Could eating clay help manage weight? | Science News for Students

Could eating clay help manage weight?

These fine dirt particles work as well as a leading drug at slowing weight gain — in rats, anyway
Mar 5, 2019 — 6:45 am EST
a photo of a spoonful of powdered clay

Someday, swallowing clay might keep you from absorbing much of the fat in your diet. But don't try it just yet.


Dry clay doesn’t sound very appetizing. But new research shows there might be a good reason to eat it. Clay can soak up fat from the gut — at least in rats. If it works the same way in people, it could stop our bodies from absorbing fat from our foods and prevent our waistlines from expanding.

Clay is a type of soil defined mostly by its size and shape. It’s made of very fine grains of rock or minerals. Those grains are so tiny that they fit together tightly, leaving little or no room for water to filter through.

In a new study, rats that ate pellets of clay gained less weight on a high-fat diet. In fact, the clay slowed their weight gain just as well as did a leading weight-loss drug.

Pharmacist Tahnee Dening did the research at the University of South Australia in Adelaide. She was testing whether clay could help carry medicines to the small intestine. But it wasn’t much of a success because the clay was absorbing the drug along the way. That got her thinking about what else clay might soak up. How about fat?

To find out, she did a few experiments.

She started with what’s in your small intestine. The small intestine sits between the stomach and the large intestine. Here, most of what you eat gets soaked in juices, broken down and absorbed by the body. Dening added coconut oil — a type of fat — into a liquid that was just like intestinal juices. Then she mixed in clay.

“These clays were able to soak up twice their weight in fat, which is incredible!” Dening says.

To see if the same thing might happen in the body, her team fed the clay to some rats for two weeks.

The researchers looked at four groups of six rats each. Two groups ate a high-fat diet, along with pellets made from different types of clay. Another group got the high-fat food and a weight-loss drug, but no clay. The final group ate the high-fat diet but had no treatments of any kind. These untreated animals are known as a control group.

At the end of two weeks, Dening and her colleagues weighed the animals. Rats that ate clay had gained as little weight as the rats that took a weight-loss drug. Meanwhile, rats in the control group gained more weight than the rats in the other groups.

The researchers shared their findings December 5, 2018, in the journal Pharmaceutical Research.

Dirt versus drugs

The weight-loss drug that the Australian team used can create unpleasant symptoms. Since it stops the gut from digesting fat, the undigested fat can build up. In people, this can lead to diarrhea and flatulence. In fact, many people stop taking the medicine because they can’t stand these side effects.

Dening now thinks that if people took clay at the same time, it might knock out some of the drug’s nasty side effects. Afterward, the clay should pass out of the body in the patient’s poop. The next step “is to give the rats different portions of different types of clay, to see which works best,” Dening says. “We also have to test it on larger mammals. Either on dogs or pigs. We should make sure it’s really safe before we test it on people.”

Donna Ryan agrees that doctors will need to make sure clay is safe before using it as a medicine. Ryan is a retired professor at Pennington Biomedical Research Center in Baton Rouge, La. Now president of the World Obesity Federation, she has studied obesity for 30 years.

Fat absorbs lots of nutrients, Ryan says. These include vitamins A, D, E and K, and the mineral iron. So she’s concerned that clay might soak up — and eliminate — those nutrients too. “The problem is that the clay can tie up iron and cause deficiency,” Ryan says. And that would be bad, she says. “We need iron to create blood cells. It also forms an important part of our muscle cells.”

Melanie Jay is a doctor at New York University’s Langone Medical Center in New York City. She helps treat people with obesity. And fat in people’s diets isn’t the only culprit, she notes. Eating lots of sugar also can contribute to obesity, she says, and “Clay does not soak up sugar.” If we’re looking for a new way to help people manage their weight, she says, “we have a very long way to go before we are giving people clay.”

Power Words

(more about Power Words)

cell     The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells.

clay     Fine-grained particles of soil that stick together and can be molded when wet. When fired under intense heat, clay can become hard and brittle. That’s why it’s used to fashion pottery and bricks.

colleague     Someone who works with another; a co-worker or team member.

control     A part of an experiment where there is no change from normal conditions. The control is essential to scientific experiments. It shows that any new effect is likely due only to the part of the test that a researcher has altered. For example, if scientists were testing different types of fertilizer in a garden, they would want one section of it to remain unfertilized, as the control. Its area would show how plants in this garden grow under normal conditions. And that gives scientists something against which they can compare their experimental data.

diarrhea     (adj. diarrheal) Loose, watery stool (feces) that can be a symptom of many types of microbial infections affecting the gut.

diet     The foods and liquids ingested by an animal to provide the nutrition it needs to grow and maintain health. (verb) To adopt a specific food-intake plan for the purpose of controlling body weight.

fat     A natural oily or greasy substance occurring in plants and in animal bodies, especially when deposited as a layer under the skin or around certain organs. Fat’s primary role is as an energy reserve. Fat also is a vital nutrient, though it can be harmful if consumed in excessive amounts.

filter     A device or system that allows some materials to pass through but not others, based on their size or some other feature. (in physics) A screen, plate or layer of a substance that absorbs light or other radiation or selectively prevents the transmission of some of its components.

flatulence     (adj. flatulent) The release of gas out the anus due to the digestion of food;  colloquially known as farting.

gut     An informal term for the gastrointestinal tract, especially the intestines.

iron     A metallic element that is common within minerals in Earth’s crust and in its hot core. It’s also a nutrient important for health.

mineral     Crystal-forming substances that make up rock, such as quartz, apatite or various carbonates. Most rocks contain several different minerals mish-mashed together. A mineral usually is solid and stable at room temperatures and has a specific formula, or recipe (with atoms occurring in certain proportions) and a specific crystalline structure (meaning that its atoms are organized in regular three-dimensional patterns). (in physiology) The same chemicals that are needed by the body to make and feed tissues to maintain health.

muscle     A type of tissue used to produce movement by contracting its cells, known as muscle fibers. Muscle is rich in protein, which is why predatory species seek prey containing lots of this tissue.

nutrient     A vitamin, mineral, fat, carbohydrate or protein that a plant, animal or other organism requires as part of its food in order to survive.

obese     Extremely overweight. Obesity is associated with a wide range of health problems, including type 2 diabetes and high blood pressure.

obesity     (adj. obese) Extreme overweight. Obesity is associated with a wide range of health problems, including type 2 diabetes and high blood pressure.

side effects     Unintended problems or harm caused by a procedure or treatment.

symptom     A physical or mental indicator generally regarded to be characteristic of a disease. Sometimes a single symptom — especially a general one, such as fever or pain — can be a sign of any of many different types of injury or disease.

vitamin     Any of a group of chemicals that are essential for normal growth and nutrition and are required in small quantities in the diet because either they cannot be made by the body or the body cannot easily make them in sufficient amounts to support health.


Journal: T.J. Dening ​et​ ​al.​ ​Spray dried smectite clay particles as a novel treatment against obesity, Pharmaceutical Research. Vol.​ ​36​, December 5, 2018, p. 21. doi:​ ​10.1007/s11095-018-2552-9.