Glycemic gobbledygook

The concept of glycemic index is meant to help determine what foods raise blood sugar a lot vs. what foods raise blood sugar a little. Dr. Jennie Brand-Miller's searchable database can be found here.

I have to admit that glycemic index provided me with a sense of false assurance for some years. It screwed up my health until I came to understand the issues a lot better.

For those of you just starting out in nutritional conversations, glycemic index (GI) represents a comparison of the blood glucose area-under-the-curve (AUC) over 2 hours after consuming 50 grams of the food in question compared to the AUC of glucose or white bread. Volunteers involved in developing these values are healthy people who are generally of normal weight.

Glucose, by definition, has a GI of 100. An equal quantity of sucrose (50% glucose, 50% fructose) has a GI of 60, lower than glucose. An equal quantity of whole wheat bread has a GI of 68-77 (Yes: The GI of whole wheat is higher than sucrose). Non-carbohydrate foods, such as eggs or avocado, have no GI since they do not impact on blood glucose.

Because the GI is also sensitive to how much carbohydrate is contained, the concept of Glycemic Load (GL) was introduced:

GL = (GI x amount of carbohydrate) / 100

GL is therefore the GI that incorporates the glycemic potential of the food of interest. GI does not vary with portion size; GL varies with portion size.

Let's take whole wheat pasta, a food regarded by most people as a healthy choice. Whole wheat pasta has a GI of 55--fairly low--and a GL of 29. A serving of 180 g (approximately 6 oz cooked) provides 50 g carbohydrates.

People who advocate that low-glycemic index foods would say that this is a desirable profile and should therefore replace high-glycemic index foods.

I say WRONG. First of all, most of us are not slender 20-somethings. We will therefore not show the same response as a young, slender person (like the GI volunteers), but will show exagerrated blood sugar responses. So this much low-glyemic index whole wheat pasta will typically yield a blood sugar of 120-200 mg/dl in non-diabetic people, high enough to trigger glycation. Sure, a high-glycemic index food, such as white flour birthday cake with plenty of sugary icing, might trigger a blood sugar of 140-250 mg/dl, much worse. But that doesn't make the lower blood sugar following pasta any less bad--it's still terrible.

Another issue: GI is assessed over a 2-hour timeline. What if blood sugar remains high in a sustained way, say, over 6 hours? That's precisely what whole wheat pasta will do: Keep blood sugar high for an extended period.

So not only does a low-glycemic index food like pasta increase blood sugar in most of us extravagantly, it does so in a sustained way.

Lastly, low-glycemic index pasta still triggers small LDL particles to an extreme degree, as I discussed in the previous Heart Scan Blog post, Small LDL: Complex vs. simple carbohydrates.

Don't be false reassured by the notion of low GI or GL. In fact, I'd go so far as to say that NO glycemic index is a GOOD glycemic index (or load). The foods we want to dominate our diet are the foods that aren't even listed in the GI database.

Comments (14) -

  • Santiago

    5/12/2010 11:12:07 PM |

    Hi
    I've seen many posts like this, but all of them seem a bit ambiguous about whether small LDL is related to BG spikes or an independent effect of carbohidrates.
    Say, someone that eats that 180g of pasta but BG stays under 100 will still produce tons of small LDL?

  • Anna

    5/12/2010 11:55:06 PM |

    Amen!

  • Michael Barker

    5/13/2010 1:32:59 AM |

    My big problem with GI or GL was fructose. It does not raise blood sugar but it does attack the liver.

  • Matt Stone

    5/13/2010 2:44:16 AM |

    If 6 measly ounces of whole wheat pasta sends your blood sugar over 120, much less to 200, you're probably seriously ill. But you talk about it like it's impossible to lower blood glucose levels to a set number of carbohydrates. That's not true at all. It's easy actually, and there's so much more complexity to this overall issue that posts like these are aggravating. I've even gotten to the point where I could eat double that glycemic load without my blood sugar spiking above 75.

  • Darrin

    5/13/2010 3:22:07 AM |

    Yeah, GI and GL are best for diabetics and others with strong insulin resistance. Although I agree that foods without GI values should be the basis of our diets (meats, most vegetables), if you have strong insulin sensitivity you'll probably be just fine with some roots, dairy, fruit, and nuts.

  • 2012

    5/13/2010 3:29:50 AM |

    perfect one.

  • Lance

    5/13/2010 12:51:59 PM |

    Several points:

    Isn't there a pretty big difference between raising your blood sugar to 120 mg/dl after a meal, as opposed to 200?

    The American Association of Clinical Endoctrinologists suggests an upper limit of 140 mg/dl two-hour postprandial blood glucose.  The International Diabetes Federation has the same figure.

    In contrast, 200 is usually considered a symptom of full-blown diabetes.  So it would really seem to depend on which figure we are talking about.

    I personally find the glycemic load a helpful piece of data.    Almost all fruits and vegetables have some kind of glycemic load.   Spinach, for example, consists of 56% carbohydrate, 14% fat, and 30% protein.  But a 10 oz. bag only has a glycemic load of 4, vs. 14 for  piece of white bread.  (Granted, you're only getting 65 calories of energy from all that spinach.)

    Regarding whole wheat pasta: perhaps different websites give different glycemic load values. Nutritiondata.com gives a value of 16 for a full cup of cooked whole wheat elbow noodles, vs. the 29 you quoted.

    http://www.nutritiondata.com/facts/cereal-grains-and-pasta/5769/2

    I find it helpful to know I can cut the glycemic load of that pasta from 16 to 8 just by eating a half-cup instead of a cup (though in fact I rarely eat pasta at all.)  The glycemic load deals with real effects of quantifiable portions of food, and as such is an interesting piece of the puzzle. But, as you have wisely pointed out many times, checking your own blood sugar is the best way to understand what is really going on...with you.

  • KENNY10021

    5/13/2010 1:06:55 PM |

    Yes it will still produce tons of small LDL.....two different issues.....carbohydrate effect LDL particle size tremendously....I can attest to this first hand......while the high BG levels have a whole host of other bad effects related to damaging cells at the core and thus disease ramifications, insulin issues, etc.

  • Ned Kock

    5/13/2010 2:44:17 PM |

    Hi Dr. Davis.

    It is worth noting that there is a huge gap between glycemic loads of refined and unrefined carbohydrate-rich foods:

    http://healthcorrelator.blogspot.com/2010/04/huge-gap-between-glycemic-loads-of.html

  • homertobias

    5/13/2010 2:59:57 PM |

    Very nicely said.  I mean it.  Maybe I'll use it in my practice.

  • Dr. William Davis

    5/13/2010 9:24:43 PM |

    Hi, Lance--

    I understand your concerns. However, I am less concerned with what the "official" organizations tell us is normal or abnormal, and more concerned with levels in which glycation develops.

    Glycation develops in a continuous fashion with blood glucose: The higher it is, the more glycation results . . . starting in the "normal" range fasting and postprandial.

  • DrStrange

    5/14/2010 1:37:11 AM |

    5/15/10  6:35 p.m. PDT

    Matt Stone, just went to your website and got attacked by Malware.

  • Apra -- The Shaman

    5/14/2010 6:47:57 PM |

    "I've even gotten to the point where I could eat double that glycemic load without my blood sugar spiking above 75."

    There's a guy in India who claims he can live on nothing but air too.

  • jpatti

    7/2/2010 2:14:40 PM |

    The reasons sucrose has such a "good" GI is cause it's half fructose.  Fructose doesn't convert to glucose so doesn't raise bg.  It is cleared from the blood by the liver which converts it to triglycerides.  So it raises serum triglycerides at least for a while.  It eventually gets cleared from the blood by adipose.

    Bread, potatoes, other starchy foods... starch is long chains of glucose, so it raises bg.  But if you have a normal system and can handle bg, you burn it as fuel instead of having fat floating in your blood until it gets deposited around your belly.  So for those without bg problems, the worse GI foods are better for health!  

    for those who DO have bg issues, the GI and GL are useless.  You don't care what happens to some average group of people, but what happens to YOUR bg.  This is what is useful whether you have diabetes or not: http://www.alt-support-diabetes.org/new.php

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Dr. William Blanchet: A voice of reason

Dr. William Blanchet: A voice of reason

I don't mean to beat this discussion to a pulp, but looking back over the comments posted on www.theHeart.org forum, I am so deeply impressed with Dr. William Blanchet's grasp of the issues, that I posted his articulate and knowledgeable comments again.

Here is one post in which Dr. Blanchet, in response to accusations of trying to profit from heart scans, provides a wonderful summary of the logic and evidence behind the use of heart scans as the basis for heart disease prevention.


Yes, I have seen a dramatic reduction in coronary events.

Of 6,000 active patients, 48% being Medicare age and over, I have seen 4 heart attacks over the last 3+ years. 2 in 85 year old diabetics undergoing cancer surgery, one in a 90 year old with known disease and one in a 69 year old with no risk factors, who was healthy, and had never benefited from a heart scan.

The problem with coronary disease is that we rely on risk factors. Khot et al in JAMA 2003 showed that of 87,000 men with heart attacks, 62% had 0 or 1 major risk factor prior to their MI. According to ATP-III, almost everyone with 0-1 risk factors is low risk and most do not qualify for preventive treatment. EBT calcium imaging could identify 98% of these individuals as being at risk before their heart attack and treatment could be initiated to prevent their MI.

Treating to NCEP cholesterol goals prevents 30-40% of heart attacks. Treating to a goal of coronary calcium stability prevents 90% of heart attacks. Where I went to school, a 40% was an F. Why are we defending this result instead of striving to improve upon it? I am not making this up, look at Raggi's study in Arteriosclerosis, Thrombosis, and Vascular Biology 2004;24:1272, or Budoff Am J Card.[I believe it's the study Dr. Blanchet was referring to.]

I strongly disagree with the assertion that the stress test is a great risk stratifier. Laukkanen et al JACC 2001 studied 1,769 asymptomatic men with stress tests. Although failing the stress test resulted in an increased risk of future heart attack, 83% of the total heart attacks over the next 10 years occurred in those men who passed the stress test. Falk E, Shah PK, Fuster V Circulation 1995;92:657-671 demonstrated that 86% of heart attacks occur in vessels with less than 70% as the maximum obstruction. A vast majority of
patients with less than 70% vessel obstruction will pass their stress test.

Regarding [the] question of owning or referring for EBT imaging, I would be amused if it were not insulting. The mistake that is often made is that EBT imaging is a wildly profitable technology. It is not nearly as profitable as nuclear stress imaging. Indeed there are few EBT centers in the country that are as profitable as any random cardiologist's stress lab.

How can we justify not screening asymptomatic patients? Most heart attacks occur in patients with no prior symptoms and according to Steve Nissen, 150,000 Americans die each year from their first symptom of heart disease. My daughter is at this moment visiting with a friend who lost her father a few years ago to his first symptom of heart disease when she was 8 years old. That is not OK! We screen asymptomatic women for breast cancer risk. Women are 8 times more likely to die from heart disease than breast cancer. We do mass screening for colon cancer and we are over 10 times more likely to die from heart attacks than colon cancer. An EBT heart scan costs 1/8th the cost of a colonoscopy.

So what say we drop the sarcasm and look at this technology objectively. Read the literature, not just the editorial comments. This really does provide incredibly valuable information that saves lives.

Yes, a 90% reduction in heart attacks in my patients compared to the care I could provide 5 years ago when I was doing a lot of stress testing and referring for revascularization. Much better statistics than expected national or regional norms. I welcome your scrutiny.



That's probably the best, most concise summary of why heart scanning makes sense that I've ever heard. And it comes from a primary care physician in the trenches. With just a few paragraphs, Dr. Blanchet, in my view, handily trumps the arguments of my colleagues arguing to maintain the status quo of cholesterol testing, stress tests, and hospital procedures.


Note:
Dr. Blanchett talks openly about his affiliation with an imaging center in Boulder, Colorado, Front Range Preventive Imaging. I'm no stranger to the accusations Dr. Blanchet receives about trying to profit from the heart scan phenomenon. Ironically, heart scanning loses money. It is a preventive test, not a therapeutic, hospital-based procedure. Free-standing heart scan centers that do little else (perhaps virtual colonoscopies) usually manage to pay their bills but make little profit. Hospitals that offer heart scans usually do so as a "loss-leader," i.e., an inexpensive test that brings you in the door in the hopes that you will require more testing.

Accusations of profiteering off heart scans are, to those in the know, ridiculous and baseless. On the contrary, heart scans are both cost-saving and life-saving.

Comments (21) -

  • wccaguy

    11/24/2007 6:19:00 PM |

    I had an opportunity to speak with Dr. Blanchet for a few minutes recently.  A great doctor and a nice guy.

    He's in Boulder, Colorado.  Here's the web site link I was able to contact him through.  (I've separated out the link onto two lines to ensure that the complete link appears in comments.  You'll need to put the two lines together as a single URL to paste into your browser.)

    http://www.bch.org/caregiver/
    physiciandetail.cfm/184

    If I lived close to Boulder, Colorado, I'd be working to make him my primary care physician.

  • Rich

    11/24/2007 8:13:00 PM |

    Dr. Davis:

    Thank you!

    About profitability: My calcium scan in California cost $500. The new-ish GE scanner that was used costs $1.8 million. I estimate that the $500 fee can only yield about $100 gross margin under high-patient-volume circumstances.

    -Rich

  • Dr. Davis

    11/24/2007 8:33:00 PM |

    I am not one to moan about the costs of running a scan center, since I've never had any financial interest in a scan center (despite numerous accusations of "secret arrangements," etc.), but costs of running a center also include:

    1) $12,000 or so a month upkeep. No kidding. The GE's of the world, though they do great engineering work, make many times their investment back just from the rich  maintenance contracts. I've seen these maintenance contracts break the back of many independent scan centers.

    2) Because physicians are so hard to educate on the value of heart scans, scan centers by necessity rely on advertising, which is very costly.

    3) Paying physicians to read scans. I can tell you from personal experience, since I do read scans and receive a small fee for each reading, that the reading fee is paltry. If I were doing this for money, I wouldn't waste my time. But it's not about money. It's about providing a necessary and important service.

    This is why independent scan centers have struggled across the country. It is getting better, but mostly because of the adoption of the new CT technologies by hospitals.

  • TedHutchinson

    11/25/2007 10:36:00 AM |

    Here are the actual prices those lucky enough to live in USA can get a Coronary Artery Scan ("heart scan") — EBT examination of heart with calculation of coronary calcium score. Includes all interpretations and comprehensive report. Radiologist examination of chest images. Report sent to patient and physician if requested. (For repeat scans, calcium volume scoring and notation of rate of progression or reversal)
    If claim is submitted to the insurance company and it is denied because it is considered "Not a Covered Benefit" $440
    35% Discount if paid at the time of service (Patient waives the rights to receive Health Insurance Claim Form) $395
    Anyone who thinks those prices are unreasonably high should see prices in the UK where Coronary Artery Scans cost £525.
    However, as it costs me about that to get my car serviced in the UK and there's no guarantee the work won't be done by an untrained lad on a job creation scheme, it's still good value.

  • Paul Kelly - 95.1 WAYV

    11/26/2007 1:28:00 PM |

    Is an EBT scan the same as a CT scan? My understanding is that it's the same thing...only faster. True? Are the levels of radiation the same?

    Thanks!

    Paul

  • G

    11/26/2007 11:16:00 PM |

    Has any had a scan in the Bay Area? I know that Walnut Creek and San Jose offer sites...  Any recommendations?  I'm thinking about getting my dad and husband xmas gifts...  I thought the price was bout $199 but I guess prices are higher now...inflation? being Calif?

    THANKS in advance!

    What is it with all you William/ Bill cardiologists...  all achieving medical miracles in a world of super-sized ego's and Pharma-driven gimmicks...

  • G

    11/27/2007 12:07:00 AM |

    Dr. Davis, You mentioned that for patients with Type 2 diabetes in your book (yes, finally got my hands on a copy! -- will need to order FAR in advance for Xmas gifts this yr! I'm giving the 'gift of life'!!) that reversal is rare?

    Now with so many tools (and the ability for you to post and share your progress) it seems like that is no longer true? Would you say so in your practice? and to what degree at this current time? what if pts are really really extremely aggressive with carbs, exercise and dramatic wt loss?

    BTW, the patient we discussed earlier (it's been about 1 mon now)is now doing substantially better.  He's exerting without angina! THANK YOU SO SO MUCH!! We actually stopped Actos and I think that made a huge difference also. (When combined with insulin, there appears to be a large increase in CHF (although person had no edema, PND or other signs), just shortness of breath with any exertion.)
    We're normalizing the Vit D and I think that has made the h-u-g-e-s-t difference (besides possibly the Actos -- no echo so don't know?). I haven't had a chance to start as many as the other interventions yet but will. He's doing a lot more raw nuts as well (and no wheat). DO you think the omega-6's are bad -- found in wheat, corn products? (I don't recall reading that here yet?) Especially for certain subpops? like high Lp(a) like my friend?

    Other labs have come back. I was wondering if I could get your thoughts briefly?
    CRP 0.5 (yes couldn't BELIEVE it!)
    DHEA-S 275 ug/dL
    TESTOST 440 ng/dL
    lipoprotein(a) 110 (wow)
    PTH 23
    Fructosamine 300 (we're getting there)
    Home glucose averages now 140s (1hour postprandially -- getting better! my goal normal < 120-130)

    Specifically, is there room to go with DHEA (for the Lp(a))? alpha-lipoic acid (not mentioned in book or blog? any experience yet?)  

    (L-carnitine and the Heart Bar are scheduled for his next visit)
    I am so grateful for all your commentary and advice...

  • Dr. Davis

    11/27/2007 12:30:00 AM |

    Thanks, G.

    I don't know much about the San Jose center, but I do know that the Walnut Creek scanner is an EBT device. They are also very interested in prevention/reversal there.

  • Dr. Davis

    11/27/2007 12:37:00 AM |

    The entire vitamin D concept is new since I wrote Track Your Plaque in 2003. Since then, I have seen type II diabetics drop their heart scan scores with addition/correction of vitamin D blood levels.

    For Lp(a), I nearly always try niacin first, then DHEA and/or testosterone as adjuncts. However, there may be little room for much testosterone supplementation, given a "middling" testosterone level. DHEA works better in females, but can still exert some effect in males (using doses of 25-50 mg per day in males). I've been disappointed with l-carnitine's effect, for the most part.

    I've not systematically used lipoic acid. I'm presuming you mean to enhance insulin responsiveness. When I have tried it, the results were small, but only in a few patients.

    Wheat avoidance, vitamin D, and exercise exert enormous effects, as you are witnessing. Keep up the great work with your people!

  • G

    11/27/2007 1:00:00 AM |

    Hi! Thank you for responding! I'm so relieved that your seeing the same progress in Type 2 DM's (and Dr. Blanchet as well)!
    I had thought as much...  I know when you published the book, it was already 'out-dated' by 12-18months, right? Your frustration is palpable but you are so correct, I certainly would not be of such enormous help to the individuals I work with if I hadn't come across your information 6-8wks ago (to share the hopefulness of actual CAD secondary and primary reversal)! Keep up the strong work!
    Regarding lipoic acid, it has been mentioned by people studying longevity (many of course support the same lifestyle changes as you -- the CRON-ers, Bruce N. Ames, etc). It is usually mentioned in conjunction with L-carnitine for mitonchondrial rejuvenation.

    I appreciate the info on the Walnut Creek site! We'll be checking it out! Take care, G

  • larry

    11/27/2007 6:45:00 AM |

    I get more impressed every time I read this blog!

    I am thinking about firing my Cardiologist and would like to know about Heart Scan Centers in Portland, OR as well as a Cardiologist to refer.

    Briefly, my medical history is that I have survived a Stroke in May 2004.

    In 2006, I didn't feel well and went to my Primary Doctor. He did a Nuclear Stress Test in his office. I was advised to not take my Beta Blockers for the test. I experienced a life threatening arrhythmia during the test. I went home and was advised to take my Beta Blocker for another test the next day. This time I was told things were fine.

    Three months later I had chest discomfort which brought me to the ER. No heart attack but sent to a Cardiologist for more testing. Again, round two of the Nuclear Stress Test and was advised not to take my Beta Blockers. I voiced my hesitation. Not being a Cardologist, I proceded to take the test. This time I had V-Tach.

    I have had a triple bypass on my left Coronary Artery and a stent the size of Rhode Island in my right Coronary Artery. Surprizing, no MI at any time.

    I have lost close to 35 pounds since surgery and am an avid bicycler. I have pedalled close to 600 miles during the month of August during lond distance events.

    The more I read about diets and heart disease, it appears to me that the AHA Cardiac Diet is a waste of time.

    Help me, Doc! Point me in the right direction!

  • Dr. Davis

    11/27/2007 12:01:00 PM |

    Hi, Larry--

    For the closest scan center, see our Scan Center listings on the www.trackyourplaque.com website. However, be warned that we rely on people like you to update us and thus the listing is neither complete or up-to-date. (As we grow, we clearly need to hire somebody just to keep this service updated.)

    I would invite you to look at our membership website, www.trackyourplaque.com. At your stage of the game, while a heart scan may or may not be possible anymore, the principles of the program still apply. I would suggest to you that, given what you've told me, the causes of your heart disease have yet to be uncovered. This will be crucial for long-term prevention/slowing/reversal of your disease.

    We are only starting to develop a listing of interested physicians. However, a lipidologist might be someone to look for in your area.

  • larry

    11/27/2007 4:49:00 PM |

    My heart disease was caused by smoking. I stopped smoking in 1993 after a lifetime of abuse. High blood prsseure was the cause of the stroke. My carotid arteries are clear.

    My LDL was 29 after surgery and my HDL was 65. I believe that exercise is key to me, but I must 'feed the machine' that propels me on my bike.

    Thanks for the imput, I will look into it..

  • Dr. Davis

    11/27/2007 10:52:00 PM |

    Don't forget about lipoprotein(a), a very important pattern that is hugely ignited by smoking.

  • Paul Kelly - 95.1 WAYV

    11/29/2007 7:42:00 PM |

    Hi Dr, Davis,

    You wouldn't believe the trouble i'm having trying to get someone to give me a CT Heart Scan without trying to talk me into a Coronary CTA. Every facility I've talked to keeps harping on the issue that calcium scoring only shows "hard" plaque...and not soft. I also had a nurse today tell me that 30% of the people that end up needing a coronary catheterization had calcium scores of ZERO. That doesn't sound right to me. What determines whether or not someone needs a coronary catheterization anyway?

    As always - thanks in sdvance for your response!

    Paul

  • Dr. Davis

    11/29/2007 11:56:00 PM |

    Paul-

    Please see an upcoming Heart Scan Blog on this question. I am embarassed and angered that scan centers dispense such information.

  • Dr. Davis

    12/6/2007 2:21:00 AM |

    Paul--

    A full length report on this topic is on the Track Your Plaque website. I would invite you to take a look. Both devices are reasonable choices for a heart scan, though EBT has less than half the radiation exposure of a 64-slice device.

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