Rachel Feltman: Happy Monday, listeners! And happy August. For Scientific American’s Science Quickly, I’m Rachel Feltman. We’re finally back with another one of our science news roundups.
I’ll start with a story that pretty much everyone I know has been asking me for science-backed advice on: Cyclospora, otherwise known as the exploding diarrhea parasite. If you’re either living outside of the U.S. or living under a rock, this microscopic parasite has been causing big gastrointestinal issues this summer. As of July 30, Michigan alone had reported more than 10,000 cases of cyclosporiasis—a disease caused by the parasite that can cause bouts of sudden, watery diarrhea—including 193 hospitalizations. That’s compared with around 40 or 50 cases in a typical year, according to the state’s chief medical executive, Natasha Bagdasarian, and it’s likely that many cases have gone unreported. Another eight states have also seen an uptick in cases that the Centers for Disease Control and Prevention has tied to the same outbreak.
First, the good news: The cases in those nine states have been linked pretty solidly to iceberg lettuce, specifically shredded lettuce sourced from Taylor Farms de Mexico. But it’s too soon to tell whether or not other, as-yet-unidentified and unrecalled streams of produce have also been contaminated. So just avoiding iceberg lettuce is good but probably not sufficient. And that means while it’s reasonable to hope that cases have peaked, public health experts say those states aren’t necessarily out of the woods yet.
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And now for some more not-so-great news: There does seem to be a second, unrelated outbreak happening as well. Now, we do tend to see spikes in cases of foodborne illness especially those related to pathogens spread by contaminated feces every summer. So, it will be normal to see some number of cyclosporiasis cases regardless. And indeed, as of last week, there were several separate instances of cyclosporiasis outbreaks with no known cause under active investigation by the Food and Drug Administration. But this second cluster is worth noting because it already includes an unusually high number of cases. In North Carolina, where state officials have started actively tracking the outbreak, there have been 718 cases reported since May, most of which have occurred since mid-June. Based on surveys, North Carolina health officials say parsley and cilantro seem to be a common denominator in many, though not all, cases.
For now, the best way to lower your risk is, unfortunately if you love salads not to eat salads. You should cook all produce if you can, and of course you should also wash produce before consuming it. Regardless of how you are going to prepare it. And you should also remember to wash your hands after handling raw fruits and veggies.
Speaking of eating healthy, which for now may mean saying no to that side salad: We’ve talked before on the show about the world’s current obsession with protein. You can go check out our May 13 episode to hear more about why “protein maxxing” can often be unnecessary. But, now new research suggests that easing up on protein could have a positive impact on your lifespan.
Here to tell us more about that story is Scientific American breaking news reporter Adam Kovac.
Adam Kovac: Hey, Rachel.
So this new study is actually a review of a lot of the other studies that have come out over the past few years about what we should be eating, how much protein is good for us. And so a lot of this was conducted in animal models like mice because it’s really hard to adjust somebody’s protein diet for their entire life. And when they reviewed all of it, they found that eating too much protein could actually have a really negative effect on a person or a mouse’s lifespan.
So there’s a few reasons that protein can affect lifespan, and one of them has to do with when you restrict the amount of protein you take in, it can actually lead to a boost in the production of a hormone called FGF21, mostly in the liver.
And so when that hormone reaches your brain, it triggers a process called sympathetic signaling, and that’s where the nervous system can cue white adipose tissue or fat to actually generate more mitochondria, and that in turn leads to the fat getting burned as fuel. So what that means is you actually reduce your chances of developing things like heart disease or diabetes or some cancers.
And there’s other reasons that restricting protein can promote a longer lifespan. One of them is that when protein is digested, the end metabolic product is something called urea, and when you have excess urea, that can actually lead to major kidney problems. But also, one of the other reasons that eating too much protein can be bad for you is foods that have a lot of protein also tend to be high in saturated fats. And as I’m sure a lot of our listeners know, eating too much of those is linked to a lot of nasty side effects like a higher risk of heart disease.
Now, turning to the results, it really varied by animal. If you look at brook trout, for instance, when they were put on a protein-restricted diet, they saw their average lifespan increase by 128 percent.
So keep in mind, this is animal models, so it’s hard to say how this reflects in human beings, but the results are pretty undeniable.
So one thing that I found really interesting is that we often think about eating a lot of protein is connected with, like, building a lot of muscle, and that’s not always the case. There’s only so much protein that your body can metabolize. And so a lot of excess protein just ends up either getting stored as fat or burnt off for energy. So you really don’t need to overdo it with protein if you’re really interested in, you know, going to the gym and seeing some gains. Everything in moderation tends to be a pretty good rule.
For the future of protein maxxing, it can be a little bit difficult to figure out what this means. This isn’t necessarily new knowledge. This paper really was just summarizing something that scientists in this area have known for quite some time. Hopefully people take this under consideration and realize that they don’t need to be buying protein-infused water and drinking that to really boost their muscle gains or anything like that. But if you’re interested in learning more, you can read about it on scientificamerican.com.
Feltman: Thanks for that, Adam.
Now let’s touch briefly on some climate news: 2025 was Europe’s worst year of wildfires on record, with more than a million hectares burning throughout the E.U. As of last week, 2026 was actually on track to beat that record thanks to grossly atypical activity in France and Spain, according to reporting by CNN. As of July 29, Spain had seen nearly double its usual wildfires for an entire year, while France had nearly three and a half times as many as average. Fires in France and Spain over the last few weeks have spurred hundreds of thousands of evacuations. One blaze in southwest France grew powerful enough to create its own weather in a phenomenon known as a pyrocumulonimbus. This is when a fire emits enough smoke to seed a cloud, with water vapor condensing around ash particles. Just like a cloud in a regular thunderstorm, these smoke monsters can produce lightning—which often creates even more fire when it strikes the hot, dry ground. The AP reports that, according to French officials, this was the first pyrocumulonimbus ever recorded in the country. Repeated heat waves are driving these unprecedented wildfires and contributing to blazes in other parts of Europe as well.
This seems like as good a time as any to talk about the concept of mental exhaustion. We all know what cognitive fatigue feels like, but how does it actually impact the choices we make? A team of neuroscientists recently tried to find out by watching how mental exhaustion changes brain activity. Here to tell us more about that story is Andrea Gawrylewski, chief newsletter editor at Scientific American.
Andrea Gawrylewski: Thanks, Rachel.
Yeah, I think this is one most people will be able to relate to. It turns out that mental exhaustion affects your decision-making. No surprises there, but scientists pinpointed the region in the brain that seems to be controlling this phenomenon.
In a recent experiment, researchers used a functional magnetic resonance imaging machine, an fMRI, to monitor the brain activity in 28 people while they were performing certain cognitive tests. Like, they asked them to recall strings of letters with varying degrees of difficulty. So after a while of wearing these people out with these tests while they’re in the brain scanner, the researchers asked them each an interesting question.
Would they like to keep going for money? Either $1 for correctly completing an easy memory test or up to $8 for correctly answering a harder memory test. What the scientists found was that as participants became more cognitively fatigued, they were much less likely to choose the more demanding option, even though they could get paid more for it.
So what region of the brain was lighting up during all this testing? As people completed ever more exhausting memory tasks, an area at the front of the brain called the dorsolateral prefrontal cortex sent out increasingly strong signals to the right anterior insula, a region toward the middle right of the brain that is known for monitoring how the body is feeling, including levels of fatigue. And as they saw, cognitive fatigue significantly decreased people’s motivation to engage in challenging tasks.
The more their brain worked, the more signals traveled between these two brain regions. And based on these patterns, the researchers were able to compute a person’s willingness to trade cognitive effort, more tests, for reward, money. These fatigue signals have likely evolved to protect us from overtaxing our cognitive and physical systems, the scientists say.
The problem is sometimes mental exhaustion can prevent us from completing tasks that restore our internal energy, like going outside for a walk or cooking a healthy meal instead of getting greasy takeout. You may be exhausted, but some tasks are worth pushing through.
If you wanna get fascinating updates like these five days a week, subscribe to my free daily newsletter Today in Science at scientificamerican.com/#newsletter.
Feltman: Thanks, Andrea! Listeners, don’t forget to subscribe to Today in Science to get more SciAm stories like that one sent straight to your inbox.
That’s all for today’s episode. Tune in on Wednesday for a special chat with the Internet’s favorite inventor: Simone Giertz herself.
Science Quickly is produced by me, Rachel Feltman, along with Fonda Mwangi and Jeff DelViscio. This episode was edited by Alex Sugiura. Marielle Issa and Aaron Shattuck fact-check our show. Our theme music was composed by Dominic Smith. Subscribe to Scientific American for more up-to-date and in-depth science news.
For Scientific American, this is Rachel Feltman. Have a great week!
