Zoe Kravitz, the 25-year-old actress who plays an anorexic and bulimic girl in the film “The Road Within,” underwent an “awful” cleanse in order to lose 20 pounds for the role.

“I did a cleanse,” she told Us Weekly during the Los Angeles Film Festival. “I tried to do it the healthiest way as possible, even though it’s not healthy to do.” Kravitz drank clay — something that other celebrities have used in the past to assist in weight loss. Clay has been used medicinally since prehistoric times, and is still used by indigenous people around the world. It was used in clay baths as a form of “mud therapy,” and various types include kaolin, smectite, bentonite, montmorillonite, and Fuller’s earth.

“I ended up drinking clay,” Kravitz said, “because it cleans out your body and fills you up. I was eating like a Mason jar of pureed vegetables a day and running.” But this diet caused her to feel “awful,” like a “space cadet,” she said, noting that she wouldn’t recommend anyone do it themselves.

Bentonite clay is composed of aged volcanic ash and has been used to treat conditions in traditional medicine, with the largest deposit found in Benton, Wyo., which is where it received its name. Advocates of clay cleanses claim Bentonite clay is able to clean out the liver, colon, and skin, as well as “balance bacteria” in the digestive system and strengthen the immune system. Various other claims include its ability to treat food allergies, food poisoning, viral infections, and even parasites. Though the clay is filled with certain minerals like montmorillonite, magnesium, and nearly 67 other trace minerals, not much scientific evidence exists to support the many claims about its health benefits.

Some studies have shown, however, that certain antibacterial clays are actually effective in treating diseases. In 2010, a study about the medicinal use of clay minerals wrote in its conclusion, “In this era when bacteria are developing antibiotic resistance to existing pharmacological agents, the potential for discovery of new broad-spectrum antibacterial agents, such as natural clay minerals, to combat pathogenic bacteria would be particularly advantageous.”

But what about weight loss? Despite lack of solid scientific evidence, some advocates of “clay cleanses” believe it rids the body of “toxins.” AboutClay writes: “The clay's immediate action upon the body is directly on the digestive channel. This involves the clay actually binding with the toxic substances and removing them from the body with the stool.”

The fact is, until there is better scientific evidence about “clay cleanses,” be aware that some studies have shown that instead of helping weight loss, eating clay can actually cause some adverse effects, like abdominal pain, bloating, diarrhea, and constipation. “MayoClinic.com reports that most detoxification diets last somewhere between seven and 10 days, but notes that evidence of the diets' success in removing toxins is not scientifically proven," LiveStrong warns on its website. "Using a detox diet to lose weight is not the healthiest way to shed a few pounds. MayoClinic.com reminds dieters that the healthiest diets include a combination of lean protein, whole grains, fruits and vegetables.”

Kravitz noted that losing weight for the role reminded her of her own struggle with eating in the past. “I think all women [struggle with weight],” she told Us Weekly. “There are a bunch of images that are thrown in our faces all the time about what we’re supposed to look like at 14, 15, 16. It’s confusing. I think every woman can identify with that struggle.”