Some people prefer their bananas yellow with a tinge of green, while others prefer the sugary sweetness of a banana with brown spots on the peel.
But it’s not just the flavor that is different, because there are distinctive effects on your body and health that depend on ripening …
Unripe green bananas have been shown to have starch that is 20 times stronger than ripe bananas.
This is a form of starch that the body struggles to break down (resists the digestive process), so it passes directly through the intestines.
This slows the rate at which the carbohydrates in fruit are converted into glucose and absorbed into the blood.
During ripening, the starch of a banana is converted into sugar: 3.2g / 100g of an unripe banana to 12g / 100g of a ripe banana
A green banana typically has a glycemic index (GI) of 30, compared to 58 for a ripe banana.
Not only is resistant starch good for stabilizing blood sugar levels, but the “good” bacteria in the colon also feed on it.
In turn, they boost digestive enzymes that help us digest carbohydrates and absorb vitamins from food, as well as protect us from any hostile microorganisms.
Professor Gordon Carlson, a consultant gastric surgeon at the Salford Royal NHS Foundation Trust, told Good Health that he eats a relatively unripe banana every day to improve his gut health. The benefits of green bananas were confirmed in a major review of 18 studies on their nutrition, published in the journal Nutrients in 2019.
This found that green bananas can help with gastrointestinal symptoms (such as diarrhea and constipation) and diseases (such as intestinal cancers).
A green banana typically has a glycemic index (GI) of 30, compared to 58 for a ripe banana
They can also help prevent or treat type 2 diabetes.
Unlike other foods, bananas contain a resistant form of starch that is increased rather than broken down by heating.
In fact, a study published in the Malaysian Journal of Nutrition in 2018 found that hot green bananas increased their resistant starch content.
Other research has shown that refrigeration of refrigerated green bananas increases resistant starch by an additional 50%.
The cooling process causes the starches to form a new structure that is even more resistant to digestion (called ‘starch retrogradation’).
During ripening, the starch of a banana is converted into sugar: from 3.2g / 100g of an unripe banana to 12g / 100g of a ripe banana.
“This is what makes them a good fast-release energy source for athletes,” says dietitian Dr Sarah Schenker.
The lower amounts of resistant starch also mean that yellow bananas are easier to digest. If you have digestive problems, green bananas can make you feel bloated or bloated.
Dr. Schenker suggests that the health benefits of yellow bananas outweigh those of green ones.
Bananas contain several compounds, such as carotenoids, which are linked to eye health and cancer prevention, and which become more “bioavailable” [available to the body] when the banana ripens, ‘he says.
“With less starch to break down, your digestive system will absorb nutrients faster.”
Bananas contain B vitamins as well as antioxidant vitamins A and C, as well as the minerals iron, magnesium, manganese and potassium.
Some of these micronutrients are lost as the banana ages, but the levels of antioxidants, which help support the immune system, peak.
Studies, including one published in 2014 in the International Food Research Journal, have shown that vitamin C levels increase with the ripening process, but decrease as the banana gets too ripe.
“These antioxidants exist to protect the fruit from consumption and tend to grow as the fruit ripens,” explains Dr. Sangeetha Thondre, a professor of nutrition at the Oxford Brookes Center for Nutrition and Health.
Yellow with brown spots
Brown spots on a very ripe banana indicate that even more starch has been converted to sugar.
Scientists have found that a fully ripe banana produces a substance called tumor necrosis factor (TNF) which has the ability to fight abnormal cells and boost our immunity against cancer.
In a 2009 study published in the journal Food Science and Technology Research, scientists at Teikyo University in Japan found that dark-spotted bananas were eight times more effective at boosting the power of white blood cells (which fight infection) than green-skinned bananas.
They reported that the degree of the fruit’s anticancer effect corresponds to the degree of ripeness – the more stains a banana has, the greater its immunity-boosting power.
Bananas produce ethylene gas, a natural compound that regulates the ripening process, causing them to turn brown.
This changes their texture and flavor as well as their nutritional value. When a banana gets overripe, much of the starch is converted into sugars, making it an excellent natural source of sweetness.
Dr. Schenker recommends using brown bananas in cooking and freezing them to blend in a blender to make sugar-free ice cream.
“Using overripe bananas in place of sugar is a healthier way to sweeten food, as bananas provide several essential nutrients: potassium, vitamin B6, folic acid and some vitamin C,” he says.
Eventually, overripe bananas can start fermenting, losing many of their nutritional benefits. They may start to smell more of alcohol than sugar and may contain up to 0.5g of alcohol per banana.
Laboratory studies have shown that you can extract ethanol (alcohol) from extremely ripe bananas, but only after adding yeast and sugar.
Try hot sandwiches
Here, Sophie Medlin of City Dietitians in London evaluates various “healthy” hot sandwiches and we then evaluated them.
Tesco free from
4 sandwiches of 70g, £ 2.20, tesco.com
Claim: “Gluten, wheat and milk free”.
Per sandwich: 161 calories; saturated fat 0.2 g; sugar 12.2 g; fiber 6.3 g; protein 2.8 g.
Verdict: A mix of gluten-free grains, fibrous psyllium husk, and bamboo fiber provides 21% of your daily fiber. Butter and milk were replaced with rapeseed oil and dried egg white.
Health Rating: 8/10
Taste: Pleasant, sticky with fruit and cinnamon, but very dry. 4/10
Seriously low in carbohydrates
4 rolls of 55g, £ 3.99, seriouslowcarb.com
Claim: ‘A fraction of the carbohydrates of a regular hot cross bun. High in protein and fiber. ‘
Per burn: calories, 113; saturated fat 1.2 g; sugar 4.2 g; fiber 4.6 g; protein 10.7 g
Verdict: Using a low-carb, high-protein wheat flour, these sandwiches have 80% fewer carbs than regular sandwiches. The low calorie sweetener erythritol can cause bloating.
Health Rating: 6/10
Taste: too spicy; minimal fruit. 2/10
Seriously low in carbohydrates
Sainsbury’s be good to yourself
6 sandwiches of 70g, £ 1.10 sainsburys.co.uk
Claim: “Less than 3% fat”.
Per sandwich: 186 calories; saturated fat 0.7 g; sugar 11.6 g; fiber 1.9 g; protein 5 g
Verdict: These are lower in calories and fat than some sandwiches, and there are several ultra-processed ingredients.
Health Rating: 2/10
Taste: Juicy but heavy and a little dry. 3/10
4 sandwiches, £ 1.65 waitrose.com
Claim: “Made with wholemeal flour”.
Per sandwich: 187 calories; Saturated fat 1.5 g; sugar 12.4 g; 4g fiber; protein 6.7 g
Verdict: Not all the extra fiber as you might expect, just 13% of the daily requirement and three teaspoons of sugar, most of it coming naturally from the fruit, but also some dextrose.
Health Rating: 6/10
Taste: First quality fruit. 7/10