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Your sense of smell may be the key to a balanced diet

The food you ate just before your walk past the bakery may impact your likelihood of stopping in for a sweet treat – and not just because you’re full.

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Photo by Otto Norin from Unsplash.com

Walking past a corner bakery, you may find yourself drawn in by the fresh smell of sweets wafting from the front door. You’re not alone: The knowledge that humans make decisions based on their nose has led major brands like Cinnabon and Panera Bread to pump the scents of baked goods into their restaurants, leading to big spikes in sales.

But according to a new study, the food you ate just before your walk past the bakery may impact your likelihood of stopping in for a sweet treat – and not just because you’re full.

Scientists at Northwestern University found that people became less sensitive to food odors based on the meal they had eaten just before. So, if you were snacking on baked goods from a coworker before your walk, for example, you may be less likely to stop into that sweet-smelling bakery.

The study, “Olfactory perceptual decision-making is biased by motivational state,” was published August 26 in the journal PLOS Biology.

Smell regulates what we eat, and vice versa

The study found that participants who had just eaten a meal of either cinnamon buns or pizza were less likely to perceive “meal-matched” odors, but not non-matched odors. The findings were then corroborated with brain scans that showed brain activity in parts of the brain that process odors was altered in a similar way.

These findings show that just as smell regulates what we eat, what we eat, in turn, regulates our sense of smell.

Feedback between food intake and the olfactory system may have an evolutionary benefit, said senior and corresponding study author Thorsten Kahnt, an assistant professor of neurology and psychiatry and behavioral sciences at Northwestern University Feinberg School of Medicine.

“If you think about our ancestors roaming the forest trying to find food, they find and eat berries and then aren’t as sensitive to the smell of berries anymore,” Kahnt said. “But maybe they’re still sensitive to the smell of mushrooms, so it could theoretically help facilitate diversity in food and nutrient intake.”

Kahnt said while we don’t see the hunter-gatherer adaptation come out in day-to-day decision-making, the connection between our nose, what we seek out and what we can detect with our nose may still be very important. If the nose isn’t working right, for example, the feedback loop may be disrupted, leading to problems with disordered eating and obesity. There may even be links to disrupted sleep, another tie to the olfactory system the Kahnt lab is researching.

Using brain imaging, behavioral testing and non-invasive brain stimulation, the Kahnt lab studies how the sense of smell guides learning and appetite behavior, particularly as it pertains to psychiatric conditions like obesity, addiction and dementia. In a past study, the team found the brain’s response to smell is altered in sleep-deprived participants, and next wanted to know whether and how food intake changes our ability to perceive food smells.

According to Laura Shanahan, a postdoctoral fellow in the Kahnt lab and the first and co-corresponding author of the study, there’s very little work on how odor perception changes due to different factors. “There’s some research on odor pleasantness”, Shanahan said, “but our work focuses in on how sensitive you are to these odors in different states.”

Pizza and pine; cinnamon and cedar

To conduct the study, the team developed a novel task in which participants were presented with a smell that was a mixture between a food and a non-food odor (either “pizza and pine” or “cinnamon bun and cedar” – odors that “pair well” and are distinct from each other). The ratio of food and non-food odor varied in each mixture, from pure food to pure non-food. After a mixture was presented, participants were asked whether the food or the non-food odor was dominant.

Participants completed the task twice inside an MRI scanner: First, when they were hungry, then, after they’d eaten a meal that matched one of the two odors.

“In parallel with the first part of the experiment running in the MRI scanner, I was preparing the meal in another room,” Shanahan said. “We wanted everything fresh and ready and warm because we wanted the participant to eat as much as they could until they were very full.”

The team then computed how much food odor was required in the mixture in each session for the participant to perceive the food odor as dominant. The team found when participants were hungry, they needed a lower percentage of food odor in a mixture to perceive it as dominant – for example, a hungry participant may require a 50% cinnamon bun to cedar mixture when hungry, but 80% when full of cinnamon buns.

Through brain imaging, the team provided further evidence for the hypothesis. Brain scans from the MRI demonstrated a parallel change occurring in the part of the brain that processes odors after a meal. The brain’s response to a meal-matched odor was less “food-like” than responses to a non-matched meal odor.

Applying findings to future sleep deprivation research

Findings from this study will allow the Kahnt lab to take on more complex projects. Kahnt said with a better understanding of the feedback loop between smell and food intake, he’s hoping to take the project full circle back to sleep deprivation to see if lack of sleep may impair the loop in some way. He added that with brain imaging, there are more questions about how the adaptation may impact sensory and decision-making circuits in the brain.

“After the meal, the olfactory cortex didn’t represent meal-matched food odors as much as food anymore, so the adaptation seems to be happening relatively early on in processing,” Kahnt said. “We’re following up on how that information is changed and how the altered information is used by the rest of the brain to make decisions about food intake.”

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Knowing the telltale signs of stroke

Learning stroke symptoms can help disrupt stroke before it disrupts your (or someone else’s) life.

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Here’s what you may not know, but has to be emphasized: Stroke can happen to anyone, happening to over 800,000 people every year in the US alone. And so it goes without saying that knowing the signs of stroke and how to prevent it can help protect you or your loved ones from disabilities caused by stroke.

The National Institute of Neurological Disorders and Stroke (NINDS), part of the National Institutes of Health, created the “Know Stroke” campaign to disrupt stroke and help people in your community who might be at risk of stroke through prevention, treatment and research.

“Seconds are critical when someone is having a stroke,” said Dr. Clinton Wright, vascular neurologist and director of the Division of Clinical Research at NINDS. “It’s important to know the signs.”

Know Stroke

Most strokes happen when the brain stops getting the blood supply it needs to work properly. Without enough blood flow, the brain starts to lose function. Two million brain cells die every minute during stroke, which is why stroke prevention is important. Preventing stroke protects you from developing disabilities that stroke may cause like speech problems, limited movement and memory loss.

Know the Signs of Stroke

Stroke symptoms often appear suddenly and can be easily missed. Treating stroke by getting to a hospital quickly is critical to prevent brain damage. If you see these signs, act F.A.S.T.:

  • Face drooping: One side of the face droops when smiling
  • Arm weakness: If both arms are raised, one drifts down
  • Speech difficulty: Slurred or strange speech
  • Time to call 911: Do not drive yourself or your loved one – call an ambulance immediately if you notice one or more of these signs

Learning these stroke symptoms can help disrupt stroke before it disrupts your (or someone else’s) life. Other signs to look for include sudden numbness, confusion, difficulty seeing, difficulty walking and severe headache, especially one that occurs in a split second, called a thunder-clap headache. Remember stroke is always an emergency that requires fast action and medical treatment.

Know How to Prevent Stroke

Some medical conditions and lifestyle considerations can put you at higher risk for stroke. For example, high blood pressure is the leading cause of stroke. Stroke can be prevented by effectively treating high blood pressure as well as high cholesterol, heart disease, diabetes, smoking and obesity. There are several ways to lower your risk for stroke:

  • Treat high blood pressure
  • Exercise regularly
  • Eat healthy and maintain a healthy weight
  • Manage diabetes
  • Quit smoking
  • Control cholesterol

Doing your best to prevent stroke from happening is the No. 1 way to lower your risk of disabilities caused by stroke. Even if you have had a stroke before, you can still take steps to reduce your risk of more strokes. Treating these risk factors may also reduce the chance of developing age-related dementia. For more information on the connection between stroke risk factors and dementia, visit mindyourrisks.nih.gov.

Know How to Recover from Stroke

As much as prevention helps lower the chances of having a stroke, it can still happen. Rehabilitation therapy is usually started in the hospital within 48 hours after a stroke. Health care workers help stroke patients relearn skills that were lost from the stroke or teach them new ways to compensate for remaining disabilities. Researchers continue to investigate how patients can restore blood flow to the brain and how to protect brain cells after stroke to improve recovery.

Know More

When you know the signs of stroke, you can help prevent a life-changing disability for yourself or someone you care about. You could even save a life. Visit stroke.nih.gov to learn more about stroke risks, prevention and research.

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NewsMakers

Acetaminophen reduces sepsis patients’ risk of having organ injury

Intravenous acetaminophen was safe for all the sepsis patients, with no difference in liver injury, low blood pressure, or other adverse events compared to the placebo group. Among secondary outcomes, they also found that organ injury was significantly lower in the acetaminophen group, as was the rate of acute respiratory distress syndrome onset within seven days of hospital admission.

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Intravenous acetaminophen reduced sepsis patients’ risk of having organ injury or developing acute respiratory distress syndrome, a serious condition that allows fluid to leak into the lungs.

This is according to a study, “Phase 2b Randomized Trial of Acetaminophen for Prevention and Treatment of Organ Dysfunction in Critically Ill Sepsis Patients”, that appeared in JAMA.

As FYI: Sepsis is the body’s uncontrolled and extreme response to an infection. In sepsis, red blood cells become injured and die at abnormally high rates, releasing so called “cell-free hemoglobin” into the blood. The body becomes overwhelmed and can’t remove this excess hemoglobin which can lead to organ damage.

While the trial did not improve mortality rates in all patients with sepsis regardless of severity, the researchers found that acetaminophen gave the greatest benefit to the patients most at risk for organ damage. With the therapy, those patients needed less assisted ventilation and experienced a slight, though statistically insignificant, decrease in mortality.

To test the therapeutic potential of acetaminophen more fully in a mid-stage clinical trial, researchers enrolled 447 adults with sepsis and respiratory or circulatory organ dysfunction at 40 US academic hospitals from October 2021 to April 2023.

Patients were randomized to receive either acetaminophen or a placebo intravenously every six hours for five days. The researchers then followed the patients for 28 days to see how they fared. They also completed a special analysis using data only from the patients with levels of cell-free hemoglobin above a certain threshold. The team’s primary interest overall was the number of patients who were able to stay alive with no organ support, such as mechanical ventilation or kidney failure treatment.

Scientists note that identifying high levels of cell-free hemoglobin as a biomarker that could be tested when patients are first admitted to the hospital would be a breakthrough, because it could help quickly determine which patients with sepsis might benefit from acetaminophen therapy.

The researchers found that intravenous acetaminophen was safe for all the sepsis patients, with no difference in liver injury, low blood pressure, or other adverse events compared to the placebo group. Among secondary outcomes, they also found that organ injury was significantly lower in the acetaminophen group, as was the rate of acute respiratory distress syndrome onset within seven days of hospital admission.

When looking more closely at the patients with higher cell-free hemoglobin, the researchers found that just 8% of patients in the acetaminophen group needed assisted ventilation compared to 23% of patients in the placebo group. And after 28 days, 12% of patients in the acetaminophen group had died, compared to 21% in the placebo group, though this finding was not statistically significant.

“While the anticipated effects of acetaminophen therapy were not realized for all sepsis patients, this study shows that it still holds promise for the most critically ill” said James Kiley. “Though, more research is needed to uncover the mechanisms and validate these results.”

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Extreme heat associated with children’s asthma hospital visits

Daytime heat waves were significantly associated with 19 percent higher odds of children’s asthma hospital visits, and longer duration of heat waves doubled the odds of hospital visits. They did not observe any associations for nighttime heat waves.

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For children seeking care at urban pediatric health centers, extreme heat events were associated with increased asthma hospital visits.

This is according to research published at the ATS 2024 International Conference.  

“We found that both daily high heat events and extreme temperatures that lasted several days increased the risk of asthma hospital visits,” said corresponding author Morgan Ye, MPH, research data analyst, Division of Pulmonary and Critical Care Medicine, University of California, San Francisco School of Medicine. “Understanding the impacts of climate-sensitive events such as extreme heat on a vulnerable population is the key to reducing the burden of disease due to climate change.”

For this study, Ye and colleagues looked at 2017-2020 electronic health records from the UCSF Benioff Children’s Hospital Oakland, which included data on asthma hospital visits by patients of the hospital, some of whom are from Benioff Oakland’s Federally Qualified Health Center, and demographics including patients’ zip codes. They used data from the PRISM Climate Group of Oregon State University to determine the timing of daily maximum (daytime heat waves) and minimum (nighttime heat waves) for each zip code. The researchers restricted their analyses to the region’s warm season (June to September). To evaluate the potential range of effects of different heat wave measurements, they used 18 different heat wave definitions, including the 99th, 97.5th and 95th percentile of the total distribution of the study period for one, two or three days.

They designed the study in a way that allowed them to determine the association between each heat wave definition and a hospital visit. They repeated the analysis for Bay Area and Central California zip codes.

The team discovered that daytime heat waves were significantly associated with 19 percent higher odds of children’s asthma hospital visits, and longer duration of heat waves doubled the odds of hospital visits. They did not observe any associations for nighttime heat waves. 

According to Ye, “We continue to see global temperatures rise due to human-generated climate change, and we can expect a rise in health-related issues as we observe longer, more frequent and severe heat waves. Our research suggests that higher temperatures and increased duration of these high heat days are associated with increased risk of hospital visits due to asthma. Children and families with lower adaptation capacity will experience most of the burden. Therefore, it is important to obtain a better understanding of these heat-associated health risks and susceptible populations for future surveillance and targeted interventions.”

The authors note that past research has suggested positive associations between extreme heat and asthma, but findings regarding hospitalizations and emergency room visits have been conflicting. Additionally, many other studies have focused on respiratory hospitalizations and not hospitalizations for asthma, specifically, and have not included or had a focus on children. This study is also unique because it investigated the effect of daily high temperatures but also the effects of persistent extreme temperatures.

This study demonstrates that even milder extreme heat temperatures may significantly impact health. These effects are more pronounced in climate-susceptible populations, including children and those who are medically vulnerable, such as those served by the urban pediatric health center in this study. The authors hope these study results will lead to more equitable health outcomes and reduce racial/ethnic disparities observed in climate-sensitive events.

“These results can be used to inform targeted actions and resources for vulnerable children and alleviate health-related stress during heat waves,” they conclude.

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