Cambridge scientists may have found a new way in which fasting helps reduce inflammation, a potentially damaging side effect of the body’s immune system that underlines several chronic diseases like Parkinson’s and Alzheimer’s. Fasting increases levels of a chemical in the blood known as arachidonic acid, which inhibits inflammation. The researchers believe it may also help explain some of the beneficial effects of drugs like aspirin.

For some time, scientists have known that our diet, particularly a high-calorie Western diet, can increase our risk of diseases, including heart disease, type 2 diabetes, and obesity, which are linked 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 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.

However, 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. 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.”

It follows the UK Prime Minister saying that fasting once a week was an “important discipline” for him as part of a “balanced lifestyle.” Rishi Sunak doesn’t eat anything for 36 hours at the start of each week, the Sunday Times reported. Fasting can help reduce inflammation, but the reason why has not been clear. Scientists at the University of Cambridge and the National Institute for Health in the USA, therefore, studied blood samples from a group of 21 volunteers who ate a 500kcal meal and then fasted for 24 hours before consuming a second 500kcal meal. The team found that restricting calorie intake increased levels of a lipid known as arachidonic acid.

Lipids are molecules that play essential roles in our bodies, such as storing energy and transmitting information between cells. As soon as individuals ate a meal again, levels of arachidonic acid dropped. When the researchers studied arachidonic acid’s effect on immune cells cultured in the lab, they found that it turned down the activity of the NLRP3 inflammasome. This came as a surprise as arachidonic acid was previously thought to be linked with increased levels of inflammation, not decreased.

Professor Bryant, a fellow of Queens’ College, Cambridge, said, “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,

She continued, “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.”