In a large study of 1372 people with MS registered with the Flemish MS Society, detailed data were collected about the lifestyle habits of the participants, particularly related to eating fish, smoking, and consumption of alcohol, coffee and tea.
This study used regression analysis (a statistical technique to examine the relative contribution of these factors) to determine the association of these factors with how quickly people reached the disability point of 6 on the EDSS scale, that is, using a cane or support to walk 100m.
The study produced some interesting results, some confirming what we know and others raising some questions. While the researchers confirmed that eating fish regularly reduced progression to disability, and smoking accelerated progression, for people with relapsing-remitting MS (RRMS), they also showed that regular consumption of alcohol and coffee slowed progression, but tea had no effect.
They also showed that these findings only applied to relapsing-remitting MS and not primary progressive MS. Fish, alcohol and coffee consumption decreased the rate of progression of the illness to disability for people with RRMS by about 40%.
Daily cigarette smoking increased the rate of progression by about 35%. None of these effects were seen for people with progressive onset MS. Some of these findings are a little difficult to explain.
The study was not an intervention study, that is, it was not a study where researchers asked people to change their lifestyles and then examined the effects of such changes on the progression of MS. Intervention studies are the strongest level of evidence.
This study looked at the correlation of various existing lifestyle factors with disease progression, and therefore, it is not certain whether the factors caused the observed differences in disease progression. The study can only demonstrate an association.
Other unknown factors might have been influenced as well, and these factors might have had their own influence, or the progression to disability might even have caused the change in lifestyle (e.g. people progressing quickly might have taken up smoking due to stress).
So the evidence is not quite as strong. When one sees results like this, it is important to see how they fit with what we know from various other studies. The reduced disease progression with fish consumption fits well with other evidence, and so reinforces that evidence. Similarly with the smoking findings.
Alcohol and coffee
As far as the alcohol and coffee consumption go, there has been very little published about any association of these factors with MS before.
Further studies should now examine whether this is a real effect. For alcohol, there are many studies showing some health benefits from regular low/moderate consumption (up to 2 standard drinks per day with at least 2 alcohol free days per week), and so this may well be a real effect.
For coffee and tea however, there are few other studies looking at this, and so these results are somewhat questionable. Most studies in basic science would suggest that tea, particularly green tea, would be likely to have more of a helpful effect than coffee.
At least, the study would suggest that there is little harm from regular coffee and tea consumption for people with MS. The issue of the study not finding any effect for people with progressive onset MS is puzzling.
While it is known that many of the currently used medications for MS are not effective in primary progressive MS, many of the lifestyle factors would appear from limited research, such as that of Swank, to reduce the progression of progressive forms of MS. Further research in this area is much needed.