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Fish May Reduce Rates of "Silent" Stroke
Brain scans find fewer brain injuries related to undiagnosed strokes in people who eat fish three or more times a week
by Craig Weatherby

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You've probably heard that the omega-3 fatty acids in fish and fish oil may reduce the risk of stroke.


Current evidence suggests that eating baked or broiled (not fried) fish at least once a week appears to reduce the risk of stroke by about 25 percent. Eating fish more than four times a week seems to reduce stroke risk a bit more.


And these positive findings have now been bolstered by the intriguing outcomes of a new brain-scan study.


Scientists from Harvard and Finland recruited 3,660 people age 65 and older, who agreed to complete diet questionnaires and undergo two brain scans, taken five years apart (Virtanen JK et al. 2008).


Key Points

  • People who eat fish frequently were 26 percent less likely have the brain lesions left by "silent", undiagnosed strokes.
  • Fried fish eaters did not have lower rates of brain lesions, probably due the high levels of omega-6 fats in deep-frying oils.
  • Eating fried fish frequently may raise the risk of stroke by 44 percent.

According to lead author Jyrki Virtanen, Ph.D., R.D., "Previous findings have shown that fish and fish oil can help prevent stroke, but this is one of the only studies that looks at fish's effect on silent brain infarcts in healthy, older people."


By "silent brain infarcts", brain researchers mean minuscule areas of scarred or dead brain tissue caused by clots from damaged blood vessels. These tiny brain wounds are termed silent infarcts because they produce no apparent symptoms.


The same vascular disease process that leads to heart attacks also causes the most common kind of stroke (ischemic), which some doctors call a "brain attack".


Prior research showed that one in five generally healthy elderly people have silent brain infarcts, which can only be found by brain scans using an MRI.


And by projecting these results on the entire population, it's estimated that about 11 million Americans suffer 22 million silent, undiagnosed strokes annually (Leary MC et al. 2003).


In fact, the annual number of silent strokes in America is about 30 times higher than the incidence of diagnosed strokes.


Silent infarcts can lead to more strokes, to gradual loss of thinking skills, and to dementia.


Scans show healthier brains in fish eaters

In addition to receiving brain scans, the study participants also completed questionnaires about the amounts and types of fish in their diets


Five years later, the brain scans were repeated in the 2,313 volunteers who were still available to participate in the study.


The findings were striking:

  • Compared to people who did not eat fish regularly, the brain scans of participants who ate broiled or baked tuna or other fatty fish three times per week or more were 26 percent less likely to show brain lesions.
  • Eating just one serving of fatty fish per week cut the rate of scan-detected brain lesions by 13 percent.
  • People who ate fatty fish regularly had healthy white matter in their brains, and no signs of the kinds of white matter associated with brain atrophy.

As Dr. Virtanen noted in a press release, high levels of omega-3s probably explain the association between eating fatty fish frequently and having healthier-looking brains:

Strokes: Silent, whispering, or worse 

Silent strokes are diagnosed with brain imaging that detects damage in people who did not have any apparent stroke symptoms.

However, some silent strokes may be better described as "whispering" because the symptoms are so minor that they don't alarm the patient.


The warning signs of stroke are:

  • Sudden numbness or weakness of the face, arm or leg, especially on one side of the body;
  • Sudden confusion, trouble speaking or understanding;
  • Sudden trouble seeing in one or both eyes;
  • Sudden trouble walking, dizziness, loss of balance or coordination;
  • Sudden, severe headache with no known cause.

People need to take these symptoms seriously and see a doctor about them, and physicians should take the symptoms seriously when patients report them.

"More research is needed as to why these types of fish may have protective effects, but the omega-3 fatty acids EPA and DHA would seem to have a major role."


Fish that provide high levels of long-chain "marine" omega-3s include Salmon, Sardines, Tuna, Sablefish, Mackerel, Herring, and Anchovies.


Fried fish seen to raise brain-lesion rates

As we reported last year, not all fish meals yield the same brain-protection benefits.


And that distinction was affirmed by the results of the new study,


According to Dr. Virtanen, "While eating tuna and other types of [fatty] fish seems to help protect against memory loss and stroke, these results were not found in people who regularly ate fried fish."


In 2005, Harvard researchers reported their finding that, compared with eating fried fish less than once a month, eating fried fish more than once per week was associated with a 44 percent higher risk of stroke (Mozaffarian D et al. 2005).


(The term "fried fish" encompasses breaded, deep-fried fish products such as fish sticks and ...






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