Does eating fish protect our brains from air pollution?
July 15, 2020
Science Daily/American Academy of Neurology
Older women who eat more than one to two servings a week of baked or broiled fish or shellfish may consume enough omega-3 fatty acids to counteract the effects of air pollution on the brain, according to a new study published in the July 15, 2020, online issue of Neurology®, the medical journal of the American Academy of Neurology.
Researchers found that among older women who lived in areas with high levels of air pollution, those who had the lowest levels of omega-3 fatty acids in their blood had more brain shrinkage than women who had the highest levels.
"Fish are an excellent source of omega-3 fatty acids and easy to add to the diet," said study author Ka He, M.D., Sc.D., of Columbia University in New York. "Omega-3 fatty acids have been shown to fight inflammation and maintain brain structure in aging brains. They have also been found to reduce brain damage caused by neurotoxins like lead and mercury. So we explored if omega-3 fatty acids have a protective effect against another neurotoxin, the fine particulate matter found in air pollution."
The study involved 1,315 women with an average age of 70 who did not have dementia at the start of the study. The women completed questionnaires about diet, physical activity, and medical history.
Researchers used the diet questionnaire to calculate the average amount of fish each woman consumed each week, including broiled or baked fish, canned tuna, tuna salad, tuna casserole and non-fried shellfish. Fried fish was not included because research has shown deep frying damages omega-3 fatty acids.
Participants were given blood tests. Researchers measured the amount of omega-3 fatty acids in their red blood cells and then divided the women into four groups based on the amount of omega-3 fatty acids in their blood.
Researchers used the women's home addresses to determine their three-year average exposure to air pollution. Participants then had brain scans with magnetic resonance imaging (MRI) to measure various areas of the brain including white matter, which is composed of nerve fibers that send signals throughout the brain, and the hippocampus, the part of the brain associated with memory.
After adjusting for age, education, smoking and other factors that could affect brain shrinkage, researchers found that women who had the highest levels of omega-3 fatty acids in the blood had greater volumes of white matter than those with the lowest levels. Those in the highest group had 410 cubic centimeters (cm3) white matter, compared to 403 cm3 for those in the lowest group. The researchers found that for each quartile increase in air pollution levels, the average white matter volume was 11.52 cm3 smaller among people with lower levels of omega-3 fatty acids and 0.12 cm3 smaller among those with higher levels.
Women with the highest levels of omega-3 fatty acids in the blood also had greater volumes of the hippocampus.
"Our findings suggest that higher levels of omega-3 fatty acids in the blood from fish consumption may preserve brain volume as women age and possibly protect against the potential toxic effects of air pollution," said He. "It's important to note that our study only found an association between brain volume and eating fish. It does not prove that eating fish preserves brain volume. And since separate studies have found some species of fish may contain environmental toxins, it's important to talk to a doctor about what types of fish to eat before adding more fish to your diet."
A limitation of the study was that most participants were older white women, so the results cannot be generalized to others. Also, researchers were only able to examine exposures to later-life air pollution, not early or mid-life exposures, so future studies should look at exposures to air pollution across a person's lifespan.
https://www.sciencedaily.com/releases/2020/07/200715163555.htm
Excessive body fat around the middle linked to smaller brain size
January 9, 2019
Science Daily/American Academy of Neurology
Carrying extra body fat, especially around the middle, may be linked to brain shrinkage, according to new research. For the study, researchers determined obesity by measuring body mass index (BMI) and waist-to-hip ratio in study participants and found those with higher ratios of both measures had the lowest brain volume.
BMI is a weight-to-height ratio. It is determined by dividing a person's weight by the square of their height. People with a BMI above 30.0 are considered obese. Waist-to-hip ratio is determined by dividing waist circumference by hip circumference. People with bigger bellies compared to their hips have higher ratios. Men above 0.90 and women above 0.85 are considered to be centrally obese.
"Existing research has linked brain shrinkage to memory decline and a higher risk of dementia, but research on whether extra body fat is protective or detrimental to brain size has been inconclusive," said study author Mark Hamer, PhD, of Loughborough University in Leicestershire, England. "Our research looked at a large group of people and found obesity, specifically around the middle, may be linked with brain shrinkage."
The study looked at 9,652 people with an average age of 55. Of that group, 19 percent were determined to be obese. Researchers measured BMI, waist-to-hip ratio and overall body fat and surveyed participants about their health. Researchers then used magnetic resonance imaging to determine brain volumes for white and gray brain matter and volumes in the various regions of the brain.
Gray matter contains most of the brain's nerve cells and includes brain regions involved in self-control, muscle control and sensory perception. White matter contains nerve fiber bundles that connect various regions of the brain.
After adjusting for other factors that may affect brain volume, such as age, physical activity, smoking and high blood pressure, researchers found that while a high BMI alone was linked to slightly lower brain volumes, those with high BMI and waist-to-hip ratios had lower gray matter brain volumes than participants who did not have a high waist-to-hip ratio. Specifically, researchers found that 1,291 people who had a high BMI and a high waist-to-hip ratio had the lowest average gray matter brain volume of 786 cubic centimeters, compared to 3,025 people of healthy weight who had an average gray matter brain volume of 798 cubic centimeters and 514 people with a high BMI but without high waist-to-hip ratio who had an average gray matter brain volume of 793 cubic centimeters. They found no significant differences in white matter brain volume.
"While our study found obesity, especially around the middle, was associated with lower gray matter brain volumes, it's unclear if abnormalities in brain structure lead to obesity or if obesity leads to these changes in the brain," said Hamer. "We also found links between obesity and shrinkage in specific regions of the brain. This will need further research but it may be possible that someday regularly measuring BMI and waist-to-hip ratio may help determine brain health."
A limitation of the study was that only 5 percent of those invited to participate in the study took part, and those who participated tended to be healthier than those who did not, so the results may not reflect the population as a whole.
https://www.sciencedaily.com/releases/2019/01/190109164233.htm