Omega-3 Fatty Acids May Prevent ALS

July 15, 2014

Foods high in omega-3 polyunsaturated fatty acids (PUFAs) may help reduce the risk for amyotrophic lateral sclerosis (ALS), also known Lou Gehrig's disease, a new study suggests.

The study, published online in JAMA Neurology on July 14, analyzed dietary data from more than 1 million people participating in 5 other major cohort studies. After controlling for age, body mass index, education, physical activity, other diseases, and intake of vitamin E and carotenoids, results showed that greater omega-3 PUFA consumption was associated with a reduced risk for ALS.

Both alpha-linolenic acid (ALA), which can be found in plant sources and nuts, and marine omega-3 PUFAs contributed to this association. Intake of omega-6 PUFAs was not associated with ALS risk.

Lead author, Kathryn C. Fitzgerald, MSc, Harvard School of Public Health, Boston, Massachusetts, explained to Medscape Medical News that the researchers decided to study the intake of PUFAs because basic science studies have suggested that they are incorporated into cell membranes and reduce oxidative stress and inflammation, both of which are thought to be involved in ALS.

"Our research findings are still too early to make any clinical recommendations, but they provide a basis for future studies," she said. She suggested that the next step could be to look for biomarkers, such as blood measurements of these fatty acids, and see whether they correlate with ALS.

Author of an accompanying editorial, Michael Swash, MD, from the Royal London Hospital, United Kingdom, described the study as "persuasive." He commented to Medscape Medical News: "These are interesting, provocative data from a well-conducted study with a large dataset. It is an intriguing result that provides a small piece of the overall puzzle."

But he noted that, as is always the case with epidemiologic studies, the results can be viewed only as hypothesis generating. "This result, however, is consistent with ongoing ideas and recent publications suggesting that the onset of the clinical disease is not the same as the onset of the pathological process, which probably starts decades earlier," Dr. Swash said.

Early Intervention Required

"This is most likely why clinical trials of treatments started once symptoms become obvious have shown such disappointing results, and have little chance of success. To prevent a disease like ALS we need to intervene much earlier."

Noting that some strong genetic factors that lead to susceptibility to ALS have been discovered, he added that this study gives further evidence that important environmental factors are also involved, which may be changeable.

"There is not enough information from this one study to make any recommendations on dietary changes at present. For that we would have to conduct a study where supplementation of these PUFAs was shown to prevent or delay onset of the disease. That would be a very costly study to do, and more observational evidence is required before this could be justified. A good start would be to replicate the current observations in another dataset," he suggested.

Dr. Swash pointed out that ALS is a devastating disease. While it has approximately the same incidence as multiple sclerosis — being diagnosed in about 4 per 100,000 per year — fewer people are living with ALS because it causes death so quickly, usually within a couple of years of diagnosis.

"ALS affects people — mostly men — in the prime of their lives, in their 50s and 60s when they should still be very productive members of society. Treating the whole population with an intervention that would reduce its risk would be worthwhile for this reason," he says.

5 Prospective Cohort Studies

For the study, the researchers analyzed data from 1,002,082 participants in 5 prospective cohorts: the National Institutes of Health–AARP Diet and Health Study, the Cancer Prevention Study II Nutrition Cohort; the Health Professionals Follow-up Study, the Multiethnic Cohort Study, and the Nurses' Health Study. Each of these studies assessed diet with food-frequency questionnaires.

Median omega-3 PUFA intake ranged from 1.40 to 1.85 g/day for men and 1.14 to 1.43 g/day for women. A total of 995 ALS cases were documented during the 9- to 24-year follow-up period.

Results showed that a greater omega-3 PUFA intake was associated with a reduced risk for ALS, with an adjusted relative risk for the highest vs the lowest quintile of 0.66. Both alpha-linolenic acid and marine omega-3 PUFAs showed significant inverse associations with ALS risk.

The researchers point out that their study has several strengths, including the large number of participants and documented cases, validated dietary assessment methods, extended follow-up, and prospective design of the 5 contributing datasets. They point out that this contrasts to most previous case-control studies, which have used prevalent cases of ALS and may have been vulnerable to recall bias.

This work was supported by the National Institute of Neurological Diseases and Stroke, the National Cancer Institute, and a grant from the ALS Therapy Alliance Foundation. The authors have disclosed no relevant financial relationships.

JAMA Neurol. Published online July 14, 2014. Abstract Editorial

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