Vegetable and fruit juice based diets are growing in popularity among busy people who don’t have the time to get in their daily fruits and veggies. Fruits and vegetables are sources of many biologically active things that help health and decrease the risk of disease.  For example fruits and veggies have molecules called polyphenols.
Polyphenols have a variety effects that have been proven in the lab such as being antioxidants, immune system stimulating, and killing bacteria.  Polyphenols are not well absorbed by the body and often continue to the colon where they can be digested by bacteria in the gut. These bacteria break down polyphenols into smaller molecules which also become food to other bacteria. Fruits and vegetables are also high in fermentable fibers which have prebiotic activities. Prebiotics are compounds that bacteria living in us, can use as food to grow. High fiber intake has many positive effects like lowered risks of cardiovascular disease, type 2 diabetes, and some cancers. 
The gut microbes play a role in our everyday health. One of these roles is that the gut microbiota has been shown to affect the development of obesity and obesity-related disease.  The two types of bacteria which are found in humans in greatest numbers are the Firmicutes and Bacteriodetes.  Studies have shown that supplementing diets with more polyphenols shows a decreased amount of Firmicutes and more Bacteriodetes. This is interesting because lowered Firmicutes levels and higher Bacteriodetes is also associated with leaner individuals, while obese people have opposite proportions.  A scientific study followed a 3-day juice-based diet of 6 blends of fruit/vegetable juices. The results showed that people lost significant amounts of weight and kept it off for two weeks. People on this diet showed increased amounts of Bacteroides bacteria which can degrade plant fibers and complex polysaccharides. 
What fruits/veggies are high in polyphenols?
The break down: Research shows that leaner people have the same gut bacteria, that the juice diet promotes. Although this may not mean instant weight loss, studies are showing that the juice diet has definite benefits to the body. Why not add more juice to your diet?
Rule of thumb: Choose fruits and veggies that are richly hued when juicing. For example, red and purple fruits often are excellent sources of polyphenols. However, don’t be afraid to stray to other colours. All fruits and veggies have nutrients and vitamins that are good for your bodies.
1. Tome-Carneiro, J. & Visioli, F. Polyphenol-based nutraceuticals for the prevention and treatment of cardiovascular disease: Review of human evidence. Phytomedicine: international journal of phytotherapy and phytopharmacology, doi:10.1016/j.phymed.2015.10.018 (2015).
2. Li AN, et al. Resources and biological activities of natural polyphenols. Nutrients. 2014;6:6020–6047. doi: 10.3390/nu6126020.
3. Dahl, W. J. et al. Health Benefits of Fiber Fermentation. Journal of the American College of Nutrition 1–10, doi:10.1080/07315724.2016.1188737 (2017).
4. Korpela K, et al. Gut microbiota signatures predict host and microbiota responses to dietary interventions in obese individuals. PloS one. 2014;9:e90702. doi: 10.1371/journal.pone.0090702.
5. Million M, Lagier JC, Yahav D, Paul M. Gut bacterial microbiota and obesity. Clinical microbiology and infection: the official publication of the European Society of Clinical Microbiology and Infectious Diseases. 2013;19:305–313. doi: 10.1111/1469-0691.12172.
6. Stenman, L. K., Burcelin, R. & Lahtinen, S. Establishing a causal link between gut microbes, body weight gain and glucose metabolism in humans - towards treatment with probiotics. Beneficial microbes 1–12, doi:10.3920/BM2015.0069 (2015).
7. Flint HJ, Scott KP, Duncan SH, Louis P, Forano E. Microbial degradation of complex carbohydrates in the gut. Gut microbes. 2012;3:289–306. doi: 10.4161/gmic.19897.
8. Henning, S. M., et al. (2017). "Health benefit of vegetable/fruit juice-based diet: Role of microbiome." Sci Rep 7(1): 2167.
In our most recent blog post, we discussed the importance of vitamins such as vitamin K2. Another crucial vitamin for healthy gut functions is vitamin D. Vitamin D represents a group of fat-soluble vitamins which are required for increasing intestinal absorption of calcium, iron, magnesium, phosphate, zinc (1). The most important in humans are vitamins D2 and D3. While this vitamin is often associated with the skin, it can be acquired from food intake just as well as from sunlight.
A study recently showed that a deficiency in vitamin D changes the intestinal microbiome and reduces vitamin B production in the gut. This means that there is a change in the type of bacteria living in our gut when we do not have enough vitamin D in our system (2). Furthermore, this lack of vitamin B leads to negative changes in our immune system. Our bodies suffer from increased inflammation and this can lead to autoimmunity – meaning our immune system is attacking healthy tissues and cells.
Finally, low levels of vitamin D have been linked with an increased risk of depression. Not only is this vitamin important for a healthy gut and a strong immune system, but also our mental health (3). It really is a molecule with several, diverse effects. Others include bone health, cancer, cardiovascular disease, cognition/dementia, pregnancy, and weight loss as well.
Therefore, it is very important to maintain normal levels of vitamin D in our blood.
What can you do?
1. Holick, Michael F. "High Prevalence of Vitamin D Inadequacy and Implications for Health." Mayo Clinic. Mayo Clinic Proceedings, Mar. 2006. Web.
2. Gominak, S. C. "Vitamin D Deficiency Changes the Intestinal Microbiome Reducing B Vitamin Production in the Gut. The Resulting Lack of Pantothenic Acid Adversely Affects the Immune System, Producing a "pro-inflammatory" State Associated with Atherosclerosis and Autoimmunity." Medical Hypotheses. U.S. National Library of Medicine, Sept. 2016. Web.
3. Black, L. J., P. Jacoby, K. L. Allen, G. S. Trapp, P. H. Hart, S. M. Byrne, T. A. Mori, L. J. Beilin, and W. H. Oddy. "Low Vitamin D Levels Are Associated with Symptoms of Depression in Young Adult Males." The Australian and New Zealand Journal of Psychiatry. U.S. National Library of Medicine, May 2014. Web.
4. Jakobsen, Jette, and Pia Knuthsen. "Stability of Vitamin D in Foodstuffs during Cooking." Stability of Vitamin D in Foodstuffs during Cooking. Food Chemistry, 1 Apr. 2014. Web.
Vitamins are essential micronutrients needed in small quantities to sustain life. We need to take vitamins from food because the human body either does not produce enough of them or none at all. There are currently 13 recognized vitamins which are either fat-soluble (stored in the fatty tissues of the body and the liver) or water-soluble (do not get stored in the body for long - they soon get excreted in urine) (1).
As you might have learned from previous blogs, the human gastrointestinal tract (GIT) is colonized by a vast array of microorganisms known as the gut microbiota. The intestinal microbiota (microbes that harbours our gut) plays a pivotal role in food digestion and energy recovery, while it can also act as an important supplier of vitamins. In humans it has been shown that members of the gut microbiota are able to synthesize vitamin K as well as most of the water-soluble B vitamins (2).
Some subtypes of Vitamin K2 can only be supplied to the host through bacteria in the gut such as Ruminococcaceae, Bacteroides, Prevotella, Alistipes, Oscillibacter, Bilophila, Odoribacter and Barnesiella species. Moreover, it seems that the Bacteroides and Prevotella species are the most prevalent in generating different subtypes of vitamin K2 (6).
The current research on Vitamin K2 and health is extremely promising. It could have life saving implications for a lot of people. Unfortunately, the average intake of this important nutrient is incredibly low in the modern diet.
What can you do?
1. Leblanc, Jean Guy, Christian Milani, Graciela Savoy De Giori, Fernando Sesma, Douwe Van Sinderen, and Marco Ventura. "Bacteria as Vitamin Suppliers to Their Host: A Gut Microbiota Perspective." Current Opinion in Biotechnology 24.2 (2013): 160-68
2. Hill, M. J. "Intestinal Flora and Endogenous Vitamin Synthesis." European Journal of Cancer Prevention 6 (1997): n. pag.
3. Marques, Tatiana Milena, Rebecca Wall, R. Paul Ross, Gerald F. Fitzgerald, C. Anthony Ryan, and Catherine Stanton. "Programming Infant Gut Microbiota: Influence of Dietary and Environmental Factors." Current Opinion in Biotechnology 21.2 (2010): 149-56.
4. Mizuta, Toshihiko, Iwata Ozaki, Yuichiro Eguchi, Tsutomu Yasutake, Seiji Kawazoe, Kazuma Fujimoto, and Kyosuke Yamamoto. "The Effect of Menatetrenone, a Vitamin K2 Analog, on Disease Recurrence and Survival in Patients with Hepatocellular Carcinoma after Curative Treatment." Cancer 106.4 (2006): 867-72.
5. Kubota, K., T. Sawada, J. Kita, M. Shimoda, and M. Kato. "6594 POSTER Effect of Menatetrenone, a Vitamin K2 Analog, on Recurrence of Hepatocellular Carcinoma After Surgical Resection â€“ Final Results of Randomized Controlled Study." European Journal of Cancer 47 (2011): n. pag.
6. Karl, J. P., X. Fu, X. Wang, Y. Zhao, J. Shen, C. Zhang, B. E. Wolfe, E. Saltzman, L. Zhao, and S. L. Booth. "Fecal Menaquinone Profiles of Overweight Adults Are Associated with Gut Microbiota Composition during a Gut Microbiota-targeted Dietary Intervention." American Journal of Clinical Nutrition 102.1 (2015): 84-93.
7. Kidd, P. M. "Vitamins D and K as Pleiotropic Nutrients: Clinical Importance to the Skeletal and Cardiovascular Systems and Preliminary Evidence for Synergy." Alternative Medicine Review : A Journal of Clinical Therapeutic. U.S. National Library of Medicine, Sept. 2010.
8. Filippis, Francesca De, Nicoletta Pellegrini, Luca Laghi, Marco Gobbetti, and Danilo Ercolini. "Unusual Sub-genus Associations of Faecal Prevotella and Bacteroides with Specific Dietary Patterns." Microbiome 4.1 (2016): n. pag.