Monday, August 6, 2012

Glycemic Index

Glycemic index (GI) is essentially a measure of how a particular food compares to white bread or pure sugar. Starchy foods with a low GI are digested and absorbed more slowly than foods with a high GI. Factors that affect GI include cooking and food processing, as well as the presence of other components such as fat, protein, and dietary fiber.

For example, orange juice is relatively sugary and it has a glycemic index of 87.  Milk contains more fat and protein, and its glycemic index is 39. It is not practical to avoid ALL high GI foods. Some low GI foods may not always be a good choice because they are high in fat.

Jessica Herschberg for reports "black beans and other legumes are low glycemic index (GI) foods, meaning the carbohydrate in them is released slowly into the body. Low GI foods can help control blood sugar levels and may enhance performance because of their steady release of energy."

When I started exercising regularly, I had to moderate the glycemic index of foods I ate in order to maintain an energy balance.  High glycemic index foods (for me at least) were consumed by my body immediately, giving me a quick "sugar high" followed by a persistent and lethargic low.  Low glycemic index foods (for me) were a way to prolong the energy gained by each meal, where sugars were released slowly via fermentation in the colon rather than digestion in the small intestine. One such food is quinoa, with a GI of 53.  There are many things to do with quinoa if you are unfamiliar with it.

Other foods I like are (GI values from Searchable GI Database, University of Sydney):
Hummus, dip, glycemic index = 6
Lentils, red, dried, boiled, glycemic index = 21
Lentils, green, dried, boiled, glycemic index = 22-37
Barley, pearled, boiled 60 min, glycemic index = 35
Oatmeal, instant, whole-grain, glycemic index = 55
Brown Rice, Japonica, short-grain, glycemic index = 62

Preparation makes a difference! For example,
Carrots, raw, glycemic index = 16
Carrots, peeled, boiled, glycemic index = 33
Carrots, boiled and ground to a smooth paste, glycemic index = 60

From Atkinson, et al. 2008, average GI derived from multiple studies by different laboratories:
Spagetti, white, glycemic index = 49 + 2
Porridge, rolled oats, glycemic index = 55 + 2
Couscous, glycemic index = 65 + 4

You know what they say, "an apple a day keeps the doctor away."
Apple, raw, glycemic index = 36 + 2
Dates, raw, glycemic index = 42 + 4
Orange, raw, glycemic index = 43 + 3
Banana, raw, glycemic index = 51 + 3

Not all vegetables are created equal, some are sweeter than others!
Sweet corn, glycemic index = 52 + 5
Sweet potato, boiled, glycemic index = 63 + 6
Pumpkin, boiled, glycemic index = 64 + 7
Potato, boiled, glycemic index = 78 + 4

Snacking is great, but healthy eating is better.
Kidney beans, glycemic index = 24 + 4
Potato crisps, glycemic index = 56 + 3
Popcorn, glycemic index = 65 + 5
Rice crackers, glycemic index = 87 + 2

Best Foods For Runners,7120,s6-242-301--10200-3-1X2X3X4X6X7-7,00.html
Oranges, Black Beans, Mixed Greens, Salmon, Whole-grain Bread, Frozen Vegetables, Whole-grain Pasta, Chicken, Frozen Mixed Berries, Dark Chocolate, Low-fat Yogurt, Sweet Potatoes

Best Foods for Cyclists
Try to choose lower glycemic index carbs for one of your high carb days and higher glycemic foods on the other. Lower glycemic index carbohydrates have been shown to be better choices for weight reduction than high glycemic carbs, according to a study published in March 2007 in the American Journal of Clinical Nutrition.

Blog for another day: Dietary Fiber!  Separate blog for another day: antioxidant and prooxidant effects of BPA.

Works Cited
Searchable Glycemic Index Database, University of Sydney
Harvard School of Public Health,
Foster-Powell K, Holt SH, Brand-Miller JC. "International table of glycemic index and glycemic load values: 2002." American Journal of Clinical Nutrition. Vol 76, Pages 5-56.
Atkinson, FS, Foster-Powell, K, Brand-Miller, JC. "International Tables of Glycemic Index and Glycemic Load Values: 2008" Diabetes Care. Vol 31, Pages 2281-2283.

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