By Suzanne Dixon, MPH, MS, RD
Healthnotes Newswire (August 20, 2009)—The debate on what type of diet promotes optimal health has been raging for decades. Is it low-carb, low-fat, or something in between? For preventing breast cancer, the latest research suggests it may be something in between, and that the quality of carbohydrates in the diet may matter more than the quantity.
By the numbers
As part of the long-running Swedish Mammography Cohort study, researchers asked 61,433 women about their eating habits and followed the group to see who got breast cancer. The researchers were particularly interested in how carbohydrates in the diet might influence breast cancer risk.
After about 17 years of follow-up, neither total carbohydrate intake nor glycemic index was strongly related to the risk of most types of breast cancer. However, the researchers found that glycemic load significantly increased risk of a type of breast cancer known as ER+/PR- (estrogen receptor-positive, progesterone receptor-negative).
Women whose diets had the highest glycemic load were 81% more likely to be diagnosed with ER+/PR- breast cancer. Carbohydrate intake was related, less strongly, to risk of this cancer type as well.
Choosing the right carbs
While glycemic index (GI) has been all the rage in the diet book industry, the lesser-known glycemic load (GL) is a better measure of the quality of carbohydrates. GI provides a way of ranking carbohydrates according to how 50 grams of carbohydrate from that food affects our blood sugar level, but it unfortunately does not take into account the serving size eaten. GL, on the other hand, takes a food’s GI into account and adds an adjustment for the amount of carbohydrates found in a normal serving size. To see why this matters, consider carrots and white pasta.
The GI of carrots is 131, while pasta has a GI of 71 (a higher GI indicates a greater adverse effect on blood sugar levels). From this, we conclude that carrots are an “unhealthy,” high-GI food, and that carrots are worse for our health than a big bowl of pasta. However, one large carrot (a serving) contains just 4 grams of carbohydrate. One serving of pasta, about a cup cooked, provides 40 grams of carbohydrate.
This means that one serving of carrots has a low, healthy GL of 5.2. The GL for a serving of pasta is quite high at 28. In order to have the same GL from carrots as from a serving of pasta, you would have to eat nearly two pounds of carrots! Considering this, along with numerous other studies indicating that diets that put stress on our blood sugar–regulating mechanisms may increase breast cancer risk, it makes sense why this study shows a high-GL diet, but not a high-GI diet, may increase breast cancer risk.
Load up on complex carbs
The following tips will put you on the right track with your carbohydrate choices:
• Go au natural. Generally, the less processed a food is, the lower its GL.
• Pick whole fruit and vegetables instead of fruit juices. The fiber in these foods naturally slows the absorption of their natural sugars, improving blood sugar control in the body.
• Don’t be fooled by GI. More information is available about the glycemic index than the glycemic load of foods, so it’s tempting to use GI as a guide for making healthy choices. Just remember that this can be misleading.
• Combine protein, fat, and carbohydrates together for the healthiest meals and snacks. For example, try a banana with peanut butter or an apple with a handful of almonds for a snack instead of a banana and apple together.
(Int J Cancer 2009;125:153–7; Willett, W. Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating. Simon & Schuster. 2001.)
Suzanne Dixon, MPH, MS, RD, an author, speaker, and internationally recognized expert in chronic disease prevention, epidemiology, and nutrition, has taught medical, nursing, public health, and alternative medicine coursework. She has delivered over 150 invited lectures to health professionals and consumers and is the creator of a nutrition website acclaimed by the New York Times and Time magazine. Suzanne received her training in epidemiology and nutrition at the University of Michigan, School of Public Health at Ann Arbor.
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