Body’s Ability to Fight off Food Poisoning Depends on Time of Day

The levels of antimicrobial molecules that help fight off food poisoning fluctuate depending on the time of day, according to a new study.
September 14, 2021

Our body’s ability to fight off food poisoning may depend on the time of day, according to a new study conducted by scientists at the University of Texas Southwestern (UTSW).

“Our findings suggest that there are peak times in which the body is more primed to fight infections,” says John F. Brooks II, Ph.D., the study’s leader and a professor of immunology and microbiology at UTSW.

The study shows that the body’s ability to produce a natural antimicrobial compound that helps to prevent the growth of microorganisms such as bacteria could fluctuate depending on the time of day. The levels of these antimicrobial molecules may actually increase during the day when we are more likely to be exposed to harmful bacteria.

Circadian cycles can affect our health

Circadian cycles are part of the body’s internal clock, generally repeating every 24 hours and helps animals’ bodies to accomplish essential functions and prepare for changes in their environment. Most animals, including humans, follow circadian cycles and one of the most well-known examples is the sleep-wake cycle.

A disruption in the circadian cycle can lead to health consequences. In humans, an increase in intestinal infection seems to be tied to chronic sleep disruption, although it’s unclear as to why this happens. The study set out to investigate whether the body’s immune response in the intestines might also fluctuate on a circadian cycle.

Antimicrobial molecule generation in mice

The researchers investigated this hypothesis by looking for patterns in the creation of natural antimicrobial compounds produced to fight food-borne illness in the gut of mice. In regular lab mice, they found that levels of a certain antimicrobial molecule that can fight food-borne illness — known as regenerating islet-derived protein 3g (REG3G) — was higher at night when the mice were more active. Mice raised to have no gut bacteria essentially had no REG3G during both day and night.

Mice that had cycling amounts of REG3G also had large amounts of segmented filamentous bacteria in their guts. This bacteria is also present in rodents, humans and nonhuman primates and they attach to the host animal’s intestinal lining during feeding, likely to drain nutrients off from the host.

The researchers saw that when the bacteria attached, REG3G production also increased in the intestines. The cycling production of REG3G had a large effect on the ability of mice to fight off infection. When mice were infected with bacteria, the mice who could not produce antimicrobial proteins like REG3G had higher rates of bacterial burden and death. Regular mice who were infected also had higher rates of bacterial burden and death when they were exposed during sunset instead of sunrise.

How does this affect humans?

If further research shows that humans follow the same antimicrobial production cycle, the results of this study could mean that the levels of antimicrobial compounds needed to effectively fight off harmful bacteria that causes food poisoning are lower overnight, when our gut defences are at their lowest.

This could also lead to innovative ways to maximize the body’s immune response. With this knowledge, scientists could use timed administration of synthetic antibiotics and oral vaccines as a more effective strategy to fight off intestinal infections, or even find new ways to avoid these infections altogether.