The true Rainbow Diet, or colourful Mediterranean diet, is naturally a high fibre diet. All those vegetables, nuts, seeds, pulses and fruit could not be anything else. And natural fibre such as lignans, pectins and inulins have a number of important benefits because they increase the numbers of good bacteria in your microbiome.
There are two forms of dietary fibre - soluble and insoluble fibre.
Soluble fibre is water soluble and forms a paste or gel in your gut - this gel is a much loved food (prebiotic) for the commensal (good) bacteria in your gut (probiotics). These bacteria make a vast array of helpful and healthy compounds (1). They rely on the carbohydrates in the soluble fibre. In particular, your good bacteria make a number of Short-Chain Fatty Acids (SCFAs) of which three make up the largest volume - propionate (which can block the formation of cholesterol and is involved in glucose metabolism), actetate (which keeps your gut acidic and healthy, promoting the growth of gut bacteria), and butyrate, arguably the most important of all (which can kill cancer cells in the gut and the body).
Good bacteria make your B vitamins, your vitamin K, your serotonin to keep you happy, glutathione to help you have good oxygen levels, and melatonin to help you get a good night's sleep.
They could not do this without enough soluble fibre.
Soluble fibre feeds and norishes them increasing their volume and diversity, which in turn promotes the immune system (the adaptive immune system). Not surprisingly then, research has shown that people who heat high levels of soluble fibre have the best immune systems.
A high fibre diet also reduces the level of plasma glucose, and people who indulge in high fibre diets live significantly longer than average. Weight loss can also be a benefit.
The gel formed by soluble fibre slows the digestion process, whereas insoluble fibre attracts water making the stools softer and helps move the waste through the intestines.
The fibre in cell membranes prevent the rapid release of sugar from the cells, but over-cooking destroys these cellulose membranes, which is why (for example) raw carrots have a very low Glycemic Index, but cooked carrots have a high GI. Whole brown rice is good for you but eating refined white rice is like eating neat sugar. Ditto pasta, breakfast cereals and various grains.
Glucose rushes can have two disastrous effects, for example glucose can directly feed (and even cause) cancer cells; and high plasma glucose can heighten insulin levels, which in turn stimulate an enzyme (Cox-2) present throughout the body, causing chronic inflammation.
Soluble fibre seems to be able to bind to fats before they are absorbed, reducing plasma cholesterol levels. Gut bacteria use fibre to bind chemicals, heavy metals and hormones to them, removing them effectively from the body.
Soluble fibre consumption and cancer
But just stop and think. People who eat high levels of soluble fibre make butyrate that kills cancer cells, they have the strongest immune systems, they have good digestion, the control their blood sugar better, and they have increased longevity.
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* Read more - Helpful links
Go to: The Mediterranean Diet, fibre and cardiovascular risk
Go to: Examples of healthy fibre
Go to: Butyrate significantly improves your health
* References
1. European Journal of Nutrition, 2018, 57 (1): 1-24; Ian Rowland et al.