Whether it’s 5:2, 16:8 or Eat Stop Eat, intermittent fasting diets have skyrocketed in popularity in recent years. Proponents of the diets claim they bring all manner of health benefits, from simple weight loss to significant falls in blood pressure, blood sugar and cholesterol.
Now, a study carried out in mice at the University of British Columbia in Canada suggests that fasting may also help to protect us from infection.
When humans or animals develop an infection, they often lose their appetite. However, it has so far remained unclear as to whether fasting could protect a host from infection or increase their susceptibility to it.
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To test this, the team fasted a group of mice for 48 hours and orally infected them with Salmonella enterica serovar Typhimurium – a bacteria responsible for a high proportion of cases of gastroenteritis in humans – part way through.
They found that the fasted mice had fewer signs of bacterial infection and very little intestinal tissue damage compared to fed mice. However, when they repeated the experiment with fasted mice infected with Salmonella intravenously the protective effect was not seen.
Similarly, the protective effect was not seen when they repeated the experiment a third time using germ-free mice – mice bred to lack a normal microbiome. This suggests that the effect was due to changes in the mice’s gut microbiomes.
When food is limited, the microbiome appears to sequester the nutrients that remain, preventing pathogens from acquiring the energy they need to infect the host, the team say.
“We saw an overall change in the composition of the microbiome, meaning an increase in some bacteria and a decrease in other bacteria,” said study leader Prof Bruce Vallance of the Division of Gastroenterology, University of British Columbia.
“However, we did not show in our study which bacteria specifically is responsible for the protective effect, just that the microbiome as a whole is mediating most of the protective effect of fasting since mice lacking a microbiome (germ-free mice) are not as protected from the infection.”
The team now plan to investigate the effect of fasting on the microbiome further with the aim of establishing whether the absence or presence of specific bacteria is responsible for the protective effect.