Could a plate of cold boiled potatoes be a revolution in dieting?
And what about green bananas?
Well, there are some nutritional scientists who think that this type of food is nature’s answer to the problems of obesity, diabetes and gut health.
The concept is based around something called ‘resistant starch’.
In short, resistant starch is that which passes through the stomach and small intestine and remains undigested.
Normally starch in foods like pasta, potatoes and white bread gets turned into sugar and absorbed into the blood really quickly, almost as fast as if you had drunk a glass of sugar water.
This causes a spike in blood glucose levels and puts those with poor insulin control at severe risk of tissue damage.
So, it has always been assumed that starchy foods were bad foods – simplistic and easy to understand, granted, but like most of these theories the truth is far more interesting than that.
You see, the resistant type of starch passes into the large intestine where it feeds the good gut bacteria that live there.
These are ones that produce vitamin B12, help release essential vitamins and benefit our immune system by controlling aggressive pathogens.
However, not all resistant starches are the same. There are four different types.
· Type 1 is found in grains, seeds and legumes and resists digestion because it is bound within the fibrous cell walls. Foods such as cashew nuts and sunflower seeds fall into this group.
· Type 2 is found in some starchy foods, including raw potatoes and green (unripe) bananas, but to be honest no-one could actually enjoy eating raw spuds and bananas so this type is less likely to form part of your diet (unless you are keen on juicing them?).
· Type 3 is formed when certain starchy foods, including potatoes and rice, are cooked and then cooled. The cooling turns some of the digestible starches into resistant starches via a process called retrogradation.
This was the basis of the Daily Mail headline considering how cold cooked starches can be converted.
· Type 4 is man-made and formed via a chemical process, which has got food manufacturers interested in how this could be mixed with other starches and then claimed to have health benefits.
One study used a mix of 30% type 4 resistant starch with normal flour to test for lowered cholesterol levels, change in waist size and body fat percentage and some positive results were seen – but more testing is needed. (I’m not sure that a man-made version should be where these companies focus should be, of course!)
Once again though, it’s not all that simple…
Because several different types of resistant starch can co-exist in the same food.
Plus, depending on how those foods are prepared, the amount of resistant starch changes. For example, allowing a banana to ripen (turn yellow) will degrade the resistant starches and turn them into regular starches.
The other problem is that because foods are composed of both digestible and resistant starches you will be eating more ‘bad starch’ in your pursuit of the ‘good stuff’.
So once again it is a good reason to include a wide and varied group of foods in your diet.
Using haricot beans (sometimes called Navy beans), lentils, pearl barley and oatmeal in recipes will boost your resistant starch levels – and these foods don’t suffer deterioration problems when they are cooked so can be used in soups and casseroles easily.
Commercially, there are maize and potato starch supplements out there …
But I think I would prefer to tuck into a nice steaming bowl of porridge or a lentil rich curry rather than sprinkling dried potato dust onto my food.
Funny thing about all this is that science seems to be catching up with the wisdom of the ages once more – our grandparents who ate local and seasonal foods really did have the right idea.
