What Really Happens to Your Body On A Juice Cleanse

The idea of a “detox” via juice is nothing new—even in the nineties health fanatics were all about the wheatgrass. Infomercials boasting the benefits of freshly pressed juice were played on loop during early Sunday mornings in the days of Jack LaLanne (he, of course, was selling his impressive Power Juicer). But in the early aughts, drinking yourself clean suddenly became a thing—instead of drinking a carrot juice in the morning alongside a balanced breakfast, the health-conscious elite started sipping liquified salads and exotic fruit blends in lieu of eating for days on end. And now, juicing is so popular that even Starbucks carries kale-tinted beverages alongside its coffee cakes and yogurt parfaits.

Cardiologist Dr. Joel Kahn, of the Kahn Center for Cardiac Longevity, doesn’t believe that guzzling green juice is the key to achieving optimal health. According to him, a three- to five-day veggie-based, organic juice cleanse may help “refocus your diet,” but there’s not a lot of scientific evidence to back it up. So is a juice cleanse actually good for you? Here’s the truth about three of the most common claims about juicing.

Claim: It helps you drop weight—the pounds melt off!

False: A juice cleanse temporarily slows down your metabolism, and the only thing you lose is water weight.

If our bodies were basic input-output machines, it would make sense that after a few days of calorie restriction we’d lose weight—but as science has shown, the human body is a little more complicated than simply “calories in, calories out.” And three days of drinking nothing but juice won’t result in lasting weight loss.

What it may help you lose, temporarily, is water weight. Because most programs fall far below the recommended caloric intake for the average adult, the body burns through glycogen (a carbohydrate) that’s been stored in the muscles and liver to maintain energy levels. Glycogen holds on to water, and when it’s used, so is any excess water, which can result in short-term water-weight loss. But as soon as the juice cleanse is over (i.e. the calorie restriction ends), you immediately gain back that water weight.

Claim: A juice cleanse detoxifies your body.

False: To really eliminate toxins, you really need fiber (which juices don’t have).

One of the biggest reasons people choose to cleanse is because they think they need to rinse the toxins out of their bodies. Sure, for those of us who use chemical-based makeup, eat the occasional non-organic apple, and sometimes imbibe in an adult beverage, a little detoxification period can’t hurt. But the best way to do that isn’t by drinking only liquids for 72 hours—it’s by increasing the amount of fiber in your diet.

The liver and kidneys act like the body’s personal filtration system, and they do a pretty good job of clearing any nasty stuff that gets in our bodies. But filling up on junk food, stressing over your job, and everyday habits that aren’t so healthy (like staying up late and snoozing that alarm the next day) can mess with how well that filtration system works—and can back you up, to put it delicately.

Fiber acts like a broom for your small intestine, cleaning you out and taking all of those toxins with it. The easiest way to get more fiber is to increase the consumption of fresh, whole foods. According to Dr. Kahn, Juices are devoid of fiber, which is an essential dietary component. “So juice cleansing is not a long-term solution to achieving optimal health,” he says. “Only a stable and clean diet without processed foods can [do that].”

Juices, unfortunately, usually strain out any of the beneficial insoluble fiber in fruits and veggies, instead leaving behind a liquid that’s high in vitamins and micronutrients but also loaded with natural fruit sugars that have basically the same effect on your body as table sugar. Blended smoothies are slightly better, because they still retain their fiber which means your body will process sugar less quickly (but try to keep them low in fructose anyway!) For true detoxification, try a food-based cleanse that has tons of veggies and healthy fats—both are necessary for healthy, normal elimination.

Claim: A juice cleanse gives your digestive system a break.

True (sort of): Juicing can be great for people with digestive issues, but it’s not a permanent solution.

Despite how it might sound, it’s actually really beneficial for those with tummy troubles to try juicing for a day, or just adding a few cold-pressed beverages in addition to a balanced, wholesome diet. For the same reason that drinking juices isn’t a great way to detox, it’s perfect for giving the digestive system a break. Because there’s almost zero fiber, the stomach and small intestine don’t have to do the usual hard work of breaking down and digesting fiber to absorb micronutrients and vitamins.

Because juice is easier to digest, it’s an easy way to get some extra nutrients for those with digestive issues like IBS, Crohn’s, or Celiac disease. One caveat: Avoid drinks that only contain fruit juices. Fruit-only blends can be very high in sugar, and because they don’t have other macronutrients like protein, fat, or carbohydrates, they can cause blood sugar levels to spike to unhealthy levels.

The main takeaway? Juice “cleansing” isn’t all it’s cracked up to be—but it’s not all bad, either. If a detoxifying program is what you’re looking for you’re better off with a whole foods program, but some with digestive issues might enjoy a short, low-sugar juice cleanse.

Photo credit: Alicia Cho