This New Study Is Revealing How Detrimental Even A 3-Day Juice Cleanse Can Be To Your Overall Health

Ah, juicing. The holy grail of wellness influencers, the staple of yoga moms, and the thing your one very Lululemon-clad friend won’t stop talking about. “It’s a cleanse,” she insists, sipping a $15 celery juice while side-eyeing your breakfast sandwich like a starved hyena. “It detoxes your system!” Sure, Rebecca. Sure.

Hate to break it to you, but according to a recent study from Northwestern University, juicing might actually be wrecking your gut — and your body is not thanking you for it.

Researchers at Northwestern decided to test what happens when people swap their usual diet for straight-up juice for only three days. They divided study participants into three groups:

1. The Juice-Only Diehards – These folks went full-send, consuming nothing but juice for their meals; a cool 800-900 calories a day, because apparently, hunger is just a mindset.

2. The Juice + Whole Foods Crew – They had juice and some actual solid food.

3. The Whole Plant-Based Food Eaters – They skipped the juicer entirely and just ate their fruits and veggies in whole form.

To see what was really going on inside their bodies, scientists took saliva, cheek swabs, and stool samples (shoutout to the poor lab techs dealing with that). Then, they analyzed the bacterial changes happening in everyone’s gut.

And, well, the results were not great for the juice-only crew. Their bad gut bacteria increased. That's the kind that’s linked to inflammation and gut permeability — aka leaky gut — which, if you believe half the wellness influencers on TikTok, is basically the root of all evil. (It’s not, but it’s definitely not great for your overall health.)

On the other hand, the whole foods-only crew saw positive shifts in their microbial changes over the course of those three days, which further suggests how harmful juice cleanses can be for your gut microbiome, by comparison.

🍎 Wait, So Juicing Is Bad for You?

Yes… and no. Juice isn’t the villain here; you’ll still get vitamins like beta-carotene, vitamin C, and vitamin E. But you’re missing something major: fiber, the part your body can’t digest but absolutely needs, according to gastroenterologist Dr. Supriya Rao.

“Removing fiber from fruits and vegetables deprives the gut of essential nutrients that support digestion and encourage the growth of good gut bacteria… Fiber slows sugar absorption, prevents constipation, and feeds gut microbes, which helps support our immunity and decrease inflammation.”

So yeah, fiber is basically your gut’s bestie. It’s not just there to “clean sweep” your intestines — it feeds the good bacteria in your gut, keeping your digestive system happy and thriving. Think of yourself as a complex sourdough starter. Your gut bacteria need real sustenance to stay healthy.

Beyond that, fiber adds bulk to your stool (never thought I’d write that), making sure everything moves along smoothly. A well-formed stool means less strain, better consistency, and fewer digestive issues like constipation or bloating. And let’s be honest, the juice cleanse devotees probably weren’t having the time of their lives in the bathroom. Without fiber, things can get a little… unpredictable.

And then there’s sugar. Sure, fresh-pressed juice is technically better than a can of Coke, but let’s not kid ourselves. Without fiber, it’s basically a sugar bomb. With nothing to slow it down, all that sugar rushes straight into your bloodstream, sending your insulin levels on a rollercoaster. Believe it or not, this can actually lead to weight gain. Dr. Rao confirms, “High sugar content in juice, even when natural, can stress the body in a similar way that processed sugary foods do. It can lead to unwanted blood sugar spikes, increased insulin resistance, and weight gain.”

Ready for another big hit? The Northwestern study also found that the increase in bad bacteria in the juice-only crew — thanks to all that sugar and zero fiber — is linked to inflammation that can affect cognitive function.

Now, it’s not like juicing is killing brain cells (though listening to an LA influencer with vocal fry might make you wonder); it can affect cognitive performance. “The gut and the brain are connected," explains Dr. Rao. "The gut-brain axis is a communication network linking the brain and your digestive system through the vagus nerve and gut microbiota. This connection plays a role in regulating your mood, digestion, and overall health.”

So, you might get a quick burst of mental clarity from the sugar rush, but without protein, fat, or fiber to keep things steady, you're setting yourself up for a crash of epic proportions; think 2008 stock market levels.

🍎 But I Swear I Feel Better When I Juice.

Let’s be real: Juice isn’t bad, per se. I’ll gladly sip a fresh-pressed orange juice or a wheatgrass-celery blend when I want to channel those effortlessly healthy people who wake up at 5:30 and do pilates. But a juice cleanse won’t “detox” you or do much for your gut or overall health.

If you love green juice, enjoy it. But if a juice cleanse has you feeling “lighter” and “clearer,” it’s not some magical weight loss trick, it’s just your body responding to a calorie crash. Cutting out processed foods is great, but you don’t need to live on liquid spinach to do it.

When you’re running on 800–900 calories a day with barely any protein, your body isn’t “resetting." It’s just running on empty. Sure, you might drop a little weight, but the moment you start eating again, your metabolism will cling to every calorie like it’s prepping for the end times.

🍎 What Should I Actually Do?

If you’re looking for a miracle shortcut that “cleanses” your system, maybe just sign up for Naked and Afraid instead. At least that way, you’ll get a survivalist badge to go with your hunger pains.

The truth is, your body already detoxes itself. (Thanks, liver and kidneys!) The best thing you can do for your gut, skin, and overall health isn’t chugging celery juice for three days straight. It’s eating real, fiber-filled food and not falling for crash diets that promise magic results. Newsflash: Despite what the clickbait articles tell you, there is no magic weight loss trick.

So next time you’re tempted to drop $12 on a beet-kale blend that tastes like freshly cut grass, maybe just… eat a salad or another balanced option? Your gut bacteria will be happy to see some fiber.

And if you really want to get "healthier," you could try some of the other boring, unsexy stuff. “Focus on your lifestyle choices. Practice stress management techniques, make sure you are getting good quality sleep, don’t smoke or drink, exercise regularly, and eat a plant-forward diet rich in whole foods (leafy greens, colorful vegetables, whole grains, fermented foods, etc.),” says Dr. Rao.

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