As I keep losing posts, I'll try to start a new thread.
Somehow my post has been misinterpreted on the sugar-cancer thread to imply that I support the consumption of processed sugar (sucrose) without limitation. This was not my intention at all. I merely wished to point out that processed sugar is frequently demonized by many and that it "feeds" cancer. In my opinion, this is misguided and I will try to explain why I think this is so. This long post is as much for my own benefit to clarify my thinking as it is to provide information that can be verified by others. Most of the references that I am basing this on are undergraduate texts on
biochemistry and molecular cell biology. Feel free to dispute any of the claims here.
First of all, sucrose is enzymatically broken down (by sucrase) in the body into glucose and fructose (another simple sugar). Both sugars are used in metabolism by first enzymatically phosphorylating them
(by hexokinase) inside cells (in the cytoplasm) so that they cannot be easily transported out of the cell. The transport of glucose and fructose into the cell is controlled by different types of glucose transporters, GLUT4, which is activated by insulin, and GLUT1 and GLUT3, which do not require insulin. Thus insulin spikes lead to increased transport of glucose into the cells via GLUT4. Cancer cells are known to preferentially take up glucose (the Warburg effect). This happens because cancer cells are typically in a hypoxic (low oxygen) environment since they are poorly supplied in oxygen by blood vessels. The hypoxic environment leads to increased levels of the protein HIF-1-alpha (hypoxia inducible factor) that is normally kept in check by oxygen dependent degradation. The HIF protein regulates the transcription of many enzymes involved in glycolysis and growth factors, such as the VEGF (vascular endothelial growth factor which promotes the formation of new blood vessels) and the GLUT1, GLUT3 transporters. Thus the cancer cell has a much higher level of enzymes involved in the conversion of glucose (and fructose) to pyruvate and 2 molecules of ATP, more glucose, and factors which promote the formation of blood vessels. Since there is little oxygen present, the pyruvate does not enter the mitochondria for oxidative phosphorylation (citric acid cycle, etc..) but undergoes a "fermentation" process in which pyruvate is converted into lactate (and NADH is oxidized to
NAD+, catalyzed by lactate dehydrogenase). The lactate can leave the cell and generally produces a locally acidic environment around the cancer cell.
I believe this is the origin of the statement that cancer thrives in an acidic environment. The reality is that the glycolysis pathway in cancer cells produces the acidic environment. The acidity is rapidly neutralized away from the cell by the natural buffering system in the body. Incidentally,
anaerobic metabolism of sugars also occurs in cells without mitochondria, such as red blood cells. The overall process is about 15 times less efficient than metabolism in the presence of oxygen, so a cancer cell must take up lots of glucose to survive (hence the importance of the GLUT1, GLUT3 transporters that do not depend on insulin). The upshot of all this is that depriving cells of glucose (low carb diet etc..) simply preferentially starves healthy cells, since cancer cells take up 10 to 15 times more glucose than normal cells.
Low sugar diets are dangerous, since glucose is fundamental to normal operation of cells, and particularly brain cells. They are also ineffective, since healthy cells are preferentially starved. Balanced, low calorie diets are a much more sensible way to fight cancer, and starvation conditions may even turn on some protective mechanisms in cells.
High insulin levels are to be avoided since they trigger higher concentrations of free insulin growth factor (IGF-1). There are receptors on the membranes of cells that are activated by IGF which stimulates cell growth through enhanced DNA synthesis, protein synthesis and cell division (via the RAS-RAF and Akt-mTOR pathways). This encourages tumor growth.
So the question remains, what foods provoke a large insulin response? This question is one where I have a fair amount of expertise since, in addition to having to deal with stage IIIc colon cancer, I have had type I diabetes for a number of years and have observed first-hand the connection between diet and insulin requirements.
The insulin response of foods is typically measured on a scale where pure glucose (i.e. dextrose or maltose) is given a score of 100. Table sugar (sucrose) has a score OF ONLY 61, since it is a
disaccharide (complex sugar) of glucose and fructose, and fructose is metabolized more slowly. I should emphasize that processed sugar produces only a moderate insulin response (not a huge insulin peak), comparable to sweet corn or orange juice. Some other scores are (source: "The New Glucose Revolution" by Brand-Miller et al.):
corn flakes: 80
white flour: 70
peanut M and Ms: 33
glutinous white rice: 92
white bagel: 72
raw banana: 52
milk chocolate: 42
and so on. The point is, the glycemic response to many common foods normally considered to be healthy is greater than that of processed sugar. My experiences are consistent with the table above. Based on
this information, I believe one should pay careful attention to the glycemic response (and portion size, determining the glycemic load) of foods and try to minimize the load as much as is comfortable. A diabetic diet is generally a common-sense, healthy diet.
As for the issue of alkalinity and cancer, the pH of blood plasma and in the cytoplasm of cells is tightly regulated to a nearly constant value by weak acid buffers. In the case of the blood plasma, one of the primary buffers is carbonic acid formed from dissolved carbon dioxide absorbed in the lungs. This buffering system adjusts very quickly to any injection of acidity since there is a readily available source of carbon dioxide. In the cytoplasm, phosphates, bicarbonates and weak acid side chains of amino acids effectively buffer the pH to a constant value. Thus, eating different foods does not change the pH in the blood or around most cells. It can influence the pH of urine,
which contains by-products of digestion, but this has no relevance to the local pH near cells.
I do think juicing and eating foods rich in anti-oxidants is a good way to provide a balanced and healthy diet (when not undergoing chemotherapy). Such a diet is particularly important for those
of us hoping to discourage a recurrence.
Principles of Biochemistry, Lehninger, Fifth edition (2009)
Molecular Biology of the Cell, Alberts et al., Fifth Edition (2008)
The New Glucose Revolution, Brand-Miller et al., (1999)
Good health to all,