It’s the latest health buzzword, linked to every major age-related disease from hypertension to heart disease, dementia, type 2 diabetes and cancer. Inflammation – that same process that causes pain, heat, redness and swelling if you stub your toe or experience a throat infection – is increasingly recognised as a vanguard of ill-health and frailty. And now a plethora of books, diets and blogs advocates an anti-inflammatory lifestyle as the ultimate route to health and happiness.

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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 build-up 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.

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 towards developing type 2 diabetes. As levels of glucose in the blood climb higher, 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.

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. 

It can be exacerbated by smoking, or even 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.

The sex hormones oestrogen and testosterone are anti-inflammatory, so as these decline, inflammation can creep up.

The best way to avoid it? Exercise. When muscle moves, it stimulates the production of anti-inflammatory cytokines, which counteract inflammation in the muscles and elsewhere in the body.

Is there an anti-inflammatory diet?

Type “anti-inflammatory” into a web search, and you’ll be confronted with thousands of books, each promising to curb inflammation by making better food choices. Says Philip Calder, a nutritional immunologist at the University of Southampton: ‘There isn’t a magic anti-inflammatory diet; an anti-inflammatory diet is a generally healthy diet.’

Omega-3 fatty acids in oily fish and polyphenols found in some fruit and vegetables, and olive oil help control inflammation in several ways, including by maintaining a beneficial balance of fats in the outer membranes of our cells, particularly our immune cells.

Polyphenols reduce inflammation by acting as antioxidants. The daily influx of fats and sugars is associated with an inflammatory response that lasts several hours, in part, because metabolising them generates free radicals that cause cellular damage. Antioxidants mop them up. Polyphenols also interfere with the production of inflammatory molecules by immune cells.

Of course, another benefit of a healthy diet is that it helps you reduce body fat – another potent source of inflammation. ‘Diet, exercise, healthy lifestyle, minimising stress, getting enough sleep... are beneficial at the molecular level and the cellular level, as well as just making you feel a lot better,’ says Lynne Cox, a biochemist at the University of Oxford.

The Daily Telegraph