Supplementary, my dear doctor

The use of diet to help control pain and symptoms is one way in which people with arthritis can do something to help themselves. Up to 75 per cent of patients believe that the food they eat affects their condition.

While there is no evidence that would stand up to scrutiny that fad diets are effective, a number of patients can certainly benefit from making some change to their diet or introducing dietary supplements.

Some studies have shown that up to 30–40 per cent of patients with rheumatoid arthritis may benefit from a diet in which a range of foods is eliminated and then reintroduced into the diet to identify “culprit foods” that they must then avoid.

Culprit foods vary considerably from one individual to the next. Some patients can remain well, off all medication and controlled by diet alone, for periods of up to 12 years.  However, such a strategy is risky and should only be carried out under the supervision of a dietician as there is a real risk of developing nutritional deficiencies.

The most important dietary intervention osteoarthritis patients can make, if they are overweight, is to reduce their body weight

Other rheumatoid arthritis patients have benefitted from sticking to a Mediterranean diet, rich in plant foods (fruit, vegetables, wholegrain cereals, beans, nuts and seeds), fish, poultry and olive oil, and with low-to-moderate amounts of dairy products, red meat and wine.

There is no evidence that patients with osteoarthritis can benefit from eliminating foods. The most important dietary intervention osteoarthritis patients can make, if they are overweight, is to reduce their body weight. Losing excess weight reduces the stress on weight-bearing joints by as much as four-fold and can help prevent the condition from getting worse.

However, it is really important to lose fat and retain muscle so osteoarthritis patients really need to combine exercise with dieting for weight loss. Doing resistance exercise (with weights) is particularly important to maintain muscle.

All arthritis patients, other than those with gout, should increase their intake of oily fish to two portions a week. Oily fish has an anti-inflammatory effect which may benefit not only patients with rheumatoid, but also those with osteoarthritis. Those who do not eat oily fish could supplement their diet with fish oil for up to three months to see whether they have fewer symptoms.

Rheumatoid arthritis patients may find that supplementing their diet with four high-strength fish oil capsules a day, even if they eat oily fish, can provide further benefit. But, because of their genetic make-up, some people will not improve with fish oil and should therefore stop supplementing.

Oily fish (but not fish-oil capsules, with the exception of cod liver oil) may also benefit arthritis patients because it is the best source of vitamin D in our diet. Low vitamin D has been linked to both rheumatoid and osteoarthritis. Vitamin D is primarily made in the skin on sun exposure; populations in northern areas have inadequate vitamin D status, particularly in the winter.

Rheumatoid arthritis patients, who do not eat oily fish, should supplement with 1,000 IU (25mcg) of vitamin D daily. Cod liver oil is an alternative source, but contains only 5 to 8mcg of vitamin D per gram. Osteoarthritis patients may also benefit.

There is evidence of the importance of vitamin C, vitamin E, selenium, copper and zinc in avoiding some joint problems, and there is some evidence of a positive effect of vitamin E on pain. Most people don’t eat the recommended levels of these nutrients, particularly selenium, and so may benefit from a supplement that supplies the recommended daily amount.

But beware: there is no scientific evidence to support taking very high doses of supplements. High doses of individual nutrients can be harmful and should be avoided.

Margaret Rayman is professor of nutritional medicine at the University of Surrey where she directs a highly respected MSc programme.