A recent study conducted by Zhang et al. revealed that exposure to discrimination is associated with dysregulations in the brain-gut-microbiome system, leading to an increased risk of obesity.

The study published in Nature Mental Health on October 2, 2023 included data based on 107 participants — consisting of 87 women and 20 men — recruited from the Los Angeles community through a volunteer sampling method.

Peri- and post-menopausal women as well as participants with certain medical conditions, psychiatric illnesses, comorbidities like vascular diseases or diabetes, substance use disorders, and those using specific medications were excluded from the experiment as these factors may influence the results.

The researchers gathered information on the participants’ BMI, race, age, sex, socioeconomic status (SES), and diet as well as collected function MRI (fMRI) images, faecal metabolomics, and clinical and behavioural measures.

Participants also had to complete the Everyday Discrimination Scale (EDS) — a measure of chronic experiences of unfair treatment.

The EDS assesses overall experiences of discrimination in daily life, without placing emphasis on any one specific type (e.g., race, gender).

Based on their EDS score, participants were categorised into high and low discrimination exposure groups.

In the study, Zhang and fellow researchers conducted a food-cue task using MRI to assess how the brain responds to different types of foods, including unhealthy sweet, unhealthy savoury, healthy sweet, and healthy savoury foods, as well as nonfood images.

They also recorded the participants' willingness to consume these foods.

Another part of the study consisted of analysing faecal samples from a subset of participants to investigate the glutamate metabolites, which are associated with the level of stress.

Structural equation modelling (SEM) was used to examine the relationships between the factors of exposure to discrimination, brain responses to food cues, and gut metabolites.

The results showed that individuals exposed to discrimination had greater brain responses to unhealthy sweet and savoury foods, especially in the frontal-striatal region which is associated with reward processing and motivation.

According to the researcher as reported by NBC News, “the heightened [food-cue reactivity] can lead people to reach for sugar and high-fat foods.”

Furthermore, individuals with high exposure to discrimination had higher levels of certain gut metabolites related to the glutamate pathway, which is significantly associated with oxidative stress, inflammation, and obesity-related mechanisms.

The findings of this study also suggests that discrimination exposure may also alter the complex bidirectional relationships between brain and gut alterations, leading to stress-induced preferences for unhealthy foods.

This suggestion may explain why individuals with high exposure to discrimination showed greater willingness to consume unhealthy foods compared to the low discrimination group.

However, the researchers also note that a limitation of the study was the generalisability as there was an under-representation of men.

Additionally, the participants of the study did not fully represent specific racial and ethnic groups, thus, the researchers did not have sufficient samples to conduct stratified analyses.

Finally, the study was solely a correlational study; longitudinal studies and experiments with more controls will be needed “to explore the causal effects of discrimination exposure and altered BGM signatures.”

Nevertheless, the study is valuable as it provides insights on the physiological impacts of discrimination on individuals.

The issue of discrimination has been a contentious topic for a significant period.

For instance, on September 13th of 2023, Hurley from The Independent reported that “Darryl George, a 17-year-old high school student in Texas, has been suspended for wearing a loc hairstyle.”

The research conducted by Zhang and colleagues not only underscores the detrimental consequences of discrimination exposure but also highlights the persistence of discrimination.

The researchers noted how SES was significantly lower in individuals with high discrimination exposure.

Overall, the study conducted by Zhang et al. illuminates the complex relationship between discrimination, the brain-gut-microbiome system, and unhealthy food preferences, emphasising the need for further research and awareness regarding the physiological consequences of discrimination.

USung Hwang

Grade 12

Seoul Foreign School