About two-thirds of humans lose their ability to produce lactase after weaning

Lactose intolerance is not the same as a dairy allergy

Lactose intolerance can develop in adulthood and can be influenced by genetic factors, culture, and dietary practices. Times of famine may have favored those who could digest dairy, naturally selecting them more, resulting in lactase persistence.

Most of the world’s population has difficulty processing lactose—but that’s not an allergy

Lactose intolerance is a digestive condition that occurs when the small intestine has difficulty breaking down lactose, a sugar found in products like milk or cheese, leading to symptoms such as diarrhea or bloating. Almost 70% of the world’s population may have lactose processing issues, particularly in Asia and Africa. This is different from a condition called cow's milk protein allergy—an immune system disorder that can cause hives and anaphylaxis.

Even in recent history, adaptations to the environment drove human evolution

Through genetics, environmental pressures, and cultural influences, humans have evolved to tolerate lactose, develop varying skin pigmentation, and acquire genetic resistance to diseases like bubonic plague. The metabolic and digestive systems of Indigenous peoples have adapted to their diet, which is influenced by the availability of food and water.

Kids often grow out of allergies to milk and eggs

Between 60% and 80% of kids with allergies to milk or eggs outgrow them by age 16. The immune system doesn’t always recognize and respond to baked forms of these allergens, so when kids eat muffins and other cooked food products, their immune system may become more habituated to them and overcome food sensitivities. Aging out of other allergies is less common.

Western babies often are missing a key gut microbe common elsewhere

Studies show infants in Europe and North America often lack Bifidobacterium infantis, a microbe widespread in babies in Africa and South Asia that helps digest breast milk and train the immune system. Researchers link the gap to antibiotics, formula use, and sanitized spaces.

Animals' stomach lining produces cheese

Cheesemaking would be impossible without rennet, the enzyme that separates milk’s liquid and solid components. Rennet occurs naturally in the stomach lining of young goats, cows, and lambs to help them digest milk, a process that also allows cheesemakers to use it to make curds. Now we have plant-based rennet that comes from thistles, artichokes, and other similar plants.

Understanding insulin

Scientists Daniel and Kelly talk with researcher Dr. Katrine Whiteson about diabetes, the history of insulin production, and Dr. Lydia Villa-Komaroff—an essential member of the team who discovered that bacteria could be induced to produce insulin. Listen to discover interesting facts about the life-saving medicine and how it works in the human body.

When people stopped using GLP-1, they regained two-thirds of the weight back

Research from 2022 found that when people stopped using the injectable form of the medication, they regained up to two-thirds of lost weight within a year. The finding suggests ongoing treatment will be required for weight loss.

How our sense of taste evolves as we age

Kids are hardwired to prefer sweets over greens, with sweetness a shorthand for calorie-rich and bitter flavor warning of potentially noxious plants. This holds true even in the womb, where fetuses have been seen via ultrasound scans grimacing as their hosts consume kale capsules. As they age into double digits and beyond, their taste cells and sense of smell diminish, leading to broader and less sensitive palates.

Gestational diabetes occurs when the body can't produce insulin during pregnancy

Globally, pregnant people are increasingly at risk to develop gestational diabetes due to rising maternal ages and obesity rates. The condition is associated with heavier fetal weight, congenital abnormalities, and perinatal mortality, which includes stillbirths and deaths of babies younger than 7 days old.

Why are some people left-handed?

About one-tenth of the world’s population are left-handed. Why does the trait exist in the first place? This five-minute video investigates how the uneven ratio of lefties and righties gives insight into a balance between competitive and cooperative pressures on human evolution.

Almost 80% of people diagnosed with autoimmune diseases are women

Yet it's still unanswered what may account for that difference. To better understand this disparity researchers are exploring factors including hormonal changes that occur around puberty, pregnancy, and menopause, as well as gut microbe differences, and aspects of X-chromosome protein-coding genes. (Some users may encounter a paywall.)

Can humans delay or reverse old age?

We're not sure yet. Researchers at the University of California San Francisco are studying why some conditions and behaviors, such as low-oxygen environments and exercise, benefit the aging process, hoping to reveal potential health applications. Some of this research focuses on klotho, a naturally occurring age-regulating hormone named after the Greek Fate Clotho. Animal studies on klotho brain injections found subjects had improved memory recall and age-related degeneration resistance.

Most people with East Asian ancestry are genetically predisposed to be less smelly

A gene variant found in 80%-95% of individuals with East Asian ancestry reduces armpit bacteria and related odors. People with this nonfunctioning ABCC11 gene variant lack a protein that transports molecules, including sweat, across cellular membranes, so their armpits are starved of sweat that bacteria may have metabolized to help them multiply.

The pancreas releases digestive enzymes and regulates blood sugar

The pancreas weighs about the same as a deck of cards and is smaller than the average adult human hand. This lopsided glandular organ controls blood sugar levels through insulin production and helps the body digest food by creating a neutralizing tonic filled with digestive enzymes.

Cells can last in the human body from days to a person's entire life

Despite claims that a person's body replaces itself every seven to 10 years, the rate at which cells die and are replaced varies by cell type. Gastrointestinal cells that line the digestive tract and stomach last only a few days, while some heart muscle cells and most neurons are around from birth until death.

How humans evolved from single-cell organisms

Humans have had a long history. 3.8 billion years in the making, to be precise. From the primordial puddle to the modern day, here's how humans have evolved from the first life.

How the gut microbiome can affect heatstroke risk

Some research suggests that our gut microbiome influences our risk of exertional heatstroke. If exercise boosts our body temperatures to unsafe levels, increasing gut permeability, that can cause a "leaky" gut—allowing bacteria and other gut microbes to leak into the bloodstream and potentially trigger endotoxemia, a potentially life-threatening inflammatory response that can occur with heat exhaustion and heatstroke.

Learn how cholera bacteria sicken humans

Once a person has ingested large amounts of the bacteria, typically through contaminated water, cholera bacteria begin producing and releasing a toxin inside their host. It attacks the mucosal lining of the intestine, making it hard to absorb liquids. This process leads to cholera's characteristic symptoms, like voluminous, watery diarrhea.

More than 200,000 people are diagnosed with leprosy annually

The disease still occurs in more than 120 countries. Brazil, India, and Indonesia continue to report more than 10,000 new cases annually.

Measles infection can cause long-term immune system “amnesia”

The measles virus attacks the body's immune system, including preying on T and B cells in the lymphatic system. These cells hold memories of past infections, which can be degraded as the virus destroys them. This leaves patients susceptible to other infections for a year or longer.

What percent Neanderthal are you?

Many of us carry around 2% Neanderthal DNA in our genes. Museum human evolution expert Prof. Chris Stringer discusses why and what it means.

Why physiology and genetics prevent king bees from existing

The mating process is fatal to male honey bees, as their endophallus detaches from their bodies and remains temporarily within the queen. Because fertilized honey bee eggs develop into female bees, if a male somehow did survive and become king, his line of succession would also abruptly end.

Adults may lose roughly 3% of their muscle mass each decade after 30

That muscle loss, formally referred to as sarcopenia [saar-ko-pee-nee-uh], averages 3% to 5%, depending on physical activity. These losses can progress with age, but resistance training helps combat some of this natural degradation.

Mitochondria—only inherited from mothers in most animals—have their own DNA

Mitochondrial DNA, or mtDNA, typically takes the shape of a circle and contains genes that code for proteins essential to the production of energy-containing molecules called ATP. When mitochondria fuse, the mixing of healthy and damaged mtDNA helps alleviate the effects of mutations that may have occurred during mitochondrial division or environmental interactions.

Indefinite cloning of some endangered species may not sustain their longevity because cloning success rates decrease as genetic mutations accumulate.

Hookworm infection, though risky, may help fight certain autoimmune conditions by tamping down the immune system's inflammatory response.

Budweiser stores yeast derived from the original 1800s strain in a secret bunker, which only the Head of Yeast Management can access—not even the CEO

Tattoos remain visible on your skin thanks to immune cells called macrophages

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

Read a deep dive on the 'all-purpose healing' peptide BPC-157.

Apeirophobia is an overwhelming fear of living forever, perhaps stemming from the brain's inability to conceptualize an infinite life.

Poison ivy is in the same family as mangoes, cashews, and pistachios—and they all produce oily urushiol in their raw, unprocessed state—but they are typically prepared in ways to avoid causing human discomfort.

See the evolution of Ebola vaccine and treatment development.

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

In 1939, baseball star Lou Gehrig delivered his inspirational 'Luckiest Man' speech after retiring due to the health condition that now bears his name.

Use this tool to calculate the dollar value of your parental mental load, from meal planning to coordinating after-school care, then see resources that help generate solutions.

About 2,000 US babies are born annually without some portion of their limbs, potentially leading to a lifetime of pricey prosthetics.

The Great Salt Lake's distinct dual coloration results from high-salinity organisms that only live in the northern portion and produce a purple protein.

Clever Hans was a 1900s horse that was believed to be able to solve math equations, tell time, and read and comprehend German, until a psychology student discovered how he got his answers.

While El Niño moves warm Pacific Ocean waters east along the equator, La Niña moves them west, shifting where rainfall will become more common for months.

Most of the observable universe's volume consists of voids and supervoids—enormous regions of space with little to no galaxies, stars, or light.

For centuries, it was common to sleep in two shifts: a few hours at the beginning of the night, and a longer period beginning around midnight

Children are now three times more likely to say they want to be a YouTuber when they grow up than an astronaut, with some even attending 'YouTube camps' that teach kids how to create content for the platform.

The Mona Lisa's celebrity status and repeated restorations have obscured what made the painting so revolutionary for its time

Salvador Dalí believed he was his own dead brother, who had died nine months before he was born

English mathematician Ada Lovelace wrote the first computer algorithm a century before computers existed and hypothesized that computing devices would one day be able to compose music—foreseeing the generative AI systems of today.