For most people with no diagnosed condition, fiber is the higher-value move. A probiotic capsule adds a few strains of bacteria; fiber feeds the trillions already living in your gut, and it is the thing almost nobody in the United States is getting enough of. The two are not substitutes, and new national data suggests a lot of people are treating them as if they were.
On September 7, 2026, Clinical Gastroenterology and Hepatology published a research letter by Kira Newman and colleagues at the University of Michigan analysing fifteen years of federal survey data. Its finding is in its title: increases in probiotic supplement use have outrun the dietary changes that actually shape the microbiome. Prevention covered it on September 13 in a piece on rising probiotic use and flat fiber intake. The numbers below are read from the study itself.
What the study found
The researchers analysed seven cycles of the National Health and Nutrition Examination Survey from 2009 through 2023, covering 62,700 respondents with supplement data, a weighted sample representing roughly 242.6 million US residents. Just over half, 50.24 percent, had taken at least one supplement in the previous 30 days, and 3.89 percent had taken a probiotic.
Probiotic use rose sharply. The increase in children and teenagers is the figure worth sitting with.
| Group | 2009 to 2010 | 2021 to 2023 | Relative increase |
|---|---|---|---|
| Under 20 years | 0.63% taking a probiotic | 5.58% | 786% |
| 20 years and over | 1.80% taking a probiotic | 6.96% | 287% |
Both trends were statistically significant at p less than 0.001. Over the same fifteen years, fiber intake did not meaningfully improve: people under 20 went from 7.37 to 7.97 grams per 1,000 calories, and adults went from 8.52 to 8.26. Every group sat below the recommended 14 grams per 1,000 calories for the entire period. After adjustment for age, sex, race and ethnicity and household income, fiber intake declined slightly, by 0.05 grams per 1,000 calories per year.
The finding that complicates the headline
It would be neat to say that people taking probiotics are the ones neglecting their diet. The study says the opposite, and the distinction matters.
Probiotic users ate more fiber than non-users, not less: 1.35 grams per 1,000 calories more in the raw comparison, and 1.12 grams more after adjusting for demographics. They also ate more high-microbial-content food. The people buying probiotics are, on average, the people already paying more attention to what they eat.
What concerned the authors is the direction of travel. That dietary advantage among probiotic users appears to be shrinking over time, which raises the possibility that the supplement is starting to stand in for the food rather than sit alongside it. Their own phrasing is that this indicates a missed opportunity for dietary interventions. It is an association in cross-sectional survey data, not proof that anyone swapped a vegetable for a capsule.
Probiotics, prebiotics and fermented foods are four different things
Much of the confusion in this area is vocabulary. The definitions below are the ones used by the International Scientific Association for Probiotics and Prebiotics, which are the reference definitions in the scientific literature.
| Term | What it means | Examples |
|---|---|---|
| Probiotic | Live microorganisms that, in adequate amounts, confer a health benefit on the host (Hill et al., 2014) | Capsules and powders with defined strains and counts |
| Prebiotic | A substrate selectively used by host microorganisms to confer a health benefit (Gibson et al., 2017) | Certain fibers in onions, garlic, leeks, asparagus, oats, bananas |
| Fermented food | Food transformed by microbial growth, which may or may not still contain live microbes when eaten | Yogurt, kefir, kimchi, sauerkraut, miso |
| High-microbial food | Food carrying a high live microbial load as eaten, above 10 million colony forming units per gram | Raw fruit and vegetables, unpasteurised ferments |
That last category is the one the Michigan study measured, using a classification scheme that sorts foods into low (under 10,000 colony forming units per gram), medium, and high (over 10 million). It is worth noting that raw fruits and vegetables fall into the high band, which is not where most people would expect live microbes to come from. Only 26.29 percent of respondents had eaten a single high-microbial food the previous day, and 31.17 percent had eaten only low-microbial foods.
What the evidence actually supports
The study cites associations between higher intake of high-microbial-density foods and lower systolic blood pressure, lower C-reactive protein, lower plasma glucose, improved serum lipids and smaller waist circumference. It then adds the caveat that most consumer coverage leaves out: it is uncertain whether those foods help because of their microbes or because of everything else they contain, including fiber, phytonutrients and calcium.
On the supplement side, the authors note that probiotic use rose sharply after 2013 to 2014 despite clinical guidelines suggesting limited benefit in most situations. That is not the same as saying probiotics do nothing. There are specific circumstances where particular strains have evidence behind them, and that is a conversation for a clinician who knows your history, not a shelf label.
One further point of context. Probiotics sold as dietary supplements are not approved by the FDA before they go on sale, and the agency does not verify the strains or counts on the bottle. We covered how that system works in are dietary supplements FDA approved.
What to do with this
| If your goal is | The higher-yield move |
|---|---|
| Feed the microbes you already have | More fiber, from more different plants |
| Add live microbes | Fermented foods with live cultures, and raw produce |
| Improve regularity | Fiber and fluid, increased gradually |
| Manage a diagnosed gut condition | A clinician, who can match a strain to the condition |
Plant variety is its own lever, separate from total grams. The reasoning behind that, and the widely cited target of thirty different plants a week, is in how many different plants you should eat in a week. For the gram target itself, see how much fiber you need a day, and for which type of fiber does what, see soluble vs. insoluble fiber.
Where SaladPower fits, precisely
One 8 oz pouch delivers 5 grams of fiber, 18 percent of the Daily Value, from six whole organic ingredients: spinach, kale, carrot, broccoli, apple and lemon. That is the prebiotic side of this page, the food that feeds what is already in your gut, and it is 2x the USDA daily recommended vegetable intake in a pouch.
On live microbes, we would rather be exact than vague. SaladPower is commercially processed, sealed and shelf-stable, which is what lets a pouch sit in a bag for months without refrigeration. That process is not designed to deliver live cultures, so if live microbes are what you are after, yogurt, kefir, kimchi and raw produce are the route. A pouch and a bowl of yogurt are answering two different halves of the same question, and there is no reason to choose between them.
Frequently asked questions
Is fiber or a probiotic better for gut health?
For most people without a diagnosed condition, fiber. It feeds the microbial community already present, and national survey data shows every age group in the United States falling short of the recommended 14 grams per 1,000 calories. Probiotics have evidence in specific clinical situations, which is a question for a clinician.
What is the difference between a prebiotic and a probiotic?
A probiotic is live microorganisms that confer a health benefit in adequate amounts. A prebiotic is a substrate, usually a type of fiber, that your existing microbes selectively use. In short, probiotics add microbes and prebiotics feed them.
How much has probiotic use actually increased?
Between the 2009 to 2010 and 2021 to 2023 National Health and Nutrition Examination Survey cycles, the share of people under 20 taking a probiotic rose from 0.63 percent to 5.58 percent, a 786 percent increase. Among adults it rose from 1.8 percent to 6.96 percent, a 287 percent increase.
Do people who take probiotics eat worse?
No. In this study probiotic users ate more fiber than non-users, by 1.12 grams per 1,000 calories after adjustment, and more high-microbial food. The authors' concern is that the gap appears to be narrowing over time, not that probiotic users have poor diets.
Do raw vegetables really count as a source of live microbes?
Yes. Under the classification used in this research, raw and minimally processed fruits and vegetables carry a high live microbial load, above 10 million colony forming units per gram, alongside fermented foods. Only about a quarter of survey respondents had eaten any high-microbial food in the previous day.
Sources
- Newman KL, Lee AA, Singh P, Kao JY, Chey WD, Higgins PDR. "Increases in Probiotic Supplement Use Exceed Microbiome-Focused Dietary Changes in US Adults and Children." Clinical Gastroenterology and Hepatology, published online September 7, 2026. doi:10.1016/j.cgh.2026.08.029. Open access.
- Prevention, "People Are Taking More Probiotics but Still Skimping on This Important Nutrient for Gut Health," September 13, 2026. Read the original article.
- Hill C, Guarner F, Reid G, Gibson GR, et al. "The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic." Nature Reviews Gastroenterology and Hepatology, 2014. doi:10.1038/nrgastro.2014.66.
- Gibson GR, Hutkins R, Sanders ME, Prescott SL, et al. "Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics." Nature Reviews Gastroenterology and Hepatology, 2017. doi:10.1038/nrgastro.2017.75.
- US Food and Drug Administration. "Daily Value on the Nutrition and Supplement Facts Labels." fda.gov.
- SaladPower Nutrition Facts panel, 8 oz pouch.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.
