And even better if at stage 5 of ripeness ...
Who would have thought that bananas promote our gut health, helping grow beneficial bacteria that ultimately strengthens our bones and delays neural degeneration in our brain?
It all starts with inulin, which is in bananas and which begins digestion only when it reaches our gut.
Resistant starches - prebiotics pass to our gut
Inulin is a term applied to a heterogeneous blend of naturally occurring carbohydrates found widely distributed in plants, notably in chicory root. Oligofructose is a subgroup of inulin. For example, bananas contain both inulin and oligofructose, neither of which are digested in the upper gastrointestinal tract.
These types of carbohydrates are called "resistant" as they are resistant to being digested in our stomach (therefore, they have a reduced caloric value). They are also called "prebiotics" in contrast to "probiotic" fermented products such as yoghurt. Probiotics contain live bacteria - you can read of them in the ingredients on a yoghurt container - whereas prebiotics are feedstock for bacteria.
Prebiotics pass through to our gut and stimulate the growth of healthy intestinal bacteria such as Bifidobacteria. Unlike other carbohydrates, inulin does not lead to a rise in blood sugar levels; in fact, inulin is found to lower blood glucose and cholesterol levels. It also increases the absorption of minerals, particularly calcium, improves our immune function, and produces healthy (LDL) cholesterol as it ferments in the gut.
Our gut has good and bad bacteria
Our colon contains both helpful and harmful bacteria.
Some strains have pathogenic effects such as the production of toxins and carcinogens, whereas others provide a health-promoting function. Among those bacteria that promote health are Lactobacilli and Bifidobacteria. By nourishing beneficial bacteria such as Bifidobacteria with inulin, it allows them to "outcompete" potential harmful organisms and thereby potentially contribute to our health.
Health benefits ascribed to Bifidobacteria include the following: inhibiting the growth of harmful bacteria, stimulating components of the immune system and aiding the absorption of specific ions and the synthesis of B vitamins. These benefits are well proven (e.g. Sanno 1986, Shimoyama et al. 1984, Takahashi 1986).
There is also evidence that Bifidobacteria boost our resistance to allergies such as hay fever, and reduces depression symptoms (known as the gut-brain axis).
Those experiments report that it takes about 15 days of regular inulin ingestion to change the bacterial makeup in the gut and to stimulate the helpful bacteria.
Combining probiotics and prebiotics is new functional food
Inulin and other prebiotics are often combined with probiotics. The combination of prebiotics and probiotics has synergistic benefits, referred to as synbiotics. This is because, in addition to the action of prebiotics that promote the growth of existing strains of beneficial bacteria in the colon, inulin improves the survival and growth of probiotic bacteria.
The synbiotic health concept is now part and parcel of the makeup of many dairy drink and yogurt products. Typically, manufacturers add (tasteless) inulin to their product, in addition to the probiotics, which makes a very functional food for everyday consumption.
Inulin has positive effects on calcium absorption
Besides reducing cholesterol and blood sugar levels, where inulin gets very interesting is that studies show that inulin has positive effects on calcium absorption. As we age, this becomes a more important outcome.
Dietary sources of inulin include a diverse variety of foods such as whole grains, onions, garlic, leeks, Jerusalem artichoke and chicory root - and bananas.
You can also buy refined inulin, which is very effective (if you have the budget). This manufactured product is typically chicory root fibre which has had the short-chain carbohydrates removed. The short-chain carbohydrates are the ones which are digested in our stomach and lead to blood sugar level elevation.
In a natural source, such as onions or bananas, the short-chain carbohydrates are digested in our stomach as the inulin continues on its journey - undigested - into our gut.
The refined and manufactured inulin all goes through to the gut. This process is helpful if you have diabetes, for example (although an onion isn't likely to spike your blood sugar).
Weight-loss programs with inulin appear to work well
Refined inulin supplementation is also often used as part of a weight-loss program. That's because it induces increased feelings of fullness. Fortunately, as well as weight loss, this has a host of other benefits as mentioned above - lowering blood cholesterol, improving blood sugar, and benefiting your gut.
A weight-loss study of 44 people with prediabetes (who were receiving counselling from a dietitian) found that a group taking inulin supplements for 18 weeks had a weight loss of 7.6% of body weight. A control group lost 4.9% of body weight. The inulin was effective.
But let's get back to calcium absorption.
Inulin increases the absorption of calcium
Ensuring your dietary calcium is absorbed is something to watch out for as you age. That's because calcium has many roles, including, bone and teeth formation, blood vessel relaxation and constriction, nerve assistance, muscle movement, and hormone balance, to name a few.
There are components in food, namely phytic acid and oxalic acid found naturally in some plants, that bind to calcium and can inhibit its absorption. Foods with high levels of oxalic acid include spinach, collard greens, sweet potatoes, rhubarb, and beans. Among the foods high in phytic acid are fibre-containing whole-grain products and wheat bran, beans, seeds, nuts, and soy isolates.
This inhibition of calcium sounds ominous concerning eating healthy greens and grains.
However, we naturally produce oxalates from our liver, and this accounts for 60 to 80% of that circulating in our bloodstream. Our diet is a secondary source, and a healthy body knows how to cope with the interactions between oxalates and minerals such as calcium.
For people who eat a variety of foods, these interactions probably have little or no metabolic consequence. The bottom line is that the calcium to oxalate ratio is more important than the high levels of oxalate.
All that said, ingestion of inulin significantly increases the apparent absorption and the balance of Ca.
Easy - eat yoghurt, milk and bananas regularly
The practical dietary outcome of this is that by regularly eating a combination of bananas, milk, and your favourite probiotics such as yoghurts, you will give your metabolism the best chance of absorbing calcium. That's good for your bones, blood vessels, muscles, and brain.
To be very specific, a banana at Stage 5 ripeness has higher levels of inulin than at any other stage. Stage 5 is when it has green tips and a yellow body. I like them at that stage, so that's when I have now taken to eating them more often.
Eat real food, an interesting colourful mixture of it, not too much, throw in your daily bananas and yoghurt, and you can't go wrong!
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