The Basics:
How does insulin work?
- In a healthy person, insulin helps turn food into energy — in an efficient manner. The stomach breaks down carbohydrates from food into sugars, including glucose. Glucose then enters the bloodstream, which stimulates the pancreas to release insulin in just the right amount. Insulin, a hormone, allows glucose to enter cells throughout the body, where it is used as fuel. Excess glucose is stored in the liver.
What is IGF-1 (Insulin-Like Growth Factor-1)?
- IGF-1 is an important protein (hormone) that stimulates cells (including many cancer cells) to grow and is involved in multiple aspects of metabolism (protein, fat and carbohydrate). IGF-1 is released by the liver in response to the pancreas’s secretion of insulin into the blood stream. Read more about IGF-1′s role in cancer development and growth here.
Elevated blood glucose levels have been associated with increased risks of the following cancers:
- pancreas, liver, colon and endometrium.
High insulin levels are associated with increased risks of the following cancers:
- colon, endometrial, breast and pancreatic
Elevated blood levels of IGF-I (insulin-like growth factor-1) have been associated with increased risks of the following cancers:
- prostate, breast and colorectum
What is insulin resistance?
- If you’ve developed a condition called insulin resistance (or “metabolic syndrome”), the body makes excess insulin, but the muscle, liver, and fat cells do not use or respond properly to the insulin. It is a state in which your cells are not responding to insulin appropriately, so the sugar in your blood cannot get into your cells.
- To compensate, your pancreas pumps out more insulin to try to get the sugar out of your blood and into your cells.
- The hyperinsulinimia (high blood insulin) that results is able to maintain normal blood sugar levels and delay the onset of diabetes.
What causes insulin resistance?
- It is estimated that 1 in 4 people (without diabetes) has a genetic predisposition for insulin resistance.
- Whether or not the insulin resistance develops depends (in large part) on your eating and exercise habits.
- Not being physically active is a huge reason why insulin resistance develops.
- In addition, gaining weight/body fat (especially around the middle) is a common trigger. And once you have insulin resistance, it’s more difficult to lose weight. So, obesity and insulin resistance is really a viscous cycle–obesity contributes to insulin resistance, and insulin resistance contributes to weight gain!
- People who maintain a healthy weight and enjoy regular physical activity rarely develop insulin resistance, even if they have an underlying genetic predisposition.
Learn more about insulin resistance.
Carbohydrates are the main source of glucose (sugar) in your diet.
(Carbohydrates get converted into glucose during digestion)
Cancer cells require sugar to grow.
- Keeping blood glucose down to a low or normal range seems to be important.
Insulin is produced whenever there is sugar in the blood.
- Individuals with high insulin levels (and an associated protein, “IGF-1″) appear to have an increased risk of cancer progression and recurrence.
Some carbohydrates raise blood glucose and insulin higher than others.
- It is important to understand their distinction.
Stay away from refined (“bad”) carbohydrates (high glycemic index) as much as possible as they cause a rapid rise in blood sugar, insulin and insulin-like growth factor-1 (IGF-1). In turn, insulin and IGF-1 stimulate factors for inflammation and the growth of cancerous cells. These high glycemic index carbohydrates include:
- white sugar
- honey
- high-fructose corn syrup
- evaporated cane juice
- flour-based products (cookies, cakes, white bread, crackers, french fries, candy, pastries, etc.)
Complex carbohydrates are considered “good” carbohydrates because they contain vitamins, minerals, fiber, and a host of important phytonutrients (many of which have been reported to prevent and fight cancer.) Unlike refined carbohydrates, complex carbohydrates do not cause the rapid rise in blood sugar and insulin (lower glycemic index) as they are digested and absorbed.
Complex carbohydrates include:
- Whole grains (brown rice, buckwheat, wild rice, quinoa, barley, whole-wheat pasta, whole-grain bread, etc.)
- Vegetables
- Legumes (beans, chickpeas, lentils, whole and split dried peas, etc.)
- Fruit (particularly the non-tropical fruits: apples, pears, oranges, grapefruits, peaches, plums, apricots, berries, etc.)
Does the sugar in fruit feed cancer?
The level of glucose in the blood is increased when fruit is eaten, but much less than in the case of refined sugars or white flour. This is partly because fruit contains fiber and many other components along with fructose (which is the form of sugar contained in fruit and in honey), and these additional components modulate the effect of the fructose. So, for example, although fructose can “make you fat”, it doesn’t increase the level of insulin in the blood, or the level of IGF, the growth hormone that accompanies insulin.
Should cancer patients stay away from sugars?
- It’s not so much about staying away from sugar, but rather decreasing your intake of high glycemic index carbohydrates. Sugar is essential to life. We just want to avoid rapid spikes in blood glucose, insulin and IGF-1 levels.
- The other issue comes down to consuming too many calories, a common problem when eating diets that are loaded with simple, high glycemic index carbohydrates. For many cancer types, obesity is a risk factor for cancer development, progression and recurrence.
- Researchers from the University of Toronto reported on women in remission for breast cancer who had been followed for a number of years. Those with the highest levels of insulin at the beginning of the study were twice as likely to suffer a relapse and three times more likely to develop metastases than women whose diet contained less sugars and who thus had lower levels of insulin. (Read more here)
- Numerous cancers (i.e. colon cancer) have been demonstrated to be sensitive to the effect of sugars in the diet, although the association has not been rigorously studied in all of them. Why do you think PET scans use a radioactively-labelled sugar to find tumors…because most tumors love sugar. When tumors metabolize the radioactive sugar they light up on the scan.
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