Resistant Starch and Why You Should Cook and Cool Your Carbs
Carbs get such a bad rap these days. You know the old saying...."carbs are the enemy." They are usually the first food group to get shunned when people start a weight loss journey. But actually some of the skinniest people on earth consume a lot of carbs.
A recent study (here) looking at Vegans, Vegetarians, Pescatarians and Omnivores, found the Vegan group were the leanest. And as vegans forgo all animal products they end up eating quite lot of carbs. However, this group is typically a pretty health conscious bunch and consume many carbohydrates in their unprocessed and whole form (ie whole grains and legumes). Interestingly, whole grains have recently been shown to help with weight loss as they boost metabolism and cause a decrease in the number of calories that are retained during digestion. See that study here
But what about regions that have a high consumption of processed carbs but still remain lean? Two countries, Japan and Vietnam, (who are listed at the bottom of the World Health Organization's Global Mean BMI Index) are great examples of this paradox as they consume large quantities of processed white rice yet remain lean. How can this be?
It is how this rice is eaten that unlocks the mystery of this paradox. The Vietnamese eat a lot of rice noodles (think pho, rice noodle salad, spring roll) and the Japanese eat a lot of their rice cold (as in sushi or in a bento that has been packed in a lunchbox to take with them to school or work). These two countries are consuming rice that has been converted into resistant starch by being cooked and cooled.
Resistant starch are starchy carbohydrates made of long chains of glucose molecules that "resist digestion" and pass through the digestive tract unchanged. Instead of getting absorbed and broken down into glucose, resistant starch travels to the colon where the gut bacteria living there convert it to short chain fatty acids via a fermentation process. These short chain fatty acids exert numerous benefits to the body including damping down inflammation, lowering blood sugar levels, reducing cholesterol and lowering blood pressure. (See my blog post on Legumes here to read more about the benefits of short chain fatty acids on the body. )
And as for helping with weight loss, the resistant starch bypasses the typical absorption process higher up in the intestines, meaning the calories are not all absorbed nor is the starch converted to glucose nor is that excess glucose stored as fat.
This is one of the reasons the Japanese and Vietnamese are so lean as they are not absorbing all of the calories from their food.
So where else can you find resistant starch other than rice noodles and cold rice? Any starchy carbohydrate like rice, potato, and pasta automatically converts to resistant starch when it gets cooked and then cooled. This is because the crystalline structure of the molecules in starch dissolves when heated and then retrogrades and rearranges into a new crystalline structure that is more compact and harder for our digestive enzymes to break down. So as long as you have cooled your carbs after cooking them you will have converted them into this new "resistant" structure. And you can reheat the food again as this does not influence the amount of resistant starch in the food.
Other foods that naturally contain resistant starch (but don't need to be cooked and cooled) are green or unripe bananas (you can even buy green banana flour now), legumes, oats (especially uncooked like in muesli and overnight oats) , whole grains (sorghum is particularly high), high maize flour, and some nuts like cashews and chestnuts.
So if you are looking to lose a little weight and you just can't stomach whole grains, try cooking and cooling your carbs. Why not cook up a batch of pasta, rice or potatoes on a Sunday and pop them in a container in the fridge. During the week you can reheat them as needed and serve them however you like. This form of meal prepping will save you loads of cooking time during the week too.