Health
Humans’ Wounds Heal Much More Slowly Than Other Mammals’
Watching wild baboons in Kenya, Akiko Matsumoto-Oda, an evolutionary biologist and primatologist at the University of the Ryukyus in Japan, had a front-row seat to the violence between these monkeys, especially the males.
“I was struck by how frequently they sustained injuries,” she said, “and, even more, by how rapidly they recovered — even from seemingly severe wounds.”
Compared with her own experiences with nicks and cuts, the baboons’ ability to heal seemed like a superpower.
In a study published on Wednesday in Proceedings of the Royal Society B, Dr. Matsumoto-Oda and her colleagues compared the healing rates of humans, chimpanzees, monkeys and mice. They found that human wounds took more than twice as long to heal as wounds of any of the other mammals. Our slow healing may be a result of an evolutionary trade-off we made long ago, when we shed fur in favor of naked, sweaty skin that keeps us cool.
When possible, the researchers wanted to study healing in a way that was less violent and more controlled than watching wild baboons.
To measure human healing, they recruited 24 patients who were having skin tumors removed at the University of the Ryukyus Hospital. To gather data on chimpanzees, which are some of our closest animal relatives, researchers observed five captive chimps at the Kumamoto Sanctuary of the Kyoto University Wildlife Research Center, which houses animals formerly used in pharmaceutical research. The chimps’ wounds, like those of wild baboons, mostly came from tiffs between the animals.
The study’s other primate subjects, all kept at the Kenya Institute of Primate Research, included olive baboons, Sykes’ monkeys and vervet monkeys. Researchers anesthetized the monkeys, surgically wounded them and then monitored their recovery. “As a field researcher, I personally believe that invasive studies should be minimized as much as possible,” said Dr. Matsumoto-Oda, who noted that bite wounds on wild baboons are often similar in size to the surgical wounds in the study, but deeper.
Finally, to compare humans and primates with more distantly related mammals, researchers anesthetized and surgically wounded mice and rats.
Based on her field observations, Dr. Matsumoto-Oda was prepared to see humans healing more slowly than the other animals. The 24 people regrew skin at about a quarter of a millimeter per day, on average.
What surprised Dr. Matsumoto-Oda more was the consistency between the healing rates of the animal subjects, including chimpanzees. There was no significant difference in the speedy skin regrowth among different primates, which grew about 0.62 millimeters of new skin per day, or between primates and rodents. Humans were the clear outliers.
Elaine Fuchs, a stem cell biologist at the Rockefeller University who studies skin growth and repair and was not involved in the new research, said the results were what she would have expected. That’s because skin healing depends on hair.
Each hair grows from a hair follicle, which also houses stem cells. Normally, those stem cells just make more hair. But when called upon, they can grow new skin instead. “When the epidermis is wounded, as in most kinds of scratches and scrapes, it’s really the hair-follicle stem cells that do the repair,” Dr. Fuchs said.
Furry animals are covered in follicles, which help quickly close up wounds in mice or monkeys. By comparison, “human skin has very puny hair follicles,” Dr. Fuchs said. And our ancestors lost many of those follicles, packing their skin with sweat glands instead. Sweat glands also have stem cells, but they’re much less efficient at repairing wounds, Dr. Fuchs said.
Why did we make that trade during evolution, giving up so much of our hair and its protective properties? The glands that make the watery, salty sweat that dampens our shirts on a hot day are called eccrine glands. Most furry mammals have them only in certain places, mainly the soles of their paws. But human ancestors went all-in on sweat — modern humans have millions of sweat glands all over our bodies, and they’re about 10 times denser than those of chimpanzees.
“We evolved to cool by sweating profusely,” said Daniel Lieberman, an evolutionary biologist at Harvard University. Our abundant sweat glands and lack of fur let our ancestors engage in physical activity in hot environments, Dr. Lieberman said, and cooled the machinery of our big brains.
The benefits of trading hair for sweat must have outweighed the costs. Dr. Matsumoto-Oda and her co-authors speculate that social support among prehistoric humans might have helped wounded people stay alive, despite our slower healing. (Or maybe they had ways to treat wounds, like orangutans and chimps seem to.)
“The evolutionary disadvantage is that wound healing is slowed,” Dr. Fuchs said, but humans also gained evolutionary advantages by losing hair.
“They can put on a coat if they need to,” she added.
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The release of an updated food pyramid this week has sparked mixed reactions from doctors and dietitians.
One of the most noteworthy shifts in the 2025-2030 Dietary Guidelines for Americans — announced by HHS officials during a Jan. 7 press conference at the White House — is a greater emphasis on “high-quality proteins,” including red meat and eggs, as well as full-fat dairy.
The new guidelines focus on “real, whole, nutrient-dense foods,” and a dramatic reduction in highly processed foods, added sugars, refined carbohydrates and unhealthy fats.
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“Protein and healthy fats are essential and were wrongly discouraged in prior dietary guidelines,” Health Secretary Robert F. Kennedy Jr. said during the press conference. “We are ending the war on saturated fats.”
Nick Norwitz, a Harvard- and Oxford-trained researcher known for his work in metabolic health, shared his reaction to the new guidelines.
The release of an updated food pyramid this week has sparked mixed reactions from doctors and dietitians. (realfood.gov)
Despite how the new pyramid is presented, he noted, the actual guidelines for saturated fat consumption haven’t changed, as they still state that, “in general, saturated fat consumption should not exceed 10% of total daily calories.”
The intake of unprocessed whole foods rich in saturated fat, especially dairy fat, tends to be associated with improved health outcomes, according to Norwitz.
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“Full-fat dairy — especially cheese, for example — tends to be associated with lower BMI, reduced rates of diabetes and even reduced dementia risk,” he told Fox News Digital. “There are, of course, nuances — but ‘ending the war’ on saturated fat seems reasonable.”
Risks vary, experts say
Experts cautioned about the potential health risks of exceeding the recommended intake of saturated fat, including higher rates of LDL “bad” cholesterol, which is known to increase the risk of cardiovascular disease.
“The recommendation to limit saturated fat to 10% of total calories is based on the research showing that higher rates increase LDL cholesterol and associated risks for cardiovascular disease,” Sherry Coleman Collins, a food allergy dietitian and expert from the Atlanta metropolitan area, told Fox News Digital.
One of the most noteworthy shifts in the 2025-2030 Dietary Guidelines for Americans is a greater emphasis on “high-quality proteins” — including red meat and eggs — as well as full-fat dairy. (iStock)
Nutrition should be personalized and is dependent on multiple factors, she said, including age, gender, activity level and genetic risk factors.
“The total saturated fat an individual might safely consume is influenced by their size and total calorie needs, as well as potentially genetic differences,” Coleman Collins said.
Norwitz agreed, adding that “the specific food source and interaction with the unique host and their broader dietary context should take the spotlight.”
Dr. Pooja Gidwani, a double board-certified doctor of internal medicine and obesity medicine in Los Angeles, pointed out that not everyone has the same “tolerance” for saturated fats.
“If increasing saturated fat leads to a meaningful rise in LDL cholesterol or ApoB (Apolipoprotein B, a protein found on the surface of certain cholesterol-carrying particles in the blood), that intake level is excessive for that individual, regardless of improvements in weight or glucose metrics,” she said.
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“This personalized approach becomes increasingly important in midlife and beyond, when cardiovascular disease becomes the dominant driver of morbidity and mortality and when tolerance for cumulative atherogenic (artery-clogging) exposure is lower.”
For those who need to reduce LDL cholesterol or have a higher cardiovascular risk, the American Heart Association recommends an even lower amount of saturated fats — less than 6% of total daily calories.
Experts cautioned about the potential health risks of exceeding the recommended intake of saturated fat, including higher rates of LDL “bad” cholesterol. (iStock)
Gidwani also cautioned that diets emphasizing saturated fat could crowd out fiber and unsaturated fats, “both of which play independent roles in cholesterol clearance, insulin sensitivity, gut health and inflammation.”
“Saturated fat-heavy patterns are also calorie-dense, which can quietly undermine long-term weight management if intake is not carefully regulated,” she added.
Not all saturated fats are equal, experts say
The effects of saturated fat depend on what specific foods are being consumed, according to experts.
“I would recommend choosing minimally processed or unprocessed forms of foods,” said Tanya Freirich, a registered dietitian nutritionist in Charlotte, North Carolina. “For example, in place of a hot dog — which has additives, nitrites, sodium and fillers — consuming a chicken thigh would be a much better choice.”
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Gidwani reiterated that the amount of processing plays a big role.
“Processed meats are consistently associated with worse cardiometabolic outcomes and represent the clearest category to limit,” she said. “The risk here is not only saturated fat, but also sodium load, preservatives and the broader dietary pattern they tend to accompany.”
“Full-fat dairy — especially cheese, for example — tends to be associated with lower BMI, reduced rates of diabetes and even reduced dementia risk,” an expert told Fox News Digital. (iStock)
Unprocessed red meat, the doctor said, can fit into an overall healthy diet in smaller amounts, particularly when consumed alongside fiber-rich plants and minimally processed foods.
“However, from a longevity perspective, it should be viewed as optional rather than foundational, especially for individuals with elevated cardiovascular risk,” she added.
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When it comes to dairy, Gidwani noted that fermented options are “metabolically more favorable” than butter or cream.
“However, saturated fat from dairy is still not necessary to prioritize for metabolic health or longevity,” she said. “Excessive reliance on dairy fat can displace healthier fat sources without offering clear long-term benefit.”
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Overall, the doctor recommends unsaturated fat sources, including extra virgin olive oil, nuts, seeds, avocado and omega-3-rich fish, as primary dietary fats.
“These consistently support lipid profiles, insulin sensitivity and vascular health,” Gidwani said. “Saturated fat can exist within a balanced diet, but it should remain secondary rather than emphasized.”
Why the big picture matters
Saturated fat is just one piece of a much wider nutrition puzzle, the experts agreed.
Unprocessed red meat can fit into an overall healthy diet in smaller amounts, particularly when consumed alongside fiber-rich plants and minimally processed foods, one expert said. (iStock)
“Our heart health is not determined by one type of fat or one type of cholesterol, but the sum of many parts — our entire diet, our exercise habits, our stress and so much more,” Freirich said.
She recommends consulting a registered dietitian for guidance on unique dietary needs based on age, gender, activity level and medical history.
“Our heart health is not determined by one type of fat or one type of cholesterol, but the sum of many parts — our entire diet, our exercise habits, our stress and so much more,” said an expert. (iStock)
New Jersey-based dietitian Erin Palinski-Wade, author of “2-Day Diabetes Diet,” added that the message should be to focus more on overall patterns.
That means “plenty of fiber-rich plants, lean protein at every meal (including those that also contain fiber, such as nuts and seeds) and a reduction in overall intake of added sugars.”
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“That change will drive true health improvements,” she said.
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Missing out on adequate sleep could be taking years off your life.
New research from the Oregon Health & Science University (OHSU), published in the journal Sleep Advances, found that poor sleep may shorten life expectancy more than other lifestyle factors like diet, exercise and loneliness.
The researchers analyzed nationwide CDC survey data, identifying trends associated with average life expectancy by county, according to a press release.
NEW HEALTH WARNING ISSUED OVER POPULAR SLEEP AID MILLIONS TAKE NIGHTLY
The study found that lack of adequate sleep led to higher mortality risk in every U.S. state and was the top behavioral driver compared to other factors, only behind smoking.
Senior study author Andrew McHill, Ph.D., associate professor and director of the Sleep, Chronobiology, and Health Laboratory in the OHSU School of Nursing, noted in a statement that he did not expect sleep to be “so strongly correlated” to life expectancy.
Poor sleep is directly correlated with shorter life expectancy, the study reveals. (iStock)
“We’ve always thought sleep is important, but this research really drives that point home: People really should strive to get seven to nine hours of sleep, if at all possible,” he said.
“This research shows that we need to prioritize sleep at least as much as we do [in] what we eat or how we exercise.”
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In a previous interview with Fox News Digital, Dr. Daniel Amen, psychiatrist and owner of Amen Clinics in California, emphasized how important sleep is for brain function and longevity.
Researchers suggest people should prioritize sleep just as much as diet and exercise. (iStock)
“Sleep is so important,” he said. “When you sleep, your brain cleans and washes itself. And if you don’t sleep seven to nine hours at night, your brain looks older than you are — there’s less blood flow, and it increases inflammation in the brain.”
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“Your brain doesn’t have enough time to get rid of the toxins that build up during the day.”
Lack of adequate sleep can lead to poor decisions and foster toxic cycles, the doctor warned.
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“If your brain has less activity in the front part, not only are you tired, but you’re also hungrier, and you’re more likely to not make the best decisions,” he said.
“Which, of course, will stress you out, and then you won’t sleep well the next night.”
A doctor suggests being “purposeful” about going to bed and waking up each day. (iStock)
One small change to promote longevity and brain health is to try getting to bed 15 minutes earlier, Amen suggested.
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“Really be purposeful about not being distracted by Netflix or your phone,” he said.
“And when you get up in the morning, say to yourself, ‘Today is going to be a great day.’ The more positive you are, the better your brain.”
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