The evidence is getting stronger that taking in too much sugar increases your risk for cancers as well as for heart attacks, diabetes and Alzheimer's disease. This week, a study from M.D. Anderson Hospital in Houston shows how sugar may cause cancers to start and then to spread to other parts of the body (Cancer Research, Jan. 1, 2016).
The Study
Mice genetically-susceptible for breast cancer were divided into four groups based on four different sugar loads. At six months of age, 30 percent of those on a starch-control diet and 50-58 percent of those on sugar-enriched diets had developed breast cancers. The researchers showed that the more fructose the mice received, the greater the concentration of 12-LOX and 12-HETE in their breast cancer cells, and the greater the spread of cancer to the lungs and other parts of their bodies. 12-LOX and 12-HETE are enzymes that increase risk for inflammation that can stimulate normal cells to become cancerous.
The group of mice eating the lowest dose of sugar took in the equivalent in humans of six teaspoons of sugar each day. A 12-ounce can of soda contains 10 teaspoons of sugar. The maximum daily amount of added sugar recommended by the United States Department of Agriculture is six teaspoons a day for women and nine teaspoons a day for men.
Are Some Sugars More Likely to Cause Cancer than Others?
All of the sugars and starches that you eat are broken down into only four sugars that can be absorbed into your bloodstream: glucose, fructose, galactose and mannose. Only glucose is allowed to circulate in your bloodstream; the other three sugars are taken up by your liver and must be converted to glucose before they can be released into your bloodstream.
This study showed that as mice were given more fructose, their LOX-12 levels rose, and they grew larger and faster growing cancers that were more likely to spread. Inflammation is an overactive immunity that increases cancer risk. Fructose appears to be a more powerful cause of inflammation than glucose, so it is more likely to stimulates the metabolic process called 12-LOX that can cause cancer cells to spread through the body.
The March to Link Sugar and Cancers
• In 1924, Otto Warburg showed that cancer cells depend primarily on sugar as their source of energy (Biochem. Z, 1924;152:319–344, and Science, Feb 1956;123:309-14).
• Until 2014 we did not know whether excess sugar caused cancer or whether cells just needed to use more sugar once they became cancerous. Now we have evidence that that excess sugar can cause cancer (J Clin Invest, 2014 Jan 2; 124(1): 367–384: Glucose transporter molecules cause cancer by activating the EPAC/RAP1 and O-GlcNAc pathways).
• Researchers at Johns Hopkins showed that two cancer-promoting genes, KRAS and BRAF, cause cancer by allowing the cancerous cells to survive when they are not supplied enough food sources of energy by increasing their absorption of sugar (Science Express, August 6, 2015).
• Normal cells live a limited number of doublings and then die. Cancer cells try to live forever and kill by becoming so numerous that they invade and destroy normal tissues in your body. Cancer cells produce a protein called PARP14 that enables them to use sugar to make them grow faster and larger and not die the way normal cells do (Nature Communications, Aug 10, 2015).
• Many studies show that anything that raises blood sugar levels in humans is associated with increased cancer risk: overweight, diabetes, excess belly fat, lack of exercise, and lack of vitamin D. Excess sugar intake is associated with at least 26 different cancers in humans. The evidence is strongest for cancers of the breast, pancreas and colon. With each passing month, new studies show an association between sugar added to foods and drinks and increased risk for certain cancers.
My Recommendations
Of the four basic sugars that you absorb from your food, fructose looks like the one most likely to cause the inflammation associated with increased cancer risk. I believe that sugars added to foods and drinks are far more likely to be associated with increased cancer risk than those same sugars consumed in their natural form in fruits and vegetables. I believe that you should eat plenty of whole fruits (but not fruit juices), and a wide variety of vegetables. I strongly recommend that you limit sugar-added foods, particularly sugar-added beverages. See also my recent report on A Cure for Cancer is Coming
