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Two Servings of Fish a Week May Help Protect Against Dementia

November 4, 2021

Older men and women who ate at least two servings of fish a week were at lower risk of developing brain changes tied to dementia. The findings add to growing evidence that fish, long heralded for heart health, is also good for brain health.

Eating fish appeared to improve vascular health, or the health of tiny blood vessels, in the brain. Poor vascular health in the brain is a common cause of dementia and can worsen symptoms of Alzheimer’s disease. There are few effective treatments of Alzheimer’s disease and other forms of dementia, so any lifestyle interventions that may help are important.

“Our results are exciting because they show something as simple as eating two or more servings of fish each week is associated with fewer brain lesions and other markers of vascular brain damage, long before obvious signs of dementia appear,” said study author Cecilia Samieri, of the University of Bordeaux in France. The study was published in Neurology.

For the study, the researchers looked at 1,623 people 65 and older living in France. None had memory problems or Alzheimer’s disease or other forms of dementia at the start of the study, and none had had a stroke or other cardiovascular problems that can impair the brain.

The study participants underwent MRI brain scans to assess their blood vessel health. The researchers looked at three brain abnormalities: white matter hyperintensities, abnormal lesions that show up as bright spots; micro-infarcts, or small regions of dead tissue; and enlarged perivascular spaces, or fluid-filled cavities in brain tissue surrounding blood vessels. These three brain changes are signs of impaired blood flow and put people at higher risk for cognitive decline and dementia as well as stroke, though people may have them without developing memory problems or disease.

Study volunteers also filled out detailed questionnaires about their diets, including how often they ate fish and seafood in a typical week. Eleven percent of the group ate fish less than once a week; 37 percent ate fish about once a week, 47 percent ate it two or three times per week; and 6 percent ate fish four or more times per week.

The researchers found that among people who ate no fish, 31 percent had high levels of the vascular brain abnormalities, compared to 23 percent of those who ate two or three servings a week, and 18 percent of those who ate four or more servings of fish per week.

The study showed only an association and does not prove that eating fish prevents dementia, only that it may lower your risk of developing the disease. In terms of dementia risk, the benefits of eating fish two or three times a week were equivalent to maintaining a healthy blood pressure, which has also been shown to lower the risk of dementia.

“Diet is a factor people can modify to possibly decrease their risk of cognitive decline and even dementia later in life,” Dr. Samieri said.

People with Alzheimer’s disease often have problems with blood vessels in the brain that may be making symptoms worse. The findings may help to explain why measures that can improve blood vessel health in midlife — like eating a heart-healthy diet, getting regular exercise and keeping cholesterol levels in check —may help to curb Alzheimer’s in old age. People who have signs of both Alzheimer’s and blood vessel disease are sometimes referred to as having “mixed” dementia (“mixed” for both Alzheimer dementia and vascular dementia).

Earlier studies have likewise found an association between eating fish and a lower risk of Alzheimer’s disease. In many of these studies, baked or broiled fish, but not fried fish, provided the greatest brain benefits. Oily fish rich in omega-3 fatty acids, like salmon and sardines, may be particularly protective.

In addition to a possible protective effect, dietary consumption of fish might also reduce the intake of less healthy food by acting as a substitution. In other words, a serving of fish might substitute for a cut of red meat high in saturated fat.

Regardless of your age, it’s never too early or too late to strive for a lifetime of robust brain health. Eating a heart-healthy diet that includes fish is a good start.

By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.

Source: Aline Thomas, MSc; Fabrice Crivello, PhD; Bernard Mazoyer, MD, PhD; et al: “Fish Intake and MRI Burden of Cerebrovascular Disease in Older Adults.” Neurology, November 3, 2021

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