One potato, two potato
9 September 2019
The poor potato is often marked as being an unhealthy food that is high in starchy carbohydrates and therefore off the menu for those that want to lose weight or following a lower glycemic index form of diet. However, while potatoes are high in easily digestible starch that can lead to blood sugar spikes, they are also high in resistant starch, especially when cooked and then cooled, and this has been shown to improve insulin sensitivity.
What is resistant starch?
Resistant starch (RS), unlike other forms of starch that are digested by enzymes in the small intestine, actually ‘resist’ digestion in the upper gastrointestinal tract in part, because it contains a relatively high percentage of something called amylose. The glucose chains in amylose are wound into a tight coil, so digestive enzymes have difficulty loosening the bonds that hold them together.
As such, resistant starches travel on down into the colon and are broken down by members of the gut microbiota, leading to the production of important health-giving metabolites called short-chain fatty acids (SCFAs), such as butyrate, which are known to be good for our health.
Research shows that SCFAS (in particular butyrate) have immune-modulating effects that help to shape our immunity and develop a healthy “set-point” and seem to play a part in kick-starting the differentiation (that is, specialisation) of immune cells that help ‘keep the peace’, called regulatory T cells.
How does cooling a potato impact the glycemic load (sugar load) of eating a potato?
Potatoes have a high sugar/starch load, but when you chill a cooked potato, the structure of some of the starch is changed and this process increases the resistant starch load. Studies have shown that the glycemic index in chilled potatoes is about 25-35% less than in freshly cooked potatoes that are still warm.
What about the type of potato and how to cook it?
White potatoes that are baked and mashed have the highest glycemic load, as they have a glycemic load that is equal to table sugar. Boiled potatoes have 20-25% less glycemic load than baked and baked potatoes. Sweet potatoes and purple potatoes also have about a 20-35% lower glycemic load than white potatoes, and a russet potato has the highest glycemic load of all.
Small potatoes have a higher ratio of skin to flesh. Since potato skins have a much lower glycemic load than the flesh, eating small potatoes means getting a lower glycemic load.
Of course, mother nature provides us with many forms of fibre - resistant, soluble and insoluble that aids our health. I will write another post next week on that, but for now, I’ll leave you to reconsider the poor demonised potato in a slightly more positive light! - remember, variety is key!
In health, Tanya x