Studies have found that overripe bananas that have brown spots are the worst ones to consume. When bananas ripen, the beneficial starches start to break down and are converted into sugar.
An overripe medium-size banana contains 17.4 grams of sugar whereas a yellow banana of the same size contains just 14.4 grams of sugar. This means there is a 3 grams rise in the sugar from glucose and fructose in the ripened bananas.
The sugar content increases because the starch in the banana which is a complex carb naturally breaks down into simple sugar over time. A yellow banana has 6.35 grams of starch, which goes down to 0.45 grams in overripe bananas.
Overripe bananas also have less fibre. Ripen bananas have 1.9 grams of fibre while yellow bananas have 3.1 grams of fibre, which makes yellow bananas great for digestion.
According to a study published in the Journal Diabetic Medicine, diabetics’ blood sugar did not spike much when they consumed unripe bananas as compared to when THEY consumed overripe bananas.
Last, but not least, the micronutrient levels of overripe bananas also decrease.