HOW, ASKS GILBERT GEE, PHD, professor of community health sciences at the UCLA Fielding School of Public Health, does somebody treating you unfairly literally make you sick? To find answers to that question, he and an interdisciplinary team of researchers at UCLA are exploring the ways racism, stress and everyday discrimination affect and alter our brains, gut microbiomes and immune systems. “Right now, there are a lot of calls to treat racism as a public health crisis,” Dr. Gee says.
Evidence demonstrates that structural racism and everyday discrimination can, in fact, lead to many negative effects on health, including obesity, diabetes, heart disease, preterm birth, anxiety, depression and suicide ideation. “The research we’re doing is what we call systems biology,” says Arpana Gupta, PhD, associate professor in the UCLA Vatche & Tamar Manoukian Division of Digestive Diseases. “It’s about looking at health and disease from more than one angle, within the body but also how the body interacts with the environment.”
The UCLA researchers, hypothesizing that everyday discrimination would affect stress responses, which in turn would influence adverse health outcomes, surveyed 154 Black, Latino, Asian and white individuals from Los Angeles. They collected data including MRI scans, anthropometrics (height, body mass index and waisthip ratios), blood samples and stool samples. They also collected questionnaire data on early-life adversity, resilience, eating habits and physical and mental health symptoms, such as stress, anxiety and depression.
Participants of all ethnic and racial backgrounds self-reported experiences of racism and discrimination, says Tien Dong, MD, PhD, assistant professor in the Division of Digestive Diseases. Most intriguing, he says, was how these experiences presented differently in the brain, body and gut for each race. Patterns in the research suggest that for Black and Hispanic individuals, discrimination leads to changes that include increased systemic inflammation. For Asian individuals, the patterns suggest possible responses to discrimination include somatization, or the production of multiple medical symptoms with no discernible known cause. Among white individuals, discrimination is related to anxiety but not inflammation.
Without stratifying the data by race, researchers observed that people who had experienced discrimination also had an increase in the emotional arousal regions of the brain. The limbic regions of the brain, which are associated with the stress response of fight or flight, showed increased connectivity.
Participants who self-rep o r t e d e x p e r i e n c e s o f discrimination also showed decreased connectivity in the frontal regions of the brain, the areas responsible for things such as cognitive reasoning, thinking, memory and executive function. “I think of the frontal region as the brakes,” Dr. Gupta says. “Our research shows that, in general, if you’re experiencing discrimination, you’re not able to pump the brakes as efficiently and effectively.”
The patterns show differences in the ways various individuals internalize and cope with discrimination and stress. These new clues give researchers a better understanding of the ways discrimination can lead to poorer health outcomes. “I think we’re getting closer to understanding mechanistically how racism gets into the body,” Dr. Gee says. “We’ve had a couple of studies in the past that give us some clues here and there, but they are snapshots of different parts of the body or different systems working in the body. I think here, what we’re trying to do is understand the totality of how racism works within the body, between the brain and the gut and other systems.”
Discrimination rewires how the brain copes with stress, the researchers say. When the stress network is disrupted, it has the potential to promote anxiety and diminish sleep and appetite, all of which have an effect on health.
Stress signals in the brain can influence the gastrointestinal process, including gene expression patterns in certain gut microbes. The gut also communicates with the brain, which affects neural signaling. Inflammation mediates the communication process between the gut and brain.
Black and Latino participants who reported discrimination had correspondingly lower levels of “helpful” anti-inflammatory gut bacteria. In Asian individuals, high levels of discrimination seemed to correspond with metabolites linked to fat and cholesterol, indicating lesshealthy eating habits.
Dr. Gee says this study “connects the dots” on how racism affects the body as one system, by showing how the ways in which discrimination is processed in the brain can affect inflammation and gut microbiome changes. Dr. Gupta believes that with more granularity in data and more work, such as looking at differences among gender, we can come closer to understanding the ways discrimination affects the body over time. This study supports the idea that social inequities affect health.
Part of what excites Dr. Gupta about this study is that it reinforces previous research that the gut microbiome is influenced by the environment more than by genetics. “As a researcher, it’s empowering to me because that means we can implement changes to counteract the effects of discrimination,” she says. “You might not be able to change your genetics, but you can change your environment or, at the very least, how you deal with the environment. You can do something that is empowering.”
