Where did the number 30 come from?
The idea is commonly linked to the American Gut Project, a large citizen-science study published in 2018. Researchers analyzed microbiome samples and questionnaire data from thousands of volunteers. Participants who reported eating more than 30 different plant types per week had gut microbial communities that differed from those of participants who reported eating 10 or fewer.
The study made dietary plant variety easier to discuss, but it did not establish 30 as a minimum requirement or prove that crossing from 29 to 30 causes a health benefit.
Association is not causation
The American Gut Project was observational. Participants chose their diets; researchers did not randomly assign people to eat a certain number of plants. People who ate more plant types may also have differed in many other ways, including overall diet, geography, lifestyle, medication use, or socioeconomic factors.
Self-reported diet data can also be incomplete, and the citizen-science sample was not designed to represent every population. The result is best understood as a useful association that supports further research—not proof that a 30-plant target prevents or treats disease.
What we can say: plant-food diversity is a reasonable way to encourage dietary variety.
What we cannot say: eating exactly 30 plants guarantees a healthier microbiome or a particular health outcome.
Why might variety matter?
Plants contain many kinds of dietary fiber and other compounds. Different compounds are processed differently by the body and by microbes in the gut. A varied set of foods can therefore provide a broader range of substrates than repeatedly eating the same small group.
That biological idea is plausible, but individual responses vary. The gut microbiome is influenced by diet as well as age, environment, medication, illness, genetics, and many other factors. More microbial diversity is not automatically better in every context, and a consumer app cannot assess the health of a person's microbiome.
What 30Plants is designed to do
30Plants helps you notice and remember the variety of plant foods you eat. It tracks unique foods across a week and offers general educational information about fibers and plant compounds. It does not analyze stool samples, measure your microbiome, diagnose a condition, or prescribe treatment.
The score intentionally stays simple. Fruits, vegetables, whole grains, legumes, nuts, and seeds receive full Plant Points; herbs, spices, coffee, tea, and extra-virgin olive oil receive quarter-points. These are the app's consistent tracking conventions, not a universal scientific scoring standard.
A sensible way to use the goal
- Use 30 as a direction for exploration, not a pass-or-fail test.
- Increase variety gradually, especially if you are not used to eating much fiber.
- Keep serving size, overall dietary balance, allergies, tolerances, culture, and budget in view.
- Seek individualized medical or nutrition advice when you have symptoms or a health condition.
For a practical starting point, see How to Eat 30 Plants a Week. For the app's exact scoring conventions, see What Counts as a Plant?
Primary research
- McDonald D, et al. American Gut: an Open Platform for Citizen Science Microbiome Research. mSystems. 2018;3(3):e00031-18. doi:10.1128/mSystems.00031-18.
- De Filippo C, et al. Impact of diet in shaping gut microbiota revealed by a comparative study in children from Europe and rural Africa. Proceedings of the National Academy of Sciences. 2010;107(33):14691–14696. doi:10.1073/pnas.1005963107.
Turn curiosity into a simple habit
Track the plants you eat, discover new options, and see your weekly variety at a glance.
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