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Studies Find No Effect of Fat, Fiber, or Salt Intake on Risk of MS, But Hints of Micronutrients

ARTICLE IN BRIEF

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Several research studies have failed to find an association between diet and multiple sclerosis progression.

WASHINGTON—Can diet affect the progression of multiple sclerosis? Not necessarily, according to a multicenter case-control study of pediatric multiple sclerosis (MS). In a preliminary analysis of the data presented here at the AAN Annual Meeting, the researchers said they found no association between MS and intake of total calories, fat, fiber, or salt.

But another smaller study presented at the meeting found that women with MS had a higher body-mass index and lower mean intake of foods containing folate, vitamin E, lutein, and quercetin — nutrients found in certain fruits and vegetables. Still, they found no direct association between diet and MS progression.

DIET AND PEDIATRIC MS

The first study, involving 14 medical centers in the United States, stems from an ongoing case-control study of genetic and environmental risk factors for pediatric MS. The researchers compared 174 cases meeting the McDonald MS criteria (patients who had MS onset before 18 years of age and less than two years' duration) with 337 controls, who were less than 20 years of age and seen at the same participating institutions.

Based on their answers to the Block Kids Food Screener, a validated dietary survey completed by patients and families, the study found no significant association between fat, fiber, and salt intake and pediatric MS in an analysis adjusted for age, sex, body mass index (BMI), race, ethnicity, and socioeconomic status.

Results of the study were reported in two presentations at the meeting, one examining the effects of fat and fiber, the other looking at salt. In his presentation on the fat and fiber findings, first author Brandon Seminatore, a medical student at the University of California, San Francisco (UCSF), pointed out that the study did not examine whether intake might have any role as a modifier of disease progression. “This analysis does not preclude the possibility that fat and fiber intake may be potential disease modifiers,” he said.

The senior study author, Emmanuelle Waubant, MD, FAAN, a professor of neurology at UCSF, said that the trial had been undertaken to investigate findings first seen in the experimental autoimmune encephalomyelitis (EAE) model of MS.

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DR. DALIA ROTSTEIN noted that neither study found a link between diet and the risk of developing MS. But, she added, “both are relatively small case-control studies, so I think the jury is still out on a lot of questions related to diet and MS.”

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DR. ELLEN MOWRY: “Knowing youre a kid with MS, you might be more or less likely to say you ate something. Its hard, though, to measure dietary intake before the disease starts and then evaluate it as a risk for MS because its so rare in children. Another challenge involves the use of screeners. These represent a good first step but may need validation against other forms of dietary assessments.”

“When the EAE animal is submitted to a low-calorie or low-fat diet, it is less likely to develop disease,” said Dr. Waubant. “And salt has also been associated with disease risk in animal models of MS. But it had never been studied in humans as a risk factor for the disease. We have now looked and found no associations. So we think there's probably no strong effect.”

Despite the study's relatively large size, she added, “It's still too small to look in depth based on people's genetic background. Down the line, when we have more patients, it's something we will continue to look at.”

DIET IN WOMEN WITH MS

The micronutrient study presented as a poster at the meeting involved 27 white women with relapsing-remitting MS and 30 healthy controls who had enrolled in a multicenter clinical trial examining the effects of supplementation with vitamin D3.

Ellen Mowry, MD, an associate professor of neurology at the Johns Hopkins Medical Center, is leading the ongoing trial, and Dr. Waubant is principal investigator at the participating UCSF center.

At their initial screening, despite enrollment being limited to BMI between 18 and 30 kg/m2, the patients and controls differed significantly on average BMI (25.3 kg/m2 vs 23.6 kg/m2, respectively, p=0.03). Based on their answers to a validated food frequency questionnaire, the MS participants also had lower mean intake of folate (243.9 mcg vs 321.4 mcg, p=0.01), alpha-tocopherol (6.7 mg vs 8.1 mg, p=0.03), magnesium (254.3 mg vs 321.2 mg, p=0.01), lutein-zeaxanthin (3634.7 mcg vs 5384.6 mcg, p=0.01), and quercetin (5.8 mg vs 11.6 mg, p<0.001).

“This is a cross-sectional study,” said Dr. Waubant. “And it's not randomized or prospective. So these preliminary findings need to be replicated.”

Even so, the authors concluded, the findings do suggest that compared with healthy controls, patients with MS eat less food containing micronutrients known to have antioxidant or anti-inflammatory properties important for neurologic health. But, they cautioned, “Whether these differences are a cause or result of MS is not clear.”

EXPERTS COMMENT

Dr. Mowry, who led the micronutrient study, praised the salt-fat-fiber study's size, phenotyping of cases, and choice of pediatric patients, for whom the recent onset of the disease may increase the possibility of detecting any effect of diet. Even so, she said, the study's design had some issues that left many questions unanswered.

“It is a cross-sectional study, and retrospective, so there might be some recall bias,” Dr. Mowry said. “Knowing you're a kid with MS, you might be more or less likely to say you ate something. It's hard, though, to measure dietary intake before the disease starts and then evaluate it as a risk for MS because it's so rare in children. Another challenge involves the use of screeners. These represent a good first step but may need validation against other forms of dietary assessments.

“I don't know exactly what to make of the results,” Dr. Mowry continued. “Maybe it's true that kids who have MS really do eat pretty similarly to their healthy peers. On the other hand, there could be differences that were missed in the study due to the way diet was assessed.”

Commenting on both studies, Dalia Rotstein, MD, MPH, an assistant professor of neurology at the University of Toronto, said, “There does seem to be some consistent evidence now in not finding a link between diet and the risk of developing MS.”

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DR. EMMANUELLE WAUBANT: “When the EAE animal is submitted to a low-calorie or low-fat diet, it is less likely to develop disease. And salt has also been associated with disease risk in animal models of MS. But it had never been studied in humans as a risk factor for the disease. We have now looked and found no associations. So we think theres probably no strong effect.”

Dr. Rotstein, who has conducted research on the role of diet in MS, added, however, that “both are relatively small case-control studies, so I think the jury is still out on a lot of questions related to diet and MS.”

Dr. Rotstein's research, which was presented last year at the ACTRIMS/ECTRIMS meeting in Boston, analyzed data from the Nurses' Health Study and Nurses' Health Study II to identify 480 incident cases of MS, and computed their dietary scores based on food frequency questionnaires. After comparing the highest and lowest quintile scores, none of the dietary indices at baseline were statistically significantly related to the risk of MS.

The effect of diet on disease course remains unknown, Dr. Rotstein said.

“I hear about diet all the time from my patients,” she added. “They're very interested in what kind of changes they can make on their own. There is a great need to study dietary factors that may be related to the course of the disease. Data in humans are still lacking.”

LINK UP TO MORE INFORMATION:

•. AAN Annual Meeting Abstract: Fat, fiber and pediatric MS: http://bit.ly/fatfiber-MS
    •. AAN Annual Meeting Abstract: A case-control study of dietary salt intake and risk of pediatric multiple sclerosis: http://bit.ly/dietarysalt-MS
    •. AAN Annual Meeting Abstract: Multiple sclerosis patients differ from healthy controls on antioxidant and anti-inflammatory nutrients from self-reported diet history: http://bit.ly/MS-diethistory