Preferences for nutrients and sensory food qualities identify biological sources of economic values in monkeys

Preferences for foods high in sugar and fat are near universal and major contributors to obesity. Additionally, human food choices are sophisticated and individualistic: we choose by evaluating a food’s nutrient content and sensory features, and trade them against quantity and cost. A study published this Monday in the Proceedings of the National Academy of Sciences reveals that such food preferences are based on subjective valuations of specific nutrients and related sensory food qualities, linking the oral-sensing mechanism of fat content to food choices.

In their latest study, PhD candidate Fei-Yang Huang and Dr Fabian Grabenhorst from the Department of Physiology, Development and Neuroscience at the University of Cambridge investigated the behavioural mechanisms behind human-like food choices in monkeys choosing liquid foods (flavoured milkshakes) with defined nutrient contents. They found that the animals consistently preferred fat and sugar to low-nutrient alternatives. Importantly, rather than maximizing calories indiscriminately, each individual animal seemed to assign subjective values to specific nutrients, flexibly trading them against offered reward amounts. The monkeys’ preferences shifted their daily nutrient balance away from dietary reference points, resembling human suboptimal eating in free-choice situations.

To understand how the animals sensed the nutrient content of the foods, the authors collaborated with Prof Michael Sutcliffe at the Department of Engineering (Cambridge) and measured the mechanical properties of liquids with different fat and sugar content. They then used both the foods’ nutrient contents and mechanical food properties to model the animals’ choices. They found that two key properties of a food’s texture—its viscosity and sliding friction—explained the behavioural preferences for liquid fatty foods: the animals’ typically preferred milkshakes that were thick and slippery, indicating higher fat content.

Overall, this research shows how human-like food preferences derive from the biologically critical components of foods, including their nutrients and oral-mechanical properties. As a next step, the authors investigate how individual neurons in the brain’s reward system process nutrients and food choices, to better understand human eating behavior and obesity.

Funding: This research was funded by a Wellcome Trust - Royal Society Sir Henry Dale Fellowship awarded to Dr Fabian Grabenhorst.

Reference: Huang, Sutcliffe and Grabenhorst (2021) Preferences for nutrients and sensory food qualities identify biological sources of economic values in monkeys. Proceedings of the National Academy of Sciences USA 118. doi: 10.1073/pnas.2101954118