Everyone knows if a car is running hot, you’re headed for a breakdown – and there is now strong evidence that it’s the same for humans, too, with studies showing a significant link between chronic inflammation and serious health issues.
Inflammation is an important part of our body’s defence system. It mobilises the immune system to combat bacteria and other pathogens, or repair damage such as a sprained muscle. That’s why infections trigger a raised temperature and the site of an injury is often warmer to the touch than the surrounding healthy tissue.
But when this short-term response does not deactivate properly, or unhealthy lifestyle choices keep it simmering away in the background, prolonged inflammation can increase your risk of cardiovascular disease, type-2 diabetes, arthritis, cancer and many other life-limiting problems.
One study estimated that three in five people will die as a result of diseases linked to chronic inflammation, and researchers warn that the numbers affected are expected to rise steadily.
Another found 50 per cent of all deaths are caused by conditions linked with inflammation, and spotlighted the link to heart disease, stroke, cancer, diabetes, chronic kidney disease, non-alcoholic fatty liver disease and autoimmune and neurodegenerative conditions.
Professor Claire Bryant, an expert in inflammation at the Department of Medicine at Cambridge University, says: “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.
“Inflammation seems to underpin most diseases of old age. As we age, we also go into a condition called inflammaging, where you start to have higher markers for inflammation in the blood.”
This age-related inflammation is linked to the reduction in muscle mass, bone strength and immunity, which are hallmarks of ageing.
Warning signs: There are no reliable tests to identify chronic inflammation. Routine blood tests often include checks of C-reactive protein, which is a marker for inflammation, but this is designed to measure short term flare-ups associated with infections or an injury rather than lower level chronic inflammation, and symptoms are easily dismissed as a feature of busy lifestyles or getting older.
Signs of chronic inflammation include aches and pains, insomnia, chronic fatigue, depression and mood disorders, gastric symptoms such as constipation, diarrhoea and acid reflux, weight gain or loss and frequent infections.
Risk factors: Professor Bryant says there is still a lot to learn, and it’s also likely that there is an element of chicken-and-egg to the risk factors for chronic inflammation, which have already been identified.
But studies have highlighted getting older, obesity, a diet high in refined sugar and saturated and trans-fats, smoking, stress and sleep disorders and low levels of sex hormones such as oestrogen and testosterone.
There are also recognised connections that could amplify some of these risk factors and promote a vicious cycle of ongoing inflammation. For instance, a diet high in sugar and fat is likely to lead to weight gain, poor sleep has been shown to increase the risk of obesity and hormone levels decline with age.
Professor Bryant explains: “Inflammation can start to ramp up and get out of control, because once it starts, inflammation becomes a bit of a vicious cycle. You have to really interfere with that with medication and dietary and lifestyle changes.”
Medical measures: Another clue to the link between inflammation and conditions such as heart disease and diabetes comes from studies that found medicines used to reduce the risk of these problems also decreased inflammation.
Statins are widely prescribed and best known for lowering cholesterol, but studies show these drugs also reduce inflammation, and researchers now believe this is one of the reasons statins protect against hardening of the arteries and coronary heart disease.
Metformin, a common treatment for diabetes, also damps down chronic inflammation. Scientists are still unpicking the mechanisms and pathways behind this anti-inflammatory action, but a study published earlier this year suggested: “Metformin could be repurposed to address a range of complications, including inflammation, infections, and even cancer.”
Hunger gains: A number of studies have shown that fasting reduces inflammation. Both alternate day fasting, where calories are tightly constricted on every second day, and time-restricted eating, where the daily calorie intake is confined to a narrow window of four to six hours, are both proven to lower inflammation, so long as this leads to reduction in body weight of at least six per cent.
Professor Bryant’s research has revealed a surprising mechanism behind this reduction in inflammation. Fasting increases levels of arachidonic acid, an omega-6 fatty acid, which had previously been identified as a driver for inflammation.
“We never expected that,” she says. “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.”
But she says there is still a lot to learn, and advises against fasting without speaking to your GP. “There are a whole range of conditions, including diabetes, where you have to be very careful.”
Fats and inflammation: Our intake of different fats and fatty acids has been shown to influence levels of -inflammation, for better or worse. Studies underline the general health advice to cut back on saturated fats and increase intakes of omega-3 fatty acids.
Saturated fats are bad news, not only because they increase the odds of being overweight, but also because they short-circuit our immune system and increase the inflammasome activity which drives inflammation.
Getting the right balance of omega-6 and omega-3 fatty acids also appears to be important. Until around 100 years ago, the ratio of omega 6 to 3 in our diet was around four to one, but as a result of increased use of omega-6 fats, such as sunflower and soya oils, the ratio in a typical Western diet is now around 20 to one – and some scientists believe this promotes low-level inflammation.
The anti-inflammatory properties of omega-3 are well documented. Professor Philip Calder, an expert in nutritional immunology at the University of Southampton, has shown two of the omega-3 fats in oily fish, DHA and EPA, “give rise to newly discovered resolvins which are anti-inflammatory and inflammation resolving”.
Sleep on it: Multiple studies confirm that disrupted sleep increases the risk of a wide range of health problems and symptoms associated with inflammation, and this research adds to the evidence of a link between inflammation and many diseases of older age.
Researchers at Oxford University calculate good sleep patterns reduce the risk of dying from cardiometabolic diseases, such as heart attack, diabetes and stroke, by up to 39 per cent, and cuts the chance of death from cancer by up to 19 per cent. A key driver for this appears to be inflammation.
Poor sleep also increases our risk of obesity and appetite for foods that are high in saturated fats and sugar, which feeds into this vicious cycle of ongoing inflammation.
Work it out: Exercise is proven to stall many of the diseases and deficits which are the hallmarks of ageing and some of this is down to its impact on inflammation and factors such as obesity and sleep, which are also drivers for inflammation.
Short bursts of intense activity appear to be particularly helpful, but at little as 20-minutes of exercise a day has been shown to lower inflammation. Resistance training is also proven to damp down inflammation, which aligns with NHS advice to do a mixture of moderate activity for at least 150 hours a week.
Follow your gut: Professor Sarah Jarvis, visiting professor of general practice at the University of Huddersfield, says there is increasing evidence that our gut microbiome – the balance of good and bad bacteria – has an impact on inflammation.
Studies show diets high in animal products, processed food, sugar and alcohol increase levels of the gut bacteria that promotes inflammation, while high-fibre plant based foods and omega-3 fatty acids encourage the growth of anti-inflammatory gut bacteria.
Lactobacillus casei, an ingredient in a number of probiotic yogurts and drinks, is one of a number of friendly bacteria which have been shown to damp down inflammation.