Think A Juice Cleanse Is Good For You? Think Again

Juice cleanses – where people exclusively consume fruit and/or vegetable juice – have often been touted as good for your health, purportedly “detoxing” you and helping you to get a bunch of vitamins and minerals to boot. The thing is, detox diets have been thoroughly debunked – and a new study has found that juice cleansing in particular might actually do more harm than good.

The study was carried out by researchers at Northwestern University, who wanted to find out if juicing might impact the oral and gut microbiome, the ecosystem of microbes that live in our mouths and digestive systems. Previous research has found possible links between changes in the gut microbiome and a range of health problems, including asthma, fibromyalgia, and loss of libido.

To investigate, the team analyzed the oral and gut microbiomes of 14 healthy adults – via cheek swabs, saliva, and stool samples – before and after following a particular diet. They all first spent three days on an elimination diet, after which they were split into three groups and asked to consume one of the following intervention diets: juice only, juice and foods, or plant-based whole foods only.

Using gene sequencing to identify the bacteria present in the samples, the researchers found none of the intervention diets caused any significant differences in cheek or fecal sample diversity or composition – saliva samples did show some differences in composition for the juice and juice and food diets, but no differences for microbial diversity.

However, for the participants on the juice and juice and food diets, there was an increase in the relative abundance – that’s how common a particular species is in a given area compared to the other species there – of some bacterial species in the mouth and gut that have been associated with inflammation and disease. The oral microbiome in particular saw the most change.

Here, it’s important to mention that juicing fruit and vegetables removes most of their insoluble fiber; this is the type that helps food to move through the digestive system and bulk to our poop. Not only could this make a juice cleanse a recipe for constipation, but the authors also point out that low fiber intake in and of itself is known to affect microbiomes.

“Most people think of juicing as a healthy cleanse, but this study offers a reality check,” said senior author of the study Dr Melinda Ring in a statement. “Consuming large amounts of juice with little fiber may lead to microbiome imbalances that could have negative consequences, such as inflammation and reduced gut health.”

It’s worth noting that this study shouldn’t lead us to jump to any major conclusions; it used a small sample size, the diet only lasted for three days, and, as the authors mention in the paper, the changes that they saw were “somewhat small in magnitude.”

They also note that "the 14-day post-intervention period showed a trend toward the reestablishing of the pre-intervention microbiota composition, demonstrating that three days of diet intervention cannot be considered sufficient to significantly modulate the microbiota composition."

Nonetheless, they argue that it’s still worth our attention. “Our intervention only lasted for three days. Given that many juice cleanses or diets that add juice may last for longer or are consumed periodically over time, we expect the potential cumulative negative effects may indeed be higher,” the authors write. “Future studies should examine these dynamics in more detail.”

The study is published in the journal Nutrients.

If you or someone you know might have an eating disorder, help and support are available in the US at nationaleatingdisorders.org. In the UK, help and support are available at beateatingdisorders.org.uk. International helplines can be found at https://www.worldeatingdisordersday.org/home/find-help