October 15, 2024

expert reaction to perspective piece discussing ultra-processed foods and public health warnings

A perspective piece published in PLOS Medicine looks at ultra-processed foods and public health warnings. 

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

“The term “ultra-processed food” (UPF) encompasses a very broad and poorly defined category of manufactured food products ranging, for example, from canned soft drinks to highly processed breakfast cereals, cakes, and commercially prepared ready meals.  In recent years, many epidemiological studies conducted across the industrialised world have shown associations between high consumption of UPF and various adverse health outcomes, but the associations, though statistically significant, are often not particularly strong.  The broad and imprecise definition of UPF, coupled with the limitations of observational research, have so far made it extremely difficult to identify causal mechanisms associated with particular foods.  Having considered the current state of knowledge, which is based largely on observational studies, the authors of this timely and thoughtful opinion piece are right to draw attention to the current dearth of definitive mechanistic research on this topic, and to emphasise the difficulties and possible adverse consequences of issuing blanket advice to consumers to avoid such a wide range of foods.”

Dr Hilda Mulrooney, Reader in Nutrition & Health, London Metropolitan University, said:

“This is an important and timely paper, given the current level of interest in UPFs and their potential effects on health.  I think this is a reasonable and realistic perspective of where we are at the moment.  It summarises a lot of complex discussion and presents a rational and cautious viewpoint, in my opinion.  It is sensible not to rush to judgment on the basis of data which does not yet demonstrate causality.  It is important to acknowledge the fact that for some groups in particular, foods classed as UPFs make very significant contributions to nutrient intakes, and these would be difficult to achieve otherwise.

“Much of the research available shows associations between UPFs and health outcomes and cannot demonstrate causality.  This distinction is important, given that many UPFs (e.g. breakfast cereals, breads) make substantial contributions to nutrient intakes in the UK population.  The contribution will be greater for some groups than others, and as the authors suggests, a group likely to be most affected by blanket advice to avoid UPFs is those on lower incomes, who are already at greater risk of poor health and health inequalities.

“The potential mechanisms of action of UPFs in relation to ill health are unknown, although several have been suggested.  If causality between poor health outcomes and intake of UPFs is demonstrated – and it has not been so far – then understanding how this is happening will be an important aspect of the health messages crafted.  Much of the research on UPFs focuses on the NOVA classification, a system which has been criticised for failing to include or acknowledge the nutritional contributions of UPFs, focusing instead on the extent and type of processing involved.  This ignores the emerging evidence that different groups of processed foods may have different effects in the body.  There may well be stronger evidence in the future which will allow focused messages in relation to specific types of UPFs and health, but at the moment we do not have this information.  Given this, and the potential for harm to already vulnerable groups of a blanket message about UPFs, the balanced approach of these authors is sensible.  What we know now does not change the messages we have already had in place for some years – to cut down on the UPFs which are high fat, salt and sugar foods and drinks as much as possible and include whole foods in the diet where possible.  We need to understand what the effects of different groups of UPFs on health may be, whether relationships observed are causal or not, and how any relationships are mediated.  We are not there yet.”

‘Ultraprocessed food (UPF), health, and mechanistic uncertainty: What should we be advising the public to do about UPFs?’ by Eric Robinson and Alexandra Johnstone was published in PLOS Medicine at 19:00 UK time on Tuesday 15 October 2024.

DOI: 10.1371/journal.pmed.1004439

Declared interests

Dr Ian Johnson: “I have no current conflicts of interest.  I have previously acted in an advisory capacity both to a leading food manufacturer (Barry Callebaut), and to government agencies including SACN, but I have received no funding of any kind from the food industry in the last 5 years.”

Dr Hilda Mulrooney: “I have no conflicts of interest to declare.”