The recommendation to consume at least 30 different plant foods per week has gained popularity in wellness circles, promising benefits such as reduced inflammation, improved heart health, enhanced energy, and a stronger immune system. This concept has inspired tracking apps and supplements claiming to deliver the nutritional advantages of consuming 30 or more plant varieties. However, experts caution that the evidence supporting this specific numerical goal remains limited.

The idea originates from a 2018 study led by microbiome scientist Rob Knight at the University of California, San Diego. Researchers analyzed stool samples from 85 adults in the United States and Britain, dividing them into groups based on whether they reported eating 10 or fewer unique plants weekly or 30 or more. Those consuming higher plant diversity demonstrated greater gut microbiome variety, which is often associated with improved health.

While the findings suggest a positive link between plant diversity and gut microbial diversity, experts note significant limitations. The study relied on self-reported dietary data and was relatively small. Nutrition researcher Arista Arca from the University of Alberta pointed out that the study showed only an association, not causation. Furthermore, a subsequent unpublished and non–peer-reviewed analysis involving over 3,000 adults indicated that consuming between 11 and 20 different plants weekly yielded microbiome diversity comparable to that seen at 30 plants.

Additional clinical trials have explored the effects of high plant variety but with mixed results. A 2025 study in Australia involving 25 adults with chronic kidney disease found that consuming 30 or more unique plants per week was linked to reduced constipation and improved gut health markers compared to lower plant intake. Another trial with about 400 participants examined a "30-plant" supplement over six weeks, reporting decreased constipation but no significant change in microbiome diversity compared with probiotic or placebo controls. Researchers emphasized that increases in fiber intake—common when consuming more plant foods—may account for observed health benefits, rather than plant variety alone.

Experts caution against viewing the 30-plant target as a definitive health prescription. “There isn’t strong evidence that 30 plants are a ‘magical threshold,’” noted Justin Sonnenburg, a microbiology and immunology professor at Stanford Medicine. He emphasized the complexity and individual variability of gut microbiomes, suggesting that a single numeric goal may not apply universally.

Dietitian Lourdes Castro of New York University encourages those who enjoy working toward the 30-plant goal to continue, as it may encourage dietary fiber diversity. However, she warns against becoming overwhelmed by the target. Arca recommends focusing instead on established nutrition guidelines, advocating for the daily consumption of 21 to 38 grams of fiber from a variety of plant sources.

Researchers also advise against relying on supplements marketed to mimic plant diversity benefits, emphasizing that whole foods remain the optimal source for supporting gut and overall health.