Friday, December 28, 2012

Glycemic Load, Overall Health, and a New Study on Colon Cancer Survival

"Glycemic index."  It's a term that likely rings a bell, but unless you're a dietician or research scientist, you can certainly be excused for not knowing exactly what it is and why it's even important.  But, like a lot of similar concepts, it's really not that complicated once you look into it a little bit.

Basically, the glycemic index is a lot like the speedometer in your car.  While a speedometer measures how fast you're moving, the glycemic index measures how fast a food you eat gets converted into glucose in your body.  The higher the number, the more quickly and strongly the food boosts blood glucose levels, which can cause a host of reactions that over the long run can lead to weight gain and an increased risk of heart disease and diabetes. Some studies have also linked diets filled with high glycemic index foods to an increased risk of some cancers, but this link isn't perfectly clear and is an active area of research.

Adding to this science base, is a new study in the Journal of the National Cancer Institute that links diets high in high glycemic index foods and carbohydrates with the return of cancer and earlier death in patients with stage III colon cancer (study).

The study, part of the federally-sponsored Cancer and Leukemia Group B trial, followed a thousand colon cancer survivors for an average of seven years and looked at the carbohydrate intake and overall glycemic load of patients' diets to see how this related to cancer recurrence and survival.  What the researchers found was that those patients with the highest overall glycemic load diets were almost twice as likely to have their cancer return (recurrence) compared to those with the lowest glycemic load diets. Overall carbohydrate intake had a similar effect.  Looking at overall survival, high glycemic load diets and high carbohydrate intake diets increased the risk of dying by 75 - 80 percent.  In the United States, the large majority of carbohydrates eaten are refined carbohydrates, which have a high glycemic index, so it's not surprising that the results for carbohydrate intake tracked closely to those of overall glycemic load.

Exactly how a high glycemic load diet may promote cancer recurrence is unknown.  But, high glycemic index foods can cause spikes in blood glucose and insulin, which can have wide-ranging effects throughout the body that some lab studies suggest can lead to cancer cell growth and inhibit cancer cell death.

Though this study doesn't provide concrete evidence that a high glycemic load diet hurts survival in colon cancer patients, it does add to overall evidence that a diet filled with low glycemic index foods is a healthy choice for everyone, and there's good evidence that it'll lower the risk of heart disease and diabetes, which are important concerns even for most cancer survivors.

In general, a diet with a lower glycemic load includes a lot of whole grains (like oatmeal, whole wheat, and wild rice) and whole fruits and vegetables. It's also low in refined grains (like white bread, white rice, and regular pasta) and sugary foods (like sweets and soda). (See figure).

For more on healthy steps after a cancer diagnosis, see Cancer Survivors' 8ight Ways to Stay Healthy After Cancer.  For general healthy steps, see 8ight Ways to Stay Healthy and Prevent Disease.


Glycemic Index of Selected Foods

High
(Over 65)
Medium
(45 – 65)
Low
(Under 45)
Glucose 100
Raisins 65
Grapes 43
Carrots 92
Coca cola 63
Dried Beans (cooked) 42
Molasses 87
Jelly 63
Pear 41
Pancakes 83
Bananas (Ripe) 62
Orange 40
Cornflakes 80
Sweet Corn 61
Apples 39
Cheerios 74
Bran Muffins 60
Chocolate 36
Baked potato 73
Table sugar 59
Wine 35
White Rice 72
Honey 58
Beer 35
Dark bread 72
Oatmeal (cooked) 58
Chocolate Milk 34
Watermelon 72
Kiwis 58
Milk 34
Corn chips 70
Muesli Cereal 56
Yogurt 33
White bread 69
Cookies (general) 55
Ice cream (full fat) 30
Bagels 69
Oatmeal Cookies 55
Strawberries 25
Pita Bread 69
Special K Cereal 54
Barley (uncooked) 25
Cornmeal 68
Orange Juice 53
Cherries 22
French fries 67
Peas 52
Peanut butter 13
Brown Rice 66
All Bran Cereal 51
Walnuts 13
Pineapple 66
Pasta 50
Broccoli 9

Ice Cream (low fat) 50
Spinach (cooked) 9

Grapefruit Juice 48
Lettuce 9

Cake 47
Eggs 0


Fish 0


Hamburger 0


Hard cheese 0
Source: Nurses Health Study Nutrient Database



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