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Resistant Starches (Prebiotics)

These are plant produced carbohydrates that the human gut cannot digest 
that are somewhat different than other forms of fiber. Resistant starches often 
have a starchy or even sweet taste and they are neither totally insoluble nor 
prone to forming gels. The main difference however is that resistant starches 
are not calorie-free. Generally, they provide us about 2 calories per gram of 
resistant starch. How is this possible given that I just stated that resistant 
starches are indigestible? 

The answer is that resistant starches are indigestible using human gut 
enzymes, but, not indegistible to many of the bacteria that inhabit the human 
colon. Thus, resistant starches pass totally unscathed all the way through the 
small intestine, but once they enter the colon they are digested but bacteria. 
However, the bacteria do not totally digest resistant starches; they turn some 
of them into fatty acids that the bacteria then secrete and which we then 
absorb as nutrient. This is why resistant starches provide a small amount of 
calories.

More importantly, resistant starches appear to selectively nourish the "good" 
kinds of bacteria in the gut and therebye promote regularity and reduce risk for 
cancer. Because of their ability to promote beneficial bacteria, resistant 
starches are also called "pre-biotic" nutrients.

Resistant starches are often found in roots of plants, but not all roots. A weird 
sunflower-like plant called a jerusalem artichoke has roots that are loaded with 
a resistant starch called "inulin" (NOT "insulin"). Regular artichokes also have a 
fair amount of inulin. A sweetener that has long been popular in Mexico is now 
being sold in the US and it is made from the root of the "blue agave" cactus 
which is also inulin-rich.
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