Rainbow Diet

Gut microbiome study links Rainbow Diet foods to good health

The Microbiome Diet!

Certain foods, like olive oil, oily fish, red wine, nuts and seeds, vegetables, fruits and pulses (legumes), consistently promote human health because new research shows they increase numbers of helpful bacteria producing anti-inflammatory and beneficial compounds. These foods are commonplace in the colourful Mediterranean diet. These foods can correct and protect.

Is the wonderful diet you are eating for your good health, or for the good health of your microbiome? As you will see, the two are inexorably linked.

The Healthy Microbiome Diet

A team of researchers from the Departments of Gastroenterology and Genetics at the University of Groningen, Holland have linked specific foods with either increases in gut bacteria promoting gut health and human health, or with gut problems, inflammation and ill health.

1425 people were followed, 331 with inflammatory bowel disease (IBD), specifically ulcerative colitis or Crohn’s, a further 223 with Irritable Bowel Disease, and 871 people with a healthy gut. Daily stool samples were submitted along with a daily dietary questionnaire.

The study looked at bacteria associated with 61 specific foods and 25 clusters of foods (for example, one cluster was meat, dairy, gravy and potatoes).

Helpful bacteria are termed ‘probiotics’. The foods that feed them and increase their numbers are termed ‘prebiotics’.

Foods that promote unfriendly bacteria, inflammation and gut damage

Of little surprise was that processed foods and animal products produced a significant growth in bacteria known to be linked to inflammation – for example to the families, Ruminococcus and Firmicutes.

People who ate foods such as French fries, sugar-rich fizzy soft drinks, mayonnaise and certain processed meats such as hams, bacon, salami and other dried meats caused an increase in Clostridium bolteae, Coprobacillus, and Lachnospiraceae, which not only are known to cause inflammation but are known to damage the gut lining. Drinking coffee caused an increase in Oscillibacter, which is linked to inflammatory bowel disease.

The researchers also linked the consumption of alcohol, spirits and sugar to unfriendly, inflammatory bacteria.

The Rainbow Diet – The Anti-inflammatory diet

The good news was that this was not the case for red wine! Indeed, red wine promoted the numbers of bacteria making crucial short-chain fatty acids (SCFAs) such as butyrate, acetate and propionate. These promote health and are known, for example, to reduce and control inflammation and cholesterol formation, while repairing the gut lining, promoting the immune system and activating vitamin D.

The foods of the colourful Mediterranean Diet were found to be particularly anti-inflammatory and health-promoting. For example, there was a food cluster containing whole grains (including bread), pulses (legumes) such as lentils, peas and chickpeas, nuts and seeds, and fish that promoted commensal bacteria while consistently reducing levels of unfriendly gut bacteria.

One commensal bacterial species was Faecalibacterium. Levels were increased when participants ate whole grains, vegetables, fruits, nuts and oily fish.

Researchers also found that unpasteurised and fermented dairy products increased commensal lactic acid bacteria such as Bifidobacterium, Lactobacillus, and Enterococcus.

The researchers concluded: We identified dietary patterns that consistently correlate with groups of bacteria with shared functional roles in both health and disease. Moreover, specific foods and nutrients were associated with species known to infer mucosal protection and anti-inflammatory effects.’ 

Chris Woollams, former Oxford University Biochemist and author of both the best selling books The Rainbow Diet’ and Heal your Gut – Heal your Body’ added, “Why am I not surprised at these findings? I have consistently advised people to nourish themselves and their friends in the gut for more than 15 years now. On the other hand, we know that if you eat a junk diet, you end up with a junk body. It’s not rocket science.

What is so good about the colourful Mediterranean diet is that it has been around for thousands of years. It is not ‘invented’ like the ‘Keto diet’ or the Paleo Diet. Sardinia has more 80, 90 and 100 year old residents than anywhere else in the world!”

The researchers concluded that eating a more plant-based diet with higher levels of whole grains, nuts and seeds, vegetables and fruits (for polyphenols), oily fish (for SCFAs) could change the makeup of the microbiome to reduce inflammation, improve gut health and overall health. Indeed dietary intervention might be a promising way forward. As Chris has always said, “The Rainbow diet can Correct and Protect”

Further reading:

Go to: Heal your gut – Heal your body

Go to: The Mediterranean diet

Go to: The Rainbow Diet book

Go to: The benefits of Polyphenols


  1. BJM Journals; Gut; Long-term dietary patterns are associated with pro-inflammatory and anti-inflammatory features of the gut microbiome; Laura A. Boite et al; April, 2021


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