You see it everywhere: the supposedly expert advice that processed grains will make your blood sugar spike while whole grains won’t. So don’t eat white bread, those supposed experts tell you. Switch to whole wheat bread instead. But… it’s a false claim.
- When at your local library searching for info on the glycemic response to foods, look for Jennie Brand-Miller, not Gary Taubes.
Let’s get right to the meat of the matter by looking at white bread versus whole wheat bread. Whole wheat bread might very well be better for you on various measures, but let’s look for now only at the glycemic effect. The following link is to a table from a paper in an actual scientific journal. The Glycemic Index figures there aren’t merely the casual opinion of some pop diet-book writer.
International Tables of Glycemic Index and Glycemic Load Values: 2008 Table 1
White wheat bread: 75
Whole wheat bread: 74
There is only 1 point difference. No, it’s not an error. So, how can that be? Have the self-styled experts even bothered to look at a table of GI values? Probably not. Unfortunately, many other people, from cardiologists to dieters to diabetics, are believing the simplistic summary that the supposed experts are putting out.
Let’s next try rice.
White rice, boiled: 73
Brown rice, boiled: 68
Not much difference there, either. So let’s look at that incarnate of processed carb evil, pasta.
Spaghetti, white: 49
Spaghetti, whole meal: 48
Once again there’s not much difference between those two, but notice that white pasta is much lower than either whole wheat bread or brown rice.
So what is the Glycemic Index exactly?
Using the two breads as an example, the research would typically proceed as the following. The people who are the subjects would eat 50 grams of white bread. Then they’d have their fingers stuck over the following two hours to measure how much their blood glucose had risen. On another day, they might do the same with 50 grams of the whole wheat bread. It’s simply a matter of taking measurements, no theory is involved.
The GI figures show that there are no simple rules to follow, such as that processed grains are necessarily high GI while the whole grains aren’t. So how would you know what is high and what is low? You have to look up each food.
Then why are the two breads so similar in GI?
Now we get more into the realm of speculation, though most of it is pretty solid. It turns out that insoluble fiber like wheat bran doesn’t have much effect on GI once it’s been all finely ground up. Modern high speed metal rollers turn the harvested wheat, both starch and bran, into a fine powder. The powdered bran doesn’t impede digestion much at all of the powdered starch that’s mingled with it.
Now, if you were to instead swallow the whole wheat berries, as they’re called, the GI would presumably be very low because the starch is still surrounded by the bran.
So there are no low GI breads?
It turns out that stone ground whole wheat bread is significantly lower than the typical whole wheat bread. Rye bread and pumpernickel (a type of rye) have lower GI values. So does sourdough bread. If you have a blood glucose meter, you can always test for yourself.
At least we all know that sugar will spike your blood sugar.
No, we don’t. Look at the GI for soda, it’s 59. Table sugar (sucrose) is half glucose but the other half is fructose. Pure glucose has a GI of 100, but fructose is low at around 20. So it makes sense that the combination would be around 100 + 20 / 2 = 60. But we don’t have to speculate, because measurements do show it’s around 60.
Practically speaking…
Some say that you can’t accurately predict the GI of a combined meal, so the GI is useless. But look at it this way, if you think that high blood glucose after a meal is a problem, then simply choose stone ground bread over either white or typical whole wheat. Arnold’s bread is known to be good on GI. For rice, long grain varieties are generally better than short grain (because they have more of the lower GI amylose type of starch than of the higher GI amylopectin type of starch). Uncle Ben’s is known to be good on GI.
(Note: I am not an employee or secret agent for Arnold or Uncle Ben.)
Choose prunes over raisins. They seem so alike yet prunes have insoluble fiber, which forms a gel. Put some psyllium (such as Metamucil) in a glass of water for ten minutes and see how difficult it would be for digestive enzymes to get at the starch. In fact, you can likely reduce the GI of any meal a lot by having it with psyllium.
Dairy is low, barley is low. While spaghetti is generally low, Ramen noodles are not. I’ve seen dates listed in various places as being low or very high; maybe it depends on the variety and where they’re grown, or on preparation. E.g., canned spaghetti is not low, because it’s gotten mushy; meanwhile, making your own spaghetti al dente results in a lower GI than from longer cooking.
Fat should be around zero on the GI, so adding fat to a meal would tend to lower the GI of the meal. By following these suggestions, you might not know the GI of your meal for sure — but you will know for sure that the GI is lower than what it would otherwise have been.
It also seems prudent to check more than one site when looking into any food. One of the authors in the study above is Jennie Brand-Miller. Though she didn’t invent the GI, I see her as an authority to be trusted in this field. Most writers of pop diet books probably need to be triple checked.
When my father was very sick and ended up with glucose intolerance, I thoroughly researched all of this and so he ate this way and never had to use the insulin that he had been prescribed. However, whenever he went into the hospital, he had to get insulin every time. So I also know very well that, in his case (being on a high dose of the corticosteriod drug prednisone), it is absolutely possible to control blood sugar without drugs.
Speaking of insulin, it should be said that the insulin response to foods is different than their GI. While the Insulin Index generally follows the GI, it doesn’t have to do so and the very notable exception is that proteins can be very insulinogenic. But that is another story.
My summary: The debate can and will go on about lo-carb or lo-fat diets. It is not known for certain whether eating low GI will help with losing fat or avoiding artery disease. But one thing should be known out there, because it’s not a matter of theory but only of measurements: whole grains are not necessarily low GI and the dreaded processed foods are not necessarily high.
note: here is the link to the study that contains the table referred to above
International Tables of Glycemic Index and Glycemic Load Values: 2008
Fiona S. Atkinson, RD, Kaye Foster-Powell, RD and Jennie C. Brand-Miller, PHD
Diabetes Care December 2008 vol. 31 no. 12 2281-2283
