By Serena Gordon
How much fish makes a difference? In this study, people who ate fish at least once a week -- or who ate fish one to three times a month and took daily fish oil supplements -- had a 45 percent lower risk of developing multiple sclerosis (MS) compared to folks who ate fish less than once a month and who didn't take fish oil supplements.
"Our study showed one more potential benefit of a seafood diet," said study author Dr. Annette Langer-Gould, who noted that eating fish regularly has already been linked to a lower risk for cardiovascular disease. She's the regional lead for clinical and translation neuroscience for Kaiser Permanente Southern California.
Multiple sclerosis is a disease of the central nervous system. The disease disrupts communication between the brain and the rest of the body, the researchers explained. One of the main signs of multiple sclerosis is the loss of myelin, a fatty substance that covers and protects the nerves. In MS, the immune system mistakenly attacks and destroys myelin.
The first time someone has symptoms of MS -- such as fatigue, numbness or difficulty walking -- for 24 hours or more, it's called clinically isolated syndrome. At this point it's not yet clear if someone has multiple sclerosis or not. They may never have another episode of symptoms, or they may go on to have MS. They are, however, at increased risk of developing MS compared to the general population, according to the National Multiple Sclerosis Society.
The current study included more than 1,100 people from Southern California. Their average age was 36. Half had been diagnosed with early MS or with clinically isolated syndrome.
The study also included an analysis of 13 genetic variations in a human gene cluster known to regulate fatty acid levels. Two of the 13 variations were linked to a lower risk of multiple sclerosis, no matter what the fish consumption was. This suggests that some people may have a genetic advantage in regulating fatty acid levels, the researchers said.
How might consuming more omega-3 fatty acids from fish help prevent multiple sclerosis?
"Omega-3s are known to be neuroprotective and anti-inflammatory, which may potentially protect against the development of multiple sclerosis," Langer-Gould suggested. But, she added, this study couldn't show a cause-and-effect relationship.
Nicholas LaRocca, vice president of healthcare delivery and policy research for the National Multiple Sclerosis Society, reviewed the new study findings.
He said, "There are a lot of health benefits from eating oily fish like salmon, but as was mentioned by the authors, this study can only show an association."
LaRocca added that researchers have been trying to find ways to change environmental factors -- such as diet -- to lower the risk of multiple sclerosis, and this might be one thing contributing the development of the disease that could be modified.
What about people who already have the disease?
Langer-Gould said the study didn't look at people with more advanced disease. But she said since omega-3s are known to protect against cardiovascular disease and people with multiple sclerosis who also have cardiovascular disease are more likely to end up disabled, eating fish isn't a bad idea.
And, she pointed out, eating fish or seafood is better than getting omega-3s from a fish oil supplement.
The study is to be presented at the American Academy of Neurology's annual meeting, April 21-27, in Los Angeles. Research presented at meetings should be viewed as preliminary until published in a peer-reviewed journal.
The study was funded by the U.S. National Institute of Neurological Disorders and Stroke.