Read Whole-Food Guide for Breast Cancer Survivors Online
Authors: Edward Bauman
When it comes to cancer, sugar is like gasoline to your car: it’s fuel. The notion that sugar “feeds” cancer has been around for almost a century, since Dr. Otto Warburg first determined in 1924 that cancer cells have a way of metabolizing energy that is essentially different from that of noncancerous cells. More-current research has shown that cancer cells are completely reliant on simple sugar to sustain themselves, consuming sugar at a rate “ten to fifty times higher than normal tissues” (Block 2009). What does this mean to you? Feeding your body simple sugars and refined carbohydrates leads to an elevation in blood sugar, also known as “blood glucose,” which, effectively, feeds tumors exactly what they need to grow.
But it’s not just sugar itself that can harm your body’s ecosystem. Ingestion of sugars and simple carbohydrates activates the release of the hormone insulin and its close relative, insulin-like growth factor (IGF-1), both of which are potent cellular-growth promoters in their own right. High levels of blood sugar and insulin have long been known to set the stage for obesity, insulin resistance (prediabetes), and diabetes. It’s now becoming crystal clear that they may be doing the same for breast cancer and other cancers as well.
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. More-complex 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.
Are All Sugars Equal?
Consider the case of high-fructose corn syrup. It actually ranks low on the glycemic index, but don’t be fooled. It affects the body in multiple other ways that help create a hospitable environment for cancer. For starters, it is not found in nature; it is manufactured. The process by which it is created uses a “mercury-grade caustic soda” (Dufault et al. 2009) followed by a process known as acid hydrolysis, used to transform cornstarch into corn syrup. Because mercury is actually used to produce this special soda, the soda itself may become tainted and pass along its mercury-contaminated contents to sodas, soups, cereals, salad dressings, and other processed foods. Concerning cancer specifically, we believe that high-fructose corn syrup may:
High-fructose corn syrup has also been associated with liver damage (Ouyang et al. 2008).
In a nutshell, although all forms of sugar seem to promote cancer and adversely affect general health, we view this information from different perspectives and to different degrees depending on the type of sugar. High-fructose corn syrup seems to be one of the
most
harmful forms of sugar. Our advice to you is to avoid it at all costs.
A Hint of Sweetness
Just because we recommend avoiding sugar doesn’t mean you need to give up sweetness altogether! Most of us love the taste of sweetness on our palates from time to time. For those occasions, try one of the following sweeteners as a tasty alternative: raw honey, maple syrup (grade B or C is less processed and contains more nutrients than grade A), blackstrap or sorghum molasses, date or palm sugar (low on the glycemic index), stevia, or xylitol. These whole-food sweeteners have a far less dramatic impact on blood glucose because they contain nutrients, one of which is chromium, known for its stabilizing effect on blood sugar. Avoid artificial sweeteners, such as aspartame and Splenda; they are not foods but chemicals, with no known benefit and several suspected harmful effects.
Weight and Breast Cancer: A Well-Established Association
It has long been known that obesity is influential in the development of breast cancer and negatively affects a patient’s prognosis. A variety of large-scale studies have confirmed this association, including the European Prospective Investigation into Cancer and Nutrition (EPIC), which reported a 31 percent greater risk of developing breast cancer in obese women compared to nonobese women (Lahmann, Lissner, and Berglund 2004). What’s more, overweight women, particularly those with ER+ tumors, have a higher risk of local lymph node involvement (Verreault et al. 1989). Sadly, it is estimated that up to 50 percent of breast cancer deaths in postmenopausal women in the United States can be attributed to obesity (Petrelli et al. 2002).
Why do we see such an elevation of risk in overweight women? It appears to come down to a constellation of risk factors that converge into what one cancer researcher has dubbed an “oncometabolic state” (Wallace 2010). Features of this oncometabolic state include an abundance of belly fat, elevated glucose or elevated fasting insulin levels (or both), excessive blood lipids (fats), abnormal blood coagulation, and elevated inflammation levels. If these markers sound familiar, it’s because they are very similar and, in fact, overlap with markers for a more well-known condition known as
metabolic syndrome
, also known as insulin resistance or prediabetes.
Elevated Blood Glucose, Elevated Fasting Insulin, or Both
The amount of sugar and simple carbs you ingest will be fairly obvious to you in light of the food choices you make. The level of sugar that circulates in your bloodstream, however, is not nearly as transparent. That’s what makes the cycle insidious. Eating sugar causes blood sugar to surge and, subsequently, the hormone insulin to spike. Leaner bodies are better able to move this excess insulin into the cells, where it’s intended to be received. In overweight bodies, the tendency is for the excess glucose and insulin to hang around in the bloodstream, causing problems as the cells become increasingly resistant to the action of insulin.
Like gasoline, sugar is highly combustible, which is why it generates intense but short-lived energy. Over time, however, the body’s ability to deal with excess sugar diminishes. Eventually this cycle leads to
dysglycemia
, or an imbalance of blood sugar levels and insulin in the body. With dysglycemia, high glucose in the blood leads to high insulin production, which, in turn, can lead to insulin resistance. This is most significant for our purposes because recent data suggest that “hyperinsulinemia [excess insulin] is an independent risk factor for breast cancer and may have a substantial role in explaining the obesity–breast cancer relationship” (Gunter et al. 2009). The literature on this topic clearly serves as a wake-up call to be mindful of blood glucose and insulin control. Fortunately, you have the power to affect these factors because they are exceedingly responsive to dietary changes.
Assessing Your Glucose and Insulin Status
To assess how your body is handling glucose and insulin, your practitioner can order blood work that examines your fasting glucose and insulin levels, and a protein called
hemoglobin A1c
(HA1c). The fasting glucose number will tell you what your blood glucose level is at a given moment. A range between 70 and 90 is generally considered optimal.
An HA1c level is taken about once every three months, and reflects an average blood-sugar level over that period of time. Be aware that it’s possible to have seemingly normal blood glucose levels and still have high levels of insulin in your body. This is important to know so that, if necessary, you can adjust your diet to bring your fasting insulin level into a safe range. This, too, can be assessed through standard laboratory blood work.
Nurse practitioner and diabetes educator Rebecca Murray is assistant clinical professor of nursing at Yale University and runs a medical practice in Groton, Connecticut, where she specializes in diabetes and insulin resistance syndrome. Based on her thousands of patient case studies, Murray suggests (pers. comm.) that an optimal range for HA1c is between 4 and 5.6, and for fasting insulin up to 12 microunits per milliliter. These numbers are based on a twelve-hour fast (ibid.). Keep in mind that if you have a very heavy meal the night before your blood is drawn, your insulin levels could be higher than normal the next morning. So, be sure to test more than once (later that week, for example) to be sure you’ve got an accurate result.
Exercise Guidelines
You don’t have to train for a triathlon to help reduce your breast cancer risk. Regular exercise of any type cuts your risk of developing the disease and prevents a recurrence. The American Cancer Society (2011a) recommends thirty to sixty minutes of exercise at least five days a week.
All forms of regular exercise can help you reduce your weight. This, in turn, reduces glucose and insulin levels. Exercise is also effective for reducing estrogen levels (which can fuel ER+ tumors, the most common type), and overweight women carry a higher estrogen load than women of a healthy weight (McTiernan et al. 2004).
In fact in 2007, the
Journal of Clinical Oncology
(Pierce et al.) provided an exciting report indicating that increased physical activity, combined with a healthy diet, was associated with an approximately 50 percent reduction in mortality in breast cancer patients.
Whether as a strategy for breast-cancer prevention or for recovery, exercise extends life. Find an exercise program you can commit to; check out your local gym or recreation center and try something new, maybe that spinning class you’ve been thinking about. Whatever you choose, maintaining an exercise routine will surely reduce your risk of recurrence.
Diet: How Eating for Health Manages Dysglycemia
In the Eating for Health approach to managing dysglycemia, we recommend a diet that contains approximately:
In short, the key to glycemic control is to minimize the amount of refined carbohydrates consumed. As often as this is said, it is hard to hear and truly understand, because breads, pasta, bagels, and pastries are so much a part of our culture.
Reimagining Breakfast: The Power of Protein
Breakfast is the most important meal of the day; after all, you have fasted all night long. And the most important macronutrient to include in your breakfast is protein. That’s because:
A high-glycemic bagel, a muffin and coffee, or a bowl of sugary cereal won’t provide the protein you need to steady your blood-sugar level; you will find yourself craving carbs again soon after eating such a breakfast, setting up a vicious cycle. If you ignore your hunger and don’t eat, your blood sugar can drop too low, setting you up for a wild ride of blood sugar crashes and spikes. You might have a sense of these crashes from symptoms such as headaches, brain fog, irritability, or cravings.