Adults who consumed high levels of omega-3 polyunsaturated fatty acids showed a markedly reduced risk of developing amyotrophic lateral sclerosis in a pooled analysis of five large prospective cohort studies that assessed diet.
Diet-derived omega-3 polyunsaturated fatty acids (PUFAs) are known to have neuroprotective effects, and those present in neural plasma membranes can modulate oxidative stress, excitotoxicity, and inflammation. But no prospective studies have explored a possible relationship between omega-3 PUFA intake and amyotrophic lateral sclerosis (ALS) risk, according to Kathryn C. Fitzgerald of the department of nutrition, Harvard School of Public Health, Boston, and her associates.
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Eating high levels of omega-3 polyunsaturated fatty acids, such as those found in fish, was associated with a 34% reduced risk of developing ALS.
In a study published July 14 in JAMA Neurology, Ms. Fitzgerald and her colleagues pooled data from the Health Professionals Follow-up Study, the Nurses’ Health Study, the Cancer Prevention Study II Nutrition Cohort, the Multiethnic Cohort Study, and the National Institutes of Health-AARP Diet and Health Study. A total of 995 ALS patients were identified among 1,002,082 participants in these studies. The five studies included detailed dietary information and tracked the occurrence of ALS in the study participants through the National Death Index.
Omega-3 PUFA intake in the highest quintile of consumption at a median of 2.11 g/day was associated with a 34% reduced risk of developing ALS, compared with the lowest quintile of consumption at a median of 0.94 g/day. This finding was consistent across all five studies. This means that adding 0.5% of energy from omega-3 PUFAs and maintaining a constant intake of omega-6 fatty acids while reducing the intake of other types of fat would reduce ALS risk by 34%. Consumption of alpha-linolenic acid, another PUFA, also was associated with significantly reduced risk of developing ALS. In contrast, consumption of omega-6 PUFAs, consumption of linolenic acid, total energy intake, and percentage of energy from other types of fat showed no association with ALS risk, the investigators said (JAMA Neurol. 2014 July 14 [doi:10.1001/jamaneurol.2014.1214]).
Foods that are rich in omega-3 PUFAs include fatty fish (salmon, sardines, tuna, herring) and fish oils; vegetable oils (corn, safflower, canola, soy, and flaxseed oils); and nuts and seeds (walnuts, chia seeds, butternuts, and sunflower seeds). Further studies are needed to confirm this protective effect in ALS and to determine whether patients who already have the disease would benefit from the addition of omega-3 PUFAs to their diets, Ms. Fitzgerald and her associates added.
The findings from Ms. Fitzgerald and her associates are persuasive and consistent with earlier suggestions that PUFAs may play a role in other neurodegenerative conditions, Dr. Michael Swash said in a related editorial (JAMA Neurol. 2014 July 14 [doi:10.1001/jamaneurol.2014.1894]).
"Ideas on long-term risk-susceptibility factors are very much welcomed in trying to unravel the mystery that is ALS. Now, in addition to genetic factors, there are the following five risk factors to work on: male sex, smoking status, BMI, physical exercise, and dietary intake of PUFAs," said Dr. Swash of the Royal London Hospital, Queen Mary University of London, and the Institute of Neuroscience at the University of Lisbon.
This study was supported by the National Institute of Neurological Diseases and Stroke, the National Cancer Institute, and the ALS Therapy Alliance Foundation. The study authors and Dr. Swash had no financial disclosures.