In public health nutrition, highly processed foods (HPFs) are increasingly linked to many diseases, including diabetes, cardiovascular diseases and cancer. There remain significant research gaps on the health effect of these foods. A Perspective on this subject, outlining a research roadmap in this area, has been published in Nature Food by Mike Gibney, Emeritus Professor of Food & Health at University College Dublin and Ciarán Forde, holder of the Chair of Sensory Science and Eating Behaviour at the Division of Human Nutrition and Health at Wageningen University & Research.
At present, there are four operational definitions of HPFs, each leading to a different conclusion as to their links to health. Such variability is unacceptable in the science of public health nutrition, state Gibney and Forde. This research roadmap should therefore give high priority to the development of an objective approach to classifying foods according to their level of processing. Any such definition must have a specified end point (e.g. facilitating taxation, restricting advertising, or food labelling) and must make sure that staple foods – which make a significant positive contribution to existing dietary habits – are not discriminated against.
Correlational versus Analytical
The present literature on processed foods and health outcomes shows a high degree of repetition of correlational studies, state Forde and Gibney. While correlational research can demonstrate a relationship between variables, such studies cannot prove cause-and-effect relationships. Therefore, a greater emphasis on analytical studies is very much needed. A major priority must be in clarifying whether HPFs, which tend to have a high energy density, are associated with obesity, independent of energy density, and whether HPFs are linked to chronic disease through their impact on nutrient profiles of populations or independent of components of HPFs such as food additives.
Sensory Properties of Highly Processed Foods
The mechanism by which processed foods promote intake is currently not known, though some speculate these foods are ‘hyper-palatable’. Evidence for such claims is lacking, and research suggests combinations of soft textures, fast eating rate and high energy density are a more likely explanation for increased energy intake from processed food. Confirming this will create new opportunities for food reformulation in the future.
The current recommendation to avoid processed food by a growing number of institutions and policy makers, poses a significant challenge for consumers. Over two thirds of our food supply is classified as processed or highly processed. The paper presents a research roadmap to address current knowledge gaps, suggests reformulating processed foods to enhance nutrient density, and calls for consensus on an appropriate food-processing classification system.