firm conclusions can be drawn about cause and effect.

“It doesn’t mean that we should completely avoid all ultra-processed foods to reduce our risk of cancer,” added ICS head of cancer research Dr Robert O’Connor.

Ultra-processed foods were often very high in energy and, in general, “the more energy-rich foods we eat, the more likely we are to put on weight”, he pointed out.

Being overweight increased chances of being diagnosed with a number of cancers, including cancers of the breast and bowel, he said. “That is why a mixed diet, rich in vegetables fruits, pulses, rice, past, eggs meat, fish and milk, is so important.”

He added: “This paper clearly indicated that other lifestyle factors were very important in understanding the findings. For example, the data clearly show that those with higher levels of processed food intake were also more likely to be smokers and exercise less - two lifestyle factors which we know increase the risks of several common cancers.”

Noting the best advice for those wanting to reduce their risk of cancer is to follow the 12-step European Code Against Cancer, Dr O'Connor said: "This includes getting out and being active, eating a healthy mixed diet rich in vegetables and fruits and reducing alcohol consumption."

Ultra-processed foods explained

Ultra-processed foods include cereals, sugary and savoury snacks, crisps, highly processed meats and breads, ready meals and sauces.

They contain - in addition to salts, sugars oils and fats - substances that imitate the taste and texture of foods prepared from scratch. For that reason, they have been described as “food-like”.

Such foods are “calorie dense” but not necessarily filling, according to nutritionists.

Ultra-processed foods are often characterised by lower nutritional quality. They invariably contain additives but also substances from packaging in contact with food, and compounds formed during production, processing, and storage.

A recent Journal of Public Health Nutrition study found the Irish shopping basket contained 46 per cent ultra-processed foods, making Ireland the third-highest consumer after Britain (51 per cent) and Germany (46 per cent).

Portugal and Italy had the lowest consumption levels at 10.2 per cent and 13.4 per cent respectively.