People tend to avoid sick people, even if they don’t consciously now that they are sick, according to a new study published in PNAS. Snip: In the perpetual race between evolving organisms and pathogens, the human immune system has evolved to reduce the harm of infections. As part of such a system, avoidance of contagious individuals would increase biological fitness. The present study shows that we can detect both facial and olfactory cues of sickness in others just hours after experimental activation of their immune system. The study further demonstrates that multisensory integration of these olfactory and visual sickness cues is a crucial mechanism for how we detect and socially evaluate sick individuals. Thus, by motivating the avoidance of sick conspecifics, olfactory–visual cues, both in isolation and integrated, may be important parts of circuits handling imminent threats of contagion. David DiSalvo from Forbes has more : Researchers injected one group of people with a harmless bacteria that triggers an immune response for a few hours, causing mild fever and fatigue, but without any really obvious signs of being sick… The researchers exposed the smell samples, photos and videos to another group of people, along with the same set of samples from healthy people… The brain scans showed a signaling effect cutting across the senses when someone looked at a photo or video of a sick person, along with being exposed to the smell samples. The overall effect is a multi-sense brain alarm telling us that someone is sick and should be avoided.
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Our brains tell us to avoid people who are sick, even when they don’t show obvious symptoms
Conventional wisdom: If you eat a lot of salt, you will get thirsty to dilute the sodium level in your blood. The excess salt will be excreted in your urine. But a new study of Russian cosmonauts is challenging this long-held belief. When the cosmonauts ate more salt, the became less thirsty. And their appetite increased – they had to eat 25 percent more to maintain their weight. From the New York Times : The crew members were increasing production of glucocorticoid hormones, which influence both metabolism and immune function. To get further insight, [Dr. Jens Titze, now a kidney specialist at Vanderbilt University Medical Center and the Interdisciplinary Center for Clinical Research in Erlangen, Germany] began a study of mice in the laboratory. Sure enough, the more salt he added to the animals’ diet, the less water they drank. And he saw why. The animals were getting water — but not by drinking it. The increased levels of glucocorticoid hormones broke down fat and muscle in their own bodies. This freed up water for the body to use. But that process requires energy, Dr. Titze also found, which is why the mice ate 25 percent more food on a high-salt diet. The hormones also may be a cause of the strange long-term fluctuations in urine volume. Scientists knew that a starving body will burn its own fat and muscle for sustenance. But the realization that something similar happens on a salty diet has come as a revelation. https://youtu.be/aJEzl31zL-I