Eating 30 different plant foods a week, not 30 portions of the same five, is linked to greater gut microbiome diversity than eating fewer than 10 types. That finding comes from the American Gut Project, one of the largest citizen-science microbiome studies ever run, and it has become one of the most repeated pieces of gut health advice for good reason.
This guide covers what actually counts as a “plant,” what doesn’t, and a realistic way to track it without turning breakfast into a spreadsheet exercise.
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Table of Contents
Where the “30 plants a week” idea comes from
The figure comes from an analysis of American Gut Project data (McDonald et al., 2018), which sequenced stool samples from thousands of participants alongside detailed diet records. People who reported eating more than 30 different plant types per week had significantly more diverse gut microbiomes than those eating 10 or fewer types.
Diversity itself is not directly a health outcome, but it is consistently associated with better markers of gut and metabolic health in other research. A more diverse microbiome generally means more bacterial species capable of fermenting a wider range of fibres into beneficial compounds.
The number 30 is not a hard biological threshold. It is the point in the data where the diversity benefit became clearly visible, and it has stuck as a practical, memorable target.
What counts as a “plant”?
This is where most people underestimate themselves. A “plant” in this context is any distinct plant-based food, not just vegetables.
| Category | Examples |
|---|---|
| Vegetables | Broccoli, spinach, onion, carrot, pepper, courgette |
| Fruits | Apple, blueberry, banana, orange, strawberry |
| Wholegrains | Oats, brown rice, quinoa, wholemeal bread, rye |
| Legumes and pulses | Lentils, chickpeas, black beans, edamame |
| Nuts and seeds | Almonds, walnuts, chia, flaxseed, sunflower seeds |
| Herbs and spices | Basil, turmeric, garlic, ginger, cumin, mint |
Most practical frameworks derived from the original research count dried herbs and spices, which makes hitting 30 considerably easier than counting vegetables alone. A curry with five different spices in it can genuinely contribute five separate plants.
What doesn’t count, or counts less than people think
The same plant eaten multiple times in a week only counts once. Eating porridge oats every morning is one plant, not seven, however consistent the habit.
Highly refined plant-derived ingredients, white flour, sugar, and most vegetable oils, do not meaningfully contribute to microbiome diversity, even though they technically originate from plants. The whole-food fibre and micronutrient content is what matters, and refining strips most of it out.
Ultra-processed snack foods that happen to contain a plant-derived ingredient somewhere on the label are not a practical route to variety. A biscuit containing wheat flour is not doing the same job as a bowl of oats.
Why variety matters more than volume
Different plant fibres feed different bacterial species. Inulin from onions and garlic favours Bifidobacterium. Resistant starch from legumes and cooled potatoes favours butyrate-producing bacteria. Pectin from apples supports a different fermentation profile again.
Our guide to prebiotic fibre covers these mechanisms in more depth if you want the science behind why diversity, not just total fibre intake, drives a more resilient gut environment. Eating the same high-fibre food every day still leaves large parts of your microbiome under-fed.
This matters more with age. Gut microbiome diversity naturally declines from your 40s onward, which is one reason dietary variety becomes more, not less, important over time.
Simple ways to increase your plant count without extra cooking
- Buy frozen mixed vegetables rather than a single frozen vegetable. Most bags contain 4 to 6 different plants in one scoop.
- Add a spoonful of mixed seeds to porridge, yoghurt, or salad. Three or four seed types in one jar is an easy way to bank several plants at once.
- Rotate tinned beans and pulses rather than buying the same one repeatedly. Chickpeas one week, black beans the next, butter beans after that.
- Use a spice rack properly. Adding two or three dried herbs or spices to a meal you already cook regularly is a genuinely easy win.
- Keep a rotating fruit bowl rather than buying the same two fruits. Frozen berries mixed varieties count as multiple plants in one bag.
Two of our other guides make this easier in practice. High fibre snacks like chickpeas, almonds, and mixed berries double as plant variety, not just fibre. And a high fibre breakfast built around oats, chia, and fruit can bank four or five plants before you’ve left the kitchen.
A note on Biome Bliss and plant variety
Biome Bliss is fermented with organic ginger and a blend of 25 further organic herbs and fruits, alongside its organic honey and apple juice base. That means a single daily dose contributes a genuinely wide range of distinct plant ingredients toward weekly variety, on top of the six probiotic strains it delivers.
You can see the full botanical breakdown, including every herb and fruit in the formula, in our guide to what’s in Biome Bliss.
Frequently asked questions
What counts as one of the 30 plants a week?
Any distinct plant-based food: vegetables, fruits, wholegrains, legumes, nuts, seeds, and dried herbs or spices. Eating the same food repeatedly only counts once. A meal with five different spices can contribute five separate plants toward the weekly count.
Is 30 plants a week actually necessary for gut health?
American Gut Project research found people eating more than 30 plant types per week had significantly more diverse gut microbiomes than those eating 10 or fewer. Thirty is not a strict biological threshold, but it reflects the range where the benefit became clearly visible in the data.
Do herbs and spices really count as separate plants?
Yes, in most practical frameworks based on the original research. This makes 30 considerably more achievable, since a single well-spiced meal can contribute several plants at once, not just the vegetables on the plate.
Can I get enough plant variety without eating more food overall?
Yes. Variety is about the number of different plants, not the total quantity eaten. Swapping which vegetables, beans, or spices you use week to week, rather than eating more food, is the more realistic route to 30.
Why does plant variety matter more than total fibre intake?
Different plant fibres feed different bacterial species. Eating a high volume of one fibre type feeds a narrower range of bacteria than eating a smaller amount of many different fibre types. Diversity of input supports diversity of the microbiome itself.
Does frozen or tinned produce count toward plant variety?
Yes. Frozen and tinned vegetables, fruit, and pulses retain most of their fibre content and count the same as fresh. Mixed frozen vegetable bags and rotating tinned beans are two of the easiest ways to add variety without extra cooking effort.
References
- McDonald D, Hyde E, Debelius JW, et al. American Gut: an Open Platform for Citizen Science Microbiome Research. mSystems. 2018;3(3):e00031-18. pubmed.ncbi.nlm.nih.gov/29795809
- Wastyk HC, Fragiadakis GK, Perelman D, et al. Gut-microbiota-targeted diets modulate human immune status. Cell. 2021;184(16):4137-4153. doi:10.1016/j.cell.2021.06.019
This article is for informational purposes only and does not constitute medical advice. If you have digestive symptoms or a diagnosed gut condition, speak with your GP before making significant dietary changes.
