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MS research update - Can oily fish help to prevent MS? - 29 October 2013

Summary

This study involved 1,879 people with MS in Sweden. For each person, there were two control participants who were matched for gender, age and residential area. All the participants answered a questionnaire, which included two questions about eating oily fish (such as herring, mackerel, tuna or salmon).

The researchers found that frequently eating oily fish was associated with a decreased chance of getting MS. Eating lean fish (such as cod or haddock) did not have this protective effect.

People who ate more oily fish had higher levels of vitamin D in their blood.

Background

The cause of MS is not well understood but it seems that both genetic and environmental factors have to come together to trigger MS in an individual. One of the environmental factors which is receiving increasing attention is vitamin D.

Vitamin D is made when the skin is exposed to sunlight. However, vitamin D can be obtained through diet with oily fish being the best source.

This study looked at whether eating oily fish could decrease the risk of getting MS.

How this study was carried out

1,879 people with MS in Sweden, aged between 16 and 70, took part in the study. Almost three quarters (72%) were women and the average age of MS onset was 34. For each person, there were two control participants who were matched for gender, age and residential area. All the participants answered a questionnaire.

Two of the questions related to eating oily fish. Fatty fish species were defined as species with a fat content of more than 3%, and lean fish species with a fat content of less than 3%. The questions were:

Specify how often, on average, you have eaten these classes of fish during the last five years.

  1. Fatty fish (i.e. herring/mackerel/tuna/salmon/trout)
    • Never/seldom; 1-3 times/month; Every week; Daily
  2. Low-fat fish (i.e. cod/pollock/haddock/whiting/pike/perch)
    • Never/seldom; 1-3 times/month; Every week; Daily

Information on the participants' sun exposure in the previous five years was assessed using three questions:

  1. How often, during the last 5 years, have you used a sun-bed?
    • Never; A few times a year; Once a month; Once a week
  2. How often, during the last 5 years, have you visited a country that is sunnier than Sweden?
    • Never; More seldom; Once a year; More than once a year
  3. If the weather is sunny, how often do you usually sunbathe?
    • Never; A few times a month; A few times a week; Daily

Vitamin D obtained from dairy products in the diet was assessed using three questions:

How often, on average, do you currently eat/use when cooking the following products?

  1. Cheese: Number of slices/day or Number of slices/week
    • Fat cheese
    • Low-fat cheese
  2. Milk: Number of glasses/day or Number of glasses/week
    • Fat (fat content 3% or more)
    • Moderate (fat content around 1.5%)
    • Low-fat (fat content around 0.5% or less)
  3. Sour milk/yoghurt: Number of glasses/day or Number of glasses/week
    • Fat (fat content 3% or more)
    • Moderate (fat content around 1.5-2%)
    • Low-fat (fat content around 0.5% or less)
    • Other

Blood samples were available, and analysed for vitamin D levels, for most participants.

What was found

The researchers found that frequently eating oily fish was associated with a decreased chance of getting MS. Eating lean fish did not have this protective effect.

When the researchers took into account the participants' sunning habits and vitamin D obtained from dairy products, the protective effect of oily fish was still seen. Similarly, gender, ancestry (Scandinavian origins or not) and a range of other risk factors, including smoking, made no significant difference to the protective effect of oily fish.

People who ate more oily fish had higher levels of vitamin D in their blood.

What does it mean?

The researchers concluded that there is something present in oily fish which is not present in lean fish which can help to protect against getting MS. They believe that the protective factor is most likely to be vitamin D.

Comment

In Sweden where the above research took place, milk and dairy products have vitamin D added but this does not happen in the UK. Consequently, dairy products like milk and cheese, are not a good source of vitamin D if you live in the UK.

Bäärnhielm M, Olsson T, Alfredsson L.
Fatty fish intake is associated with decreased occurrence of multiple sclerosis. .
Mult Scler. 2013 Oct 24. [Epub ahead of print]
abstract

More about vitamin D

Vitamin D has several important roles in the body including making strong bones and teeth as well as regulating immune responses.

Lack of vitamin D may be involved in causing MS but it may also have a role in moderating relapses and disability in people who are already diagnosed with MS, as there is some evidence that lower levels of vitamin D are associated with higher relapse rates and greater disability. Also, one study found that people with progressive forms of MS had lower levels than those with relapsing remitting MS.

Some small studies have suggested that treatment with vitamin D may reduce the number of relapses experienced and two larger studies, involving about 250 people each, are still ongoing.

What might be a good diet for MS is the subject of much debate but perhaps the best evidence for what might be helpful is the increasing data on a positive role for vitamin D.

Sources of vitamin D

Vitamin D can be obtained in several ways. It is manufactured by the skin when it is exposed to sunlight, can be obtained in the diet or as supplements.

Vitamin D (vitamin D3) is created in the skin when exposed to ultraviolet B (UVB) radiation in sunlight. In the UK, between May and September, about 20 to 30 minutes a day spent outdoors in short sleeves in direct sunshine in the middle of the day will meet vitamin D needs for most fair skinned people. It is important not to get red or burnt as this raises the risk of skin cancer.

Between October and April, the sunlight in the UK usually has too low a level of ultraviolet B for vitamin D to be made.

Vitamin D is found in some foods including oily fish, such as salmon and sardines, and cod liver oil. Lower amounts are found in eggs, fortified fat spreads and breakfast cereals and in powdered milk.

In Sweden where the above research took place, milk and dairy products have vitamin D added but this does not happen in the UK.

Vitamin D dosage

Levels of vitamin D in the blood of people in the UK are generally low. The Department of Health reports that a quarter of the population have no more than a third of what is considered an adequate level.

For people with MS who have difficulty getting outdoors regularly or who find heat increases fatigue, supplements can also be useful. However, there is much debate as to what is an appropriate dose for people with MS.

The recommended daily intake in the UK (400IU) is based on reducing the risk of rickets and is widely considered to be too low. In August 2012, the European Food Safety Authority increased the Tolerable Upper Intake Levels (the levels that can be taken daily without causing harm) to 4000IU. Some authors feel this is also too low. NICE has begun to consider the implementation of existing guidance on vitamin D, a review that will look at its role in general rather than specifically in MS. A consultation on the draft version of this is expected towards the end of 2013.

You can read more about vitamin D in the A to Z of MS.

Research by topic areas...

Symptoms and symptom management

Valadbeigi A, Weisi F, Rohbakhsh N, et al.
Central auditory processing and word discrimination in patients with multiple sclerosis.
Eur Arch Otorhinolaryngol. 2013 Oct 23. [Epub ahead of print]
abstract

MS relapses

Ramo-Tello C, Grau-López L, Tintoré M, et al.
A randomized clinical trial of oral versus intravenous methylprednisolone for relapse of MS.
Mult Scler. 2013 Oct 21. [Epub ahead of print]
abstract

Drugs in development

Kappos L, Gold R, Arnold DL, et al.
Quality of life outcomes with BG-12 (dimethyl fumarate) in patients with relapsing-remitting multiple sclerosis: The DEFINE study.
Mult Scler. 2013 Oct 22. [Epub ahead of print]
abstract

Kita M, Fox RJ, Phillips JT, et al.
Effects of BG-12 (dimethyl fumarate) on health-related quality of life in patients with relapsing-remitting multiple sclerosis: findings from the CONFIRM study.
Mult Scler. 2013 Oct 22. [Epub ahead of print]
abstract

Sheikh SI, Nestorov I, Russell H, et al.
Tolerability and pharmacokinetics of delayed-release dimethyl fumarate administered with and without aspirin in healthy volunteers.
Clin Ther. 2013 Oct;35(10):1582-1594
abstract

Other treatments

Vollmer TL, Robinson MJ, Risser RC, et al.
A randomized, double-blind, placebo-controlled trial of duloxetine for the treatment of pain in patients with multiple sclerosis.
Pain Pract. 2013 Oct 24. [Epub ahead of print]
abstract

Epidemiology

Fragoso YD, Adoni T, Almeida SM, et al.
Multiple sclerosis in South America: month of birth in different latitudes does not seem to interfere with the prevalence or progression of the disease.
Arq Neuropsiquiatr. 2013 Sep;71(9A):573-9.
abstract
Read the full text of this paper

Causes of MS

Hedström AK, Hillert J, Olsson T, et al.
Smoking and multiple sclerosis susceptibility.
Eur J Epidemiol. 2013 Oct 22. [Epub ahead of print]
abstract

Olival GS, Lima BM, Sumita LM, et al.
Multiple sclerosis and herpesvirus interaction.
Arq Neuropsiquiatr. 2013 Sep;71(9B):727-30.
abstract
Read the full text of this paper

Paediatric MS

Etemadifar M, Afzali P, Abtahi SH, et al.
Safety and efficacy of mitoxantrone in pediatric patients with aggressive multiple sclerosis.
Eur J Paediatr Neurol. 2013 Oct 7. [Epub ahead of print]
abstract

Psychological aspects

Lehmann P, Eling P, Kastrup A, et al.
Self-reported sleep problems, but not fatigue, lead to decline in sustained attention in MS patients.
Mult Scler. 2013 Apr;19(4):490-7.
abstract

Physical activity

Briken S, Gold S, Patra S, et al.
Effects of exercise on fitness and cognition in progressive MS: a randomized, controlled pilot trial.
Mult Scler. 2013 Oct 24. [Epub ahead of print]
abstract

Schmidt S, Wonneberger M.
Long-term endurance exercise improves aerobic capacity in patients with relapsing-remitting multiple sclerosis: impact of baseline fatigue.
J Neurol Sci. 2013 Oct 9. [Epub ahead of print]
abstract

Mehanna R, Jankovic J.
Movement disorders in multiple sclerosis and other demyelinating diseases.
J Neurol Sci. 2013 May 15;328(1-2):1-8.
abstract

Prognosis

Kalincik T, Vivek V, Jokubaitis V, et al.
Sex as a determinant of relapse incidence and progressive course of multiple sclerosis.
Brain. 2013 Oct 18. [Epub ahead of print]
abstract

Pathophysiology

Pietroboni A, Arighi A, Deriz M, et al.
Brain temperature in multiple sclerosis.
Mult Scler. 2013 Oct 24. [Epub ahead of print]
abstract

Leavitt VM, Wylie G, Chiaravalloti N, et al.
Warmer outdoor temperature is associated with task-related increased BOLD activation in patients with multiple sclerosis.
Brain Imaging Behav. 2013 Oct 23. [Epub ahead of print]
abstract

Conference

Abstracts of ECTRIMS (Congress of the European Committee for Treatment and Research in Multiple Sclerosis) 2013. October 2-5, 2013. Copenhagen, Denmark.
Mult Scler. 2013 Oct;19(11 Suppl):8-597.
abstract

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