When we talk of starch what comes to our mind? That gloopy & sticky feeling-potato, bread, grain, pasta. Not all starches are the same, depending upon their molecular structure, they can be quick digested, slowly digested or not digested at all. Today we will be discussing starches that cannot be digested at all- either in the stomach or small intestine & reach to large intestine( or gut). These sets of starches that cannot be digested or in other words resist digestion are referred to as resistant starches.
Resistant starches are nothing, but complex carbohydrates having repeating units called polysaccharides in macronutrient terms -poly means many & saccharides means different forms of sugar such as sucrose, fructose, glucose & many more.
Starch are made up of two type of polysaccharides
- Amylopectin: A highly branched molecule with a lot of surface area. These are easily accessible to digestive enzymes. Since these are more readily broken down, these are easily digestible & spike sugar level (glucose).
- Amylose: These are straight chain polysaccharide molecules. This linear structure makes it less or not accessible for digestion. As such these foods are digested slower, resist release of sugar & hence leads to a slow spike in sugar level. It is this molecular structure that makes up resistant starch, making it inappropriate for digestion in stomach & small intestine, paving way for this food to be fermented by bacteria in the gut(large intestine). In the gut, different bacteria offer different advantages of producing amylase enzymes needed to breakdown these Amylose structures.
Just for the sake of understanding “ose” at the end refers to sugar & “ase” at the end refers to enzymes that degrade the sugar.
The beneficial bacteria that produce amylase are Ruminoccus Bromii. This bacteria initiate the breakdown of resistant starch molecules, enabling other bacteria to use fragments to product short chain fatty acids such as Butyrate
Short chain fatty acids(SCFA) are linked to our gut health. SCFA are nothing but beneficial metabolites that arise out of the end product of fermentation of food (we eat) by bacteria. These are natural chemical compounds are formed from microbial fermentation in the gut. SCFA ( poop or our bacteria) play an important role in health of our gut lining, regulating our brain function, metabolism & immune system. SCFA (in chemistry terms) have less than 6 carbon atoms.
- Butyrate– 4 carbon atoms; C4H8O2
- Propionate– 3 carbon atoms;C3H6O2
- Acetate– 2 carbon atoms;C2H4O2
Since SCFA are the main source of energy for cells found around your large intestine, regulate your metabolism & immune system, appetite, body composition, each SCFA has a different abundance & role in the gut. Acetate has the highest abundance followed by Propionate & then Butyrate. The ratio of these SCFA are also important.
The ratio of acetate to propionate is important for regulating liver fat metabolism. This ratio is also said to control gut-immune response to the gut microbiome.
Let us discuss each of these SCFA in detail.
- Acetate: Acetate is the most abundant SCFA since many bacteria can produce it. It also acts as an essential source of energy for many bacteria- since they metabolize acetate to produce butyrate.
- Propionate: Propionate is involved in release of glucose from liver & hence helps in regulating our blood glucose levels. It also helps in the release of anti-inflammatory molecules & those that control our appetite. As such this SCFA is really important to prevent us from attracting type 2 diabetes
- Butyrate: Butyrate is one of the most essential SCFA for gut health. It provides fuel for intestinal cells & helps maintain integrity of gut lining. It also helps in the release of anti-inflammatory molecules & those that control our appetite.
Resistant starch is considered to be vital for our gut health due to the importance of these SCFA & amazing bacteria that ferment it.
The abundance of SCFA released by our gut bacteria depends upon:
- Amount & type of carbs we eat
- Abundance or lack of SCFA producing bacteria present in our gut & feed
If we eat sufficient resistant starch, we feed beneficial bacteria & probiotic bacteria that produce short chain fatty acids. Which of the bacteria are important for our gut health?
- Bacteroides thetaiotamicron
- Akkermansia muciniphila
- Bifidobacterium
- Eubacterium rectale
- Faecalibacterium prausnitzii
- Lactobacillus
- Ruminococcus bromii
- Roseburia
By sequencing & analyzing your gut microbiome, we can actually learn who are the folks living in our gut & how we can improve abundance & diversity of beneficial bacteria in our gut by making personalized dietary interventions. Sign up here for a free discovery call, if you want to make bacteria in your gut work in favor of improving your overall health.
Nice Article