Deep Sleep May ‘Rinse’ Day’s Toxins From Brain

Amy Norton wrote . . . . . . . . .

The deep stages of sleep may give the brain a chance to wash itself free of potentially toxic substances, a new study suggests.

Researchers found that during deep sleep, the “slow-wave” activity of nerve cells appears to make room for cerebral spinal fluid to rhythmically move in and out of the brain — a process believed to rinse out metabolic waste products.

Those waste products include beta-amyloid — a protein that clumps abnormally in the brains of people with dementia, said researcher Laura Lewis, an assistant professor of biomedical engineering at Boston University.

Lewis stressed that the findings, reported in the Nov. 1 issue of Science, do not prove that deep sleep helps ward off dementia or other diseases.

But the ultimate goal of research like this is to understand why poor sleep quality is linked to higher risks of various chronic conditions, from dementia to heart disease to depression, she said.

Researchers have known that cerebral spinal fluid, or CSF, helps clear metabolic byproducts from the brain, so that they do not build up there. They’ve also known that the process appears to amp up during sleep. But various “hows” and “whys” remained.

So the investigators recruited 11 healthy adults for a sleep study using noninvasive techniques: advanced MRI to monitor fluid flow in the brain, and electroencephalograms to gauge electrical activity in brain cells.

Sleep is marked by REM and non-REM cycles. During REM sleep, breathing and heart rates are relatively higher, and people often have vivid dreams. Non-REM sleep includes stages of deep — or slow-wave — sleep. During those stages, there’s a slow-down in brain cell activity, heart rate and blood flow, and research has found that deep sleep may aid memory consolidation and allow the brain to recover from the daily grind.

“There are all these fundamental things your brain is taking care of during deep sleep,” Lewis said.

Her team found that housecleaning may be one. When study participants were in deep sleep, each pulse in slow-wave brain activity was followed by oscillations in blood flow and volume, which allowed CSF to flow into fluid-filled cavities in the central brain.

CSF moved in “large, pulsing waves” that were seen only during deep sleep, Lewis explained.

Based on what’s known about the work of CSF, experts said it’s reasonable to conclude that slow-wave sleep promotes the flushing of waste from the brain.

The study “elegantly” illustrates the importance of deep sleep, according to Dr. Phyllis Zee, a sleep medicine specialist not involved in the work.

It “helps to explain how and why sleep is important for keeping neurons healthy — facilitating the removal of toxic molecules,” said Zee, a professor of neurology at Northwestern University Feinberg School of Medicine, in Chicago.

“One can think of sleep as a top way to take care of your brain,” she said.

Another sleep medicine specialist agreed. “There is growing evidence, with this study and others, that sleep plays a role in clearing toxins from the brain,” said Dr. Raman Malhotra, an associate professor of neurology at Washington University in St. Louis.

Other research has suggested that sleep loss can promote the buildup of “unwanted proteins” in the brain, said Malhotra, who also serves on the board of directors of the American Academy of Sleep Medicine.

A recent government study, for instance, found that one night of sleep deprivation triggered an increase in beta-amyloid in the brains of healthy adults.

“As we learn more about this role of sleep,” Malhotra said, “it may help explain why individuals who don’t get enough sleep, or suffer from sleep disorders, are at higher risk of certain chronic health conditions.”

The latest study involved younger adults with no health problems. Lewis said that it will be important to find out whether healthy older adults, or people with certain health conditions, show any differences in CSF dynamics during deep sleep.

A big question for future research, she said, will be whether alterations in those dynamics precede the development of disease.

Source: HealthDay


Today’s Comic

Study Finds Shark Fins & Meat Contain High Levels of Neurotoxins Linked to Alzheimer’s Disease

In a new study, University of Miami (UM) scientists found high concentrations of toxins linked to neurodegenerative diseases in the fins and muscles of 10 species of sharks. The research team suggests that restricting consumption of sharks can have positive health benefits for consumers and for shark conservation, since several of the sharks analyzed in the study are threatened with extinction due to overfishing.

Fins and muscle tissue samples were collected from 10 shark species found in the Atlantic and Pacific Oceans for concentrations of two toxins—mercury and β-N-methylamino-L-alanine (BMAA). “Recent studies have linked BMAA to neurodegenerative diseases such as Alzheimer’s disease and amyotrophic lateral sclerosis (ALS),” said Deborah Mash, Professor of Neurology and senior author of the study.

Researchers at the UM Rosenstiel School of Marine and Atmospheric Science and UM Miller School of Medicine detected concentrations of mercury and BMAA in the fins and muscles of all shark species at levels that may pose a threat to human health. While both mercury and BMAA by themselves pose a health risk, together they may also have synergistic toxic impacts.

“Since sharks are predators, living higher up in the food web, their tissues tend to accumulate and concentrate toxins, which may not only pose a threat to shark health, but also put human consumers of shark parts at a health risk,” said the study’s lead author Neil Hammerschlag, a research assistant professor at the UM Rosenstiel School and UM Abess Center for Ecosystem Science and Policy.

Shark products including shark fins, cartilage and meat are widely consumed in Asia and globally in Asian communities, as a delicacy and as a source of traditional Chinese medicine. In addition, dietary supplements containing shark cartilage are consumed globally.

Recently scientists have found BMAA in shark fins and shark cartilage supplements. The neurotoxic methyl mercury has been known to bioaccumulate in sharks over their long lifespans.

About 16 percent of the world’s shark species are threatened with extinction. The shark species sampled in this study range in threat status from least concern (bonnethead shark) to endangered (great hammerhead) by the International Union for Conservation of Nature (IUCN).

“Our results suggest that humans who consume shark parts may be at a risk for developing neurological diseases.” said Mash.

“People should be aware and consider restricting consumption of shark parts. Limiting the consumption of shark parts will have positive health benefits for consumers and positive conservation outcomes for sharks, many of which are threatened with extinction due in part to the growing high demand for shark fin soup and, to a lesser extent, for shark meat and cartilage products.” said Hammerschlag.

Source: University of Miami’s Rosenstiel School

Study Finds High Exposure to Food-borne Toxins

In a sobering study published in the journal Environmental Health, researchers at UC Davis and UCLA measured food-borne toxin exposure in children and adults by pinpointing foods with high levels of toxic compounds and determining how much of these foods were consumed. The researchers found that family members in the study, and preschool children in particular, are at high risk for exposure to arsenic, dieldrin, DDE (a DDT metabolite), dioxins and acrylamide. These compounds have been linked to cancer, developmental disabilities, birth defects and other conditions. However, the study also points to dietary modifications that could mitigate risk.

“Contaminants get into our food in a variety of ways,” said study principal investigator Irva Hertz-Picciotto, professor and chief of the Division of Environmental and Occupational Health at UC Davis. “They can be chemicals that have nothing to do with the food or byproducts from processing. We wanted to understand the dietary pathway pesticides, metals and other toxins take to get into the body.”

Researchers assessed risk by comparing toxin consumption to established benchmarks for cancer risk and non-cancer health risks. All 364 children in the study (207 preschool children between two and seven and 157 school-age children between five and seven) exceeded cancer benchmarks for arsenic, dieldrin, DDE and dioxins. In addition, more than 95 percent of preschool children exceeded non-cancer risk levels for acrylamide, a cooking byproduct often found in processed foods like potato and tortilla chips. Pesticide exposure was particularly high in tomatoes, peaches, apples, peppers, grapes, lettuce, broccoli, strawberries, spinach, dairy, pears, green beans and celery.

“We focused on children because early exposure can have long-term effects on disease outcomes,” said Rainbow Vogt, lead author of the study. “Currently, the U.S. Environmental Protection Agency only measures risk based on exposures of individual contaminants. We wanted to understand the cumulative risk from dietary contaminants. The results of this study demonstrate a need to prevent exposure to multiple toxins in young children to lower their cancer risk.”

The researchers used data from the 2007 Study of Use of Products and Exposure-Related Behavior (SUPERB), which surveyed households in California with children between two and five to determine how their diets, and other factors, contribute to toxic exposure. Specifically, SUPERB homed in on 44 foods known to have high concentrations of toxic compounds: metals, arsenic, lead and mercury; pesticides chlorpyrifos, permethrin and endosulfan; persistent organic pollutants dioxin, DDT, dieldrin and chlordane; and the food processing byproduct acrylamide. Toxin levels in specific foods were determined through the Total Diet Study and other databases.

Perhaps most disturbing, preschool-age children had higher exposure to more than half the toxic compounds being measured. Even relatively low exposures can greatly increase the risk of cancer or neurological impairment.

“We need to be especially careful about children, because they tend to be more vulnerable to many of these chemicals and their effects on the developing brain,” says Hertz-Picciotto.

Though these results are cause for concern, the study also outlines strategies to lower family exposure. For example, organic produce has lower pesticide levels. In addition, toxin types vary in different foods. Certain pesticides may be found in lettuce and broccoli, while others affect peaches and apples.

“Varying our diet and our children’s diet could help reduce exposure,” said Hertz-Picciotto. “Because different foods are treated differently at the source, dietary variation can help protect us from accumulating too much of any one toxin.”

Families also can reduce their consumption of animal meat and fats, which may contain high levels of DDE and other persistent organic pollutants, and switch to organic milk. While mercury is most often found in fish, accumulation varies greatly by species. Smaller fish, lower on the food chain, generally have lower mercury levels. In addition, acrilomides are relatively easy to remove from the diet.

“Acrilomides come from chips and other processed grains, said co-author Deborah Bennett, associate professor of Environmental and Occupational Health at UC Davis. “Even if we set aside the potential toxins in these foods, we probably shouldn’t be eating large amounts of them anyway. However, we should be eating fruits, vegetables and fish, which are generally healthy foods. We just need to be more careful in how we approach them.”

The study also highlights a number of policy issues, such as how we grow our food and the approval process for potentially toxic compounds. Though the pesticide DDT was banned 40 years ago, the study showed significant risk of DDE exposure.

“Given the significant exposure to legacy pollutants, society should be concerned about the persistence of compounds we are currently introducing into the environment,” said Bennett. “If we later discover a chemical has significant health risks, it will be decades before it’s completely removed from the ecosystem.”

While the study has profound implications for dietary habits, more work needs to be done to quantify risk. Specifically, researchers need to determine how these food-borne toxins interact collectively in the body.

Source: UC Davis