Fibre is essential in the diet to keep the digestive system in good shape. A lack of fibre causes problems such as constipation and irregular bowel movements, or worse.
Fibre-rich foods such as green leafy vegetables create optimal digestive health by assisting friendly gut bacteria. Certain fruits are also high in fibre. One of these is the banana.
Amazingly, the nutritional content of bananas varies with levels of ripeness. In the unripe state, bananas contain more digestive-resistant starch, which is ideal for optimal gut health.
However, most people prefer to eat sweet, fully ripened bananas, and tend to shun those that appear rather green. Indeed, that an unripe fruit is ‘healthier’ than a ripe one is counterintuitive.
The sugar content of fruits tends mimic their nutrient content. The sweeter the fruit, the more vitamins and minerals are contained. So, sweetness levels generally indicate fruit quality.
However, getting vitamins and minerals are not the only reason why we eat fruits. Dietary fibre is equally as important, and unripe bananas are best for that because of the higher levels of digestive-resistant starch they contain.
Fibre can be either soluble or insoluble, but for health, the fermentability of the fibre is most important. Digestive-resistant starches have low viscosity and therefore resist digestion in the small intestine. Instead, they ferment slowly in the colon.
Resistant starches are prebiotics, feeding healthy gut bacteria. The slow fermentation means less gas is released. They also bulk up stools and help to maintain regular bowel movements.
Because digestive-resistant starches are indigestible, they do not cause spikes in blood sugar levels. Indeed, they help to improve insulin regulation, reducing the risk of insulin resistance.
Mango and papaya are two other fruits high containing digestive-resistant starch when unripe. Vegetables with this beneficial fibre are lentils, white beans, potato and tapioca starch, and brown rice flour.
For ordinary white potatoes – which raise blood sugar levels quickly – cooling them in the refrigerator actually alters their molecular structure, turning a bad food into a healthier one containing digestive-resistant starch.
Green bananas are practically all starch – up to 70 to 80 per cent dry weight. Most of this starch is digestive-resistant starch, which works wonders for treating diarrhoea. As the they ripen, the starch turns to sugars such as fructose.
Green papaya are rich in antioxidants, fibre and an enzyme called papain. This enzyme aids protein digestion and eases inflammation. But be careful: unripe papaya contains latex, to which some people are allergic.
As for unripe mangos, the Langra variety contains as much vitamin C as nine lemons or three oranges, on top of digestive-resistant starch. The acids in these green fruits boost bile secretion, act as an intestinal antiseptic, and as a liver tonic.
However, try not to eat more than one unripe mango per day because of the risk of throat irritation and indigestion. Also, never drink cold water immediately after eating green mango because the water coagulates mango sap, which can cause irritation.