You’ve decided to try the 30 plants a week challenge and you’re already second-guessing your lunch. Does the pinch of cumin count? What about the dried chilli? You’ve seen conflicting things online — someone says mushrooms are out, someone else says they’re fine — and you’re not sure whether the oats in your breakfast are even in play.
The honest answer is that it depends slightly on who you ask, and that’s actually fine.
How the 30 plants a week challenge works
The core rule is simple: any food that comes from a plant source counts as one plant, logged once per week regardless of how often you eat it. Eating broccoli every day still scores one point for that week. The goal is breadth, not repetition. A bowl of rice and chickpeas with spinach, tomatoes, and a pinch of cumin already gives you five distinct plants in a single meal.
The key word is recognisable. The plant should be identifiable as itself — an ingredient you could name. That principle does most of the work when you hit edge cases.
Where the counting idea comes from
The 30-plant figure comes from the American Gut Project, one of the largest citizen science microbiome studies to date. Researchers asked participants to report how many different types of plant foods they typically ate in a week, then compared those responses with gut microbiome samples. People reporting 30 or more distinct plant foods per week showed significantly higher gut microbial diversity than those reporting fewer than ten.
The method was a self-reported food-frequency questionnaire. Participants weren’t asked to distinguish between botanical kingdoms or apply taxonomic rules, they simply answered a multiple choice question about what they ate. That matters for how you interpret the grey areas, and explains why there are few definitive answers. The Microsetta Initiative, which continues this work, operates in the same spirit.
What counts, what doesn’t, and how much
The underlying logic for deciding is consistent: the plant should be doing something for your gut, usually through fibre, polyphenols, or both, and you should be able to identify it.
What generally doesn’t count:
| Food | Verdict | Why |
|---|---|---|
| Fruit juice | Doesn’t count | Fibre removed in processing |
| White rice, white bread | Doesn’t count | Highly refined, low fibre |
| Heavily processed snacks | Doesn’t count | Plant source unidentifiable |
| Refined sugars and oils | Doesn’t count | No meaningful plant content remains |
| Meat, fish, dairy, eggs | Doesn’t count | Not plant-derived |
Potatoes sit in a grey area. Some guides, including Tim Spector’s, leave them out because they’re relatively starchy with modest fibre. Others count them when eaten with the skin on, where most of the fibre is. Either approach is defensible — pick whichever feels honest to you.
Herbs and spices are where counting conventions diverge most. Some popular frameworks, including those from Zoe, assign herbs, spices, garlic, coffee, and tea a quarter-point each, acknowledging that portions are small. Other guides count each as a full point: thyme is a distinct plant with its own polyphenols regardless of the quantity used. If logging a pinch of dried thyme feels like gaming the system, skip it. If it doesn’t, count it. Both positions are reasonable.
Olive oil is similar. It doesn’t appear in every plant-counting guide, but it comes from a real plant. Whether you log it as a point or leave it out doesn’t change the spirit of the challenge.
Mushrooms — the most debated exception
Mushrooms are biologically fungi, not plants, and strict interpretations of the challenge exclude them on that basis. The counter-argument runs like this: mushrooms contain beta-glucans, chitin, and other polysaccharides that feed gut microbes in ways distinct from typical plant fibre, and excluding them misses the point of the original research.
Many nutrition practitioners count different mushroom species separately. A common view in gut-health communities is that the point is diversity for your microbiome, not passing a botany exam. The American Gut Project, which motivated the whole framework, was measuring dietary diversity and microbiome outcomes rather than policing the line between kingdoms.
Both positions are scientifically defensible. If you include mushrooms — and count button, shiitake, and oyster separately — you’re in good company.
Colours and varieties — why a red pepper and a green pepper are two plants
Different colours within the same vegetable family often have distinct polyphenol profiles. A red pepper and a green pepper are the same species but contain different concentrations of different phytochemicals: carotenoids are higher in red, chlorophyll-based compounds dominate in green. That difference is meaningful for gut microbe diversity, which is why most guides count them separately.
The same logic applies to red onions versus white onions, different apple varieties, black beans versus kidney beans, and red cabbage versus green cabbage. Anthocyanins give purple and red foods their colour; carotenoids account for orange and yellow; glucosinolates are concentrated in brassicas. These compounds have different effects.
If you already eat a particular food regularly, swapping in a different variety or colour is one of the lowest-effort ways to increase your weekly count.
It’s guidance, not a rulebook
Research shows a correlation between plant diversity and microbiome diversity, and counting is a practical way to build the habit of seeking variety.
How strictly you count is a personal choice. Herbyvore was designed with exactly this in mind: sensible defaults based on the research — mushrooms counted, potatoes with skin included, herbs logged as a full point — but nothing is mandatory. Adjust the rules to fit how you actually eat, log a week, and see where you land.
Important note: any significant changes to your diet, especially if you have medical conditions or specific health goals, should be discussed with a qualified healthcare professional first.