Americans are taking more probiotic supplements than they used to, but their diets have not changed nearly as much.
A new analysis of national health and nutrition data found that probiotic use rose sharply among both adults and young people from 2009 to 2023. Over the same period, fiber intake stayed well below recommended levels and changed little overall. The study does not show that people are replacing healthy foods with supplements. In fact, people who took probiotics generally ate more fiber and more foods thought to support the gut microbiome than people who did not.
The study, published in Clinical Gastroenterology and Hepatology, used data from seven rounds of the National Health and Nutrition Examination Survey, a long-running federal survey that tracks what Americans eat and which supplements they use. Researchers analyzed supplement information from 62,700 people and dietary records from more than 54,000.
Among people younger than 20, probiotic use rose from 0.63% in 2009-10 to 5.58% in 2021-23. Among adults, it increased from 1.8% to 6.96%.
That is a large percentage increase, especially among young people, but the starting point was very low. In simpler terms, probiotic use among people younger than 20 rose from fewer than 1 in 100 to about 1 in 18. Among adults, it went from about 1 in 56 to roughly 1 in 14.
The researchers then looked at whether Americans were making similar changes in what they ate.
Fiber was one of the clearest areas where little had changed.
Among people younger than 20, average fiber intake rose only slightly over the study period. Among adults, it dipped a bit. In both groups, intake remained far below the level used by the researchers as a recommended benchmark.
The researchers also looked at foods likely to contain more live microbes, such as some raw fruits and vegetables and fermented foods. Those foods may help support a diverse gut microbiome, although their benefits are not necessarily because of the microbes alone.
Consumption of those foods changed only modestly compared with the sharp rise in probiotic use.
Still, the findings do not support the idea that probiotic users were ignoring diet.
People who took probiotics tended to eat more fiber and more of these gut-supportive foods than people who did not take probiotics. That pattern remained even after researchers accounted for differences such as age, income, sex and race or ethnicity.
So the study cannot show that supplements are replacing healthier food choices.
What it does show is a mismatch in how fast the two trends are moving: probiotic use has grown quickly, while fiber intake and other diet changes have barely budged.
That matters because a probiotic supplement and a fiber-rich diet are not interchangeable.
Foods such as vegetables, fruits, beans and whole grains provide fiber along with vitamins, minerals and other plant compounds. Some fermented foods also contain live microorganisms. A probiotic supplement, by contrast, usually contains selected strains of bacteria or yeast.
The study also did not test whether taking probiotics improved or worsened people's health. It looked at supplement use and eating patterns, not changes in symptoms, disease risk or the makeup of the gut microbiome.
And probiotics are not a one-size-fits-all tool. Their usefulness depends on the product and the reason someone is taking it. The authors note that professional guidelines find limited evidence for probiotic use in many digestive conditions.
There are other limits to keep in mind. The study relied partly on people recalling what they ate, which can be imperfect. Survey participation also dropped over time, especially in the most recent years. And because the study compared different groups of people at different points in time, it cannot show how one person's habits changed over the years.
The study reported no grant funding. Several authors disclosed financial relationships with pharmaceutical, diagnostic and digestive-health companies. Kira Newman has consulted for Takeda and received research support from Pfizer. Allen Lee has consulted for GSK and Atmo Biosciences. William Chey reported consulting, research support, stock options and patents involving several gastrointestinal health companies, including Salix, Atmo and FoodMarble. Peter Higgins has consulted for AbbVie and Curacle. The authors did not report that these companies funded this study.