Dietary Sugar and Cancer: A Sweet Relationship?

Dietary Sugar and Cancer: A Sweet Relationship?

Over the past several decades, a vast number of studies have made the connection
between sugar and cancer. In fact, a casual search on PubMed
(www.ncbi.nlm.nih.gov/pubmed), the online search engine of the U.S. National
Library of Medicine, brings up over twenty thousand articles on “glucose and
cancer.” (For our purposes, “glucose” is another word for sugar.) Clearly, this is an
area of intensive investigation!

As you remember from chapter 2, refined carbohydrates, such as white bread,
rice, pasta, and many cereals, convert to sugar before they’re even swallowed. So
keep in mind that when we say “simple” or “refined” carbohydrates, we’re also
talking, in essence, about sugar. One long-range Swedish study conducted in the late
1980s suggested a link between simple carbs and a common type of breast cancer,
estrogen-receptor positive, progesterone-receptor negative (ER+/PR–). The study
analyzed the eating habits of 61,433 women and concluded that “a high carbohydrate
intake may increase the risk of developing ER+/PR– breast cancer” (Larsson,
Bergkvist, and Wolk 2009).

Put simply, “When we lower blood glucose, we can slow cancer growth,”
explains nutritionist, cancer specialist, and author Patrick Quillin (2005, 119). A
1985 study (Santisteban et al.) on rats demonstrated this link dramatically. First,
aggressive cancer cells were injected into the rats. Then, the rats were fed diets
containing assorted quantities of sugar to see which tumors would grow the most
rapidly. As anticipated, the rats with the highest levels of blood glucose fared poorly
and had the shortest survival time, while those with the lowest glucose levels lived
the longest. It makes sense, then, to eat foods that do not disrupt the balance of
sugars in your body. To help do this, we check a food’s glycemic index: a numerical
ranking, from 0 to 100, of a food’s potential to alter blood glucose levels. Glucose
itself is ranked 100 on the index. White bread has a high glycemic index, which
means it converts to glucose quickly, causing a rapid surge in blood sugar. Morecomplex
carbohydrates, such as whole grains and beans, create a more gradual
change in blood glucose and are considered to have a lower glycemic index.

Proteins and fats fall low on the glycemic index as well.
As a general rule, leafy vegetables—such as broccoli, lettuce, and cabbage—
have a lower glycemic index than root vegetables, like potatoes, carrots, yams, and
beets. Most bread, pasta, muffins, cereal, bagels, and all other refined grains are
carbohydrates with a high glycemic index. Therefore when planning a healthy meal,
try to include larger portions of carbohydrates with a low glycemic index and
smaller portions of carbohydrates with a high glycemic index.

You may also be familiar with the term glycemic load. Glycemic load takes into
account the amount of carbohydrates in a typical portion of food, so many
nutritionists consider it a more accurate measure of a food’s effect on blood sugar.
For example, a small portion of white rice would have a much lower glycemic load
than a plateful of rice. In the Swedish study mentioned previously (Larsson,
Bergkvist, and Wolk 2009), women whose dietary intake fell into the highest
category of glycemic load had an 81 percent increased risk of ER+/PR– tumors.