Inflammation: what it is, anti-inflammatory diet, symptoms and treatment

The BHF explains that inflammation is the body's natural defence system. When you are injured or infected, the immune system releases chemicals that increase blood flow and bring immune cells, which clear out harmful particles, to the damaged area.

It is therefore a normal and useful process in the short term. Problems arise when the response does not switch off, or is triggered when there is nothing to heal.

The BHF says research suggests what we eat can influence inflammation. Foods such as blueberries, olive oil, spinach, green tea, turmeric and oily fish may have anti-inflammatory effects, while processed meats, foods high in saturated fat and sugary drinks can promote it. It adds that most studies have been done in labs on concentrated extracts, so it is unclear if individual foods alone can prevent or cause inflammation.

The strongest evidence, the BHF says, comes from population studies on whole diets. Patterns rich in fruit, vegetables, wholegrains, unsaturated oils, beans, nuts and fish, such as the DASH and Mediterranean diets, lower heart disease risk, partly by improving cholesterol and blood pressure and reducing inflammation.

There is no official anti-inflammatory diet. The BHF advises eating a diverse range of fruit, vegetables, wholegrains, fish and healthy oils rather than focusing on specific foods. If you have a chronic inflammatory condition such as rheumatoid arthritis or inflammatory bowel disease, it says to talk with your doctor before making dietary changes.

• Fruit and vegetables: the BHF suggests at least 5 portions a day, in different colours.

• Wholegrains, beans, lentils, nuts and seeds: sources of fibre that feed healthy gut bacteria.

• Oily fish such as mackerel, salmon and sardines: the BHF suggests a portion a week, and says omega-3 foods are more beneficial than supplements.

• Fermented foods such as yogurt, kefir and kimchi.

• Foods linked to more inflammation: processed meat, and sugary and fatty foods such as sugary drinks, cakes and biscuits.

• The BHF notes that in the UK "anti-inflammatory" is not an authorised health claim, so no commercially sold food should carry it on a label.

Inflammation does not have one set of symptoms, because it depends on where in the body it is and what is causing it. Our sources describe it through specific conditions.

In joints, the NHS says arthritis causes pain, swelling and stiffness, and that symptoms may suddenly get worse in what is called a flare-up that can last several days. For rheumatoid arthritis the NHS adds that some people have more general symptoms such as tiredness and weight loss.

Chronic inflammation inside blood vessels may cause no symptoms at all until a heart attack or stroke occurs. The BHF says chronic inflammation plays a key role in atherosclerosis, the build-up of fatty material in blood vessel walls.

Short-term inflammation follows injuries and infections. Long-term (chronic) inflammation, the BHF says, can result from persistent infections, autoimmune disorders like rheumatoid arthritis and lupus, or lifestyle factors like smoking and obesity.

Rheumatoid arthritis shows how an autoimmune cause works. The NHS says it is an autoimmune disease, meaning the immune system attacks the cells that line the joints by mistake, making them swollen, stiff and painful. It is not clear what triggers this, though the NHS says risk is higher if you are a woman, have a family history or smoke.

Treatment depends on the cause. For pain and swelling the NHS says NSAIDs can help, and that they are commonly used for headaches, painful periods, sprains and strains, colds and flu, and conditions such as arthritis. Some are sold in shops and pharmacies, such as ibuprofen, aspirin and diclofenac gel; others, such as naproxen, need a prescription.

NSAIDs can cause side effects. The NHS lists indigestion, stomach ache, feeling or being sick, diarrhoea, dizziness, rash and headaches as common, and says rare serious effects include stomach ulcers or bleeding, kidney problems and allergic reaction. The NHS says to ask your doctor or pharmacist if you are unsure, particularly if you take other medicines such as anticoagulants, steroids or blood pressure tablets.

For arthritis the NHS says there is currently no cure but treatments can manage symptoms, including physiotherapy, occupational therapy, medicines to relieve pain, swelling and inflammation or reduce immune system activity, and surgery if symptoms are severe. For rheumatoid arthritis the NHS says early diagnosis and treatment enable many people to have months or even years between flares.

Alongside diet, the BHF says you can help control inflammation by not smoking, staying physically active and maintaining a healthy weight. These habits also help lower cholesterol, blood pressure and blood sugar.

The NHS arthritis page gives similar advice for joints: regular low-impact exercise such as swimming, walking, pilates and yoga, a healthy balanced diet, a healthy weight, not smoking and not drinking too much alcohol.

For joint inflammation the NHS says to see a GP if you have unexplained pain, swelling or stiffness in your joints that does not go away in a few days.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you have severe pain and swelling in just one joint that started suddenly, pain that does not improve with paracetamol, a red or hot joint, sore joints with a high or low temperature or feeling hot, cold or shivery, or sore joints with sore eyes or problems with vision.

On the NHS, persistent inflammation is usually assessed by a GP, who may arrange blood tests and, if an autoimmune condition is suspected, refer you to a specialist such as a rheumatologist. The NHS says that in many areas you can refer yourself to NHS community musculoskeletal services for back or joint help.

Private rheumatology and general medicine consultations are also available on a self-paid basis or through insurance.