What if i told you that you could lose weight by eating rice and potatoes. Seems like a dream right? Welcome to the world of resistant starches. As the name indicates these are starches that are resistant to digestion by humans. For example when you cook and cool rice or potatoes they from resistant starches. These starches pass through the stomach and small intestine unaltered. The two immediate benefits are : firstly you are not absorbing regular amount of calories though you are eating them. Secondly you feel fuller for much longer which means you don’t eat further.
But the benefits do not end there. Actually the magic starts after these starches enter your large intestine. They are acted on by the gut bacteria and produce short chain fatty acids (SCFA) like acetate, propionate and butyrate. These SCFA’s are the best possible food for the cells that line the colon. The whole process improves the gut health and attracts the right flora. Butyrate in particular is know to prevent colon cancer, speed up your metabolism and reduce inflammation. Now lets dive deeper into the basics and benefits of resistant starches.
Resistant Starch 101:
Any starch comprises two types of polysaccharides, Amylopectin and Amylose. Amylopectin is highly branched and thus has a larger surface area which makes digestion easier. Easy digestion means glucose spike, followed by insulin spike. On the other hand Amylose is a straight chain, which limits the amount of surface area exposed for digestion. Resistant Starches are dominated by Amylose and thus are digested very slowly. There are four main types of resistant starches, details of the same are depicted in the picture below.
RS1: This type are physically inaccessible as they are bound by fibrous cell walls and cannot be broken down by the digestive enzymes. Most lentils and unprocessed grains have them.
RS2: This type is intrinsically resistant to digestion and is present in raw produce like potatoes and plantains.
RS3: This type is formed when high starch foods are cooked and cooled. Classic examples are rice and potatoes
RS4: This type is formulated chemically by extracting from sources like maize.
The scientific community has been researching the benefits of resistant starches for many years and the exploration is going on. However some of the major benefits can be summarised as below:
Reducing effective calorie intake: It is estimated that we can absorb only half the calories from resistant starches. For example 100 grams of normal carbohydrates would mean 400 calories (1 gram = 4 calories), whereas 100 grams of resistant starches would only mean 200 calories as the remaining calories are not absorbed.
Improving satiety and insulin sensitivity: As the resistant starches are fermented in the colon, a positive response in found in metabolic activities. A research study in which subjects were given a dose of indigestible carbohydrates in the evening meal and tested for various metabolic markers post breakfast the next day, satiety improved with colonic fermentation, gastric emptying rate (GER – the rate at which food exits stomach) decreased with increase in fermentation. Glucose response decreased with increased fermentation.
Fat oxidisation and reduced fat storage: Resistant starches are known to increase the fat burning and thus reduce the fat accumulation. A study published in the Nutrition and metabolism journal reported a 23% increase in fat oxidisation with a 5.7% increase in resistant starch content of the carbohydrates.
Improved Digestion: Resistant starches add bulk to the stool which helps in regular bowel movements. This could be a major relief for people with Irritable Bowel Syndrome (IBS).
If there is one rule that supersedes all my advice, it is the rule of SLOW (Seasonal – Local – Organic – Whole). I would never advice any supplements of chemically processed resistant starches.We would need around 30-40 grams of RS in our diet every day. Being in India we are blessed with amazing sources of resistant starches. My favourite would be plantain. It has been a part of local cuisine and grows abundantly. Plantain flour has 35 grams of RS per 100 grams. Another exceptionally good source is green gram or moong. Raw green gram has a stunning 22.9 grams of RS per 100 grams. No wonder moong sprouts are considered super foods. Lotus seeds have 19.7 grams and cashews have 12.9 grams per 100 grams.
A lot of unprocessed millets and lentils would have resistant starch. Another great source would be beans. White beans and kidney beans are known to have good content of resistant starch. Tubers such as sweet potatoes and colacasia (arbi/chamagadaa) have resistant starch.
And finally I can’t but appreciate the traditional food wisdom. Rice cooked and cooled can form RS3 (5.4 g /100g) and when we look at the traditional dish called “Saddi Annam/Pazhaya Saadam / Pazham Kanj /Paani wala chawal” its basically cooked and cooled rice. I have written an entire article on this here. The same can be achieved by cooking and cooling potatoes. I still remember that my mother would cook the potatoes separately and let them cool before roasting them on the pan. Roasted and cooled potatoes pack 19.2 grams of RS per 100 grams.
While the science is still young, I see absolutely no harm in trying this, especially from whole foods and local produce. The benefits of a healthy gut has been established beyond doubt and resistant starches no doubt are helping the cause. My only word of caution would be to take it slow, as along with short chain fatty acids, some gases are also released during the fermentation in colon. So if you experience bloating and gas, just reduce the quantity!