Recent studies on mice suggest that fasting for an entire day can have a negative impact on the immune system. A team of researchers from the Icahn School of Medicine at Mount Sinai in New York analysed blood and tissues samples from five mice that had been deprived of food for 24 hours. The results showed that the mice had a reduced number of monocytes, a type of white blood cell which helps fight infections.
When the mice were given access to food again, the number of monocytes increased fourfold. To understand the implications of fasting on the immune system, the researchers injected 45 mice with a strain of bacteria. 23 of the mice had fasted for 24 hours prior to the injection. After 72 hours, nearly 90 per cent of the fasting mice had died, compared to 60 per cent of the mice that had not fasted. These mice also exhibited greater levels of inflammation.
Despite this, Satchidananda Panda at the Salk Institute for Biological Studies in California states that most common fasting regimens for humans don’t last 24 hours. Nonetheless, the study’s lead researcher, Filip Swirski, warns that “balance is important” when it comes to fasting and that it may have an unanticipated negative effect on the immune system.