food The fats about sh oils Many of us have heard that fish oils and fatty acids are beneficial for those with arthritis, but what do they do? WORDS: PETER STANNETT ere told time and time again that oily fish is good for us, and that we should be consuming more as part of a healthy diet. But why? Fish oils contain fatty acids, and only two of these alpha-linolenic acid, an omega-3 fatty acid and linoleic acid, an omega-6 fatty acid are essential for humans (hence known as essential fatty acids). Fatty acids have a number of functions. Their main purpose in relation to arthritis is that they influence cytokine (proteins released by cells) production and eicosanoids (compounds derived from fatty acids), which are involved with antiinflammatory responses. How this is achieved, and the interaction between omega-3 and omega-6 fatty acids, is relevant to their role in arthritis. Apart from easing symptoms, they are also involved in the production of anti-inflammatory prostaglandins (fats), inhibiting the production of pro-inflammatory cytokines and preventing white blood cell proliferation, among others. NOW FOR THE SCIENCE BIT How to get that anti-inammatory eect Oily fish such as mackerel, salmon, sprats and sardines are the richest sources of two types of long-chain polyunsaturated fatty acids (PUFAs). However, for an antiinflammatory effect, researchers suggest that, if a serving of 150g is taken as an average, six to seven portions would need to be consumed in a week. Other researchers have suggested almost double that is needed to help inflammation. However, this is unrealistic and some fish may be contaminated with toxins, which could be harmful if consumed in excess. Fish oil supplements can be an effective alternative to increase the intake of longchain PUFAs. Fish oil supplements The amount you should take per day depends on the content of the supplement and the amount of fatty acids you are getting through your diet. If no oily fish is consumed, 21g long-chain omega-3 PUFAs are required. If two portions of oily fish are consumed per week, an additional 14.5g from fish oil capsules would be needed to bring it up to an anti-inflammatory or therapeutic dose. Cod liver oil is not the same as fish oil, but does contain a less concentrated source of long-chain PUFAs as well as vitamin A, D and E. Vitamin D can reduce the risk of osteoarthritis progressing low levels are often seen in elderly people. Be aware, however, that excessive intake of vitamin A is harmful in pregnancy. n Peter Stannett is information ocer at Arthritis Care; visit www.arthritiscare.org.uk Phospholipids (cellular building blocks), fats and glycolipids (which are a type of fat) are made up of fatty acids. The body can produce its own fatty acids, although it cannot produce those with double bonds on the acyl chain to produce alphalinolenic acid and linoleic acid, which are called the essential fatty acids. Some other fatty acids in foods can be converted from short chain fatty acids. Fatty acids are labelled using the number of carbon atoms on the acyl chain, followed by the number of double bonds in the chain. So, alpha-linoleic acid (ALA) is denoted as 18:3 (omega-3) and linoleic acid (LA) as 18:2 (omega-6). ALA and LA are known as polyunsaturated fatty acids (PUFAs) because they have more than one double bond. Because they have 18 carbon atoms, they are known as short-chain polyunsaturated fatty acids, and they can be converted to long-chain PUFAs.