The Glycemic Index

Last week I mentioned that carbs such as potatoes, bread, rice, and pasta are bad because they are the equivalent of dumping a couple of teaspoons of sugar directly into your blood, which causes a spike in blood sugar levels, triggering a responsive release of insulin, which is usually too much, pushing the blood sugar level low, which results in hunger. Does that mean all carbs are bad?

The answer is no, just those carbs that are high on the glycemic index. The glycemic index is a relative ranking from zero to 100 of carbohydrates in accordance with their effect on blood glucose (blood sugar). Carbs that are high on the index are those that are metabolized quickly, resulting in the spike in blood glucose levels. Carbs low on the index are metabolized more slowly, releasing their sugars more gradually. A ranking of 55 or lower on the glycemic index is consider better than a higher ranking. Not surprisingly, the foods most people consider the best tasting are high on the list. Here’s a list from Harvard Medical School of 60 typical foods.

FOOD Glycemic index (glucose = 100)
HIGH-CARBOHYDRATE FOODS
White wheat bread* 75 ± 2
Whole wheat/whole meal bread 74 ± 2
Specialty grain bread 53 ± 2
Unleavened wheat bread 70 ± 5
Wheat roti 62 ± 3
Chapatti 52 ± 4
Corn tortilla 46 ± 4
White rice, boiled* 73 ± 4
Brown rice, boiled 68 ± 4
Barley 28 ± 2 (I’m not sure why they put barley on the “high” list)
Sweet corn 52 ± 5
Spaghetti, white 49 ± 2
Spaghetti, whole meal 48 ± 5
Rice noodles† 53 ± 7
Udon noodles 55 ± 7
Couscous† 65 ± 4
BREAKFAST CEREALS
Cornflakes 81 ± 6
Wheat flake biscuits 69 ± 2
Porridge, rolled oats 55 ± 2
Instant oat porridge 79 ± 3
Rice porridge/congee 78 ± 9
Millet porridge 67 ± 5
Muesli 57 ± 2
FRUIT AND FRUIT PRODUCTS
Apple, raw† 36 ± 2
Orange, raw† 43 ± 3
Banana, raw† 51 ± 3
Pineapple, raw 59 ± 8
Mango, raw† 51 ± 5
Watermelon, raw 76 ± 4
Dates, raw 42 ± 4
Peaches, canned† 43 ± 5
Strawberry jam/jelly 49 ± 3
Apple juice 41 ± 2
Orange juice 50 ± 2
VEGETABLES
Potato, boiled 78 ± 4
Potato, instant mash 87 ± 3
Potato, french fries 63 ± 5
Carrots, boiled 39 ± 4
Sweet potato, boiled 63 ± 6
Pumpkin, boiled 64 ± 7
Plantain/green banana 55 ± 6
Taro, boiled 53 ± 2
Vegetable soup 48 ± 5
DAIRY PRODUCTS AND ALTERNATIVES
Milk, full fat 39 ± 3
Milk, skim 37 ± 4
Ice cream 51 ± 3
Yogurt, fruit 41 ± 2
Soy milk 34 ± 4
Rice milk 86 ± 7
LEGUMES
Chickpeas 28 ± 9
Kidney beans 24 ± 4
Lentils 32 ± 5
Soy beans 16 ± 1
SNACK PRODUCTS
Chocolate 40 ± 3
Popcorn 65 ± 5
Potato crisps 56 ± 3
Soft drink/soda 59 ± 3
Rice crackers/crisps 87 ± 2
SUGARS
Fructose 15 ± 4
Sucrose 65 ± 4
Glucose 103 ± 3
Honey 61 ± 3

There are some surprises, at least to me, on this list. Rice crackers, typically thought of as a diet snack, have a GI value of 87, while chocolate is only 40. White spaghetti is better than couscous.  Potato chips are actually better than popcorn (another supposedly “healthy” snack food). Of course, this list is only one measure of a food’s value.  While chocolate might have less than half the GI of rice crackers, there’s no accounting for the number of calories in similar portions. And popcorn, if it’s unbuttered, has far less fat than potato chips.

Nevertheless, for people with Type 1 or Type 2 diabetes, a glycemic index evaluation of all foods is now recommended by the American Diabetes Association, the Canadian Diabetes Association, the UK Diabetes Association and others to maintain blood glucose levels and thereby better manage or prevent diabetes.

Week 2 Results

Week 3 began yesterday, so it’s time to see if this low carb eating is still helping weight loss. Again, it’s kind of hard to tell from the bathroom scales, but it looks like I’m down another 1-1 1/2 lbs. for the week, making my total weight loss somewhere in the 3-4 lb. range, having started around 211 and now being somewhere in the 207-208 range.

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