You and Your Diet

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One of the main areas of interest in altering diet to help people with psoriatic arthritis, has been in the use of fish oils. More precisely it is the type of fatty acids present in large quantities in the fish oils which are of importance. These are known as the n-3 or omega-3 long-chain polyunsaturated fatty acids, eg DHA and EPA.

Evidence suggests that these n3 fatty acids may help with some inflammatory conditions such as rheumatoid arthritis but the beneficial effect in psoriasis is less certain. Large, double blind, placebo-controlled studies have shown that fish oil or fish oil combined with evening primrose oil, did not produce any clinical benefit in the treatment of psoriasis (Soyland et al 1993, Oliwiecki et al 1994). However another study concluded that dietary advice to include 170g of oily fish daily led to a modest clinical improvement in ((chronic-plaque)) psoriasis (Collier et al 1993).

There is good evidence that n3 fatty acids have an important role in maintaining heart health and can reduce the risk of having a fatal heart attack. The British Nutrition Foundation (1992) suggested an intake of 2­3 medium servings of oil-rich fish per week and the Dept of Health (l994) recommended an intake of one portion of oily fish per week. Examples of oil-rich fish are mackerel, salmon, kippers, herrings, sprats, trout, sardines and pilchards. Tinned tuna is not a good source because of losses incurred during processing.

Another fatty acid, alpha-linolenic acid, can be converted into n3 fatty acids in the body. Good sources of this are linseed (flax) oil, rapeseed (canola) oil, soyabean oil and some nuts, particularly walnuts. Meat and meat products and green leafy vegetables are also useful sources.

Fish liver oils, such as cod liver oil are rich in Vitamin A and D. These vitamins are very useful for the elderly and housebound but can be toxic if the recommended intake is exceeded. Fish body oils do not have these high levels of vitamins.
There is concern about various toxic compounds such as mercury, dioxins and polychlori­nated biphenyls in oily fish and fish oils. The Food Standards Agency (FSA) published results of a survey of fish oil supplements bought from UK retailers and 2 brands were withdrawn from sale. However exposure to dioxins has decreased considerably over the past 20 years and the FSA has recommended that people should continue to eat oily fish regularly as part of a balanced diet to reduce the risk of heart disease.

In 1996 (Naldi et al) a study found that people with the highest intakes of fresh fruit, carrots, tomatoes and beta-carotene were less likely to have psoriasis. Betacarotene is found in many fruits and vegetables, particularly yellow or red varieties. There is a clear link between eating a diet sufficient in fruit and vegetables and reduced risk for some diseases, but the usefulness of taking betacarotene as a supplement is not established and may even be harmful. It seems to be the complex mixture of constituents in foods which is beneficial for health, rather than a high intake of one particular nutrient.
Both under-nutrition and obesity can be a risk with arthritic conditions. Poor nutrition, because of difficulties shopping and preparing meals will take it’s toll on health such as in reducing immune function, muscle weakness, delayed wound healing and poor morale.

Obesity can easily develop when mobility is reduced or with an inappropriate dietary intake. Excess weight will increase the burden on joints and add to mobility problems. Losing weight means changing eating habits for ever, not just for a few months. Exercise is also important for weight control as well being essential to preserve strength and range of movement.

Health experts agree on the following advice to ensure a balanced diet and to help with weight control and prevention of common diseases:

  •  enjoy a variety of different foods
  •  eat plenty of foods rich in starch and fibre
  •  eat at least five fruit and vegetable portions a day
  •  eat moderate amounts of lean meat or alternatives
  •  eat or drink moderate amounts of lower-fat milk and dairy foods
  •  eat fatty foods sparingly and choose lower-fat alternatives
  •  use less salt at the table and when cooking

Many people find it difficult to prepare foods and so their diet can be limited for that reason. Aids such as electric can openers are available in general and specialist shops. Different cooking methods such as stir-frying, microwave ovens and electric steamers can avoid the need to handle pans of hot water

New products available in supermarkets also take some of the work out of cooking. Hot food counters can offer ready roasted meats, and chilled counters have ready to eat smoked fish, low fat cheeses, salads and lean meats.

Increasingly people are using complete ready prepared meals. Choose meals with care, avoiding pastry and rich, creamy sauces which are high in fat. To help stay within healthy eating guidelines look for meals which are less than 20g fat and less than 2g salt (0.7g sodium) per serving. Try to base the other meals in the day on simple, unprocessed foods, such as cereals, breads, fruit and vegetables.

So diet does not by itself hold the key to treatment of psoriasis, but it’s influence on health as a whole is indisputable. Whatever our lifestyle we can aim for a balanced, enjoyable diet.


''Soyland E, Funk J, Rajka J et al.(11 993) Effect of dietary supplementation with very long chain fatty acids in patients with psoriasis. New England Journal of Medicine 328(25):1812-6
Oliwiecki S, Burton A (1994) Evening primrose oil and marine oil in the treatment of psoriasis. Clinical and Experimental Dermatology 19(2):127-9.
Collier PM, Ursell A, Zaremba K et al. (1993) European Journal of Clinical Nutrition 47(4)251-4
Department of Health (1994) Nutritional Aspects of Cardiovascular Disease. Report on Health and Social Subjects No. 46. HMSO, London
British Nutrition Foundation (2000) n-3 Fatty Acids and Health Briefing Paper.
Naldi L, Parazzini F, Peli L et al (1996) Dietary factors and the risk of psoriasis. Results of an Italian case-control study. British Journal of Dermatology ''