Where does 30 come from?
The number comes from the American Gut Project, a large citizen science study. People who ate more than 30 different types of plant a week had more diverse gut microbiomes than people who ate 10 or fewer, although each of those two groups was small, at just over 40 people.1 It is an observed association rather than proof, and 30 is not a magic threshold, but it is a useful, memorable target.
The idea makes sense: different plants contain different fibres and plant compounds, and different microbes specialise in breaking them down. A varied diet feeds a wider range of them.
What counts?
Each different plant counts once a week, however often you eat it. Plants include:
- Vegetables and fruit, fresh, frozen or tinned
- Wholegrains such as oats, brown rice, buckwheat, barley and quinoa
- Beans, lentils and chickpeas
- Nuts and seeds
- Herbs and spices (many people count these as a small fraction each, as you eat less of them)
- Extras such as extra virgin olive oil, coffee, tea and dark chocolate are counted by some, though they add less fibre
Easy ways to get there
- Buy mixes. A bag of mixed seeds, mixed beans or mixed salad leaves adds several plants at once.
- Top everything. A spoonful of seeds or chopped nuts on porridge, yoghurt or salad is an easy win.
- Swap, don't add. Change the grain you usually reach for, or use two kinds of bean in a chilli instead of one.
- Use your freezer. Frozen berries, peas, spinach and edamame make variety easy and cut waste.
- Cook with herbs and spices. They add flavour, polyphenols and points.
Fibre too: UK guidance is 30g of fibre a day for adults.2 Higher fibre intakes are linked with lower rates of several major diseases.3 If you are increasing fibre, go gradually and drink plenty of water, as a sudden change can cause wind and bloating.4
The free 10-day reset download that comes with the book includes a tracker for counting your plants each week: guthealthcookbook.com/
Sources
- McDonald D et al. American Gut: an open platform for citizen science microbiome research. mSystems, 2018. doi.org/10.1128/mSystems.00031-18
- Scientific Advisory Committee on Nutrition. Carbohydrates and Health. Public Health England, 2015. www.gov.uk/government/publications/sacn-carbohydrates-and-health-report
- Reynolds A et al. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. The Lancet, 2019. doi.org/10.1016/S0140-6736(18)31809-9
- NHS. How to get more fibre into your diet. www.nhs.uk/live-well/eat-well/digestive-health/how-to-get-more-fibre-into-your-diet/
