February 14, 2018

expert reaction to study looking at highly processed foods and cancer

A study, published in the BMJ, reports a possible association between intake of highly processed food in the diet and cancer.

Dr Ian Johnson, Nutrition researcher and Emeritus Fellow, Quadram Institute Bioscience, said:

“This is a very large observational study with careful and rigorous methods of data collection.  The authors have identified some rather weak associations, of low statistical significance, between some types of cancer and diet.  The problem is that the definition of ultra-processed foods they have used is so broad and poorly defined that it is impossible to decide exactly what, if any, causal connections have been observed.

“For the general public, the best approach to minimising the risk of most types of cancer remains to avoid tobacco use of any kind, take account of national diet and alcohol guidelines, eat substantial quantities of fresh fruit and vegetables, and maintain one’s body-weight within the recommended range.”

Prof. Tom Sanders, Professor emeritus of Nutrition and Dietetics, King’s College London, said:

“This study reports that the consumption of ultra-processed food was associated with an increased risk of cancer (12%) in both men and women.  The study also shows an association (an 11% increase in risk) with ultra-processed food for breast cancer especially in post-menopausal women.  There were no significant effects on specific cancer sites in men but the number of men studied was small as most of the men failed to provide online dietary records.

“The term ultra-processed food is difficult to define in terms of food quality, and is not widely used by nutritional scientists.  This study appears to be focused on demonstrating that industrially processed foods increase the risk of cancer.  The ultra-processed foods are focused on foods such as pot noodles, breakfast cereals, industrially-processed bread, pizza, cakes, crisps, ready-to-eat desserts, meat balls and chicken nuggets, confectionery, and fizzy drinks including those that are artificially sweetened.  However, the definition excludes many home-made or artisanal foods such bread, cakes, biscuits, butter, meat, cheese, tinned fruit and vegetables as well as sugar and salt used in domestic food preparation.  From a nutritional standpoint, this classification seems arbitrary and based on the premise that food produced industrially has a different nutritional and chemical composition from that produced in the home or by artisans.  This is not the case.

“The paper indicates that drinks and sugar-containing foods such as desserts and confectionery were the main sources of ultra-processed food rather than processed meat products (mechanically recovered meat, nitrite treated meat), which have been previously been linked to risk of breast and colon cancer.  The latest update on breast cancer by WCRF does not show a relationship with sugary foods or non-alcoholic beverages, but confirms the known association with physical activity, unhealthy weight gain in adult life and alcohol intake with risk of post-menopausal breast cancer.

“What people eat is an expression of their life-style in general, and may not be causatively linked to the risk of cancer.  So it is necessary to rule out what are called confounding factors – things already known to cause cancer such as smoking, obesity, alcohol intake and low intakes of fruit and vegetables, as the accompanying editorial notes.  The authors have attempted to do this with some statistical adjustments, which do not appear to alter their results.  However, the high-consumers did differ in several aspects that may have contributed to the risk associated with ultra-processed food intake.  For example, the participants who consumed a lot (33.3%) of these ultra-processed foods compared with those who consumed very little (about 18.7%) were more likely to be current cigarette smokers (20.2%  vs 16.9%),  physically inactive (24.7 vs 20.9%) and more likely to be taking oral contraceptives (30.8%  vs. 22.0%).

“In conclusion, the approach of categorising dietary patterns that depend on industrially processed food in relation to disease risk is novel but probably needs refining before it can be translated into practical dietary advice.”

* Paper: ‘Consumption of ultra-processed foods and cancer risk: results from NutriNet-Santé prospective cohort’ by Thibault Fiolet et al. will be published in the BMJ on Wednesday 14 February 2018.

Editorial: ‘Ultra-processed foods and cancer’ by Adriana Monge and Martin Lajous will be published in the BMJ on Wednesday 14 February 2018.

Declared interests

Dr Ian Johnson: “I have no conflicts of interest.”

Prof. Tom Sanders: “Scientific Governor of the British Nutrition Foundation.  He is now emeritus but when he was doing research at King’s College London, the following applied:

Tom does not hold any grants or have any consultancies with companies involved in the production or marketing of sugar-sweetened drinks. In reference to previous funding to Tom’s institution: £4.5 million was donated to King’s College London by Tate & Lyle in 2006; this funding finished in 2011. This money was given to the College and was in recognition of the discovery of the artificial sweetener sucralose by Prof Hough at the Queen Elizabeth College (QEC), which merged with King’s College London. The Tate & Lyle grant paid for the Clinical Research Centre at St Thomas’ that is run by the Guy’s & St Thomas’ Trust, it was not used to fund research on sugar. Tate & Lyle sold their sugar interests to American Sugar so the brand Tate & Lyle still exists but it is no longer linked to the company Tate & Lyle PLC, which gave the money to King’s College London in 2006.

Tom also used to work for Ajinomoto on aspartame about 8 years ago.

Tom was a member of the FAO/WHO Joint Expert Committee that recommended that trans fatty acids be removed from the human food chain. Tom has previously acted as a member of the Global Dairy Platform Scientific Advisory Panel and Tom is a member of the Programme Advisory Committee of the Malaysian Palm Oil Board. In the past Tom has acted as a consultant to Archer Daniel Midland Company and received honoraria for meetings sponsored by Unilever PLC. Tom’s research on fats was funded by Public Health England/Food Standards Agency.”