A daily blend made with more than 30 plant ingredients changed more types of gut bacteria than one commonly studied probiotic strain in a randomized trial of adults with relatively low fiber intake.
The findings offer support for the idea that varied plant fibers can nourish many of the microbes already living in the gut. But the study did not test whether eating 30 different whole plant foods produces the same results, nor did it show that the blend was better than probiotics as a category.
The six-week trial was funded by ZOE Ltd., which sells the Daily30 plant blend tested in the study. ZOE contributed to the study design, data collection, analysis and manuscript preparation. Most of the authors were ZOE founders, employees, consultants or stock-option holders, and another company helped develop the blend.
The study, published in the British Journal of Nutrition, included 349 adults in the United Kingdom. Participants were assigned to consume a 30-gram serving of the plant blend, a similar-calorie serving of bread croutons or a capsule containing the probiotic strain Lacticaseibacillus rhamnosus GG.
The blend contained more than 30 vegetables, fruits, nuts, seeds, herbs, spices and mushrooms. Participants consumed the concentrated powder each day rather than adding dozens of separate foods to their meals.
After six weeks, researchers found changes in 57 bacterial species among participants taking the plant blend. The probiotic group showed changes in four species, while the crouton group showed changes in 14.
That difference does not automatically mean the plant blend produced a healthier microbiome. A probiotic containing one bacterial strain would not necessarily be expected to reshape a large number of resident species, and probiotics may affect health without creating broad, lasting changes in microbiome composition.
The study also cannot establish that the blend is better than probiotics generally. Probiotic products contain different strains, combinations and doses, and evidence for their effects depends on the specific product and condition being studied.
Researchers classified the species that increased in the plant-blend group as being associated, on average, with more favorable health markers. Species that decreased tended to be associated with less favorable markers.
Those classifications were based on a microbiome ranking developed by ZOE. They reflect associations found in previous research, not proof that increasing or decreasing a particular species will improve an individual’s health.
The gut microbiome also cannot always be divided neatly into “good” and “bad” bacteria. A microbe’s effects may depend on its strain, abundance, interactions with other organisms and the wider diet.
Participants taking the plant blend also reported improvements in several digestive symptoms. According to the researchers, 55% reported less indigestion, 35% reported less severe constipation, 18% reported less heartburn and 37% reported less flatulence.
Some participants also reported greater energy and happiness. Those outcomes were based on personal ratings, however, and participants could tell whether they were consuming a powder, croutons or a capsule. Expectations about the intervention could therefore have influenced how they described their symptoms and well-being.
The percentages also show how many people in the plant group reported improvements, not necessarily how much better they did than participants in the comparison groups. Changes that occur within one group do not by themselves establish that the intervention caused the improvement.
A separate meal experiment included 34 participants. They ate a carbohydrate-rich meal with or without the plant blend and then rated their hunger, fullness, satisfaction and energy.
Adding the blend was associated with greater fullness and meal satisfaction and less hunger and desire to eat. Because the experiment involved a small subgroup and short-term subjective ratings, it cannot show that the product reduces appetite or changes food intake over time.
“The fact that Daily30 altered 57 distinct bacterial species in just six weeks informs how we should approach gut health,” said lead author Sarah Berry, a professor at King’s College London and chief scientist at ZOE. “Rather than introducing isolated strains through a pill, these results prove we can achieve a far greater impact on the gut microbiome composition by nourishing our existing microbes with a diverse array of plants.”
The trial supports the narrower conclusion that the specific plant blend changed more measured bacterial species than the single probiotic strain tested. It does not prove that broader microbiome change is always more beneficial or that plant-based interventions should replace probiotics used for specific medical purposes.
It also does not establish that people need the tested product to support their gut microbes. A varied diet containing vegetables, fruits, beans, whole grains, nuts and seeds can provide different forms of fiber and other compounds that gut microbes use.
The study participants began with relatively low fiber intake, so the additional plant material may have represented a meaningful change from their usual diets. Results could differ among people who already eat a fiber-rich and varied diet.
The trial lasted only six weeks and did not measure whether the observed microbiome changes reduced disease risk or improved long-term health. It also did not compare the blend with adding an equivalent amount of fiber through ordinary whole foods.
The findings nevertheless add to evidence that feeding the existing microbiome may affect it differently than swallowing a single bacterial strain. They also reinforce why the word “probiotic” does not describe one uniform intervention.
The research was funded by ZOE Ltd., which sells the Daily30 product tested in the trial. The funder contributed to the study design, data collection, analysis and manuscript preparation. Two authors are ZOE co-founders, several are consultants and many are current or former employees who receive or have received stock options. Indi Supplements contributed to development of the plant blend.