by Patrick Quillin, PHD, RD, CNS

During the last 10 years I have worked with more than 500 cancer patients as director of nutrition for Cancer Treatment Centers of America in Tulsa, Okla. It puzzles me why the simple concept "sugar feeds cancer" can be so dramatically overlooked as part of a comprehensive cancer treatment plan.

Of the 4 million cancer patients being treated in America today, hardly any are offered any scientifically guided nutrition therapy beyond being told to "just eat good foods." Most patients I work with arrive with a complete lack of nutritional advice. I believe many cancer patients would have a major improvement in their outcome if they controlled the supply of cancer's preferred fuel, glucose. By slowing the cancer's growth, patients allow their immune systems and medical debulking therapies-- chemotherapy, radiation and surgery to reduce the bulk of the tumor mass--to catch up to the disease. Controlling one's blood-glucose levels through diet, supplements, exercise, meditation and prescription drugs when necessary can be one of the most crucial components to a cancer recovery program. The sound bite--sugar feeds cancer--is simple. The explanation is a little more complex.

The 1931 Nobel laureate in medicine, German Otto Warburg, Ph.D., first discovered that cancer cells have a fundamentally different energy metabolism compared to healthy cells. The crux of his Nobel thesis was that malignant tumors frequently exhibit an increase in anaerobic glycolysis--a process whereby glucose is used as a fuel by cancer cells with lactic acid as an anaerobic byproduct--compared to normal tissues.1 The large amount of lactic acid produced by this fermentation of glucose from cancer cells is then transported to the liver. This conversion of glucose to lactate generates a lower , more acidic pH in cancerous tissues as well as overall physical fatigue from lactic acid buildup.2,3 Thus, larger tumors tend to exhibit a more acidic pH.4

This inefficient pathway for energy metabolism yields only 2 moles of adenosine triphosphate (ATP) energy per mole of glucose, compared to 38 moles of ATP in the complete aerobic oxidation of glucose. By extracting only about 5 percent (2 vs. 38 moles of ATP) of the available energy in the food supply and the body's calorie stores, the cancer is "wasting" energy, and the patient becomes tired and undernourished. This vicious cycle increases body wasting.5 It is one reason why 40 percent of cancer patients die from malnutrition, or cachexia.6

Hence, cancer therapies should encompass regulating blood-glucose levels via diet, supplements, non- oral solutions for cachectic patients who lose their appetite~ medication, exercise, gradual weight loss and stress reduction. Professional guidance and patient self-discipline are crucial at this point in the cancer process. The quest is not to eliminate sugars or carbohydrates from the diet but rather to control blood glucose within a narrow range to help starve the cancer and bolster immune function.

The glycemic index is a measure of how a given food affects blood-glucose levels, with each food assigned a numbered rating. The lower the rating, the slower the digestion and absorption process, which provides a healthier, more gradual infusion of sugars into the bloodstream. Conversely, a high rating means blood-glucose levels are increased quickly, which stimulates the pancreas to secrete Insulin to drop blood-sugar levels. This rapid fluctuation of blood-sugar levels is unhealthy because of the stress it places on the body (see glycemic index chart, p. 166).

Sugar In the Body and Diet

Sugar is a generic term used to identify simple carbohydrates, which includes monosaccharides such as fructose, glucose and galactose; and disaccharides such as maltose and sucrose (white table ?ugar). Think of these sugars as different-shaped bricks in a wall. When fructose is the primary monosaccharide brick in the wall, the glycemic index registers as healthier, since this simple sugar is slowly absorbed in the gut, then converted to glucose in the liver. This makes for "time-release foods," which offer a more gradual rise and fall in blood-glucose levels. If glucose is the primary monosaccharide brick in the wall, the glycemic index will be higher and less healthy for the individual.

As the brick wall is torn apart in digestion, the glucose is pumped across the intestinal wall directly into '\ the bloodstream, rapidly raising blood-glucose levels. In other words, there is a "window of efficacy" for glucose in the blood: levels too low make one feel lethargic and can create clinical hypoglycemia; levels too high start creating the rippling effect of diabetic health problems.

The 1997 American Diabetes Association blood-glucose standards consider 126 mg glucose/dl blood or greater to be diabetic; 111125 mg/dl is impaired glucose tolerance and less than 110 mg/dl is considered normal. Meanwhile, the Paleolithic diet of our ancestors, which consisted of lean meats, vegetables and small amounts of whole grains, nuts, seeds and fruits, is estimated to have generated blood glucose levels between 60 and 90 mg/dl.7 Obviously, today's high-sugar diets are having unhealthy effects as far as blood-sugar is concerned. Excess blood glucose may initiate yeast overgrowth, blood vessel deterioration, heart disease and other health conditions.8

Understanding and using the glycemic index is an important aspect of diet modification for cancer patients. However, there is also evidence that sugars may feed cancer more efficiently than starches (comprised of long chains of simple sugars), making the Index slightly misleading. A study of rats fed diets with equal calories from sugars and starches, for example, found the animals on the high-sugar diet developed more cases of breast cancer.9 The glycemic index is a useful tool in guiding the cancer patient toward a healthier diet, but it is not infallible. By using the glycemic index alone, one could be led to thinking a cup of white sugar is healthier than a baked potato. This is because the glycemic index rating of a sugary food may be lower than that of a starchy food. To be safe, I recommend less fruit, more vegetables, and little to no refined sugars in the diet of cancer patients.

What the Literature Says

A mouse model of human breast cancer demonstrated that tumors are sensitive to blood-glucose levels. Sixty-eight mice were injected with an aggressive strain of breast cancer, then fed diets to induce either high blood-sugar (hyperglycemia), normoglycemia or low blood-sugar (hypoglycemia). There was a dose-dependent response in which the lower the blood glucose, the greater the survival rate. After 70 days, 8 of 24 hyperglycemic mice survived compared to 16 of 24 normoglycemic and 19 of 20 hypoglycemic. 10 This suggests that regulating sugar intake is key to slowing breast tumor growth.

In a human study, 10 healthy people were assessed for fasting blood-glucose levels and the phagocytic index of neutrophils, which measures immune-cell ability to envelop and destroy invaders such as cancer. Eating 100 g carbohydrates from glucose, sucrose, honey and orange juice all significantly decreased the capacity of neutrophils to engulf bacteria. Starch did not have this effect.ll

A four-year study at the National Institute of Public Health and Environmental Protection in the Netherlands compared 111 biliary tract cancer patients with 480 controls. Cancer risk associated with the intake of sugars, independent of other energy sources, more than doubled for the cancer patients. 12 Furthermore, an epidemiological study in 21 modern countries that keep track of morbidity and mortality (Europe, North America, Japan and others) revealed that sugar intake is a strong risk factor that contributes to higher breast cancer rates, particularly in older women.13

Limiting sugar consumption may not be the only line of defense. In fact, an interesting botanical extract from the avocado plant (Persea americana) is showing promise as a new cancer adjunct. When a purified avocado extract called mannoheptulose was added to a number of tumor cell lines tested in vitro by researchers in the Department of Biochemistry at Oxford University in Britain, they found it inhibited tumor cell glucose uptake by 25 to 75 percent, and It Inhibited the enzyme glucokinase responsible for glycolysis. It also inhibited the growth rate of the cultured tumor cell lines. The same researchers gave lab animals a 1.7 mg/g body weight dose of mannoheptulose for five days; it reduced tumors by 65 to 79 percent.14 Based on these studies, there is good reason to believe that avocado extract could help cancer patients by limiting glucose to the tumor cells.