Diet and MS: Part 2
In my previous post, I introduced the Swank diet. In this post, I will discuss my reservations about the methodology with this study.
First of all, it must be pointed out that the study published by Dr. Swank was not a controlled trial. This means that subjects were not randomly assigned to conform to his diet or not. Instead, they chose whether or not to participate in his diet. This means that only people with significant will-power were able to adhere to his diet, and it is possible that other aspects of this will-power led them to have improved outcomes. Such subjects may have been less likely to smoke, for example, compared to subjects who could not conform to the diet, and smoking is a known risk-factor for worsening disease.
Another possibility is that patients whose MS worsened simply gave up on the diet, feeling that it was not working for them. Thus, patients who had naturally more benign MS may have had an easier time adhering to the diet, rather than the diet causing them to have benign MS.
Additionally, no one in the study was blinded. This means that the subjects and evaluators knew what sort of diet they were eating. Thus, subjects may have been motivated, both consciously and unconsciously, to minimize their descriptions of their MS symptoms. Similarly, the examiners grading the subjects may have suffered from similar motivations in evaluating the disability of the subjects. Also, compliance with the diet was based on subjects’ reports, and there is no way to verify the accuracy of their reports.
There have been several subsequent studies that investigated the relationship between diet and MS. These studies were recently summarized by the Cochrane Library, a database that reviews and summarizes the results of medical studies to draw overall conclusions about a variety of different topics. Generally speaking, this database tends to only summarize trials that are large and without significant methodological flaws. It noted that most studies of diet were of such poor quality that in many cases no meaningful conclusions could be drawn from them.
From the studies they did examine, the Cochrane Library concluded that:
“Polyunsaturated fatty acids seem to have no major effect on the main clinical outcome in MS (disease progression), and does not substantially affect the risk of clinical relapses over 2 years. However, the data available are insufficient to assess any potential benefit or harm from polyunsaturated fatty acids supplementation.”
In addition to dietary recommendations, a number of supplements and vitamins have been proposed to treat MS. These include:
- omega-3 fatty acids
- linoleic acid
- cod liver oil
- vitamin B12
- Ginkgo biloba extracts
- coenzyme Q10
- vitamin D
It has been estimated that over half of MS patients take some such supplements. When it came to evaluating the adequacy of studies into vitamins and supplements, the authors reported that “No studies on vitamins and antioxidant supplements were found that met our criteria.” In other words, there really have not been any large, well-controlled studies of vitamins and supplements in MS.
According to the Cochrane review paper:
“Evidence bearing on the possible benefits and risks of vitamin supplementation and antioxidant supplements in MS is lacking. More research is required to assess the effectiveness of diet interventions in MS.”
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