Cambridge scientists may have identified a new approach for fasting to reduce inflammation, a potentially harmful side effect of the immune system that underpins a variety of chronic diseases. In a study published in Cell Reports, the researchers reveal how fasting increases levels of arachidonic acid, a molecule in the blood that prevents inflammation. According to the researchers, it could also help explain some of the benefits of medications like aspirin.
Scientists have long known that our food, particularly a high-calorie Western diet, might increase our risk of diseases such as obesity, type 2 diabetes, and heart disease, all of which are associated to chronic inflammation in the body.
Inflammation is our body’s natural response to injury or infection, but this process can be triggered by other mechanisms, including by the so-called ‘inflammasome’, which acts like an alarm within our body’s cells, triggering inflammation to help protect our body when it senses damage. But the inflammasome can trigger inflammation in unintentional ways – one of its functions is to destroy unwanted cells, which can result in the release of the cell’s contents into the body, where they trigger inflammation.
This provides a potential explanation for how changing our diet – in particular by fasting – protects us from inflammation, especially the damaging form that underpins many diseases related to a Western high calorie diet.
Professor Bryant
Professor Clare Bryant from the Department of Medicine at the University of Cambridge said: “We’re very interested in trying to understand the causes of chronic inflammation in the context of many human diseases, and in particular the role of the inflammasome.
“What’s become apparent over recent years is that one inflammasome in particular — the NLRP3 inflammasome — is very important in a number of major diseases such as obesity and atherosclerosis, but also in diseases like Alzheimer’s and Parkinson’s disease, many of the diseases of older age people, particularly in the Western world.”
Fasting has been shown to lower inflammation, however the exact mechanism is unknown. To assist address this question, a team led by Professor Bryant and colleagues from the University of Cambridge and the National Institute for Health in the United States examined blood samples from 21 volunteers who ate a 500kcal lunch and then fasted for 24 hours before eating another 500kcal meal.
The researchers discovered that calorie restriction boosted levels of arachidonic acid, a type of lipid. Lipids are chemicals that serve crucial functions in our bodies, such as storing energy and conveying information between cells. When they ate again, their arachidonic acid levels decreased.
When the researchers studied arachidonic acid’s effect on immune cells cultured in the lab, they found that it turns down the activity of the NLRP3 inflammasome. This surprised the team as arachidonic acid was previously thought to be linked with increased levels of inflammation, not decreased.
Professor Bryant, a Fellow of Queens’ College, Cambridge, added: “This provides a potential explanation for how changing our diet – in particular by fasting – protects us from inflammation, especially the damaging form that underpins many diseases related to a Western high-calorie diet.
“It’s too early to say whether fasting protects against diseases like Alzheimer’s and Parkinson’s disease as the effects of arachidonic acid are only short-lived, but our work adds to a growing amount of scientific literature that points to the health benefits of calorie restriction. It suggests that regular fasting over a long period could help reduce the chronic inflammation we associate with these conditions. It’s certainly an attractive idea.”
The findings also hint at one mechanism whereby a high-calorie diet might increase the risk of these diseases. Studies have shown that some patients that have a high-fat diet have increased levels of inflammasome activity.
“There could be a yin and yang effect going on here, whereby too much of the wrong thing is increasing your inflammasome activity and too little is decreasing it,” Dr. Bryant said. “Arachidonic acid could be one way in which this is happening.”
According to the researchers, the discovery may potentially provide light on an unanticipated mechanism by which so-called nonsteroidal anti-inflammatory medications like aspirin work. Normally, arachidonic acid is rapidly broken down in the body; however, aspirin inhibits this process, resulting in an increase in arachidonic acid levels, which reduces inflammasome activity and hence inflammation.
Professor Bryant said: “It’s important to stress that aspirin should not be taken to reduce risk of long terms diseases without medical guidance as it can have side-effects such as stomach bleeds if taken over a long period.”
