From the standpoint of heart health, the Tsimane are a model group. A population indigenous to the Bolivian Amazon, the Tsimane demonstrate next to no heart disease. They have minimal hypertension, low prevalence of obesity and and their cholesterol levels are relatively healthy. And those factors don’t seem to change with age.
Also minimal is the incidence of Type-2 diabetes. Which leads scientists to consider the role of diet in the Tsimane’s cardiovascular health — and how it might be impacted over time as the population becomes more exposed to globalization and market forces.
A Heart Healthy Diet
That’s where UC Santa Barbara anthropologists Thomas Kraft and Michael Gurven come in. They are part of the Tsimane Health and Life History Project, an initiative supported by the National Institutes of Health, which conducted the first systematic study that examines what the Tsimane consume on a regular basis and compares it to that of the Moseten, a neighboring population with similar language and ancestry, but whose eating habits and lifeways are more impacted by outside forces. The researchers’ findings appear in the American Journal of Clinical Nutrition.
“Our prior work showed that the Tsimane have the healthiest hearts ever studied, so naturally there’s a lot of interest in understanding why and how,” said Michael Gurven, a professor of anthropology at UC Santa Barbara, co-director of the Tsimane Health and Life History Project and the paper’s senior author.
“The obvious first contender is, what are they eating? And are they eating what we think is best for heart health?
“We conducted a detailed analysis of the Tsimane diet and then compared it to what modern Americans typically eat, and to the diets that claim to be heart healthy,” he continued.
“Maybe the Tsimane just happen to follow one of those without knowing about them.”
These diets — Paleo, Okinawan and DASH, among others — are often promoted because of their proposed health benefits, and in the case of Paleo, that our bodies have evolved to benefit from particular types of food.
Changes Over Time
The connection to the Moseten is an added benefit of the study. Ethnolinguistically and genetically very similar to the Tsimane, the Moseten, an isolate in Bolivia, are much more acculturated in a number of ways than are the Tsimane.
“They provide a forecast of what Tsimane health might look like 20 years from now,” Gurven said.
“They represent what is happening to many indigenous populations over time. To what extent may changes in their diet increase the prevalence of heart disease and diabetes?”
Using the same measurement strategy employed by the U.S. Centers for Disease Control and Prevention’s National Health and Nutrition Examination Survey, the researchers interviewed 1,299 Tsimane and 229 Moseten multiple times about everything they had eaten or drunk in the previous 24 hours. Using published and their own nutritional estimates for all items, and a variety of methods to estimate portion size, they provided a detailed breakdown of daily food intake.
The high-calorie (2,433-2,738 kcal/day) Tsimane diet was characterized by high carbohydrate and protein intake, and low fat intake (64, 21 and 15 percent of the diet, respectively). In addition, the Tsimane don’t eat a wide variety of foods, relative to the average U.S. or Moseten diet. Almost two-thirds of their calories are derived from complex carbohydrates, particularly plantains and rice. Another 16 percent comes from over 40 species of fish, and 6 percent from wild game. Only 8 percent of the diet came from markets.
Despite the low dietary diversity, the researchers found little evidence of micronutrient deficiencies in the Tsimane’s daily intake. Calcium and a few vitamins (D, E and K) were in short supply, but the intake of potassium, magnesium and selenium — often linked to cardiovascular health — far exceeded U.S. levels. Dietary fiber intake was almost double U.S. and Moseten levels.
Over the five years of study, the researchers saw the Tsimane’s total energy and carbohydrate intake increase significantly, particularly in villages near market towns. Their consumption of food additives (lard, oil, sugar and salt) also has increased significantly. The Moseten, the researchers noted, consumed substantially more sugar and cooking oil than did the Tsimane.
Quantity and Quality
The conclusion: A high-energy diet rich in complex carbohydrates is associated with low cardiovascular disease risk, at least when coupled with a physically active lifestyle (Tsimane adults average 17,000 or so steps per day, compared to Americans’ 5,100). Moving away from a diet that is high in fiber and low in fat, salt and processed sugar represents a serious health risk for transitioning populations. Evidence of nutrition transition in Bolivia parallels trends in increasing body fat and body mass index among Tsimane, suggesting the low prevalence of cardiovascular disease — as among the Tsimane — may not persist.
According to Gurven, avoiding the pitfalls of changing diets and lifestyles will be critical for groups like the Tsimane. Many other indigenous populations in South America, Africa and Southeast Asia are in similar situations. And rates of obesity, type-2 diabetes and heart disease are high among indigenous groups whose lifeways are no longer traditional — including many North American Indian and Australian aboriginal populations.
And for the Tsimane, change is not far on the horizon.
“This is a key time,” said Thomas Kraft, a postdoctoral researcher in anthropology at UC Santa Barbara and the paper’s lead author.
“Roads are improving in the area, as is river transport with the spread of motorized boats, so people are becoming a lot less isolated compared to the past. And it’s happening at a pretty rapid pace.”
Added Sugar and Fat
Anecdotally, Gurven added, the Tsimane Health and Life History Project’s biomedical team is seeing more diabetic patients among the Tsimane than they have previously. That’s likely due to the increased regular intake of refined sugar and fat that occurred over the course of the study. As Kraft noted, with the Tsimane’s ability to buy large kilo bags of sugar and liters of cooking oil, the researchers calculated a 300 percent rise in consumption of those products.
“They’re basically deep frying and adding lots of sugar to drinks when they can,” he said.
And consuming a lot of calories.
“But they’re also physically active — not from routine exercise, but from using their bodies to acquire food from their fields and the forest,” added Gurven, “which is also an important lesson. You can’t look at what you’re eating irrespective of what you’re doing with your body. If you’re physically active, you can probably get away with more flexibility in the diet.”
Calorie count aside, the high carbohydrate content of the Tsimane diet isn’t “unprecedented,” according to Kraft.
“One of the other artery-protecting diets is the Okinawan diet from Japan. It comes out at about 85 percent carbohydrate. But a common feature they share is that pretty much across the board, they’re complex carbohydrates — it’s sweet potatoes in the Okinawan diet; here it’s plantains and manioc.”
The Moseten diet has fewer total calories and less carbohydrates than the Tsimane diet, but the Moseten eat a broader range offoods, including more fruits, vegetables, dairy and legumes. The Moseten also buy more of their food, including soda, bread, dried meat and processed items. The Moseten diet could provide insight into the Tsimane diet of the future, the researchers suggest.
“We’re still analyzing their health indicators, but we expect the Moseten to show more risk factors related to diabetes and heart disease,” said Gurven.
The Energy Balance
In addition to finding that the Tsimane consume more calories per day than the Moseten do, the researchers note the Tsimane are also more physically active (with much of their labor devoted to the hard work of slash and burn farming, hunting, fishing and foraging). They expend more energy activity, but may also have a higher resting energy expenditure due to higher rates of infection and persistent immune activity.
Overall, the findings suggest that no single diet protocol offers the key to health. The picture is much more complicated.
“It definitely sheds light on the diversity of diets that are compatible with good cardiovascular health,” said Kraft.
Added Gurven, “We’re at a unique point in history where for many of us, our daily decisions are more about what not to eat. We have to work hard not to overeat. Throughout most of human history, it was the opposite. It was so hard to get those calories we needed to survive.”
And in terms of the Tsimane’s eagerness to incorporate sugar and other additives into their diets despite the associated health risks,
“Telling folks to watch what they’re eating, don’t eat too much of this or that — that mentality is hard to convey when getting food is unpredictable and a daily grind,” Gurven continued. “Getting calories cheaply with less effort — who wouldn’t?”
When Activated, ‘Social’ Brain Circuits Inhibit Feeding Behavior In Mice
Researchers at Stanford demonstrated that direct stimulation of fewer than two dozen neurons linked to social interaction was enough to suppress a mouse’s drive to feed itself.
Feeding behavior and social stimulation activate intermingled but distinct brain circuits, and activating one circuit can inhibit the other, according to a new study by researchers at Stanford University.
The researchers demonstrated in mice that direct stimulation of fewer than two dozen nerve cells, or neurons, linked to social interaction was enough to suppress the animals’ drive to feed themselves — a finding with potential clinical significance for understanding and treating eating disorders such as anorexia.
The researchers made these findings by developing a technique for teasing apart separate but closely intertwined sets of neurons in the brain.
A paper detailing the findings and the method used to obtain them was published online Jan. 16 in Nature. The senior author is Karl Deisseroth, MD, PhD, the D.H. Chen Professor and professor of bioengineering and of psychiatry and behavioral sciences and a Howard Hughes Medical Institute investigator. Lead authorship is shared by postdoctoral scholars Joshua Jennings, PhD, and Christina Kim, PhD, along with staff scientist James Marshel, PhD.
Social curbs on eating behavior
“We know social situations can inhibit the urge to eat,” Deisseroth said.
“One example is the behavior of people at different levels of dominance in a social hierarchy. You’re not going to dive into that plate of ribs when you’re dining in the presence of royalty.”
Anorexia is another example.
“People with anorexia report that a powerful driver, at the disorder’s onset, was feedback from others indicating they’d be rewarded for restricting their food intake,” said Deisseroth.
Virtually nothing is known about the neural underpinnings of this inhibition, he said.
“We sought to understand, at the level of individual neurons, how these potentially competing drives may negotiate with each other, and how the brain circuits associated with feeding versus social behavior may interact.”
Deisseroth’s group focused on a part of the brain called the orbitofrontal cortex, a sheet of cells that, in both mice and humans, lies on the brain’s outer surface toward the front of the organ. This brain region, which is similar in the two species, has been shown in human imaging studies to be active when subjects are wishing for, seeking, obtaining and consuming food, or when they’re socially engaged.
Exploring the interactions of feeding and social drives was guaranteed to be tricky.
“It’s not as if there is a cluster of ‘feeding’ neurons’ and another cluster of ‘social’ neurons sitting in two neatly labeled clumps in the orbitofrontal cortex, so you can just position an electrode in one or the other cluster and find out all you need to know,” Deisseroth said.
The neurons driving and responding to these different activities are interspersed, scarce and scattered throughout the orbitofrontal cortex like sprinkles on a cupcake. Plus, they all look pretty much the same.
So the researchers designed a sophisticated system for simultaneously stimulating and monitoring activity in multiple designated neurons. This let them determine which orbitofrontal-cortex neurons were active during feeding-associated or social activities, or both, or neither. The technology also allowed them to stimulate on the order of 20 neurons identified as dedicated to one or the other activity and watch what behavior resulted.
Over the past decade and a half, Deisseroth has pioneered the development of an experimental approach called optogenetics, in which a gene for a light-sensitive protein called an opsin is inserted into neurons so they can be activated by pulses of laser light reaching them via an implanted optical fiber. Recent advances in his lab have optimized one such opsin to the point where his team can stimulate numerous selected, behaviorally categorized neurons at a time in a mammal.
“This study builds on our initial demonstration in mammals of single cell control with optogenetics in 2012, but now marks the first demonstration of control of mammalian behavior by the manipulation of multiple, individually specified neurons,” he said.
The scientists inserted the gene for this improved opsin into the orbitofrontal cortex of mice, along with another gene that causes neurons to fluoresce in proportion to their activity. A tiny lens at the tip of the optical fiber guided light across numerous targeted neurons with near simultaneity, causing as many as two dozen designated neurons to fire together.
Food vs. friends
During the experiments that followed, the mice were constrained by an apparatus that kept their heads comfortably fixed in place. In one set of experiments, mice were exposed to a spout that occasionally issued a drop of a high-calorie solution, which could be readily licked up. For each mouse, Deisseroth’s colleagues recorded which orbitofrontal-cortex neurons among the several hundred in their field of view lit up during this activity.
Optogenetically stimulating just 20 feeding-responsive neurons enhanced the mice’s licking activity in the presence of the high-calorie solution, tying those neurons causally to feeding behavior.
To identify social-responsive neurons in the mice’s orbitofrontal cortex, the scientists introduced juvenile mice — which older mice perceive as nonthreatening potential buddies and set about sniffing — and tracked activity levels in the neurons in the field of view. They were able to identify specific neurons responsive to the exploratory social interaction.
Optogenetically stimulating social-responsive orbitofrontal neurons in the presence of a caloric reward reduced the amount of time the mice spent licking the solution. So did the natural-stimulation equivalent: exposure to juvenile mice. The more the social interaction, the less the interest in calories.
While the mice in this study weren’t a disease model, Deisseroth noted the findings’ potential clinical significance.
“We’ve been able to pinpoint otherwise indistinguishable orbitofrontal-cortex neurons involved in feeding and social drive states,” he said.
“A key goal was to know which neurons actually matter for behavior. Now that we do, we can examine them more closely to look for, say, surface-protein markers or wiring differences that distinguish them from one another. If there are any distinctions like that, it will deepen our understanding of how competing drives are negotiated among neuronal cell types in the cerebral cortex — and could even lead to pharmaceutical interventions that reduce social inhibition of food consumption among people with anorexia.”
Drexel and Arizona State Researchers Look at Risk of Infection From Water in the Air at Home
Water spray from showers, faucets and toilets can carry Legionella bacteria. New research from Drexel and Arizona State is helping us to better understand our risk of infection if we inhale aerosols in the spray generated by these indoor water fixtures.
“Don’t drink the water” might be good enough advice to keep you from getting sick in some places, but according to researchers from Arizona State and Drexel University, the admonition should probably be expanded to “…try not to breathe the water either.”
In research recently published in the journal Environmental Science & Technology, the group takes a closer look at how the spray from showers, sinks and toilets can expose us to the bacteria responsible for the most waterborne disease outbreaks in the country.
“Most people in the United States think we have a handle on our water quality problems and drinking water isn’t something we need to worry about anymore. If anything, the recent water crisis in Flint, Michigan, and frequent Legionnaires’ disease outbreaks across the nation have demonstrated that’s not the case,” said Kerry Hamilton, PhD, an assistant professor in the Ira A. Fulton Schools of Engineering at Arizona State University and former doctoral researcher at Drexel, who led the investigation into how the Legionella pneumophila bacteria can grow and spread in indoor water supplies.
Legionella, the bacteria that causes pneumonia-like Legionnaire’s disease, has been responsible for a number of recent outbreaks and can be fatal in 10-25 percent of infections, according to the Centers for Disease Control and Prevention. While it is considered one of the deadliest waterborne diseases in the United States, it is actually contracted via inhalation or aspiration. This means to accurately understand environments that could increase one’s risk of exposure, researchers need to examine places where people are exposed to water in the air.
“To protect people from infections, we first need to understand the risks,” Hamilton said.
“If we can better model and predict how water quality degrades under different circumstances, we can more efficiently target resources and prevent disease outbreaks.”
The research considered a variety of factors to assess risk of exposure — from any combination of showering, using a sink or flushing a toilet — using water with a range of bacterial concentrations. It also took into consideration that older people or people who already have a health condition are at greater risk of becoming ill from Legionellaexposure. And it is one of the first studies to closely examine how water-efficient fixtures, in a green building for example, can affect risks.
“We found that shower risks were highest, likely due to the amount of time a person would be exposed to the water spray. Risk of exposure from water efficient fixtures tended to be slightly less if concentrations are comparable to those at conventional water fixtures, because they produce fewer inhalable aerosol particles due to a less powerful or more distributed spray,” said Charles Haas, PhD, LD Betz Professor of Environmental Engineering in Drexel’s College of Engineering, who was a co-author of the paper and has been an advocate for the study of exposure risk from breathing water spray.
“However, modeling differences in Legionella concentrations in conventional and water efficient buildings remains a research gap our related work aims to address.”
As one might expect, risk is greater when exposure from multiple sources is considered or when it is adjusted for populations that are less able to fight off infection.
The researchers created their assessment using available data on aerosol particle volume, size and spray for a variety of showers, faucets, and toilets.
While the study focuses specifically on Legionella pneumophila bacteria, it sets a framework for assessing the risk of being exposed to any bacteria lurking in indoor water sources. Thus, it could be used more broadly to guide prescriptions for “acceptable levels” of bacteria in building water systems.
This is an understudied area of water quality, according to Hamilton, because the Environmental Protection Agency’s regulatory responsibility ends at the property line. So most existing indoor water quality guidelines are not based on risk assessment research.
But that doesn’t mean Legionella can’t make its way into household water supplies. In homes with particularly elaborate systems or where water can rest or stagnate for long periods of time, such as seasonal homes or new homes designed for water efficiency, Legionella colonies can form.
“There are many guidelines in the literature about how to create a ‘cutoff’ value, but none are based on technical reasoning,” Hamilton said.
“Most of the guidelines are based on what people are doing in practice. Our research simulates an appropriate concentration limit based on a risk level that is consistent with other water quality policies in order to give better guidance for monitoring water quality in buildings.”
Nudging Does Not Necessarily Improve Decisions
Nudging is a well-known and popular concept in behavioral economics. It refers to non-coercive interventions that influence the choices people make by changing the way a situation is presented. A well-known example of this is placing the salad bar near the cafeteria entrance to promote a healthy diet. It has been shown that simple change has an effect on the food people choose to eat for lunch. However, is a light salad really the best option from the employee’s perspective, or is it their employer who will benefit from staff who perform better in the afternoon? And, is improving the decisions we make really that simple?
Measuring the quality of a decision
Whether a nudge ultimately results in a person making decisions that are better suited to their needs is an important factor in assessing the effectiveness of nudges. This is the starting point of the research work of Nick Netzer and Jean-Michel Benkert from the Department of Economics at the University of Zurich. How do you measure whether a nudge improves a decision in the eyes of the person being nudged? “We can’t determine whether a nudge improves the choices a person makes until we understand how they reach their decisions,” says Nick Netzer, putting the hype surrounding nudging into perspective.
“Depending on which behavioral model we take as a starting point, it is possible to measure the effectiveness of nudges – or not.”
Traditional economics assumes that a person’s preferences can be inferred from their decisions and behavior. According to the rational behavior model, a person’s decision to have a salad or a steak for lunch is based on which meal meets their needs. When it comes to assessing nudges, however, this model is problematic, since nudging manipulates precisely the behavior that is supposed to shed light on a person’s preferences. The researchers therefore looked to alternative behavioral models to determine the assumptions under which a nudge can be assessed in a meaningful way.
According to the “satisficing” model, a person will consider their alternatives subsequently and choose the first one that meets their needs in a satisfactory way. The person will order the salad because it is the first option that adequately fulfills their requirements. Although they might have enjoyed the steak more, they will not consider that option, since they have already made up their mind. In this model, hardly any conclusions can be drawn about the true preferences of a person, and their decisions cannot be improved through nudging either.
If we assume decisions are made according to the limited attention model, however, the situation changes: This model is based on the idea that a person will only ever consider a certain number of possibilities – for example, only the first three meals on a menu that features five options. The person will then ponder these options and choose the best meal out of this selection. Unlike with the satisficing model, conclusions can be drawn about a person’s preferences, as the UZH researchers have now shown. Decisions that are based on such a decision-making process can be improved by nudging. Therefore, if you know that a salad is indeed an ideal meal, then placing it among the first three items on the menu will ensure that a person will at least consider this meal and maybe also choose it.
Success of nudges depends on decision-making process
It is therefore necessary to know what a person’s true needs and preferences are in order to assess the success of nudges when it comes to improving decisions. If we do not have this information, any nudging that takes place is done without knowing what is in a person’s best interests.
“Our findings show that the success of nudging greatly depends on how we view the human decision-making process,” says Nick Netzer.
“We can’t conclusively determine whether nudging makes sense as long as current scientific knowledge in economics, psychology and neuroscience doesn’t allow nudging to be assessed in a consistent manner.”
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When Activated, ‘Social’ Brain Circuits Inhibit Feeding Behavior In Mice
Researchers at Stanford demonstrated that direct stimulation of fewer than two dozen neurons linked to social interaction was enough to...
Drexel and Arizona State Researchers Look at Risk of Infection From Water in the Air at Home
Water spray from showers, faucets and toilets can carry Legionella bacteria. New research from Drexel and Arizona State is helping...
Nudging Does Not Necessarily Improve Decisions
Nudging is a well-known and popular concept in behavioral economics. It refers to non-coercive interventions that influence the choices people...
Fighting The Crave For Fattening Food? Just Surround Yourself In Its Scent
Just a whiff of fried food may entice you to order a high-calorie meal. But breathe it in for longer...
How Bad Will My Postpartum Depression Be In 12 Months?
A new Northwestern Medicine study was able to successfully predict if a new mother would experience worsening depressive symptoms over the...
Gastric Bypass Surgery May Benefit Muscle Strength More Than Previously Thought
Washington, DC – Gastric bypass surgery improves relative muscle strength and physical performance in people with obesity, according to a study published in...
High Intake Of Dietary Fiber And Whole Grains Associated With Reduced Risk Of Non-Communicable Diseases
People who eat higher levels of dietary fibre and whole grains have lower rates of non-communicable diseases compared with people...
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