The 30 Plants a Week Rule
Feed gut-microbiome diversity by eating 30 different plants every week
- Difficulty
- Easy
- Time to result
- ~weeks to results
- Steps
- 5
- Confidence
- 90%
The rule reframes healthy eating from 'eat less' to 'eat a wider variety of plants.' The colon houses an ecosystem of bacteria that ferment the plant fibres we can't digest, producing metabolites such as short-chain fatty acids (notably butyrate) that control inflammation, interact with 70% of the body's immune cells living in the bowel, and support the 95% of serotonin made in the gut. Each plant type feeds different species, so diversity matters more than quantity. Eating the same foods on repeat, even 'clean' ones like sweet potato and broccoli daily, limits the fibres available and narrows the microbiome. Targeting 30 different plants a week (roughly five a day, counting nuts, seeds, whole grains and pulses) keeps the ecosystem fed and communicating well with the brain and body.
Origin
Shared by dietitian Sophie Medlin, chair of the British Dietetic Association for London, drawing on gut-microbiome research including the work of John Cryan. Extracted from Deep Dive with Ali Abdaal.
Core principles
- 01Diversity of plants, not volume of food, is what feeds a healthy microbiome
- 02Different fibres feed different bacterial species that each do different jobs
- 03Eating the same 'healthy' foods on repeat still starves key gut bacteria
- 04A varied plant intake produces metabolites (butyrate, serotonin) that reach the brain
- 05Adding plants naturally displaces less-healthy foods
How to run it
- 1
Reframe the goal as variety
Stop counting only calories or single 'superfoods' and instead track how many different plants you eat across the week.
Pro tip Keep a running tally on your phone or fridge; hitting 30 is easier than it sounds once nuts, seeds and grains count.
- 2
Load breakfast with plant diversity
Build a breakfast that already contains five-plus plants, such as a whole-grain base with mixed seeds, nuts and dried or freeze-dried berries.
Pro tip Freeze-dried berries add variety and last in the cupboard.
- 3
Spread plants across the day
Add a handful of nuts mid-morning, two different veg at lunch, fruit in the afternoon and veg again in the evening.
Pro tip Spreading it out makes 30 a week feel achievable rather than a chore.
- 4
Diversify your staples
Rotate grains beyond oats and wheat, swap white rice for whole grain, and add lentils or pulses to bulk out meals.
Pro tip Leaving skins on root vegetables adds both fibre and variety.
Watch out Cutting out whole grains entirely (low-carb) starves crucial bacterial species.
- 5
Let plants crowd out the junk
As you snack more on nuts and fruit, you naturally eat fewer processed snacks, improving the overall pattern.
Pro tip A jar of trail mix in the car replaces impulse sweets.
In the wild
Someone eats sweet potato and broccoli five days a week believing they are being disciplined, yet struggles with focus, low energy and frequent minor infections. Because their plant range is tiny, whole populations of beneficial bacteria go unfed. Widening to 30 different plants a week, without eating more overall, restores microbiome diversity and the metabolites that support brain and immune function.
→ Better focus and fewer bugs without any calorie change, just more plant variety.
Common mistakes
Confusing volume with variety
Eating a large amount of the same few plants still limits the fibres your bacteria receive; the metric is distinct plant types, not quantity.
Relying on supplements instead
Probiotic capsules can't compensate for a monotonous diet; the bacteria need diverse plant fibre to survive once they reach the colon.
Is it for you?
Best for
Busy people with no obvious gut symptoms who want better focus, energy and immunity.
Not ideal for
People with diagnosed gut conditions who need a clinician-tailored treatment diet.
From the transcript
“the most important thing for your gut health is that you're eating 30 different plants a week”
“if you break it down into days you're looking for about five different plants a day”
From the episode
Heal Your Brain: How Your Gut Secretly Controls Your Brain Health - Dietitian Sophie Medlin
Dietitian Sophie Medlin