Starch is a type of carbohydrate, alongside fibre and sugar which make up the big three.
It's found in fruits, vegetables and grains (most plants) and there are three forms: Rapidly digestible starch (RDS, in the form of amylopectin), slowly digestible starch (SDS, in the form of amylose), and resistant starch (RS, a type of amylose which is indigestible).
The body breaks down starch into energy, unless it cannot (non-digestible). Or on the flip side, most plants store their energy in the form on starch!
RDS is rapidly converted to energy - think bread, pasta, cooked potato, cereals, and rice - whilst SNS takes a little longer, meaning your energy levels are more sustainable as a result - think grains, legumes, or "less cooked" (al dente) carbs like rice or potato.
RDS benefits: Fast acting form of energy, making it great pre or post workout or if you're trying to gain weight.
SDS benefits: Slow released form of energy due to the smaller spike in glucose, which also means insulin levels rise less.
RS on the other hand usually passes through the digestive system undigested, making it a prebiotic, a little like most insoluble fibres! Examples include grains, seeds, pulses, greener bananas, and carb sources that undergo cooking then cooling like rice or corncakes.
RS benefits: Helps to reduce cholesterol and triglyceride (fat) levels in the blood, gut bacteria feed on it to produce short-chain fatty acids which helps the body burn fat for fuel, it can help slow rising blood glucose levels, it reduces hunger, provides energy for cells in the gut that keep the lining intact, and finally feeds gut bacteria (helping to support a balanced gut).
Resistant starch is pretty great, I know!
There's also a forth called modified starch which is typically used by industries such as baking, and it's altered to withstand heat/cold. This kind isn't so good for your health, because it's often heavily treated (with chemicals like sulphuric acid or chlorine - also containing maltodextrin or MSG) and in short is "messed around with".
Okay so what can you do with this knowledge?
Firstly... consume a balance of starches! Each has their own benefits as listed above. Keep a lid on your consumption of RDS, using it to improve training performance/recovery in particular. Consume a foundation of SDS for sustained and stable energy. And be sure to consume a variety of resistant starches for the array of benefits discussed - for your gut health needs!
And as always... try to consume these plant-based foods in their cooked or natural form, steering away from or moderating the processed refined forms.