Juice based diets are all the rage these days. You can find a lot of discussion and fantastical claims on the internet about their effectiveness as a weight loss tool, as well as their benefits to our overall health. [1], [2], [3]. As a scientist, one is usually skeptical of these claims as a juice based diet does not necessarily confer the balance of nutrients that is more typically recommended for the maintenance of health, and the sources of these claims are not often written from a fact and evidence based perspective. This is not a judgement as to whether or not they are true, but an indicator that perhaps, just maybe, some intrepid scientists may want to dive into this phenomenon more thoroughly.

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One part of our bodies that we are coming to find plays a large role in dictating our overall health is our Microbiome. The microbiome is the collection of all bacteria and other microorganisms that live in our digestive tracts. The composition (aka the relative amounts of the different types of these organisms) has been found to change relative to whether or not we are healthy [5] and it is thought that maintaining a healthy microbiome composition aides in maintaining our own health.

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In light of all that today lets discuss an article recently published May 19, 2017 in the journal Nature: Scientific Reports titled "Health benefit of vegetable/fruit juice-based diet: Role of microbiome."

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The authors in this article decided to investigate the health claims of juice based diets (stating outright that there just hasn't been sufficient scientific evidence to support the claims and anecdotal evidence touted by many). They hypothesized that changes to the microbiome composition (as the types of microorganisms that thrive will be dependent on the particular subset of nutrients which are available for them to live off of) that occur from participating in a juice based diet may cause the health benefits that many claim these diets to have.

To go further into the nutrient argument, fruits and vegetables contain a variety of polyphenolic compounds, which have been observed to have antioxidant, and antimicrobial properties. [8] It is also known that polyphenols aren't absorbed particularly well in our small intestines, meaning that many will pass through into the large intestine, home to the vast majority of the members of our microbiome.[9]

It is possible that the effects these compounds have (especially antimicrobial ones) will result in bigly (LOL) changes (the best changes, everyone is saying it, the smartest of people...)

...to the types of bacteria that are thriving there, and that changed microbiome composition will lead to downstream health effects.

So What Did They Do?

The researchers put people on a very brief juice diet of three days (which doesn't seem like much but hey that was the study),

6 bottles daily of mixtures of greens, roots, citrus, lemon, cayenne and vanilla almond

which was followed then by a more traditional 14 day diet. They then investigated whether or not the juice diet caused changes to the composition of the participants microbiomes, as well as looked at more traditional health indicators like body weight.

Speaking of body weight... what happened from the juice diet?

Image Sourced From The Primary Article

Their results are depicted in the plot above. After the juice only portion of the diet the participants were seen, on average, to have lost about 1.7 ± 1.2 kg (which doesn't at all look like the error bars in the plot...) and after returning to their normal diet were seen to have kept some of the weight off, remaining down 0.91 ± 0.9 kg (or 0.9 plus or minus all of it?... again that error bar doesn't look like it accounts for as much as the text reports). So it appears that the participants lost some weight and kept it off as a result of the brief juice diet (or they didn't... the error is huge.. but I will report what the authors discuss!).

Did The Juice Diet Change The Microbiome Composition?

Image Sourced From The Primary Article

Here we are looking at the authors reported determination of the composition of the bacteria residing in the participants bodies (they determine this by looking at the peoples poop... there I said it! And then sequencing the bacteria's ribosomal 16S rRNA segment to identify what was there). What we can see is that after the completion of the juice only portion of the diet, the microbiome composition did change.. and in a pretty significant way! The participants showed a statistically significant increase in the amount of bacteroidetes and cyanobacteria and decrease of firmicutes.

The authors listed some more specific information with the participants showing a massive increase over baseline amounts of Halospirulina (a reported 1467% increase) a cyanobacteria and drastic reduction in Streptococcus (showing only 8% of what was there prior to the juice diet) one of the firmicutes.

What Do The Authors Conclude?

• Their study illustrated that a juice diet resulted in a statistically significant reduction in body weight, that was kept off up to 14 days after resuming a normal diet.
• The relative proportion of Bacteroidetes has been associated with a decrease in body weight, the authors observed that the juice diet drastically increased the Bacteroidetes population, which is consistent with prior findings. The inverse is true for Fermicutes, which are correlated with increased body weight, also consistent with their findings here. Less Fermicutes, and lower body weight.

In summary the 3-day vegetable/fruit juice-based diet induced significant changes in the intestinal microbiota which were associated with weight loss. Further mechanistic studies are required to confirm that changes in the microbiota are directly linked to weight loss.

So what they showed here is that a microbiome composition change resulted from the juice diet, and the juice diet did result in lower weight.

• To limit the length of this post I did not discuss a few of the other of the authors findings, including that the juice diet resulted in an increase in blood and urine nitric oxide levels (which is an indicator of vasodilation and may point to beneficial effects for heart health) as well as the participants showing reduced amounts of lipid oxidation (as measured by urine malondialdehyde concentrations, indicating that the juice diet did have an increased amount of antioxidant compounds which did have a detectable effect on the body).

My Personal Thoughts?

It's clear that a lot more study should be performed on this, but it certainly does look like a juice diet is a pretty healthy option (and seemingly effective). That said I remain skeptical of many of the outlandish claims that you can find out there.

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Still... maybe...

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Sources

1. http://juicing-for-health.com/benefits-of-juice-fast
2. http://www.huffingtonpost.com/woodson-merrell-md/juice-cleanses_b_4549641.html
3. http://www.shape.com/lifestyle/mind-and-body/your-body-juice-cleanse
4. https://en.wikipedia.org/wiki/Microbiota
5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4290017/
6. https://www.nature.com/articles/s41598-017-02200-6
7. https://en.wikipedia.org/wiki/Polyphenol
8. http://www.mdpi.com/2072-6643/6/12/6020
9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2871118/

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Images from figures in Nature: Scientific Reports articles are available for reuse under a Creative Commons license (all figures will be appropriately attributed and linked back to the article of reference).

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