Deadly Carbohydrates The Lethal Sugar/Cancer ConnectionOctober 2014
By Stephanie Martinson
A new study shows what researchers have suspected for years—consuming carbohydrates dramatically increases the risk for a common type of breast cancer, a kind that is notoriously hard to treat.1
The study, published earlier this year in Cancer Epidemiology, Biomarkers & Prevention, revealed that postmenopausal women treated for breast cancer were:
- Two times more likely to have recurrence if their carbohydrate intake remained stable or increased after surgery,
- 70% more likely to have a recurrence if their tumors tested positive for “insulin-like growth factor-1,” or IGF-1 (IGF-1 increases in response to excess carbohydrate intake),
- Likely to have a 5-fold increase in the risk of recurrence if they had the combination of an IGF-1 receptor-positive tumor plus a stable or increased carbohydrate intake.1
While the study focused on reducing future cancer recurrences, it has tremendous implications for women who have not yet experienced breast cancer, and for that matter, for everyone concerned about preventing cancers in the future.
A powerful way to reduce cancer risk is to get control of your intake of refined carbohydrates, IGF-1, and insulin levels.2 Yet despite the known risks of excess carbohydrate intake (obesity, cancer, and vascular disease), cutting out carbs can be challenging for most people.
This article investigates the connections between carbohydrate intake and breast cancer risk. It then explores recent data showing how consuming and absorbing too many carbohydrates is associated with elevations in IGF-1, which increases the risk of breast cancer recurrence. It concludes with real-world solutions to help mitigate the adverse impact of excessive carbohydrate intake.
The Breast Cancer/Carbohydrate Connection
There is growing interest among the scientific community in the relationship between carbohydrate consumption and cancer, with a special focus on breast cancer.
Diets high in readily digested carbohydrates (like those found in most processed foods) are associated with increased cancer risks. Women who consume great amounts of foods with a high glycemic index (the rate at which carbohydrates raise blood sugar levels) have a 57% increased risk of breast cancer, while those who eat food with a high glycemic load (a product of the glycemic index and the total available carbohydrate content of a food) have as much as a 153% increase in risk.3
This increased risk has been specifically identified in people who are overweight or obese. Overweight women, for example, are 35% more likely to get breast cancer if they eat a lot of foods with a high glycemic index.4 Asian women whose primary carbohydrate source is white rice are 19% more likely to develop breast cancer with every 100-gram (about 3 ounces) increment in their rice intake per day. But those who eat brown rice, a slower-digesting starch, are 24% less likely to develop breast cancer with every 100-gram increment of rice consumed per day.5 When glucose levels get so high that they enter the diabetic range, breast cancer risk grows to twice that of postmenopausal women with normal sugar levels.6
In addition to increasing the risk of developing breast cancer in postmenopausal women, glycemic load and total carbohydrate consumption are also associated with the worst kinds of breast cancer, namely those lacking receptors for estrogen and progesterone molecules.7 Triple negative breast cancers—in which cancer cells do not contain receptors for estrogen, progesterone, or HER2—cannot be treated with treatments that oppose hormone actions. This leaves patients to suffer through more deadly, and often less effective, treatment options, thereby lowering survival rates substantially.8
On the other hand, the Nurses’ Health Study, a large, women’s health-focused research project, demonstrated that women who followed a diet high in vegetables and low in carbohydrates were 19% less likely to develop estrogen receptor negative breast cancer.9
Carbohydrates And Cancer Risk
There is a deeper problem with high carbohydrate consumption, even when blood sugar levels don’t rise.
High-carbohydrate diets produce chronic elevations of insulin as the body tries to deal with the excess sugar.4 Protein glycation caused by excess glucose also contributes to insulin resistance, raising blood glucose levels and potentially insulin levels as a result.10 Because insulin is a growth factor, elevated insulin levels represent a potential breast cancer threat because it appears to stimulate breast cancer cells to grow and reproduce.11
Studies now reveal another danger—one that goes beyond glycation and insulin levels—which raises a woman’s risk for breast cancer in relation to her carbohydrate intake.
This danger is posed by a growth factor so closely related to insulin that it is called “insulin-like growth factor-1,” or IGF-1. IGF-1 now appears to be a culprit that links high-carbohydrate intake to cancer risks throughout the body, but with special relevance for breast and possibly prostate cancers.1,12
How IGF-1 Increases Breast Cancer Risk
Serum levels of IGF-1 are associated with breast cancer risk in premenopausal women, and the higher the IGF-1, the greater the risk.6,13 Studies show this risk increase to be between 60 to 86%, compared to women with lower levels. For premenopausal women 50 or younger, this increased risk grows to 150%.14,15
Some studies, however, demonstrate about a 38% increase in breast cancer risk in women older than 50 with high IGF-1 concentrations.16,17
IGF-1 has a strong impact on breast cancer because two of its functions, promoting tissue growth and suppressing programmed cell death (apoptosis ), are hallmarks of malignant cells. The actions of IGF-1 are necessary for growth and development through childhood.18 But in adults, higher levels of IGF-1 can pose problems, including increasing cancer risk and shortening life span.19
IGF-1 is a protein hormone similar in structure to insulin.20 It is a growth factor involved in normal mammary gland development and promotes healthy cell proliferation, growth, and reproduction and thereby helps the developing mammary gland form correctly.21
In adults, increased carbohydrate consumption appears to raise IGF-1 production and increase the risk of cancer.19,22 In children, IGF-1 appears to be more beneficial, since rapid cell replication and cell survival is desired.20,23 In addition to stimulating cell growth and division, IGF-1 appears to suppress apoptosis,24,25 one of the body’s many defense mechanisms against cancer. When this protective mechanism fails, abnormal, precancerous cells survive and reproduce instead of being naturally removed from healthy tissue.14,26
These two mechanisms—growth promotion and diminished apoptosis—are hallmarks of malignant cells. That’s why high levels of IGF-1, with its ability to promote tissue growth and suppress apoptosis, are a potent cancer promoter.14,22,27 Lab research shows that when developing mammary cells are exposed to high levels of IGF-1, it causes the cells to form large sphere-like clumps with sustained proliferative activity, abnormal changes suggestive of carcinogenesis.21
IGF-1 can promote cancer through its local effects on specific cell types. Making matters worse, cancers that develop under IGF-1 stimulation are often resistant to chemotherapy and radiation.28,29 Recent evidence suggests IGF-1 and estrogen work together to promote cancer in human breast tissue.30
How Inhibiting IGF-1 Reduces Cancer Risk
On its own, IGF-1 is not the problem. Like most signaling molecules, IGF-1 exerts specific actions on cells only when it binds to specific IGF-1 receptors. IGF-1 receptors are found in many tissues. This increased IGF-1 signaling and receptor expression is recognized as one factor in breast cancers becoming resistant to treatment.29
IGF-1 receptor levels are higher in other cancers as well, including prostate cancer. High IGF-1 levels, along with reduced levels of the main serum-binding protein IGF-BP3 (insulin-like growth factor binding protein 3) in the blood predispose men to developing prostate cancer.31 As with breast cancers, increased IGF-1 signaling is associated with prostate cancers becoming independent of hormonal control. This makes them much more difficult to treat with conventional anti hormone therapies.32
Fortunately, in studies that used antibody molecules to inhibit IGF-1 binding to IGF-1 receptors, several factors needed for cancer progression were inhibited, including protein synthesis, cell growth, and survival.33 Furthering this point, people with a congenital IGF-1 deficiency have significantly reduced rates of cancer.19
In addition, research shows that the antidiabetic drug metformin (which has multiple health-promoting benefits) suppresses IGF-1 signaling in human pancreatic cancer cells in culture.34
Research has shown that women with plasma IGF-1 levels less than 120 ng/mL are more likely to survive breast cancer.35 In fact, lowering IGF-1 plasma levels has now been recommended to:35
- Reduce the risk of developing breast cancer in high-risk women,
- Slow breast cancer progression in patients in the early stages of their disease,
- Lower the risk of breast cancer recurrence, and
- Increase the probability of surviving breast cancer.
For these reasons, Big Pharma is keenly pursuing drugs that inhibit IGF-1 receptor binding or signaling for use against a variety of cancers, though to date many of these study results have been miserable.26,36-39
Fortunately, there are a number of natural ways to reduce the damage caused by IGF-1.
Reduce Your Body’s Exposure To Carbohydrates And IGF-1
The most direct way to reduce your body’s exposure to the carbohydrates that induce IGF-1 activity and its related cancer risk is to eat a diet containing fewer carbohydrates and simple sugars. However, this is challenging for many people, particularly those who are also trying to reduce consumption of animal proteins and fats.40 Similarly, you can lower overall exposure to carbohydrate breakdown by consuming a diet high in fiber (which is not readily broken down by the intestine); but again, high-fiber diets can be unappealing and uncomfortable for many people.40
A more palatable and practical option to reduce carbohydrate exposure is to use specific nutrients that limit or slow starch breakdown in the intestine, which in turn reduces blood sugar levels and insulin levels.40 By reducing these levels, you can “turn down the volume” on the IGF-1 system and gain more control of your dietary risk for cancer.23,41,42
Table 1 (next page) offers examples of some of the nutrients known to be most effective at reducing your body’s exposure to excessive dietary carbohydrate, potentially modulating IGF-1 and insulin levels.
As you can see from Table 1, there are many options for gaining control of your body’s exposure to excess carbohydrates. Note that these products act by several different mechanisms; this is a critical and widely recognized factor in the effectiveness of these natural supplements.