Phytochemicals & Chemoprevention

Cancer and Sugar Metabolism

Date: April 14, 2002

by Chaya Venkat

Cellular Starvation Is A Feature of Cancer

Did you know that roughly 40% of all cancer patients die of malnutrition, literally starved to death by their cancers?

We are all sensitized to watch out for the so-called "b-symptoms" of fatigue and weight loss, symptoms that tells the doctors that CLL is on the warpath. Did you ever wonder why even with extra helpings of Ben & Jerry's Chunky Monkey ice cream, the weight just kept dropping?

The key to the questions is sugar metabolism, and how healthy cells and cancer cells use this food as a source of energy. Back in 1931, Dr. Otto Heinrich Warburg first discovered that cancer cells have a fundamentally different energy metabolism compared to healthy cells. He was awarded the Nobel prize for this discovery.

Normal cells in the body use sugar as a fuel for cellular functions in an elegant and extremely efficient process called the Krebs cycle. In this process, sugar is "burned" using oxygen that we absorb through our lungs, and the final products are carbon dioxide and water. All of the energy in the sugar is completely wrung out in this aerobic process. There are times when the body's cells need energy in large quantities, and not enough oxygen is available to generate it by this aerobic process. An example is during vigorous exercise. When oxygen is limited, because your cells' energy needs outstrip your lungs capacity to supply oxygen, cells can derive energy from "anaerobic" (non-oxygen based) glycolysis. This is basically a type of fermentation of sugar, a process that does not need oxygen. This is a very inefficient way of producing energy, less than 5% of the total energy available from the sugar is actually generated in this way. A large amount of lactic acid is produced in the process, which is transported over time to the liver for further processing. You athletes out there, you can attest to the effect of build up of lactic acid in your muscles, the sense of tiredness and fatigue that accompanies.

Cancer cells have very high energy requirements, especially when they are growing rapidly in numbers. But they cannot utilize sugar, their favorite food source, with the efficiency of normal cells. They have defective mitochondria, which locks them into the anaerobic fermentation route. Put the two facts together, the high energy requirement of cancer cells and their inefficient use of sugar, and you can understand what is happening when you eat that extra slice of pecan pie. The sugar is basically going to feed the cancer, and the normal cells in your body get very little benefit from the consumed calories. Your liver has to work extra hard to boot, converting all that lactic acid. Sounds like a good thing, in our diet crazy culture, but not so good if you have CLL and the weight keeps dropping, no matter how many calories you eat.

The build up of lactic acid in the body as the cancer cells gobble up sugar may explain some of the fatigue symptoms, even though you have been taking it easy all day. (Another contributor to tiredness can be low levels of hemoglobin and red blood cells as a result of the CLL, causing anemia and poor oxygen transport in the body).

Here is an interesting tidbit. You may have heard of PET scan (positron emission tomography). This is an extremely accurate way of pinpointing the location of cancer cells in your body, much more effective than CAT scans or ultrasound. Guess how they do it: they give you a low dose of radioactive material, along with sugar, prior to the scan. The cancer cells absorb the sugar to the tune of 40 times more than the normal cells, and in the process they also get 40 times more of the radioactive tracer. The scan then looks for the sources of radiation in the body, thereby pin-pointing the location of the cancer cells. Even small clusters of malignant cells and very small malignant lymph nodes can be identified this way.

In hospitals, when a patient is wasting away and needs nutrition in a hurry, an intravenous drip of mostly glucose solution is used. In the case of cancer patients, this would be like throwing gasoline on a fire, in an attempt to put it out. Slowly but surely, many hospitals are switching to low sugar, low carb intravenous drips for cancer patients.

Yes, that's right, carbohydrates are also implicated. When there is not much sugar available, the body starts making some from other available nutrients. Carbohydrates are good candidates. Those of you who have had some experience with diabetes know that not all carbohydrates are created equal. There is something called glycemic index (GI), which measures how fast and easily a given carb gets converted to sugar. Heavily refined carbohydrates have a high GI, which is bad. Whole grain bread, for example is better than white Wonder bread. Vegetables are better than sugar rich fruits.

Want to starve your cancer cells, slow them down and make it really difficult for them to grow and flourish? You may want to consider drastically reducing your sugar intake; make like you are a diabetic, in terms of your dietary choices, even if you are not diabetic. Stay away from the candy and ice cream, it is not going to help you slow the weight loss, it will only feed your cancer. Concentrate on high protein diet, rich in low GI vegetables and carbohydrates. Actually, all of this is just simple good nutrition for any one, not just cancer patients.

I believe vigorous exercise plays a role too, in rapidly sopping up the easily available sugar in the blood stream. Basically your normal cells go into competition with the cancer cells for a limited resource, namely blood sugar. And normal cells have the advantage of being much more efficient in how they use the sugar. There have been several messages from members that document that their lymphocyte count did not grow during periods of vigorous exercise, such as getting into training to run a marathon.

This is an interesting and important subject, and useful in the sense that you can actually do something about your nutrition and exercise, as opposed to just waiting for that second shoe to drop. 

References:

http://www.mercola.com/article/sugar/sugar_cancer.htm;
http://www.mnwelldir.org/docs/nutrition/sugar.htm.

Abstract:

Nutritional and physiological consequences of tumour glycolysis.

Dills W L Jr.

Department of Chemistry, University of Massachusetts at Dartmouth

A frequent characteristic of many malignant tumours is an increase in anaerobic glycolysis, that is the conversion of glucose to lactate, when compared to normal tissues. The causes of this intensification involve changes in enzyme and glucose transporter levels, shifts of the isoenzyme patterns in the cancer cells to those similar to foetal tissues and a breakdown in the normal control mechanisms, most notably the Pasteur effect. The host must adapt, with a corresponding increase in gluconeogenesis. This change, along with other adaptations made by the host, eventually results in the syndrome known as cancer cachexia, which is characterized by anorexia and depletion and redistribution of the host energy stores. In some ways many malignant tumours behave much like parasites, drawing upon the host for nutrients such as glucose and returning waste products such as lactate to the host for recycling or disposal. This cycling of glucose and lactate between host and tumour has been the target for a number of proposed and tested treatments, with regard to the possible inhibition of tumour growth and/or possible prevention of some or all of the cachectic effects. Some of these suggested treatments have reached the point of clinical testing and show promise for continued research.
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[Metabolico-nutritional changes in the cancer patient]

[Article in Italian]

Rossi Fanelli F, Cangiano C, Muscaritoli M, Cascino A.

The severe impairment of the nutritional state, which usually accompanies malignant diseases, heavily contributes to the high morbidity and mortality rates observed in cancer patients. Nevertheless, the utility of an artificial energy supply to these patients is still controversial because the nutrients given to replete the host may also stimulate tumor growth. Consequently, a correct nutritional approach for cancer patients should be based upon a well-defined understanding of tumor as well as host-metabolic needs. In this regard, the most typical metabolic abnormalities observed in cancer patients and experimental animals are examined.

Specific modifications of the plasma levels of different groups of amino acids--including glucogenic, aromatic, sulphur-containing and branched-chain amino acids--have been observed in cancer patients independently of the their degree of malnutrition, glucose tolerance and tumor diffusion. This may reflect a series of specific modifications induced by the neoplastic tissue on host's protein turnover. Little information is available regarding the protein metabolism in the neoplastic tissue. A number of attempts have been made to reduce tumor growth by withholding single amino acids considered essential to the tumor; nevertheless, the results obtained are still controversial. The two major abnormalities of carbohydrate metabolism observed in cancer patients are an increased glucose turnover and an impaired glucose tissue disposal. The former seems to be due to an increased glucogenesis, whereas the latter may be attributed to an insulin resistance in contrast to the high anaerobic glucose utilization observed in the neoplastic tissue.
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