How discrimination turns our stomach

Skin color, age, sex... Discrimination takes many forms but always has the same intent: to reject and exclude a person or a group of people. According to a study of different American populations, discrimination may affect not only the digestive system (specifically the gut microbiota), but also the brain system and the communication between the two (known as the gut-brain axis). More surprisingly, the effects and mechanisms at play could depend on the person’s ethnicity.

Effects of discrimination: causing havoc with the gut microbiota in African-Americans

Among African-Americans, high discrimination, usually based on skin color, can even affect the bacteria found in the gut microbiota, creating a condition known as dysbiosis.

For example, the researchers found increased levels of bacteria, especially a proinflammatory species called Prevotella copri, in African-Americans who had been subjected to high levels of discrimination. Brain images (using MRI, or Magnetic Resonance Imaging) reveal stimulation of areas involved in the regulation of negative emotions. In terms of mental health, although high discrimination led to increased levels of anxiety and stress (as with other groups), there was no observable association between discrimination and mental health (unlike for other communities). According to the authors, discrimination does trigger strong inflammation among African-Americans, but this group is more resilient and less prone to depression.

Different mechanisms for other communities

Comparable assessments of the gut microbiota, blood markers, brain activity, and mental state revealed very different responses in the other groups.

• Among Hispanics, discrimination was also associated with inflammation, but it was overcome by better coping strategies and cognitive control.
• Asians appeared to demonstrate very different mechanisms: increased discrimination went hand in hand with increased metabolites related to cholesterol and brain activity, suggesting that they dealt with stress by eating foods high in fat.
• Finally, the discrimination experienced by Caucasians was primarily based on age and sex. It was associated with anxiety but not inflammation. Their guts contained a lower concentration of P. copri compared to the Hispanic and African-American communities. The MRI results for this group also showed brain changes that could indicate coping difficulties.