Why Plant Variety Matters More Than You Think - The Science Behind 30 Plants a Week

Where did the idea of 30 plants a week come from?

If there is one dietary change that you might consider, make it this one. Eat 30 different plants per week.

And there are very good reasons for this: the evidence comes from the American Gut Project, one of the largest gut bug (gut microbiota) studies to date. When researchers compared people eating a wide variety of plant foods each week with those eating very few, they found a clear pattern: people eating 30 or more different plants had more diverse and healthier gut bugs. 1

These folk had more good gut bugs like Fred (to give him his full name, Faecalibacterium prausnitzii) and a broader pool of species — all signs of a healthy gut bug community.12

What happens when you eat 30 plants a week?

Over time, increasing the range of plants you eat increases the diversity of gut bug species rather than simply enlarging it. A more varied diet encourages a broader range of species to establish and persist, creating a system that is more stable, resilient, and adaptable. Greater gut bug diversity is consistently associated with better metabolic regulation, strengthened immunity, and lower levels of inflammation.

In a randomized cross-over trial in adults with chronic kidney disease, a high-diversity plant-based diet targeting 30 or more unique plant foods per week shifted the gut microbiome toward increased production of beneficial short-chain fatty acids and reduced overall symptom burden.3

These are slow, cumulative processes rather than dramatic short-term shifts, and they reduce the long-term risk of conditions such as type 2 diabetes, heart disease, and even mood disorders.245 People often describe practical changes as well: more regular bowel habits, fewer digestive symptoms, and a steadier relationship with hunger and satiety.

In the long term, this translates into a gut bug community that is better able to handle disruptions such as illness, stress, travel, or short periods of dietary change without losing its overall function. In this sense, eating a wider range of plants is a way of supporting your body over time — one that quietly influences metabolism, immunity, and overall resilience.

How do plants help gut bugs?

Plants support gut bugs in two main ways: by providing fibre and polyphenols. These work differently, but together they shape both the health, composition and diversity of your gut bug community.

Fibre: feeding gut bugs and building diversity

Most of the fibre in plants passes through your small intestine undigested and reaches the large bowel, where it is food for your gut bugs. When gut bugs digest and ferment fibre, they produce short-chain fatty acids (SCFAs), including butyrate, propionate, and acetate. You can’t make these essential compounds, that’s why you need healthy gut bugs and why you need to feed them well.

Short chain fatty acids perform many essential roles. They help maintain the integrity of the gut lining, support immune signalling, and keep inflammation in check. Butyrate is a primary fuel source for the cells lining the colon and is closely linked with a healthy gut barrier.67

Different plants contain different types of fibre. The greater the variety of plants you eat, the broader the range of fibres you provide — and the wider the range of gut bugs that thrive in your gut. This is one of the main reasons diversity of plants, rather than sheer quantity, is so strongly associated with diversity of gut bugs.48

Polyphenols: plant compounds that support gut bugs and human health

Polyphenols, also known as plant antioxidants, are a large family of plant compounds responsible for many of the colours, flavours, and protective properties of plants. They are found in foods such as berries, herbs, spices, nuts, seeds, vegetables, tea, and coffee. We have a table of the polyphenol content of foods under macronutrients here.

Unlike most vitamins and minerals, many polyphenols are poorly absorbed in the small intestine. Instead, they reach the large bowel, where gut bugs transform them into smaller, biologically active compounds. In this way, your gut bugs don’t just benefit from polyphenols — they help unlock their effects for you. These by-products help regulate inflammation, support your metabolism and contribute to the body’s antioxidant systems.74

Different plants provide a range of fibres and polyphenols. The greater the plant mix that you eat, the greater the diversity of your gut bugs and the greater the preponderance of good compared to bad gut bugs.

You feed your gut bugs with fibre — and they in turn produce chemicals for you, that you must have for health and happiness

What do your gut bugs do for you?

A healthy, diverse gut bug community is consistently associated with stronger immune balance, lower levels of chronic inflammation, and better metabolic health. Their influence extends well beyond the gut itself.25

Gut bugs play a role in regulating hormones involved in appetite and energy balance, including GLP-1, which is part of the body’s natural system for controlling hunger and blood sugar handling. They also contribute to the production of short-chain fatty acids that influence how sensitive your tissues are to insulin and how efficiently energy is used.67

There is also a well-described connection between gut bugs and the brain. Some of the chemicals produced during fibre fermentation influence neurotransmitter pathways, including those involved in serotonin signalling. This is one reason why dietary patterns that support gut bug diversity are often associated with improved mood and a greater sense of wellbeing.5 Taken together, this means that feeding your gut bugs well is not a narrow “gut health” strategy — it is part of a broader system that links digestion, immunity, metabolism, and brain function.

How do poor gut bugs affect you?

When gut bug diversity is low and a small number of species dominate, the balance shifts in less helpful directions. A less diverse gut bug community is associated with higher levels of bad gut bugs, increased inflammation, and poorer metabolic control.4

A consequence is increased permeability of the gut lining, sometimes referred to as “leaky gut,” where bacterial components pass into the bloodstream. This stimulates immune responses that, over time, contribute to chronic, low-grade inflammation and disease.

Poor gut bug profiles have also been linked with weight gain, insulin resistance, and a higher risk of metabolic conditions such as type 2 diabetes and heart disease.25 This does not mean gut bugs act in isolation — sleep, stress, physical activity, and overall diet all play a role — but gut bugs appear to be one of the central mediators between what you eat and how your body responds to it.

In practical terms, diets that are narrow, highly processed, and low in plant variety, favour a smaller, less resilient gut bug community. Over time, your health suffers and your body’s ability to recover may worsen, particularly during periods of illness or stress.

What does it take to eat 30 plants a week?

The benefits of eating a greater variety of plants come from long-term patterns, not short-term challenges. The aim is to gradually widen the range of plants you eat and to keep that variety in place over months and years. If you don’t achieve 30 different plants a week, don’t feel a failure, try for 20 different plants and if it’s a bad week, at least try for 10 different plants that week.

This is not a call to eat a restrictive diet or for vegetarian eating. Plant variety works best as part of a balanced meal that includes adequate protein and natural fats, whether from meat, fish, eggs, or dairy. The goal is expanding your diet, not excluding healthy food.

Each different plant counts once per week, while portion size is not fixed, a good starting point, is that one plant “helping” is approximately a handful in size. Eating seven apples during a week counts just as one plant. Plants include all vegetables, fruit, legumes, whole grains, nuts, seeds — and yes, herbs and spices too. Herbs and spices are especially useful as they are rich in polyphenols. If you eat a variety of herbs and spices in a single meal, this counts as one plant helping.

Your aim is simply to keep adding variety. Thirty plants a week sounds ambitious — until you start counting. Here’s a recipe of a vegetable tray bake, which in one meal gives you 9 different plants, the herbs and spices counting as one plant.

Tray Roasted Vegetable Bake

(9 plants in one meal)

This is a simple tray-bake we make regularly. It’s a good example of how quickly plant variety adds up without thinking too hard about it.

Vegetables used

• Brussels sprouts
• Sugar snap peas
• Cauliflower
• Celeriac
• Broccoli
• Tomatoes: A mix of cherry, red, yellow, and large
• Onion
• Garlic
• Herbs-thyme and oregano-to taste (Salt and pepper, olive oil to taste)

How it’s made

Chop the vegetables. Place the vegetables into a large roasting tray lined with foil (to keep the tray clean), toss with herbs and spices, and season well. Drizzle with extra virgin olive oil. If you like spicy food, coat the vegetables with harissa paste. Roast for 40 minutes at 200 degrees (400F), until soft, caramelised, and slightly crisp at the edges. Turn at 20 minutes. Serve with either meat, chicken, or fish for a balanced meal. You can experiment with your own mix of vegetables and make seasonal changes.

For your pudding, add a bowl of berries and cream, (strawberries, blackberries and raspberries), sprinkled with smashed walnuts.

You will have eaten a total of 13 plants in one meal! You can experiment with your own mix of vegetables and make seasonal changes. Now, you only need 3 different plants for the next 6 days, to reach your goal of 30 different plants a week.

Eating a wider range of plants is not about following a dietary trend. It is about supporting your very own biological system, your body and your gut bugs. Interconnected systems that influence how your body functions, how it handles food, stress, and how it determines your health. Variety builds better health — in your gut bugs, and in you — and it does so through ordinary meals, repeated consistently, rather than dramatic interventions.