Wheat starches are composed of polymers (repeating chains) of the sugar, glucose. 75% of wheat carbohydrate is the chain of branching glucose units, amylopectin, and 25% is the linear chain of glucose units, amylose.

Both amylopectin and amylose are digested by the salivary and stomach enzyme, amylase, in the human gastrointestinal tract. Amylopectin is more efficiently digested to glucose, while amylose is less efficiently digested, some of it making its way to the colon undigested.

Amylopectin is therefore the “complex carbohydrate” in wheat that is most closely linked to its blood sugar-increasing effect. But not all amylopectin is created equal. The structure of amylopectin varies depending on its source, differing in its branching structure and thereby efficiency of amylase accessibility.

Legumes like kidney beans contain amylopectin C, the least digestible—hence the gas characteristic of beans, since undigested amylopectin fragments make their way to the colon, whereupon colonic bacteria feast on the undigested starches and generate gas, making the sugars unavailable for you to absorb.

Amylopectin B is the form found in bananas and potatoes and, while more digestible than bean amylopectin C, still resists digestion to some degree.

The most digestible is amylopectin A, the form found in wheat. Because it is the most readily digested by amylase, it is the form that most enthusiastically increases blood sugar. This explains why, gram for gram, wheat increases blood sugar to a much greater degree than, say, chickpeas.

The amylopectin A of wheat products, “complex” or no, might be regarded as a super-carbohydrate, a form of highly digestible carbohydrate that is more efficiently converted to blood sugar than nearly all other carbohydrate foods.

Comments (18) -

  • Jim Purdy

    5/22/2010 3:30:00 PM |

    "... gram for gram, wheat increases blood sugar to a much greater degree than, say, chickpeas. "

    Well, that ain't good.

  • David

    5/22/2010 4:21:52 PM |

    I've really enjoyed these last couple of posts about wheat. Very informative and accessible. Thanks for taking the time to make this kind of info available to the wider audience.


  • Anonymous

    5/22/2010 5:12:17 PM |


  • pjnoir

    5/22/2010 8:48:14 PM |

    WOW- a classic lose-lose. 25% remains in your colon, to become a bacteria feast and the rest (75%) increases blood sugar and insulin production to store it as a fat cell.  hmmmmm, thank goodness for science, we may save ourselves.

  • Anonymous

    5/22/2010 10:15:53 PM |

    Dr. Davis,

    While not on a directly related note, do you have any general feelings on moderate consumption of buckwheat as a carbohydrate source? From what I have read, this "pseudo" grain seems to be far less problematic than true grains. It would still not give most folks a license to consume it ad libitum, but I am curious if you'd consider this a decent choice in controlled amounts (with the actual amount varying by context and the overall health of the person in question).

    -Dave Balon

  • Mike

    5/22/2010 10:37:12 PM |

    Excellent explaination, Dr Davis.

  • Anonymous

    5/23/2010 1:55:46 AM |

    I'm really enjoying your posts about wheat.  Very interesting.  Thanks

  • Apolloswabbie

    5/23/2010 3:27:45 PM |

    Thank you Dr. D

  • Jill

    5/24/2010 3:04:47 PM |

    Dear Heart Scan Blog,

    I am a student at the  University of Rochester working on an internship project in conjunction with to collect primary user data about side effects and benefits from commonly used treatments for Atherosclerosis & Arterial Disease.  The goal is to build a large, public access database of unbiased, anecdotal data about Atherosclerosis & Arterial Disease treatments.

    We want to let both patients and practitioners know about how they can participate in or benefit from the project.  Users can add their experiences with a treatment and learn more about how the treatment is affecting them by taking a short, confidential survey. They can also use RateADrug to compare aggregate data for different Atherosclerosis & Arterial Disease treatments- both conventional and alternative ( - and forward the results of their own surveys to their doctors or family members.

    Rateadrug is an independent data gathering and information website that does not accept funding or advertisement from drug companies.

    Would it be possible for you to make this information available to your viewers so they can help us collect important data on Atherosclerosis & Arterial Disease treatments?

    Thank you in advance. I'd be happy to speak with you if you have any questions or comments.

    University of Rochester student intern

  • Dr. William Davis

    5/24/2010 10:28:41 PM |

    Hi, Paul--

    Yes, indeed. The data relating high-carbohydrate intake with multiple forms of cancer is getting very scary.

  • Anonymous

    5/25/2010 4:18:17 AM |

    Wow, I am a long time fan of heartscanblog, but Paul's citation is the most misleading EVER.   The authors found that carbs were associated with pancreatic cancer only in the FIRST FOUR years of follow-up, whereas fat and saturated fat were associated with pancreatic cancer during follow-up GREATER than four years.  Since pancreatic cancer takes years to develop, the authors conclude that carbohydrates are NOT CAUSAL to pancreatic cancer - fat may be.

  • DrStrange

    5/25/2010 2:43:32 PM |

    "The data relating high-carbohydrate intake with multiple forms of cancer is getting very scary."

    I would think at least in part from the higher blood sugars.  Much less problematic w/ whole, intact grains (boiled vs ground into flour and refined (and then higher temp. baked or fried)!

  • discombobulated

    5/25/2010 7:50:36 PM |

    I love your blog.  We have switched out diets to something much closer to what you recommend due to the fact that my husband's psoriasis gets so much better if he avoids wheat,potatoes, corn, refined sugars, and dairy.  We figure it's better than using steroids for the problem.  We also have one son who has been biopsied for celiac after is blood work and we were told he doesn't have the correct atrophy but does have a damaged intestine.  

    So we are committed to eating this way.  But one thing I have wondered about is if you feel that carb blockers work for blocking starch.  There are times when I would kill for a baked potato but try not to because it starts a negative cycle.  And now I know that it's not so hot for my heart either.  

    This post made me wonder if there isn't some merit in them.

  • Breast Augmentation Los Angeles

    5/26/2010 6:20:52 PM |

    Thanks for discussing this.I thought whet is sort of better than the white bread for the diabetic and the heart patients.

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  • Mary Wier

    7/10/2012 8:38:03 AM |

    Bill and I found our Wheatbelly book and have been off gluten for 9 months, it was hard at first but we now
    feel so different, Bill's blood sugar dropped 25 points, and we look at all our food so differently now!
    The display of wheat rolls and pastry at our buffet looks more and more like hidden poison.
    We are off sugar, too it is so tempting but our body says, Thank you Dr. Davis!