A number of reports show that animals have the ability to select foods based on their micronutrient composition. A team of international researchers wanted to find out if humans also have this ability. In response to this challenge, researchers developed an approach that derives evidence from patterns of choices across a range of food images.
The new report harkens back to controversial research carried out in the 1930s by pediatrician Dr. Clara Davis, who devised an experiment based on the hypothesis that children's bodies instinctively “knew best.” Davis put 15 babies on a self-selecting diet which allowed the babies to eat whatever they wanted. The babies had a choice of 33 food items and while no child ate the same combination, they all maintained a good state of health, which Davis took as evidence of "nutritional wisdom."
According to researcher Stephen Strauss, “Davis convinced unmarried teenage mothers and widows who could no longer support their families to place their infants in what amounted to an eating-experiment orphanage set up in Chicago.
"An eventual total of 15 children participated; the 2 boys who were studied the longest were followed over a 4 1/2-year period: that is to say, the amount of every single thing eaten or spilled at every single meal over the first 4 1/2 years of their eating life was assiduously recorded. To this was added records of changes in height and weight, the nature of bowel movements, and regular bone radiographs and blood tests. Davis reported that the experiment had generated somewhere between 36,000 and 37,500 (she was inconsistent on the figure) daily food records.”
The research led by Davis would be considered unethical today, therefore scientists had to find a new approach to pick up where Davis left off.
Continuing the quest
Lead author Jeff Brunstrom, Professor of Experimental Psychology at the University of Bristol, along with his team, approached the challenge ethically by simply showing people images of different fruit and vegetable pairings.
The research involved 128 adults in total in two experiments (Study 1, N = 45; Study 2, N = 83). The first study showed people prefer certain food combinations more than others, with participants preferring ‘varied’ over ‘monotonous’ pairs (same-food pairs were less attractive).
“However, and even after controlling for explicit nutritional knowledge (Study 2) and food energy density (Study 1 and 2), we observed a significant tendency to select pairings that offered: i) greater total micronutrient intake and ii) greater ‘micronutrient complementarity’ (MC), i.e., a broader range of micronutrients.
"In a separate analysis, a similar pattern was observed in two-component meals (e.g., steak and fries) drawn from a large national nutrition survey in the UK (1086 records). Specifically, the MC of these meals was greater than would be predicted by chance (p < .0001) and when a meal provided an excess of micronutrients (>100% daily recommended amount) then this occurred less often than by chance (p < .0001), i.e., ‘micronutrient redundancy’ was avoided,” the authors noted.
The researchers added that this work provides new evidence that micronutrient composition influences food choice (a form of ‘nutritional wisdom’) and it raises questions about whether nutritional requirements are otherwise met through dietary ‘variety seeking’. In turn, it also exposes the potential for a complexity in human dietary decision making that has not been recognized previously.
"The results of our studies are hugely significant and rather surprising. For the first time in almost a century, we've shown humans are more sophisticated in their food choices, and appear to select based on specific micronutrients rather than simply eating everything and getting what they need by default,” said Professor Brunstrom.
(2022). DOI: 10.1016/j.appet.2022.106055
“Micronutrients and food choice: A case of ‘nutritional wisdom’ in humans?”
Authors: J. Brunstrom et al