The influence of nutrition on both the risk and progression of MS
There has been an explosion of interest in the role of vitamin D in the last ten years. Despite its name, vitamin D is actually a hormone that performs many roles in the body. We have long known that it acts together with calcium to keep bones healthy and we now know that it is also involved in the regulation of T cell-mediated immunity, hence a possible reason why it may influence autoimmune conditions such as MS.
The risk of MS is greater in higher latitudes with less sunshine than closer to the equator. Many theories have been considered to explain this, including the role of vitamin D. While an active form of vitamin D can be obtained in small amounts from the diet, most of us rely on the conversion of vitamin D, from an inactive to an active form, by the action of sunlight on our skin. This requires only 15-20 minutes exposure on our hands and face on most days during the summer months.
Research suggests that low circulating levels of vitamin D in the population may increase risk of MS. This is particularly associated with low levels of vitamin D in pregnant women and an increased risk of MS in their children. This suggests that vitamin D supplements for young women may be an effective future strategy to reduce risk of MS, but this is still very much a subject of on-going research.
Low levels of vitamin D have repeatedly been shown in studies of people with MS and supplementation is an intriguing topic of research. At present there is no consensus on whether vitamin D would be an effective treatment to reduce the rate or severity of MS relapses and caution is advised in the use of cod liver oil as it can adversely interact with other medications. While the Cochrane Collaboration - an independent body that reviews the published research about drugs and treatments - has advised that there is inadequate evidence to support use, NICE (the National Institute for Health and Clinical Excellence) is soon to begin updating its clinical guidance on MS and will undoubtedly consider any new evidence on the role of vitamin D.
Dietary fat and type of fat
There is still debate on whether dietary fat influences both the risk of developing MS in the first place and the rate and severity of relapses once it is established. The interpretation of nutritional research is very complicated. Research on fat intake may be confounded by other nutrients in the diet or other environmental variants. Changing one nutrient in a diet always causes parallel changes in other nutrient levels and that could affect results.
People who adhere to a very low fat diet in long-term studies may also be different in their disease pattern from those who don't manage to cope with a strict regime. They may also differ in their health choices, such as whether they take vitamin supplements. While many scientists and many people with MS do believe that there is good evidence to show that people with MS would benefit from a diet low in animal fat, there are just as many who feel that this is not proven. The jury remains out and unfortunately as this type of research is very difficult to do, we are unlikely to resolve this for a very long time.
Studies suggest that over 50% of people with relapsing remitting MS are overweight or obese, which is similar to levels in most populations. The majority of people with MS would therefore benefit from a low fat diet, using small amounts of vegetable oils in preference to animal fats to reduce the risk of obesity and heart disease, especially if activity levels are also low.
Where weight loss is a problem, an appropriate choice of food with a higher fat content needs to be included in the diet and guidance from a dietitian may be helpful.
The use of supplements of omega-3 (eg fish oil) and omega-6 (eg linoleic acid from sources such as sunflower and safflower oil) has remained popular over the past decade. While a re-evaluation of earlier research by NICE in 2003 encouraged their use, a Cochrane review of 2007 concluded that there was presently no evidence of benefit. Both omega-3 oils and omega-6 oils influence the inflammatory response in MS in complex ways that remain poorly understood, so further research in this field would be very welcome.
The dietary intake of people with MS
A number of relatively small studies have examined dietary intake in MS. Around 60% of subjects reported taking fish oil supplements and similar proportion took multivitamins. People were taking a wide variety of vitamin and herbal supplements, such as cranberry juice, ginkgo biloba, ginseng, St John's wort, evening primrose oil and valerian.
There is a growing concern for the risks associated with taking multiple preparations, especially if taken together with prescribed medication. Herbal supplements such as ginkgo biloba, St John's wort and ginseng are known to interact with common medications and may reduce their effectiveness or worsen side effects. It's important that you let your doctor know of any vitamin or herbal preparation you take.
A scan of the internet shows an array of special MS diets that usually involve taking a wide range of dietary supplements to compensate for very restricted menu patterns. Although individuals can choose their preferred diet, to date there is no credible research to support the use of any of these regimes, though this of course may change in future years.
So where does this leave us regarding dietary advice for people with MS? In essence our approach today remains that of encouraging healthy eating principles: a varied diet based on lean meats, wholegrain cereals and low fat dairy products with a good variety of fresh fruit and vegetables. Eating should be a pleasure, so enjoy your food. It's your food, your diet and your choice.
There is better awareness today among health professionals that people with MS care about their diet and use food choice as a self-management tool. As such, diet should be recognised as an important part of holistic care and it would be ideal if everyone had the support to identify a personal nutrition care plan. Evidence suggests that this remains a luxury for most. To address this we really need to continue to work towards providing evidence, through further research, that diet therapy has a positive influence on well-being in MS.
Written by Anne Payne, dietitian, Plymouth University for Open Door - February 2012
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