The Magic Number 30: Where It Came From and How to Achieve It

This suggestion stems from the 2018 landmark ‘American Gut Microbiome’ study.¹ This study analysed over 10,000 stool samples from healthy individuals residing across 45 different countries, predominantly the United States and the United Kingdom. The results found that those consuming 30 or more different plants each week had greater microbial diversity, one of the key indicators of a “healthy” gut, than those consuming less than 10 plants per week.  

 So, what does this mean for our health?  

The term “gut health” nowadays  appears to be synonymous with a healthy “gut microbiome”. However, while “gut health” is defined as “the absence of gastrointestinal symptoms and disease”, there is no universally accepted profile for a “healthy” gut microbiome. This is due to the large inter- and intra-variability that exist, and the many combinations of the thousands of different microbial species which can reside within the gut microbiome. Instead, in research, a gut microbiome is considered optimal when it is diverse, stable and resilient.²

Have you heard the saying ‘you are what you eat’? When it comes to our gut microbiota, the composition  adapts quickly according to the foods we eat.³ Eating a diverse diet with a variety of plants results in consumption of numerous nutrients and phytochemicals including vitamins and minerals, prebiotics and probiotics, polyphenols, and fibre. Fibre is our gut bugs’ favourite food. It feeds the gut microbiota, increasing the number and types of beneficial bacteria (e.g., Lactobacilli and Bifidobacteria), thus creating more diversity.  

Polyphenols are the chemicals found in plants that give them their vibrant colour, for example, anthocyanidins give the red, purple, and blue colours in foods such as berries, cabbage, and cherries. There are over 8000 types of polyphenols. They provide many different health benefits so eating the colour of the rainbow ensures consumption of a wide range. Polyphenols have been shown to support gut health by encouraging growth of good bacteria by acting similarly to prebiotics. They also have anti-inflammatory properties.^4,5 

Whilst 30 plants a week may sound like a lot, the list of foods that count is broad, and goes far beyond just fruits and vegetables. 

• The same item can only be counted once (so if you eat oats for breakfast every day, this is still 1 point).  
• Different colours = more points. Two red apples = 1 point. 1 red + 1 green apple = 2 points.  

Alarmingly, the most recent National Diet and Nutrition Survey found that less than 0.1% of the UK population follow dietary guidelines such as The Eatwell Guide.^6-7 See the image below for 8 helpful tips for you and your patients on including more plants into your daily menu.         

1. There is no official definition of a “healthy” gut microbiome, however, it is considered optimal when it is diverse, stable, and resilient. 
2. Plant diversity contributes to gut health and overall health due to the range of nutrients it provides.  
3. The number 30 is based on self-reported data and there are no weight recommendations in order to gain a plant point.  
4. Do what is manageable for you or your patients. Start small and increase.  

1. McDonald et al (2018) American Gut: an Open Platform for Citizen Science Microbiome Research, American Society for Microbiology 3(3)
2. Lozupone CA, Stombaugh JI, Gordon JI, Jansson JK, Knight R. Diversity, stability and resilience of the human gut microbiota. Nature. 2012;489(7415):220-230. doi:10.1038/nature11550.
3. De Angelis et al (2019) Cur Med Chem 26(19): 3567-83
4. Singh AK et al (2019) Nutrients 11(9): 2216.
5. Alves-Santos AM et al (2020) Journal of Functional Foods 74: 104169
6. Office for Health Improvement and Disparities (2016) National Diet and Nutrition Survey. Available at: https://www.gov.uk/government/collections/national-diet-and-nutrition-survey (Accessed: 21 February 2025) 
7. Public Health England (2016) The Eatwell Guide. Available at: https://assets.publishing.service.gov.uk/media/5bbb790de5274a22415d7fee/Eatwell_guide_colour_edition.pdf (Accessed: 21 February 2025)