New research measuring the importance of religion in 109 countries spanning the entire 20th century has reignited an age-old debate around the link between secularisation and economic growth. The study, published in Science Advances, has shown that a decline in religion influences a country’s future economic prosperity.
While it is well documented that rich countries tend to be secular whilst poor countries tend to be religious, it is still unclear if secularisation causes wealth or the other way around?
The subject has long been debated by classic scholars of social science including French sociologist Emile Durkheim, who claimed that religion fades away once economic development has satisfied our material needs, whereas German sociologist Max Weber, argued that changes in religion drive economic productivity. The debate continues to this day.
Researchers from the Universities of Bristol (UK) and Tennessee (US) used data from birth cohorts from the World Values Survey to get a measure of the importance of religion spanning the entire 20th century (1900 to 2000).
The findings revealed that secularisation precedes economic development and not the other way around. Although this does not demonstrate a causal pathway, it does rule out the reverse.
Furthermore, the findings show that secularisation only predicts future economic development when it is accompanied by a respect and tolerance for individual rights. Countries where abortion, divorce and homosexuality are tolerated have a greater chance of future economic prosperity.
Damian Ruck, the study’s lead researcher in the University of Bristol Medical School (Population Health Sciences), said: “Our findings show that secularisation precedes economic development and not the other way around. However, we suspect the relationship is not directly causal. We noticed that secularisation only leads to economic development when it is accompanied by a greater respect for individual rights.
“Very often secularisation is indeed accompanied by a greater tolerance of homosexuality, abortion, divorce etc. But that isn’t to say that religious countries can’t become prosperous. Religious institutions need to find their own way of modernising and respecting the rights of individuals.”
Alex Bentley from the University of Tennessee, added: “Over the course of the 20th century, changes in importance of religious practices appear to have predicted changes in GDP across the world. This doesn’t necessarily mean that secularization caused economic development, since both changes could have been caused by some third factor with different time lags, but at least we can rule out economic growth as the cause of secularization in the past.”
The study was funded by grants from the Wellcome Trust and the EPSRC (Engineering and Physical Sciences Research Council).
By now you’ve probably heard of bone broth, the meaty elixir that’s beloved around the web. Made by stewing bones in water with vegetables and spices, it’s full of flavor, nutrients, and it’s an excellent addition to all sorts of things, whether that’s a bowl of pho or a mushroom risotto. People love bone broth so much, there are now even restaurants that specialize in it in major cities across the country. Of course, if you don’t want to trek all the way to a specialty restaurant in NYC, you’ll have to satisfy your bone broth cravings on your own.
Though it may seem like a fairly straightforward process, there are lots of details involved in making bone broth that you should be aware of before you take on the project. To find out more about what you need to do to make it good, SELF talked to Marco Canora, chef and founder of Brodo in NYC (one of those restaurants that specializes in bone broth!). He told me all about the tips only experts know, the common mistakes you should be on the lookout for, and the surprising way you can put your finished project to work.
You might be wondering about the difference between bone broth and stock.
At least, I know I have. Canora is here to tell you that it’s not much! “They are essentially the same [thing],” he explains, “meaty bones, plus aromatics, plus water, plus heat—but bone broths have somewhat longer cook times to maximize nutrient extraction.”
Typically, you can make a stock in a few hours, but bone broths require much longer (anywhere from 12 to 24 hours). That’s how long it can take to break down the collagen-containing connective tissue in the bones. Collagen is responsible for giving the broth a gelatinous texture when it’s at room temperature or below. Never fear, though—a little bit of heat will turn that freaky meat Jell-O back into the soupy broth you actually want. By the way, bone broth often comes with a lot of health claims, and while it is a good source of protein, there isn’t much evidence to support the claims that it can make your skin look younger or relieve joint pain.
You can use bones from any animals, but use the ones with the most connective tissue.
Chicken bones, duck bones, cow bones, and so on, you can use whatever you prefer to make your bone broth. Just be sure to pick bones with a lot of connective tissue, like neck bones, feet, or knuckles, says Canora. He explains that that connective tissue is where all those extra nutrients come from, and is essential to making your bone broth a bone broth and not a stock. Though you won’t be able to find bones in the meat section at the supermarket, you will almost always be able to find them behind the butcher counter.
Before you really get started, you may need to blanch your bones.
For this story, I took the task of making bone broth upon myself, and as I was researching recipes, I found that some of them suggested blanching the bones and some didn’t. Blanching is a process when you boil something, in this case bones, to remove the impurities. When I asked Canora if I needed to include this step in the process, he said I should, but only if my bones aren’t up to snuff. “If one uses lesser quality bones, I would recommend blanching and skimming.”
My cow bones weren’t the finest quality. I live in Berlin and I don’t really know how to ask for “the best bones” in German, so I just went ahead and blanched to be safe. Honestly I’m glad I did, because when I blanched them, it made all this gunky foam rise to the top of the pot. My house smelled like a tannery! As you can see from the above photo, it was…a little freaky. If this happens to you, though, it’s totally fine. The bones weren’t bad—this process just gets rid of all the nasty bits that would make your broth taste kind of funky.
To do it, add your bones to a large stock pot and cover them completely with cold water. Bring the pot to a boil and let it simmer for 20 minutes. Drain out the water and set aside.
Roasting the bones is the next thing on your to-do list.
I know this seems like a lot of steps to make broth, but trust me, they’re all necessary. Especially roasting, which will brown your bones and ultimately give your broth a rich, flavor and caramel color.
After blanching (if you’ve decided to blanch), transfer the bones to a parchment paper-lined baking sheet and cook them for about an hour at 375 degrees F, says Canora. Just be sure not to burn them, as he explains that can impart a bitter flavor on the finished broth.
Get your vegetables and spices in place.
You can’t make bone broth with only bones—you need veggies and spices to deepen the flavor. Which ones? Well, Canora recommends sticking with a basic mirepoix, which is a combination of carrots, onions, and celery. As for spices, all you really need are bay leaves and peppercorns, though if you’d rather mix it up you can add other whole spices like star anise or chili peppers. Some recipes also recommend adding about a tablespoon or two of apple cider vinegar, but when I asked Canora about that he said you’d need to use a lot of vinegar to really affect the flavor, so it’s not necessary.
You can get experimental with what you add to the broth if you like, but you can also doctor it up after it’s finished.
I decided to follow Canora’s instructions and keep it simple with just the veggies, bay leaves, and peppercorns. The nice thing about broth is that if you make it plain, you can always doctor it up later. Keeping it plain increases its versatility, so you can use it in a bunch of different things, rather than just one specific thing. For example, if you want to use it in a risotto, you don’t necessarily want it to be spicy, but if you brew it with chili peppers, it’s going to be spicy no matter what. Rather, just wait till the end to spice it up with a chili oil or chili flakes so that way you can use it in your risotto and your spicy soup.
Cover the contents of your pot completely with water and let it stew slightly covered with a lid for a long, long time over low heat.
Like, a really long time. According to Canora, “Too little time produces a watery, flavorless broth,” which is more of a stock than a bone broth. In general, you should let your pot simmer over low heat for anywhere from 12 to 24 hours. Don’t leave the pot going overnight (that’s dangerous!). Instead, turn it off, cover it up, and resume cooking it in the morning when you wake up—the results will be the same, and it’s way safer than leaving a flame going while you sleep.
During the first few hours, check on it occasionally to skim off any foam from the top.
“If you spend the time and effort skimming the broth in the early stages of cooking, blanching isn’t required,” says Canora. So if you’ve decided not to blanch, you’ll have to spend more time skimming off the funky stuff during the first few hours of the stewing process.
Either way, check on your broth occasionally over the first few hours just to make sure you’re getting any bits out that might affect the flavor later.
Store it in the fridge if you want to use it right away, or keep it in the freezer if you want to save it for later.
To store bone broth in the fridge, you’ll need to cool it down as fast as possible so that bacteria doesn’t start to form (try dunking the stock pot in a bowl of ice water) and store it in a clean airtight container—doing this will give it a lifespan of about a week, says Canora.
If you want it to last closer to three months, stick it in the freezer. Canora recommends pouring it into an ice tray, that way you can pop one out when you need a little broth for a recipe that you’re cooking.
Try it in soups, stir-fries, or even drink it by itself.
Yep, that’s right—Canora loves to drink bone broth like you would tea. It’s a warm satisfying drink that lands somewhere between a beverage and a soup, and it’s the perfect thing for when you want something hot that isn’t necessarily sweet.
Other than that, you can use your bone broth all the ways you normally might. Turn it into soup, cook rice in it, or add it to your sauces for a meaty flavor. And you don’t need to travel all the way to a specialty shop in New York to enjoy it.
The risk of developing autism-spectrum disorders is determined by the mother’s microbiome — the collection of microorganisms that naturally live inside us — during pregnancy, new research from the University of Virginia School of Medicine suggests. The work raises the possibility that preventing forms of autism could be as simple as an expectant mom modifying her diet or taking custom probiotics.
Further, the UVA scientists were able to use their discovery to prevent the development of autism-like neurodevelopmental disorders in lab mice. They found they could halt the development of such disorders by blocking a particular inflammatory molecule produced by the immune system. Targeting this molecule, interleukin-17a, offers another potential avenue for preventing autism in people, the researchers say. They caution, however, that this approach would be much more complex because of the risk of side effects.
“We determined that the microbiome is a key contributor in determining susceptibility [to autism-like disorders], so it suggests that you could target either the maternal microbiome or this inflammatory molecule, IL-17a,” said lead researcher John Lukens, PhD, of UVA’s Department of Neuroscience. “You could also use this [IL-17a] as a biomarker for early diagnosis.”
Microbiome and Autism
The groundbreaking work from Lukens and his colleagues sheds light on the complex relationship between the health of the mother’s microbiome and the healthy development of her children. “The microbiome can shape the developing brain in multiple ways,” explained Lukens, of UVA’s Center for Brain Immunology and Glia (BIG) and UVA’s Carter Immunology Center. “The microbiome is really important to the calibration of how the offspring’s immune system is going to respond to an infection or injury or stress.”
But an unhealthy microbiome in the mom can create problems: Lukens’ work shows that it can make her unborn offspring susceptible to neurodevelopmental disorders. The researchers found that the IL-17a molecule was a key contributor to the development of autism-like symptoms in lab mice.
The good news: The microbiome can be modified easily, either through diet, probiotic supplements or fecal transplant. All of these approaches seek to restore a healthy equilibrium among the different microorganisms that live in the gut.
“In terms of translating our work to humans, I think the next big step would be to identify features of the microbiome in pregnant mothers that correlate with autism risk,” Lukens said. “I think the really important thing is to figure out what kind of things can be used to modulate the microbiome in the mother as effectively and safely as we can.”
Another Option for Preventing Autism
Blocking IL-17a also might offer a way to prevent autism, but Lukens said that path carries much more risk. “If you think about pregnancy, the body is basically accepting foreign tissue, which is a baby,” he said. “As a result, maintenance of embryonic health demands a complex balance of immune regulation, so people tend to shy away from manipulating the immune system during pregnancy.”
IL-17a previously has been implicated in conditions such as rheumatoid arthritis, multiple sclerosis and psoriasis, and there are already drugs available that target it. But Lukens noted that the molecule has an important purpose in stopping infections, especially fungal infections. Blocking it, he said, “could make you susceptible to all kinds of infections.” And doing so during pregnancy could have complex ripple effects on a child’s development that scientists would need to sort out.
For their next steps, Lukens and his team plan to explore the potential role of other immune molecules in the development of autism and other such conditions. IL-17a may be just one piece in a much larger puzzle, he said.
While Lukens’ work links the immune system with neurodevelopmental disorders, he emphasized that this in no way suggests that vaccines are contributing to the development of autism. “There’s a definite link between the immune response and the developing brain,” he said. “It just doesn’t have anything to do with vaccines. It’s much, much earlier.”
Lukens’ work is but the latest research from UVA to speak to the importance of the microbiome in maintaining good health. For example, one of Lukens’ colleagues in the Department of Neuroscience, Alban Gaultier, PhD, found that probiotics in yogurt can reverse depression symptoms.
Sugar improves memory in older adults — and makes them more motivated to perform difficult tasks at full capacity — according to new research by the University of Warwick.
Led by PhD student Konstantinos Mantantzis, Professor Elizabeth Maylor and Dr Friederike Schlaghecken in Warwick’s Department of Psychology, the study found that increasing blood sugar levels not only improves memory and performance, but makes older adults feel happier during a task.
The researchers gave young (aged 18-27) and older (aged 65-82) participants a drink containing a small amount of glucose, and got them to perform various memory tasks. Other participants were given a placebo — a drink containing artificial sweetener.
The researchers measured participants’ levels of engagement with the task, their memory score, mood, and their own perception of effort.
They found that increasing energy through a glucose drink can help both young and older adults to try harder compared to those who had the artificial sweetener. For young adults, that’s where it ended, though: glucose did not improve either their mood or their memory performance.
However, older adults who had a glucose drink showed significantly better memory and more positive mood compared to older adults who consumed the artificial sweetener.
Moreover, although objective measures of task engagement showed that older adults in the glucose group put more effort into the task than those who consumed the artificial sweetener, their own self-reports showed that they did not feel as if they had tried any harder.
The authors concluded that short-term energy availability in the form of raised blood sugar levels could be an important factor in older adults’ motivation to perform a task at their highest capacity.
Heightened motivation, in turn, could explain the fact that increased blood sugar levels also increase older adults’ sense of self-confidence, decrease self-perceptions of effort, and improve mood. However, more research is needed to disentangle these factors in order to fully understand how energy availability affects cognitive engagement, and to develop clear dietary guidelines for older adults.
Konstantinos Mantantzis, a PhD student from the University of Warwick’s Department of Psychology, commented:
“Over the years, studies have shown that actively engaging with difficult cognitive tasks is a prerequisite for the maintenance of cognitive health in older age. Therefore, the implications of uncovering the mechanisms that determine older adults’ levels of engagement cannot be understated.”
Dr Friederike Schlaghecken, from the University of Warwick’s Department of Psychology, commented:
“Our results bring us a step closer to understanding what motivates older adults to exert effort and finding ways of increasing their willingness to try hard even if a task seems impossible to perform.”
Arriving at your favorite beach only to discover it’s closed because of bacterial contamination can be a bummer. But even worse would be unknowingly swimming in waters polluted with fecal material — a very real possibility, given that current detection methods can require up to 24 hours to obtain results. Now, researchers reporting in the ACS journal Environmental Science & Technology have identified computer models that provide accurate short-term forecasts, or “nowcasts,” of beach water quality.
The number of beach closings due to fecal microbes has risen in recent years. In the U.S., beaches in the Great Lakes region rank high among those with the worst problems. According to the Michigan Department of Environmental Quality, 30 beaches in the state were either closed or had advisories associated with them in early July 2018 because of high bacteria levels. Collecting water samples and then analyzing them in the lab takes time, even with modern techniques, which puts swimmers at risk of infection with nasty stomach bugs while testing is ongoing. But computer simulations for predicting water quality are complex and not always reliable. Jie Niu and Mantha S. Phanikumar wondered if they could identify simpler computer models that could accurately predict current beach conditions from past data.
The researchers compared the abilities of five computer models to nowcast bacterial levels at four sites in Southern Lake Michigan. The models varied in the number of input parameters, from only past levels of bacteria at the sites, to more complex data, such as daily rainfall, water temperature and water turbidity. The team found that the two best models incorporated past bacterial levels and several of the other parameters. However, a new model developed by the researchers also performed well. This approach, which combined two techniques called wavelet transform and artificial neural network analysis, required only bacterial data from the past, with no additional inputs. The researchers concluded that the new model is a potentially useful tool for beach management, especially when detailed data on beach conditions aren’t available.
In the age of Instagram and Snapchat, everyone wants to have perfect pearly whites. To get a brighter smile, consumers can opt for over the counter teeth-whitening treatments or a trip to the dentist to have their teeth bleached professionally. But both types of treatments can harm teeth. According to an article published in ACS Biomaterials Science & Engineering, researchers have now developed a new, less destructive method.
Teeth can become discolored on their outer surfaces when people consume colored foods and drinks, such as coffee, tea or red wine. As a result, many people turn to non-invasive whitening treatments that bleach the teeth. Currently, the most common bleaching agent is hydrogen peroxide, which steals electrons from the pigment molecules that cause teeth discoloration, and this process can be sped up by exposing teeth to blue light. But high concentrations of hydrogen peroxide can break down a tooth’s enamel, causing sensitivity or cell death. So, Xiaolei Wang, Lan Liao and colleagues wanted to see if a different blue-light-activated compound could be a safer, but still effective, alternative.
The team modified titanium dioxide nanoparticles with polydopamine (nano-TiO2@PDA) so that they could be activated with blue light. In a proof-of-concept experiment, the nano-TiO2@PDA particles were evenly coated on the surface of a tooth and irradiated with blue light. After four hours of treatment, the whitening level was similar to that obtained with hydrogen-peroxide-based agents. The group notes that no significant enamel damage was found on the surface of the tooth, and the treatment was significantly less cytotoxic than hydrogen peroxide. In addition, the nano-TiO2@PDA therapy showed antibacterial activity against certain bacteria.
Even when people have well-connected social networks beyond their home cities and across state lines, they are still most frequently interacting with people who are very geographically near.
That is one of the major outcomes of an expansive, 16-month study of more than 51 million geo-tagged tweets generated by more than 1.7 million Twitter users across the U.S. The study was funded, in part, by the National Science Foundation.
San Diego State University professor Ming-Hsiang Tsou and alumnae Su Yeon Han led the collaborative study, also adopt mapping techniques which allowed for visual analysis of the information.
This type of foundational research is part of a growing body of literature and computational modeling efforts using social media and big data to improve measurements and predictions of human behavior.
“You can Skype and Zoom with anyone. People can buy anything they want from Amazon. It doesn’t matter the location,” said Tsou, founding director of SDSU’s Center for Human Dynamics in the Mobile Age.
With the rise of the Internet and the new era of globalization, some have argued that the world is flat — geography is dead.
“But we disagree with that,” Tsou said, noting that even with shipments, regional supply still influences availability and expedience of a delivery. “The concept of distance is not dissolved, but it has shifted. Now it is more about probability: What is the likelihood, because of distance, that your followers will be your friends in real life?”
If they do not live very close, highly unlikely, Tsou said.
Collaborating with Keith C. Clarke, a geography professor at the University of California, Santa Barbara (UCSB), Han and Tsou published their findings in an article, “Revisiting the Death of Geography in the Era of Big Data: The Friction of Distance in Cyberspace and Real Space.” The article recently appeared in the online issue of the International Journal of Digital Earth.
The team collected tweets via the Twitter Streaming API (application programming interface) between November 2015 and January 2016. Identifiable data, such as a person’s user name, age, gender and occupation, were not included in the dataset.
The team focused on the online and real space interactions of users in four major cities: Chicago, Houston, Los Angeles and New York. Spatial interactions generally include trips, telephone calls and emails, and the team broadened the definition to include any type of connection between places, including people viewing social media messages of those living in other places and “following” others online.
“When we are analyzing social media, or big data, while also handling the geospatial information, we can more precisely analyze data from a regional perspective,” Tsou said.
Studying geo-tagged tweets was essential, as social media data became a proxy for human connection and mobility, said Han, the lead author, now a post-doctoral researcher at the University of California, Riverside (UCR). Han was involved in the study during her time as a post-doctoral researcher at SDSU.
With the massive database of tweets prepared for analysis, the team considered three main issues: how people followed one another, the awareness they had of the cities of their followers and whether they traveled to cities where their followers were located. To compare interactions online versus those in real space, the team studied origins and travel destinations of Twitter users, producing detailed data maps to easily visualize findings.
Of note, the team found that Twitter users averaged 90 percent of their tweets in a single city during the 16-month study period — most often their home city.
In real space, and despite some variation, the team also found that users in all states tended to follow others and have followers well beyond their immediate geographic region — often nationwide. However, according to the study, people are far less likely to have strong awareness of or even give mention to the cities of their faraway followers.
A sizable number of New York, Chicago and Houston users had online connections that were densely consolidated in regions just beyond their own cities, but seldom had real space interactions with people who lived beyond 5 or 6 hours away. For users in those cities, very immediate geographic proximity determined real space interactions with followers; making an hours-long drive to maintain a connection less likely.
“We know that people are communicating much more frequently with nearby people than those who are far away,” Han said. “Even in cyberspace, the same thing is very likely to happen because, in many cases, people get to know each other in real space and also communicate with the same people online.”
Los Angeles: The Exception
Users in Los Angeles generally had an expanded network of friends nearby while being well-traveled regionally and nationally. However, they did not enjoy the same level of real life interactions with followers in their very immediate vicinity. The researchers attribute that partially to the entertainment industry, where individuals generally follow well-known celebrities and organizations that never follow them in return.
Based on the findings, the team offered an addendum to the Tobler’s First Law of Geography advanced by UCSB Professor Emeritus Waldo R. Tobler, who passed in February 2018. Tobler explained that everything is relational, but nearer things are more closely related. The team noted instead: “In both real space and cyberspace, everything is related to everything else, but near things are more related in real space than in cyberspace.”
The team’s research, Han said, could more readily help determine ways to use social media to identify and address social issues and concerns.
“If you are a public health official who wants to spread information about disease prevention, you will be interested in looking at how far and quickly the information spread among people through social media,” Han said. “Also, if you are a political campaigner who wants to spread an election pledge through social media, you will want to see how far and quickly the information spread through people in the social media.”
In a new study published in the journal Peer J this week, researchers at UniSA’s Body in Mind Research Group have found people suffering osteoarthritis in the knees reported reduced pain when exposed to visual illusions that altered the size of their knees.
UniSA researcher and NHMRC Career Development Fellow, Dr Tasha Stanton says the research combined visual illusions and touch, with participants reporting up to a 40 per cent decrease in pain when presented with an illusion of the knee and lower leg elongated.
“We also found that the pain reduction was optimal when the illusion was repeated numerous times — that is, its analgesic effect was cumulative,” Dr Stanton says.
The small study — 12 participants — focused on people over 50 years with knee pain, and a clinical diagnosis of osteoarthritis.
Dr Stanton says the research provides “proof of concept” support that visual illusions can play a powerful role in reducing pain.
“We have shown that pain is reduced significantly when a visual stimulus, in this case a smaller or an elongated joint, is provided, but not only that, when exposed to that illusion repeatedly, pain decreases even further,” she says.
“It seems that seeing is believing, and by understanding the neurological processes at work we may be able to ease pain more effectively for people with chronic conditions, reduce their reliance on medications and find alternative physical therapies to help manage conditions like osteoarthritis.
“This research adds to a growing body of evidence that the pain experienced in osteoarthritis is not just about damage to the joint.
“There are other factors at play and the more we understand about these natural mechanisms for reducing pain and how they are triggered, the more opportunity we have to develop a range of treatments to manage chronic conditions.”
Even in areas with moderate-to-high levels of traffic pollution, regular physical activity reduced the risk of first and recurrent heart attack, according to new research in Journal of the American Heart Association, the Open Access Journal of the American Heart Association/American Stroke Association.
“While exercise is known to reduce cardiovascular disease risk; pollution can increase the risk of cardiovascular disease, including heart attacks, asthma and chronic obstructive lung disease,” said Nadine Kubesch, Ph.D., lead author and researcher at the University of Copenhagen in Denmark. “Currently there is little data on whether poor air quality cancels out the protective benefits of physical activity in preventing heart attacks.”
Researchers in Denmark, Germany and Spain evaluated outdoor physical activity levels (sports, cycling, walking and gardening) and nitrogen dioxide (NO2 pollutant generated by traffic) exposure in 51,868 adults, age 50-65, comparing self-reported activities and lifestyle factors against heart attack. Over a 17.7-year period, there were 2,936 first heart attacks and 324 recurrent heart attacks.
To estimate average NO2 exposure, researchers used national traffic pollution monitoring data for each participants’ address and found:
Higher levels of were associated with more heart attacks, however, the risk was lower among those who were physically active.
Moderate cycling for four or more hours per week cut risk for recurrent heart attack by 31 percent; and there was a 58 percent reduction when all four types of physical activity (together totaling four hours per week or more) were combined, regardless of air quality.
Those who participated in sports had a 15 percent lower rate of initial heart attacks and there was a 9 percent risk reduction associated with cycling, regardless of air quality
Compared to participants with low residential NO2 exposure, those in higher risk areas had a 17 percent increase risk in first heart attack and 39 percent for recurrent heart attack.
In participants who developed a heart attack (first or recurrent), the average NO2 exposure level was 18.9 micrograms per cubic meter air (μg/m3) with an overall average of 18.7 μg/m3, which is below the current NO2 European Union exposure guideline (50 μg/m3 over 24 hours).
“Our study shows that physical activity even during exposure to air pollution, in cities with levels similar to those in Copenhagen, can reduce the risk of heart attack,” Kubesch said. “Our research supports existing evidence that even moderate levels of regular physical activity, such as active commuting, are sufficiently intense to get these health benefits.
An analysis of more than 1,000 people with and without psychiatric disorders has shown that nitrates — chemicals used to cure meats such as beef jerky, salami, hot dogs and other processed meat snacks — may contribute to mania, an abnormal mood state. Mania is characterized by hyperactivity, euphoria and insomnia.
The findings of the Johns Hopkins Medicine study, which was not designed to determine cause and effect, were published July 18 in Molecular Psychiatry. Specifically, it found that people hospitalized for an episode of mania had more than three times the odds of having ever eaten nitrate-cured meats than people without a history of a serious psychiatric disorder.
Experiments in rats by the same researchers showed mania-like hyperactivity after just a few weeks on diets with added nitrates.
While a number of genetic and other risk factors have been linked to the manic episodes that characterize bipolar disorder and may occur in other psychiatric conditions, those factors have been unable to explain the cause of these mental illnesses, and researchers are increasingly looking for environmental factors, such as diet, that may play a role.
The researchers say that their new study adds to evidence that certain diets and potentially the amounts and types of bacteria in the gut may contribute to mania and other disorders that affect the brain.
“Future work on this association could lead to dietary interventions to help reduce the risk of manic episodes in those who have bipolar disorder or who are otherwise vulnerable to mania,” says lead author Robert Yolken, M.D., the Theodore and Vada Stanley Distinguished Professor of Neurovirology in Pediatrics at the Johns Hopkins University School of Medicine.
Mania, a state of elevated mood, arousal and energy that lasts weeks to months, is generally seen in people with bipolar disorder, but can also occur in those with schizoaffective disorder. Manic states can lead to dangerous risk-taking behavior and can include delusional thinking, and most of those affected experience multiple hospitalizations in the course of their psychiatric illness.
Bipolar disorder affects an estimated 1 to 3 percent of the population of the United States and costs an estimated $25 billion a year in direct health care costs, according to a study in the Journal of Affective Disorders.
Yolken, trained as an infectious disease expert, was originally interested in whether exposure to infections such as viruses transmitted through food might be linked to any psychiatric conditions. Between 2007 and 2017, as part of an ongoing study, he and colleagues collected demographic, health and dietary data on 1,101 individuals aged 18 through 65 with and without psychiatric disorders. Approximately 55 percent of the participants were female and 55 percent were Caucasian, with 36 percent identifying as African-American.
Those with psychiatric disorders were recruited from patients receiving care at the Sheppard Pratt Health System in Baltimore. Individuals with no history of psychiatric disorders were recruited from posted announcements at local health care facilities and universities in the region.
A study of their records between 2007 and 2017 showed that, unexpectedly, among people who had been hospitalized for mania, a history of eating cured meat before hospitalization were approximately 3.5 times higher than the group of people without a psychiatric disorder. Cured meats were not associated with a diagnosis of schizoaffective disorder, bipolar disorder in people not hospitalized for mania or in major depressive disorder. No other foods about which participants were queried had a significant association with any of the disorders, or with mania.
“We looked at a number of different dietary exposures and cured meat really stood out,” says Yolken. “It wasn’t just that people with mania have an abnormal diet.”
Nitrates have long been used as preservatives in cured meat products and have been previously linked to some cancers and neurodegenerative diseases, so Yolken suspected they may also explain the link to mood states such as mania.
The dietary survey did not ask about frequency or time frame of cured meat consumption, so the researchers couldn’t draw conclusions about exactly how much cured meat boosts one’s risk of mania, but Yolken hopes future studies will address this.
To get at the roots of the association, Yolken collaborated with researchers studying the impact of nitrates on rats.
Kellie Tamashiro, Ph.D., associate professor of psychiatry and behavioral sciences, and M.D./Ph.D. student Seva Khambadkone, both of Johns Hopkins, and others divided a group of otherwise healthy rats into two groups: one received normal rat chow, and the other received both normal chow and a piece of store-bought, nitrate-prepared beef jerky every other day. Within two weeks, the rats receiving the jerky showed irregular sleeping patterns and hyperactivity.
Next, the team worked with a Baltimore-based beef jerky company to create a special nitrate-free dried beef. They repeated the experiment, this time giving some rats the store-bought, nitrate-prepared jerky and others the nitrate-free formulation. The animals that ate the nitrate-free meat behaved similarly to a control group, while the animals that consumed the nitrates once again showed sleep disturbances and hyperactivity similar to that seen in patients with mania — increased activity during normal sleep times and in new environments.
The results were then replicated with a specially formulated rat chow that had either nitrate added directly to the chow, or no nitrate.
Importantly, the amount of nitrate being consumed on a daily basis by the rats — when scaled up to the size of a human — was equivalent to the amount a person might eat for a daily snack, such as one beef jerky stick or hot dog.
“We tried to make sure the amount of nitrate used in the experiment was in the range of what people might reasonably be eating,” says Yolken.
When the group analyzed the gut bacteria of the different groups of rats, they found that animals with nitrate in their diet had different patterns of bacteria living in their intestines than the other rats. Moreover, the animals had differences in several molecular pathways in the brain that have been previously implicated in bipolar disorder.
While the team also cautions that it’s too early to take any clinical messages from the results, and occasional cured meat consumption is unlikely to spur a manic episode in most of the population, Yolken says the findings add to evidence of the multiple factors that contribute to mania and bipolar disorder.
“It’s clear that mania is a complex neuropsychiatric state, and that both genetic vulnerabilities and environmental factors are likely involved in the emergence and severity of bipolar disorder and associated manic episodes,” says Khambadkone. “Our results suggest that nitrated cured meat could be one environmental player in mediating mania.”
Yolken’s group recently published results of a separate study showing that when people with bipolar disorder are given probiotics — which can change the composition of gut bacteria — after a manic episode, they are less likely to be rehospitalized in the following six months. “There’s growing evidence that germs in the intestines can influence the brain,” says Yolken. “And this work on nitrates opens the door for future studies on how that may be happening.”
This work was supported by a National Institute of Mental Health Silvio O. Conte Center grant (MH-94268) and by the Stanley Medical Research Institute.