The steep rate of death from stroke in a swath of Southern states often referred to as America's “stroke belt” may be linked to a higher consumption of fried fish in that region, new research suggests. A study published in the journal Neurology shows people living in the stroke belt — which comprises North Carolina, South Carolina, Georgia, Alabama, Mississippi, Tennessee, Arkansas and Louisiana — eat more fried fish and less non-fried fish than people living in the rest of the country, and African-Americans eat more fried fish than Caucasians. “Differences in dietary fish consumption, specifically in cooking methods, may be contributing to higher rates of stroke in the stroke belt and also among African Americans,” says study author Fadi Nahab, medical director for the Stroke Program at Emory University Hospital in Atlanta.
The research, part of a large government-funded study, Reasons for Geographic and Racial Differences in Stroke (REGARDS), involved 21,675 participants from across the country; the average age was 65. Of the participants, 21% were from the “stroke buckle,” the coastal plain region of North Carolina, South Carolina and Georgia where stroke mortality rates are even higher than they are in the rest of the stroke belt. Another 34% were from the rest of the stroke belt and 44% were from the other states.
Participants were interviewed by phone and then given an in-home physical exam. The questionnaire asked how often they ate oysters, shellfish, tuna, fried fish and non-fried fish. The American Heart Association recommends people eat fish high in omega-3 fatty acids—essential fatty acids humans get through their diet—at least twice a week, baked or grilled but not fried. Fewer than one in four overall ate two or more servings of non-fried fish a week. Stroke belt residents were 32% more likely to eat two or more servings of fried fish each week than those in the rest of the country.
African-Americans were more than 3.5 times more likely to eat two or more servings of fried fish each week than Caucasians, with an overall average of about one serving per week of fried fish compared with about half a serving for Caucasians. When it came to eating non-fried fish meals, stroke belt residents ate an average of 1.45 servings per week, compared with 1.63 servings eaten by people elsewhere.
“This is good stuff. It's a well-done study, but I think one thing to bear in mind is that it's not specifically a study of stroke risk. You're looking at a community and seeing how it's behaving on the whole,” says Daniel Labovitz, a stroke neurologist at Montefiore Medical Center in the Bronx. “This study can't tell you causation. It can't tell you there's a direct link between one thing and another, it just tells you they're associated,” says stroke neurologist Victor Urrutia, an assistant professor at Johns Hopkins University School of Medicine.
How might eating fried fish impact stroke?
It could be that frying the fish leaches out the omega-3s, says Jeremy Lanford, stroke director at Scott & White Healthcare in Roundrock, Texas. Or the increased fat calorie content from the frying oil may contribute to stroke, says author Nahab. He also notes that fish used for frying, such as cod and haddock, tend to be the types lower in healthy fats. More research is needed to tease out whether cooking methods affect stroke risk, Labovitz says. “In other words, is fried fish a problem, or is it another red herring?” he says.
The study was supported by the National Institute of Neurological Disorders and Stroke, the National Institutes of Health, and the Department of Health and Human Services. Funding was provided by General Mills for coding of the food frequency questionnaire.
Researchers employed imaging techniques to examine and analyze brain anatomical differences between 55 female IBS patients and 48 female control subjects. Patients had moderate IBS severity, with disease duration from one to 34 years (average 11 years). The average age of the participants was 31.
Investigators found both increases and decreases of brain grey matter in specific cortical brain regions.
Even after accounting for additional factors such as anxiety and depression, researchers still discovered differences between IBS patients and control subjects in areas of the brain involved in cognitive and evaluative functions, including the prefrontal and posterior parietal cortices, and in the posterior insula, which represents the primary viscerosensory cortex receiving sensory information from the gastrointestinal tract.
“The grey-matter changes in the posterior insula are particularly interesting since they may play a role in central pain amplification for IBS patients,” said study author David A. Seminowicz, Ph.D., of the Alan Edwards Centre for Research on Pain at McGill University. “This particular finding may point to a specific brain difference or abnormality that plays a role in heightening pain signals that reach the brain from the gut.”
Decreases in grey matter in IBS patients occurred in several regions involved in attentional brain processes, which decide what the body should pay attention to. The thalamus and midbrain also showed reductions, including a region – the periaqueductal grey – that plays a major role in suppressing pain.
“Reductions of grey matter in these key areas may demonstrate an inability of the brain to effectively inhibit pain responses,” Seminowicz said.
The observed decreases in brain grey matter were consistent across IBS patient sub-groups, such as those experiencing more diarrhea-like symptoms than constipation.
“We noticed that the structural brain changes varied between patients who characterized their symptoms primarily as pain, rather than non-painful discomfort,” said Mayer, director of the UCLA Center for Neurobiology of Stress. “In contrast, the length of time a patient has had IBS was not related to these structural brain changes.”
Mayer added that the next steps in the research will include exploring whether genes can be identified that are related to these structural brain changes. In addition, there is a need to increase the study sample size to address male-female differences and to determine if these brain changes are a cause or consequence of having IBS.
The study was funded by the National Institutes of Health.
Additional authors include M. Catherine Bushnell, Ph.D., of McGill University, and Jennifer B. Labus, Joshua A. Bueller, Kirsten Tillisch and Bruce D. Naliboff, Ph.D., all of UCLA.
A study of UK schoolchildren has revealed that Black Africans, Indians and Bangladeshis have a similar or lower prevalence of asthma than White children, while Black Caribbean and Mixed Black Caribbean/White boys are more likely to have asthma. Researchers writing in the open access journal BMC Pediatrics studied the occurrence of asthma, investigating ethnic differences in risk factors.
Melissa Whitrow and Seeromanie Harding from the Social and Public Health Sciences Unit of the Medical Research Council, UK, used data taken from 51 London schools to investigate a random selection of 11-13 year old pupils. The final sample for analysis included 1219 children who identified themselves as 'White UK', 933 'Black Caribbean', 1095 'Black African', 459 'Indian', 215 'Pakistani', 392 'Bangladeshi' and 299 'Mixed White UK and Black Caribbean'.
According to Whitrow and Harding, “Social and environmental factors may influence risk of asthma through early life exposures regulating the allergic inflammatory response and/or later life exposures to allergens. A positive association between body mass index (BMI) and asthma has also been reported. We aimed to investigate the influence of these factors on ethnic differences in asthma prevalence”.
The researchers found that a family history of asthma and psychological well-being were consistent correlates for asthma regardless of ethnicity. Less than six years of residence in the UK had an independent protective effect for Black Caribbeans and Black Africans, possibly reflecting continuing protection from early life exposures in their home countries. A gender difference was observed for Indians and Bangladeshis, with less asthma in girls than boys. Speaking about these results, the authors said, “These findings point to early protective influences which are not properly understood. International comparisons could provide useful insights into prevention of asthma, for ethnic minority children and for all children”.