By Dr. Mercola
Are you getting enough fiber in your diet? If not, your health may suffer in more ways than one. A common sign your diet is lacking in fiber is constipation and irregular bowel movements, but that's really just the tip of the iceberg.
Fiber-rich foods like vegetables promote optimal gut health by nourishing beneficial gut bacteria. Certain fruits are also high in fiber, including underripe bananas, papayas and mangoes.
These fruits have yet another feature that makes them interesting. Their nutritional content changes depending on their ripeness, and in their unripened state, they contain higher amounts of digestive-resistant starch, which is important for optimal gut health.1
The idea that an unripe fruit might be healthier than a ripe one may seem seriously counterintuitive.
The sugar content of a fruit is typically used as an indicator of quality — not because the sugars are in and of themselves necessarily an indicator of quality, but they're typically associated with the plant's mineral content. Hence, it can be used as a marker of quality.
To measure sugar content, a refractometer or so-called Brix meter is used. The most common Brix meters measure on a scale of 0 to 32 degrees Brix, and the sweeter the fruit, the higher the nutritional content is thought to be.
However, in the case of mango, its vitamin C content is actually much higher in the unripe fruit than in the ripened one. Vitamins and minerals are also not the sole reason for eating fruits though. Fiber is also important, and in some cases unripe fruit is a better option.
What's so Great About Digestive-Resistant Starch?
Fiber is typically classified as either soluble or insoluble. However, from a health standpoint, the fermentability of the fiber is what's really important. Digestive-resistant starches are low-viscous fibers that resist digestion in the small intestine and slowly ferment in your large intestine.2
Here, resistant starches act as prebiotics, feeding healthy bacteria. Due to their slow fermentation, they won't make you gassy. They also add significant bulk to your stools, and help you maintain regular bowel movements.
Best of all, since they're indigestible, resistant starches do not result in blood sugar spikes. In fact, research suggests resistant starches help improve insulin regulation, reducing your risk of insulin resistance.3,4,5,6
Besides underripe banana, papaya and mango, other foods high in resistant starch include white beans, lentils, seeds and products like potato starch, tapioca starch and brown rice flour.
(Interestingly, cooking a normally digestible starch such as potato or pasta and then cooling it in the refrigerator will alter the chemistry of the food, transforming more of it into resistant-type starch.7)
As noted by Authority Nutrition, "before it ripens, a banana is almost entirely starch, which composes up to 70 to 80 percent of its dry weight. A large part of this starch is digestive-resistant starch. As the banana ripens, the amount of starch and resistant starch decreases and is converted into sugars."8
Because of their high-resistant starch content, green bananas can be used to safely treat diarrhea in children and adults.
Most people don't like the taste and texture of unripe banana, but when prepared properly and combined with other foods it can be quite tasty. Here's a sample recipe for a green banana salad from Cooks.com:9
Green Banana Salad (eight servings)
• 2 cups water
• 1 teaspoon (tsp.) salt
• 3 green (unripe) bananas, peeled
• 2 medium carrots, shredded
• 1 small cucumber, sliced
• 1 avocado, cubed
• 1 tomato, chopped
• 1 celery stalk, sliced
1. Place bananas, water and salt in a pot and bring to a boil.
2. Reduce heat, cover and simmer for about five minutes or until the bananas are tender.
3. Drain the water and allow bananas to cool.
4. Cut the bananas into one-half-inch slices and toss with remaining ingredients and vinaigrette dressing (below). Chill and serve.
• 1/3 cup virgin olive oil
• 1 clove garlic, chopped
• 1/2 tsp. dark mustard
• 2 tablespoons (Tbsp.) wine vinegar
• 1 tsp. salt
• Dash of pepper
Like bananas, there are some notable differences between ripe and unripe papaya. While both ripe and green (unripe) papaya are rich in antioxidants, fiber and papain, an enzyme that helps with protein digestion and dampens inflammation, green papaya contain higher amounts of papain and potassium.10
Caution is in order though, as unripe papaya contains latex fluid, which may cause an allergic reaction in some individuals, so please be aware of this before you try it. Green papaya is also contraindicated for pregnant women, as it promotes uterine muscle contractions.
On the other hand, women with irregular menstrual cycles may benefit from unripe papaya juice for this same reason.
Perhaps even more so than unripe banana, green papaya typically needs to be incorporated into a recipe with other ingredients in order to satisfy the taste buds. Here's a sample recipe from The New York Times:11
Green Papaya Salad
• 1 large clove of garlic, peeled
• ¼ tsp. salt
• 1 Tbsp. dry-roasted salted peanuts (plus additional for garnish)
• 2 fresh bird chilies or serrano chilies, sliced
• 2 Tbsp. fresh lime juice
• 1 to 2 Tbsp. fish sauce (nam pla or nuoc nam), to taste
• 2 plum tomatoes, 1 large round tomato or 8 grape tomatoes, coarsely chopped
• 1 small to medium green (unripe) papaya (for a total of 4 to 6 cups)
• 1 Tbsp. dried shrimp
• ½ pound long beans, trimmed and cut into 1.5-inch lengths
• Lettuce for serving
1. Using a blender or mortar, mix garlic, salt, peanuts, chilies, sugar and shrimp (if using) into a paste. Transfer to a large bowl and mix in lime juice and fish sauce.
2. Lightly crush tomatoes and beans (if using) with a fork, then add to bowl and mix lightly.
3. Peel and coarsely grate the green papaya. Discard the seed and inner membrane.
4. Lightly fold in the papaya with the rest of the mixture. Season to taste.
5. Line bowl with lettuce leaves and add the papaya salad. Sprinkle with peanuts and serve.
Surprising Health Benefits of Green Mango
There are over 500 varieties of mango, some of the most popular of which include Malda, Alphonso, Langra, Sipia, Sukul and Bumbaiya. Interestingly, unripe mango is an exceptionally rich source of vitamin C. Green (unripe) Langra mango contains as much vitamin C as 35 apples, nine lemons or three oranges.12
I have seven mango trees in my yard that are just about ready to ripen and look forward to trying them underripe. In India, green mango is used as a natural remedy for:
• Gastrointestinal (GI) disorders: Green mango, eaten with salt and honey is used to treat a range of GI problems, including diarrhea, dysentery, piles, morning sickness, indigestion and constipation.
• Liver problems: The acids in unripe mango increase bile secretion and act as an intestinal antiseptic. It also helps purify your blood and acts as a liver tonic. Green mango with honey and pepper is used for stomach ache due to poor digestion, hives and jaundice.
• Blood disorders: The high vitamin C content of unripe mango helps improve blood vessel elasticity and increases formation of new blood cells. It also aids absorption of iron and decreases bleeding. According to the Indian magazine Deccan Herald:13
"Eating an unripe mango daily during the summer season prevents ... infections, increases body resistance against tuberculosis, cholera, dysentery, anemia etc.
It tones the heart, nerves and cures palpitation of the heart, nervous tension, insomnia and weakness of the memory ... Eating raw mango with salt quenches thirst and prevents loss of sodium chloride and iron during summer due to excessive sweating. It tones up the body and helps one to tolerate the excessive heat."
As with green papaya, there's a caveat. Avoid eating more than one unripe mango per day, as it may cause throat irritation and/or indigestion when eaten in excess. Also avoid drinking cold water immediately afterward, as it coagulates the sap, thereby increasing the risk of irritation.
Green Mango Salad
If the idea of eating green mango with salt and honey — as is traditional in India — doesn't appeal to you, here's a sample recipe for green mango salad from Bon Appétit:14
Green Mango Salad (eight servings)
• 2 red or green Thai chilies with seeds, chopped
• 1 clove garlic, chopped
• ½ cup fresh lime juice
• ¼ cup fish sauce (nam pla or nuoc nam)
• 2 Tbsp. olive oil
• 4 green mangoes, julienne cut
• 2 medium shallots, sliced
• ½ cup unsalted, dry-roasted peanuts, chopped
• ½ cup fresh cilantro
• ¼ cup fresh mint leaves
• 2 Tbsp. toasted dried shrimp (optional)
• 2 Tbsp. toasted sesame seeds
• Natural salt, such as kosher or Himalayan salt
1. Using a blender, purée chilies, garlic, lime juice, fish sauce and olive oil.
2. Toss mangoes, shallots, peanuts, cilantro, mint, dried shrimp (if using) and sesame seeds in a large bowl and fold in the purée. Salt to taste.
The Importance of Fiber for Health
Remember, fiber is an important component of your diet that can go a long way toward improving your gut microbiome. This in turn will help prevent health problems associated with leaky gut syndrome. Some of the most important byproducts from the fiber fermentation process are short-chain fatty acids like butyrate, propionate and acetate. These short-chain fats:
- Help nourish and recalibrate your immune system, thereby helping to prevent inflammatory disorders such as asthma and Crohn's disease15,16
- Increase specialized immune cells called T regulatory cells, which help prevent autoimmune responses. Via a process called hematopoiesis, they're also involved in the formation of other types of blood cells in your body
- Serve as easy substrates for your liver to produce ketones that efficiently fuel your mitochondria and serve as important and powerful metabolic signals
- Stimulate the release of a gut hormone known as peptide YY (PYY), which increases satiety, meaning it helps you feel fuller17
- Butyrate in particular affects gene expression and induces apoptosis (normal programmed cell death), thereby decreasing your risk of colon cancer
Fiber Differentiates 'Good' Carbs From the 'Bad'
Grains, rice, pasta, potatoes, fruits and vegetables are all carbohydrates. However, from a health standpoint they're not created equal, and it's the fiber content that differentiates "good" carbs from the "bad." Most all vegetables and certain fruits are very high in fiber, which means they're very low in net carbs, and when it comes to carbs, it's the net carbs you need to pay careful attention to.
Vegetables typically top the list in terms of high fiber content, but as you can see, certain fruits can fit the bill as well, while adding a bit of "culinary adventure" to your cooking. While there are individual differences, as a general rule, most people could benefit by:
- Restricting net carbs to less than 50 grams per day (if you exercise a lot or are very active, you might be able to increase it to 100 grams). To determine your net carbs, simply subtract the fiber from the total carbs, and that's your total non-fiber or "net" carbs
- Increasing fiber to approximately 50 grams per 1,000 calories