The 30 plants a week recommendation — eating 30 different plant foods weekly for gut microbiome diversity — has become one of the most evidence-based and practically accessible nutritional targets available. Research from the American Gut Project found that people eating 30 or more plant types weekly had significantly greater gut microbiome diversity than those eating fewer than 10.
Why 30 different plants, not just 30 servings
The key finding from the American Gut Project was that variety of plant foods — not just total quantity — predicted gut microbiome diversity. Different plant foods contain different types of fibre (fructans, cellulose, pectin, inulin, resistant starch) that feed different gut bacterial species. A monoculture diet of one type of plant fibre, however large, does not produce the bacterial diversity that a diverse array of plants does.
What counts as one plant
All fruits, vegetables, whole grains, legumes, nuts, seeds, and herbs count as separate plants. A sprinkle of mixed herbs on cooking counts as 2-3 plants. A grain salad with quinoa, barley, and bulgur wheat counts as 3 plants. A smoothie with banana, spinach, and flaxseed counts as 3 plants. 30 per week becomes achievable with deliberate variety rather than large volumes.
Practical strategies for 30 plants
Keep a mixed spice rack and use different herbs regularly — one of the easiest ways to add plant diversity with minimal effort. Choose mixed grain products over single grains. Vary your salad leaves weekly. Add seeds (sunflower, pumpkin, sesame, chia) as a regular topping. Vary your fruit by the week. A Friday audit — counting distinct plants eaten that week — quickly identifies easy additions to reach the 30 target.
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Frequently asked questions
Do spices and herbs really count towards the 30 plants a week target?
Yes. The American Gut Project research included herbs and spices as distinct plant foods contributing to diversity. Each different herb or spice counts as one plant. A mixed spice blend counts as the number of individual spices in it. Herbs and spices also contribute polyphenols that act as prebiotics feeding beneficial gut bacteria — their inclusion in the count reflects their genuine microbiome contribution, not just a mathematical convenience.
Can you reach 30 plants a week on a budget without buying lots of different produce?
Yes. Tinned and frozen plant foods count equally with fresh. A bag of mixed frozen vegetables, a tin of mixed beans, a few different grains, and a varied spice rack can account for 15 or more distinct plants at very low cost. Dried legumes such as lentils, chickpeas, and black beans are among the cheapest foods per portion available in UK supermarkets and count as separate plant entries.
How does the gut microbiome diversity from 30 plants translate into health benefits?
Greater gut microbiome diversity is associated with reduced markers of systemic inflammation, better metabolic health outcomes including insulin sensitivity, more stable mood through the gut-brain axis, and more resilient immune function. The mechanism is that diverse plant fibres feed different bacterial species, each producing different short-chain fatty acids — particularly butyrate — that nourish the gut lining and regulate immune and inflammatory responses throughout the body.
Is the 30 plants target equally important for people who already eat a lot of vegetables?
Total vegetable quantity and plant variety are distinct factors. Someone eating large amounts of the same four or five vegetables will have lower microbiome diversity than someone eating moderate portions of 30 different plants. The diversity effect appears to be independent of total fibre intake, meaning variety adds benefit even for people who already eat a high-fibre diet. Rotating your vegetables and grains is therefore valuable regardless of total intake.
Are there any risks to rapidly increasing plant variety and fibre intake?
Increasing dietary fibre rapidly — particularly from legumes and cruciferous vegetables — commonly causes temporary bloating, wind, and altered bowel habits as the gut microbiome adjusts. This settles for most people within two to four weeks. Increasing plant variety gradually over two to three weeks rather than attempting 30 plants immediately minimises digestive discomfort. Adequate hydration is important when increasing fibre, as fibre requires water to move through the bowel effectively.