BOSTON — The first prospective population-based study of dietary patterns and risk for multiple sclerosis (MS) has found no relationship between eating a high-quality, healthy diet and a reduced risk of developing MS.

One caveat was that the study focused on current diets in adults only, and it is possible that diet in adolescence may be more important regarding risk for MS, it was noted.

"We did not find any evidence that overall dietary quality is associated with the risks of multiple sclerosis," Dalia Rotstein, MD, from Brigham and Women's Hospital, Boston, Massachusetts, concluded. "However further research is required to determine the possible role of dietary quality in the early years and in individual dietary elements."

She presented the research at MS Boston 2014, the 2014 Joint Americas and European Committees for Treatment and Research in Multiple Sclerosis (ACTRIMS/ECTRIMS) meeting.

However, other studies presented at the same session of the conference showed that patients with MS and other comorbidities have more MS disability. With this in mind, Dr Rotstein told Medscape Medical News, "We do know that healthy diet can help people in general and reduce other comorbidities, especially cardiovascular disease, so this will help MS in the long run."

Another study presented at the meeting showed no effect of a plant-based diet very low in saturated fat on MS endpoints, although numbers were small.

However, it was linked to a significant reduction in fatigue, which was correlated with improvements in body mass index and total cholesterol. This caused the researchers, led by Vijayshree Yadav, MD, Oregon Health & Science University, Portland, to conclude that "a diet very low in saturated fats may yield longer-term quality-of-life benefits and vascular health benefits in MS subjects."

"As other studies presented here have shown patients with comorbidities have worse MS outcomes, the changes we have seen in this small study are likely to translate into better MS outcomes in the long term," Dr. Yadav told Medscape Medical News.

Nurses' Health Study

Dr. Rotstein and colleagues evaluated the diets from 185,000 women participating in the Nurses' Health Study (NHS) 1 and 2 who were prospectively followed (from 1984 in NHS 1 and from 1991 in NHS 2) and filled in dietary pattern questionnaires every 4 years. Records also showed 480 validated incident cases of MS in the 2 NHSs.

From the dietary information, the researchers calculated scores on various different indices of healthy eating: the alternative healthy eating index, the alternative Mediterranean diet score, and the DASH diet (Dietary Approaches to Stop Hypertension). They also used the information on the principal components of the diet to designate 2 separate diets: the Western diet (high in red meat, sugar, and refined grains) vs the Prudent diet (high in vegetables, fruit, legumes, fish, poultry, and whole grains).

They calculated baseline and mean cumulative scores for each of the above diets and investigated whether there was any relationship between these scores and the risk for MS. They used a Cox proportional hazard analysis with adjustment for known factors affecting MS risk, including age, latitude of residence at age 15, body mass index at age 18, total energy intake, and supplemental vitamin D intake.

Results found no evidence for an inverse relationship between a high-quality diet and the risk of developing MS on any of the dietary scores.

Dr. Rotstein noted that the study had many strengths, with a prospective design, participants well characterized with extensive data collection and known confounders of MS risk, and dietary scores collected at multiple different time points. But she added that dietary scores are inherently subjective.

Adolescence: A Critical Window?

On this point, she noted that obesity in adolescence has shown a strong link to an increased risk of developing MS. But studies in adults have been more mixed, and obesity in adults has not been definitely linked with an increased risk for MS.

"Our study was conducted purely in adults, with a youngest age of 25," she noted. "All we can say from our results is that there does not appear to be a direct relationship between diet quality and risk of developing MS as an adult. We cannot say anything about eating habits in adolescence and risk of MS from these data. It is possible that the adolescent years are a critical window, but our study doesn't answer that question."

She also noted that the "high-quality" diets evaluated in this study were all aimed at preventing cardiovascular disease. "It is possible that different patterns would be better for preventing immunological diseases, but we don't know that."

She added: "I have many MS patients who believe that diet may have affected them developing the disease and they feel guilty that they cannot or did not comply with a healthy diet, so these results can provide some reassurance in that regard."

Dr. Rotstein said that although a specific MS diet has not yet been found, there was a great deal of support for vitamin D. "The one nutritional factor that has been shown time and time again to be linked to MS is vitamin D deficiency. I tell all my patients to take vitamin D supplements, but other than that I think it is an open question as to whether other dietary factors affect the disease. So far there is nothing definitive to show that."

Low-Saturated-Fat Diet

The other study presented here by Dr. Yadav and colleagues, looking at a low-saturated-fat diet in MS, was inspired by the work of Dr. Roy Swank in the 1950s. Dr. Swank suggested that individuals who consumed high amounts of saturated fat were at higher risk for MS.

The study evaluated a plant-based diet very low in saturated fat known as the McDougall diet. The composition of the diet is estimated at 10% fat, 14% protein, and 76% carbohydrate, with a focus on starches such as potatoes, corn, rice, beans, oats, fruits, and vegetables. Meat, fish, and dairy are not recommended.

For the study, 61 participants were randomly assigned to this diet or to a control group. The diet group underwent dietary training in a 10-day residential program and then completed monthly food-frequency questionnaires for 1 year.

Results showed no discernible effect on the MS disease process, with no significant changes in the number of active lesions, relapse rate, or Extended Disability Status Scale scores. But the researchers say the study was probably too small and had too short a follow-up to detect such changes.

They did find, however, significant improvement in fatigue measured by an almost 50% reduction in the Modified Fatigue Impact Scale score in the diet group.

Patients in the diet group also lost an average of 20 pounds in weight and had improved cholesterol and mental health scores.

Dr. Rotstein and Dr. Yadav have disclosed no relevant financial relationships.

MS Boston 2014: The 2014 Joint Americas and European Committees for Treatment and Research in Multiple Sclerosis (ACTRIMS/ECTRIMS) meeting. Abstracts PS5.1, PS5.3, and P055. Presented September 11, 2014.

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