Some people skip breakfast as part of a popular new diet. Doing so, however, is a bad idea, says a new study.
Fasting might be harmful to fighting off infection, according to the study by researchers at the Icahn School of Medicine at Mount Sinai Hospital in New York. Missing what the team calls “the most important meal of the day” also could even lead to a greater risk of heart disease.
Read More »Sets Off a Brain Response
The study, which was conducted on mice, is the first to show that skipping meals sets off a response in the brain that negatively impacts immune cells. It also could lead to an improved understanding of how chronic fasting might impact the body over the long term.
Awareness is growing that fasting is healthy, says lead author Dr. Filip Swirski, director of the Cardiovascular Research Institute at Icahn Mount Sinai. Indeed, evidence is abundant for the benefits of fasting, he adds, but this study presents a word of caution that fasting might also carry a health risk.
He explains that this study is a “mechanistic” one that delves into the fundamental biology that lies behind fasting. It shows that there is a link between the immune and nervous systems, Swirski says.
Two Groups Analyzed
The researchers aimed at a better understanding of how fasting affects the immune system—whether it be a fast of only a few hours that is relatively short or one that is as long as 24 hours.
In the study, researchers analyzed two groups of mice. One group ate a breakfast meal—the largest meal of the day—right after waking; the other group ate no breakfast. Researchers collected blood samples from both groups firstly when they woke up, secondly four hours later, and finally eight hours later.
When they examined the blood work, the researchers noted a definite difference in the group that had fasted. They found that there was a difference in the number of monocytes—white blood cells created in the bone marrow—that travel through the body. As they travel they perform a number of critical functions, from heart disease to infection and even to cancer.
Fasting Mice Radically Affected
At the start of the tests all the mice had the same number of monocytes, but after four hours the monocytes in the mice that fasted were radically affected, the study found. The researchers noted that as many as 90% of these cells disappeared from the bloodstream; the number fell even more after fasting for eight hours. At the same time the number of monocytes in the bloodstream of the group that did not fast remained the same.
In those mice that fasted, the research team found that the monocytes returned to the bone marrow in order to hibernate. At the same time, the production of new cells in the bone marrow lessened. The monocytes in the bone marrow—which typically have a short lifespan—changed significantly. Because they remained in the bone marrow, they stayed alive longer. They also aged in a different way than the monocytes that remained in the blood.
Cells Rushed Back
When the mice were fed again after being without food for 24 hours, those cells that had been hiding in the bone marrow rushed back into the bloodstream within the space of a few hours. This rush led to a raised level of inflammation. As a result, instead of protecting against infection, these changed monocytes become more inflammatory thereby rendering the body less resistant to fighting infection.
The study is one of the first to discover a link between the brain and the immune cells during fasting. The researchers found that specific areas of the brain control the way in which the monocytes act during fasting.
Why People Become ‘Hangry’
The findings showed that fasting causes a stress response in the brain. That reaction, they explain, is what makes people become “hangry” (feeling angry as well as hungry). Such a reaction instantly sets off a large migration of these white cells from the blood back to the bone marrow and then a sudden return into the bloodstream once food is introduced again.
Useful Advance
Swirski emphasizes that the new study is a useful advance toward a full understanding of how the body works.
On the one hand, he notes, the study shows that fasting cuts back on the number of monocytes that are circulating in the bloodstream. This might be seen as a good thing because the cells are an important part of inflammation.
On the other hand, however, the reintroduction of food causes a surge in the number of monocytes back into the bloodstream, which can create problems.
As a result, fasting regulates the pool of monocytes in ways that are not always good when it comes to the body’s ability to respond to a challenge such as an infection, Swirski explains.
Because these cells are so vital when it comes to other diseases, such as cancer and heart disease, it is critical to understand how their function is controlled.
The study is published in the journal Immunity.
