Plant diversity & fibre

Eating a wide variety of plants and more fibre is one of the best-supported, cheapest things you can do for your gut and long-term health — no test required.

Start today

Add one plant type you have not eaten this week to your next meal — a handful of beans, a new vegetable, some seeds or herbs.

Why it matters

Fibre and plant variety feed a diverse gut microbiome and are linked to lower long-term disease risk. It is the free, universal core underneath the expensive "personalised nutrition" marketing.

The evidence (moderate)

Higher fibre intake is consistently linked to lower all-cause and cardiovascular mortality in large dose-response meta-analyses (the strongest part of this picture), and greater plant diversity is associated with a richer gut microbiome. A small randomised trial of fermented foods increased microbiome diversity and lowered inflammatory markers over ~10 weeks.

Where it's thin: Much of the microbiome evidence is observational (association, not proof), and the popular "30 plants a week" target comes from observational data, not a trial testing that exact number. Whether a paid personalised microbiome or after-meal "score" improves outcomes beyond general advice — more fibre, more variety, fewer ultra-processed foods — is not yet established.

How to do it

• Aim for a wide variety of plants across the week — vegetables, fruit, legumes, nuts, seeds, whole grains, herbs and spices all count
• Add one extra plant type to a meal you already eat (beans in a salad, seeds on yoghurt)
• Most people eat far too little fibre — build meals around plants, not just protein and starch
• A useful target is ~25–30 g fibre/day (many adults get about half that); increase gradually and with water to avoid bloating
• The "30 different plants a week" idea is a memorable diversity heuristic — count types, not amounts; different-coloured veg, herbs and spices all count
• Include some fermented foods (yoghurt, kefir, sauerkraut, kimchi) most days
• Different fibres (soluble, insoluble, resistant starch) feed different gut microbes, so variety matters as much as total grams
• Legumes and whole grains are the highest-yield swaps for both fibre and diversity
• A small RCT found fermented foods raised microbiome diversity and lowered inflammatory markers over ~10 weeks — promising, not definitive
• The "30 plants" number comes from observational microbiome data (association), not a trial proving that exact target — treat it as a helpful nudge, not a validated dose
• Higher microbiome diversity correlates with health markers, but causation runs both ways, and commercial microbiome "scores" are not proven to guide diet better than simply eating more varied plants
• After-meal (postprandial) glucose and fat responses vary a lot between people — but you do not need a paid test to benefit from the universal advice: more fibre, more plant variety, fewer ultra-processed foods

Safety — read before starting

Increase fibre gradually with plenty of water to avoid bloating. If you have a diagnosed gut condition (IBD, significant IBS, recent gut surgery), change fibre and fermented-food intake with your clinician.