Diet and arthritis: what the evidence shows

To be clear from the start, arthritis has no dietary cure, whether a food, an eating plan or a supplement. How much diet can help depends heavily on the kind you have. Weight is the main route by which food affects osteoarthritis. Rheumatoid arthritis and the other inflammatory kinds are driven by the immune system, so medicines do the controlling and food can only back them up. The sections below take each in turn, then the claims worth doubting, and finally the signs that need medical help.

Here diet has its firmest evidence. In osteoarthritis, especially of the knee, shedding surplus weight brings pain down and lets the joint move and bear load more easily, and NICE advises weight loss for anyone with osteoarthritis who is living with overweight or obesity: any amount is likely to help, and losing a tenth of your body weight is likely to help more than a twentieth. Part of the effect is mechanical, since the force through the knees when walking can be two or three times your body weight. Part may be chemical, since fat tissue can feed inflammation. In an 18-month trial in people with knee osteoarthritis and excess weight, those who lost weight by diet had lower forces through the knee and a lower level of a marker of inflammation than those who only exercised, and diet combined with exercise eased pain and improved function the most. Eating a balanced diet with the right amount of energy to reach and hold a healthy weight does more for osteoarthritis than any other change to what you eat, and exercise alongside it helps you keep muscle while you lose fat.

For people with an inflammatory arthritis such as rheumatoid arthritis, a Mediterranean pattern of eating, built on olive oil, fish, pulses, nuts, wholegrains, fruit and vegetables, with less red and processed meat, has been found helpful by some. The omega-3 fats in oily fish and fish-oil capsules may slightly lessen joint pain and the stiffness of the morning. A large review of the research found moderate evidence of small benefits from some foods and nutrients, and no strong evidence that any single change makes a meaningful difference, so think of this as healthy support rather than treatment. Weight matters here too: excess weight can make some specialist medicines, such as biologics, work less well, and may keep the disease more active.

None of this takes the place of your disease-modifying medicines (DMARDs): they hold the disease in check and guard the joints from damage, so carry on taking them as prescribed. Some arthritis medicines interact with particular foods or drinks; ask your team whether yours do.

Much of the popular advice about diet and arthritis has little evidence behind it:

• Nightshades are fine. Studies show no link between tomatoes, peppers, aubergines or potatoes and inflammation.
• There is no evidence that gluten causes arthritis. Research has not tied it directly to any type of arthritis. Coeliac disease is a different matter, and a gluten-free diet is the treatment for it, but it has to be diagnosed first, since it can be missed by testing once gluten has been cut out.
• Cutting foods out is no general fix. Exclusion diets have no evidence in osteoarthritis. Some people with rheumatoid arthritis, though only a few, react badly to a particular food; a dietitian can run a supervised exclusion programme to identify it, which is safer than cutting foods out for good on your own. Fasting is not recommended.
• Glucosamine and chondroitin have no strong evidence of a meaningful benefit in osteoarthritis, and NICE advises against glucosamine.
• Probiotics have no proven benefit in inflammatory arthritis, as gut health and arthritis explains.
• Be wary of miracle cures. No diet or supplement has been shown to cure arthritis, so costly plans that promise to are best left alone.

A good diet earns its place even when the joints themselves gain little. Because rheumatoid arthritis and some other kinds raise the chance of heart disease, eating along Mediterranean lines and keeping to a healthy weight look after the heart as well as the joints, and your general health too. If you are weighing up a weight-loss medicine, weight, weight-loss medicines and your joints covers what it can and cannot do; if you have gout, gout and diet covers urate, alcohol and why crash diets are best avoided.

Problems with food seldom need quick help in arthritis, but some gut and joint signs do, and for those the two lists that follow name the right service, beginning with 999 or A&E.

Treat any of these as a 999 or A&E emergency: call 999 and do not drive yourself to A&E.

• Severe illness with suspected sepsis: a high fever with shaking, confusion, rapid breathing, or feeling dramatically worse over hours
• With a fever or feeling unwell, a rash that does not fade when you press it, a stiff neck with eyes that cannot bear bright light, or skin, lips or tongue turning blue, grey, pale or blotchy, since these can be signs of meningitis or sepsis, as can a very bad headache, confusion or a first seizure with a fever or feeling unwell; on black or brown skin the rash and the change of colour may be easier to see on the palms of the hands or the soles of the feet
• A joint you cannot put weight on or move, or that has moved out of place, or, after a fall or injury, very bad pain or any tingling or numbness
• A stomach ache that came on very suddenly or is severe, or a stomach that hurts when you touch it, since its cause has to be found at once
• Vomiting blood, or bleeding from the back passage that is heavy or will not stop, most of all with faintness, confusion or pain in the abdomen, or vomit that is black or dark brown, since heavy bleeding in the gut needs treatment in hospital
• Lips, mouth, throat or tongue that suddenly swell, a throat that feels tight, very fast breathing or a struggle to breathe or to swallow, skin, tongue or lips turning blue, grey or pale (on black or brown skin this may be easier to see on the palms of the hands or the soles of the feet), becoming suddenly very confused, drowsy or dizzy, or fainting and not being able to be woken, since this can be a severe allergic reaction, anaphylaxis, which can follow a dose of any medicine

Any of these needs an assessment that is urgent, on the same day, from your GP or NHS 111:

• A joint that is hot and swollen, with a fever or feeling unwell, since an infected joint has to be ruled out at once, at A&E or through NHS 111
• A joint that has become hot and very swollen suddenly, or is worsening quickly, even without a fever, since an infected joint does not always announce itself with one
• Joint pain with a fever, or feeling hot, cold or shivery, or generally unwell, since an infection in or around a joint has to be found the same day
• Stools that are black or dark red, or bloody diarrhoea, since the gut may be bleeding and the cause needs finding that day; bleeding from the back passage that is heavy or will not stop belongs to the first list

A joint that becomes hot and swollen for the first time, which can be gout or an infection, belongs to the same-day list. Weight lost without trying is for a GP within days. A stomach ache that is severe or came on suddenly, or one with a stomach that hurts when you touch it, belongs to the first list; one that lasts, keeps returning or grows much worse, or that comes with bloating that will not settle or keeps recurring, weight lost without trying or diarrhoea lasting more than a few days, is for your GP or NHS 111 that day, as gut health and arthritis sets out with the other gut signs; if coeliac disease is a possibility, keep eating gluten until the diagnosis is confirmed. No referral is needed to be seen here; next-working-day appointments can almost always be arranged, and same-day appointments are sometimes possible. If you take a DMARD or a biologic, the warning signs that belong to each are set out in our guides to DMARDs and biologics and JAK inhibitors. If you cannot tell how urgent something is, asking is never a mistake.

Start with a clear diagnosis, because eating for osteoarthritis and eating for rheumatoid arthritis call for different priorities. Each condition has its own guide, rheumatoid arthritis and osteoarthritis, and arthritis and exercise explains why movement matters as much as food. Before a big change in what you eat, speak to your team; and a diet is never a reason to stop a treatment you have been prescribed.

Can a change of diet cure arthritis?

No. Neither a diet nor a supplement has been shown to cure arthritis, and a change of diet is unlikely to do as much as medical treatment. In inflammatory arthritis such as rheumatoid arthritis, medicines are what control the disease and diet plays a supporting part; in osteoarthritis, its biggest contribution comes through weight. Do not stop a prescribed treatment in favour of a diet.

Which change to my diet does the most good?

Losing any extra weight, if you have osteoarthritis. Strong evidence shows that it eases the pain and helps the joint do its work, the knees in particular, because a lighter body means a lighter load on the knee at each step. NICE advises that any weight loss is likely to help, and that losing a tenth of your body weight is likely to help more than losing a twentieth.

Do tomatoes, peppers and other nightshades make arthritis worse?

Studies have not linked nightshade vegetables, such as tomatoes, peppers, aubergines and potatoes, and inflammation. They carry useful vitamins and minerals, so cutting them out without advice from a doctor or dietitian is not recommended.

Are fish oil and omega-3 worth taking?

It may help a little in inflammatory arthritis. Oily fish, or fish-oil supplements, may ease joint pain and morning stiffness, though the benefit in studies is small, and a supplement can take up to three months to help. The British Dietetic Association suggests two portions of oily fish a week for rheumatoid arthritis; check with your doctor before starting a supplement, and keep it alongside your treatment, not in place of it.

Is an anti-inflammatory or exclusion diet worth trying?

The Mediterranean pattern, which this guide describes in its own section, has some research behind it, though the findings are not conclusive. Exclusion diets have no evidence behind them in osteoarthritis; in rheumatoid arthritis they sometimes help, but the food involved differs from person to person and may reflect an allergy or intolerance rather than the arthritis. Cutting out whole food groups on your own risks running short of nutrients, so if you want to try it, do it with a doctor or dietitian, and keep up your prescribed treatment throughout. If you suspect coeliac disease, do not cut out gluten before the diagnosis is confirmed, because the tests need gluten in your diet to give an accurate result.