Do you love your carbs but want to cut down on calories? Looking to improve your gut health too? Then you need to know about Resistant Starches.
Carbohydrates typically have 4 calories per gram but Resistant Starches are only around half that. Plus they offer significant health benefits too.
This is a nutrition secret you need to know!
Sounds amazing. Tell me more.
OK, but first a little bit of basic chemistry.
We all know that carbohydrates are sugar molecules bonded together in different amounts and different ways to form simple starches or complex starches.
Simple starches are found in things like fruit, milk, added sugar, sweets, and lots of processed foods.
Simple starches require little or no digestion to break down into glucose in the body. As our enzymes break down these simple starches into sugar molecules, our bodies release insulin to deal with the sugar spike.
Complex carbohydrates include wholegrains, vegetables, cereals, brown rice, etc (remember that the more refined, the less complex!). The body has to work on these foods to break them down. This has many beneficial effects – slower digestion, feeling full for longer, less sugar spike etc. Plus these carbs tend to come with more fibre in the cell walls which is great for us all.
But what is a resistant starch?
Resistant Starch is exactly what it sounds like – it is “resistant” to our digestive enzymes, therefore it does not cause the release of insulin. It passes through the digestive tract pretty much unscathed until it reaches the large intestine. Here it is “fermented” by the good bacteria which reside there - about 90% of the cells found in our body is actually gut bacteria! - and acts like a kind of soluble fibre.
Although scientists have known about resistant starch for decades, it is only in recent years that we've understood how they affect our bodies.
Many studies have shown that resistant starch can have powerful health benefits including improved insulin sensitivity, lower blood sugar levels, reduced appetite (they make you feel full for longer) and benefits for digestion.
There are 4 forms of resistant starch.
Type 1 is found in the cell walls of grains and seeds.
Type 2 is made up of raw starches such as potatoes, green bananas, some fruits and some legumes.
Type 3 is the little miracle I want to talk about here - and the one we can make most use of; foods that get their resistant starch from the cooking then cooling process. This includes potatoes, sweet potatoes, rice, yams and some whole grain breads. This process is also known as retrogradation..
Type 4 is man-made or chemically produced. This form is typically used by food manufacturers who add it to processed food items.
(Many foods contain different types of resistant starch and the way food is stored and prepared can alter the proportion of RS e.g. allow green bananas to ripen and the resistant starch turns into digestible starch.)
How does retrogradation work?
Let's take potatoes as an example. Potatoes are naturally high in resistant starch i.e. starches that are resistant to our digestive system, but cooking changes the chemistry to make the starches more digestible. (This is why we don't eat raw potatoes!) Now we can digest the starches and get lots of calories from the potato - 4kcals per gram.
Let those potatoes cool down, however, and some of the starches change again and become resistant again. Now, when you eat those 'tatties', a proportion of the starches will pass through your stomach and intestines into your colon where your friendly bacteria will chomp away and release the nutrients - but only around 2 calories per gram. They also produce a short-chain fatty acid called butyrate which feeds the cells of the colon so improving the health of the colon.
Same with rice. And pasta. And some root vegetables. Even better, you can then reheat these foods and they still have a high level of resistant starch. In fact, heating and cooling again increases the resistant starches even more and you get a higher proportion of the lower calories carbs.
Isn’t nature amazing?
This even works with bread. Yes, bread!! You can keep your loaf in the freezer, take it out to toast or defrost and you will be absorbing less calories, and giving your gut a healthy boost.
This chart shows the effect on blood sugar levels of cooking, cooling and reheating pasta.
See more on this clip: BBC Trust Me. I'm a Doctor
Why you should be eating more resistant starch - and it's not just about less calories.
A typical western diet contains many processed foods which are high in sugar and unhealthy fats. These foods can cause an imbalance of bacteria in the gut.
More and more studies show that the balance of good to bad bacteria in your digestive system is linked to overall health and disease. These benefits include weight loss, digestive health, immunity support and more.
Resistant starch works in a similar way to fibre and acts as a probiotic which feeds the ‘good’ bacteria, allowing them to proliferate and force out the ‘bad’ boys.
As the resistant starches are fermented by the bacteria in your colon they lower the pH level which is known to reduce inflammation. Today, cancers of the bowel are common throughout the world. and research is showing the effect of resistant starches on improved bowel health and may help prevent bowel cancers from forming.
As I mentioned above, butyrate is a short-chain fatty acid which supports bowel health. Other SCFAs made during the fermentation process pass into the blood stream and have multiple benefits around the body.
There is also evidence that resistant starches help the body absorb more minerals from our food.
We are still discovering the amazing effects of resistant starch but you don't need to wait. Get cooking and cooling now!!
What did you think?
Do let me know if you found this article interesting / helpful / boring. I'll take your feedback into account in future posts.
More than anything I'd love to know if it has any impact on you and your diet. Please leave a comment or get in touch.
More Reading
Website dedicated to Resistant Starch research https://resistantstarchresearch.com/
Clinical trials https://resistantstarchresearch.com/clinical-research-summary-chron-resistant-starch-
RS and gut health https://resistantstarchresearch.com/posts/resistant-starch-butyrate-and-gut-barrier-integrity/
BBC experiment BBC Trust Me. I'm a Doctor