Scientists shed light on inflammation’s pros and cons
It helps protect our bodies, but can also lead to many serious problems
It’s the latest health buzzword, linked to every major age-related disease from heart disease to dementia, Type 2 diabetes and cancer. Inflammation — that same process that causes pain, heat, redness and swelling if you stub your toe or get a throat infection — is increasingly recognized as a vanguard of ill-health and frailty. Now a plethora of books and blogs advocate an anti-inflammatory lifestyle as the ultimate route to health and happiness.
So what is inflammation, and why is it so dangerous?
“Inflammation is the way your body tries to defend itself against danger,” says Dan Davis, an immunologist at the University of Manchester and author of The Beautiful Cure. Without it, wounds would fester and mild infections could kill us. When we become injured or infected with a bacterium or virus, our tissues respond by releasing chemicals called cytokines. These summon immune cells to help kill infectious agents, as well as cells to help repair any damage by laying down new tissue.
The inflammation associated with such events tends to be severe and is often painful, but it usually disappears once the problem has been dealt with. However, in chronic inflammation — which is the type associated with age-related disease and frailty — levels of these inflammatory chemicals are lower but remain raised for far longer.
“That’s when it becomes detrimental,” says Janet Lord, director of the Institute of Inflammation and Ageing at the University of Birmingham. “Chronic inflammation is like a grumbling, low level of inflammation, which can go on for years.”
The effects on the body can be deadly. For instance, in atherosclerosis, a buildup of fatty plaques in the blood vessel walls triggers inflammation. If a piece of it breaks off and triggers a clot, this can cause a heart attack or stroke.
Inflammation may also contribute to the buildup of fatty materials in the first place. “In the late ’90s, people started saying that heart disease is an inflammatory disease, and you can lower people’s risk by treating them with anti-inflammatory drugs like aspirin,” says Philip Calder, a nutritional immunologist at the University of Southampton.
More recent research has also revealed that statins — primarily prescribed to lower cholesterol — also have an anti-inflammatory effect, which may be another means by which they reduce the risk of heart disease.
Inflammation also makes insulin — the hormone that enables glucose to be released from food — work less well, a first step toward developing Type 2 diabetes. As levels of glucose in the blood climb, this irritates the body’s tissues, triggering further inflammation.
In muscle, chronic inflammation activates enzymes that produce the hormone cortisol, which can trigger breakdown of muscle and bone. “This is one of the reasons why you become frailer as you grow older,” says Lord.
Some scientists even believe that inflammation may be the cause of clinical depression — at least in a subset of cases. Chronic inflammation in middle age, meanwhile, is increasingly being linked to memory loss and dementia as people grow older. And obesity researchers are turning their attention to the role inflammation plays in weight gain.
The causes of chronic inflammation are the usual lifestyle culprits. A major source of inflammation is body fat, or adipose tissue. As we gain weight, our fat cells find it increasingly difficult to receive enough oxygen.
“That’s a danger signal to cells, and the way we respond to danger is through inflammation,” explains Calder. “Being obese is a risk factor for heart disease, and maybe one of the reasons is that adipose tissue drives low-grade inflammation.”
It can be exacerbated by smoking, or vaping, because some of the inhaled chemicals trigger an immune response. Other sources of low-level inflammation include lack of sleep, emotional stress, and a diet high in sugar and certain types of fat.
But even healthy non-smokers may have some grumbling, lowgrade inflammation in their bodies — particularly as they get older.
The sex hormones estrogen and testosterone are anti-inflammatory, so as these decline, inflammation can creep up.
Aging is also associated with the accumulation of senescent cells, ones that refuse to die, instead growing larger and more stressed. “One of the key things they do is to switch on a pile of inflammatory genes,” says Lynne Cox, a senescence researcher at the University of Oxford. This aging-related inflammation even has a name: “inflammaging.”
What’s the best way to avoid it? One proven strategy is exercise. When muscle moves, it stimulates the production of anti-inflammatory cytokines, which counteract inflammation in the muscles and elsewhere in the body.
“Hippocrates, in 400 BC, said that exercise is man’s best medicine, but his message has been lost over time, and we live in an increasingly sedentary society,” says Lord. “As we get older, levels of inflammation in the body tend to creep up, but if you keep your weight down and keep physically active then you can prevent inflammaging; it is not inevitable.”
Inflammation is the way your body tries to defend itself against danger. Chronic inflammation ... can go on for years.