The Diabetes-Cancer Connection

Unfortunately, some people diagnosed with cancer also have belly fat or large waists, a sign of insulin resistance and possible pre-diabetes. But, most medical doctors overlook the obvious signs of insulin resistance and pre-diabetes because the patient's fasting blood sugar is still in the normal range. In addition, being overweight or obese is associated with increased risks of cancers of the esophagus, breast (postmenopausal), uterus, colon, kidney, pancreas, thyroid, gallbladder, and possibly other cancer types. Don't let this medical oversight cause you to miss the opportunity to prevent a cancer diagnosis from happening to you! After all, it's a lot easier to prevent cancer than it is to fight it.

Evidence linking diabetes and high insulin levels to certain cancers has grown stronger over the past several years, leading scientists to investigate potential mechanisms.

A growing body of evidence is finding that having diabetes or signs of insulin resistance may lead to an increased risk of certain cancers.

The connection is strongest among certain types of cancers, including kidney, breast, prostate, pancreatic and colorectal.

“The trend emerging [in this area] is that the type 2 diabetes associated with high insulin levels is the biggest problem relating to cancer risk,” said Michael Pollak, M.D., a professor at the Department of Oncology and Director of the Cancer Prevention Research Unit at McGill University. But it’s not just type 2 diabetes, he added, this link is evident for everyone with pre-diabetes, which is a much larger group.

The Insulin-Cancer Connection

According to the Centers for Disease Control and Prevention, approximately 40 percent of Americans – 41 million people – are estimated to have pre-diabetes, a condition that increases the risk of developing diabetes. Hyperinsulinemia, too much insulin in the blood, is a sign of prediabetes. People can be unaware they have prediabetes for years before symptoms and rising glucose levels result in a diabetes diagnosis.

Hyperinsulinemia, type 2 diabetes and cancer all share a major risk factor: high body fat. AICR’s second expert report found that high body fat is convincingly linked to increased risk of several cancers, including pancreatic and colorectal.

The hormonal changes spurred by high body fat may be leading to increased risk of cancer and type 2 diabetes. Hyperinsulinemia could also act independent of body fat to increase cancer risk. “We know that lots of tumors have insulin receptors and research suggests insulin plays an important role in cancer, but it does not have to be a direct link,” said Dr. Pollak. “There may be other areas that insulin could affect.” Yet insulin, which stimulates cell proliferation and growth, appears to be one of the key mediators.

High levels of insulin, independent of body fat, are linked to increased production of insulin-like growth factor 1 (IGF-1). And IGF-1, which shares a similar structure to insulin, plays a key role in cell growth, proliferation and inhibiting apoptosis.

A Complex Link

Some of the strongest findings relating to diabetes, hyperinsulinemia and cancer risk relate to colorectal cancer, but – as in other cancers – there are no clear answers. In one recent study, researchers from the University of Minnesota found that women diagnosed with diabetes had a 50 percent higher chance of developing colorectal cancer than women without the disease. The researchers drew upon data from approximately 45,000 participants of a large screening study that began in the 1970s. The study analyzed data on women with no history of colorectal cancer or self-reported diabetes for eight years, who later developed colorectal cancer.

“We didn’t have information on insulin level, so we used diabetes as a proxy,” said lead study author Andrew Flood, Ph.D., Assistant Professor in the Division of Epidemiology and Community Health and the Masonic Cancer Center at the University of Minnesota School of Public Health. “But a lot of people have undiagnosed diabetes,” said Dr. Flood. “If insulin is the problem, then we thought people who were prediabetic would have elevated levels of insulin.”

To test this hypothesis, the researchers included women who were likely prediabetic at the beginning of the follow-up period (they were later diagnosed with diabetes). It is likely these women had hyperinsulinemia. Surprisingly, the link to cancer was lower – although still significant -- with the addition of the hyperinsulinemia group. “It could be that the people diagnosed with diabetes during follow-up hadn’t been hyperinsulinemic long enough to increase risk, or that people need to be hyperinsulinemic to a greater degree to see an effect.”

Responding to Insulin

After eating carbohydrates, the pancreas responds by producing enough insulin to transport the glucose from the bloodstream into the cells. Glucose is the cells’ energy source and without it, cells cannot function. If the cells do not respond to insulin (insulin-resistant), the pancreas pumps out more. Over time, it can take ever-increasing amounts of insulin for the cells to take in enough glucose. People with pre-diabetes and type 2 diabetes can have both high glucose and insulin levels. In some cases, blood can measure a normal glucose level but insulin levels are still elevated.

Recurrence and Outcome

In some cases where there is only a moderate link between insulin resistance and cancer risk, there is a strong relationship to cancer behaving aggressively and recurrence. In a preliminary finding, Dr. Pollak and his colleagues examined data from a trial involving approximately 600 post-menopausal breast cancer patients. Along with other hormones, insulin was measured at time of diagnosis and ten years later. The researchers found that obese participants who had the highest insulin levels at diagnosis showed significantly increased risk of disease recurrence.

Dr. Pollak’s results mirror studies in prostate and other cancers that show high levels of insulin or blood glucose are linked to advanced adenomas, recurrence or mortality. A study by Dr. Flood, for example, found that patients who recently had potentially precancerous polyps removed from their colon or rectum and who had elevated insulin and glucose levels were at higher risk of recurrence compared to those with the lowest levels. And patients having the highest glucose levels had especially elevated risk for recurrence of advanced adenoma.

FYI: Other disease pathology connections include: diabetes-heart disease, obesity-cancer, obesity-diabetes, and obesity-heart disease.

Key Point: The good news is that many of the nutritional principles used to manage diabetes and control blood glucose levels can be used to treat most cancers, i.e. a plant-based diet of green, leafy and bright-colored vegetables, raw juices, onions, garlic, plant oils, whole fruits, filtered water, etc. However, for treating cancer, the vegetables and fruits should be organic. Also, it is imperative to avoid the processed foods that contain refined flour, sugar, HFCS, PHO (trans fats), vegetable oils, and saturated fat and avoid most beverages especially soda, diet soda, bottled fruit juices, and cow's milk; plus, fast foods of course.

Note: For more information concerning alternative treatment strategies for cancer, go to the following web pages:
http://www.deathtodiabetes.com/Cancer_and_Diabetes.html
http://www.deathtodiabetes.com/Cancer_Fighting_Foods.html
http://www.deathtodiabetes.com/Cancer_Cure_Naturally.html

Reference: AICR ScienceNow Volume 25, Summer 2008 http://preventcancer.aicr.org/