Glycemic Index, Glycemic Load and Cancer Risk

 
This article provides an overview of glycemic index and glycemic load. We discuss what these numbers mean and why they are important for cancer prevention and total health.

Glycemic Index (GI) and Glycemic Load (GL) are words that are used in many popular diet books and news articles. This article provides an overview of Glycemic Index (GI) and Glycemic Load (GL). We provide PRACTICAL information on what these numbers mean. We discuss why GI and GL are important for cancer prevention and total health. We provide ideas for using this information in a dietary plan to reduce cancer risk. Factors such as age, gender, and genetics cannot be changed, but diet and nutrition can! This type of information will allow people who want to reduce their risk of cancer to take concrete and practical steps to accomplish this goal.

Note: Numbers appearing at the end of sentences indicate research references. References are listed at the end of each article.

What Are Glycemic Index & Glycemic Load?

About Glycemic Index

Glycemic Index (GI) is a number value that tells us how quickly the carbohydrate in a certain food will raise blood sugar in the body. The higher the number, the more quickly the carbohydrate from a given food will raise your blood sugar. Specifically, glycemic index is a standardized number that refers to how quickly 50 grams of carbohydrate from a specific food will turn into blood sugar in the body. This is compared to a 'reference' food. Most commonly, white bread or white table sugar is used as the reference food. In summary, glycemic index tells us how quickly 50 grams of carbohydrate from a specific food will turn into blood sugar in the body, as compared to 50 grams of carbohydrate from bread or table sugar. 

This allows us to rank foods, regarding how quickly they increase blood sugar in the body. The reference food, which is most often white bread, is given a value of 100. So, carbohydrate from foods that have a glycemic index below 100 is absorbed more slowly than carbohydrate from bread. Carbohydrate from foods that have a glycemic index above 100 is absorbed more quickly than carbohydrate from white bread.

What is glycemic load and why is it important? 

Glycemic Index does NOT tell us how many carbohydrates are in a SERVING of a specific food. This is why Glycemic Load (GL) can be more useful. Glycemic load takes into account the glycemic index of a food AND how many carbohydrates are in a normal SERVING of that food. To see why this is helpful, we can compare carrots to white pasta.

Using white bread as the reference food, 50 grams of carrot carbohydrate has a glycemic index of 131 and 50 grams of pasta carbohydrate has a glycemic index of 71 (1). This might make us think carrots are an unhealthy food and that they will raise our blood sugar faster than white pasta. However, one whole carrot (a serving) contains only 4 grams of carbohydrate. One cup of pasta (a serving) has 40 grams of carbohydrate. This means that the glycemic load, which adjusts glycemic index for serving size, is much lower for carrots.

A SERVING of carrots has a glycemic load of 5.2. The glycemic load for a serving of pasta (1 cup) is very high at 28 (1). In order to have the same glycemic load from carrots, you would have to eat nearly TWO pounds of them! This shows how glycemic index can be misleading. Just because a food has a high glycemic index, does NOT mean it will raise blood sugar quickly, when eaten in a normal serving size!

Why are these numbers important?

Glycemic Index and Glycemic Load are important because research studies tell us that eating higher glycemic index foods, eating a higher glycemic load diet, and eating more simple sugar may increase risk of several types of cancer including cancers of the breast, colon & rectum, endometrium (uterus), lung, ovary, pancreas and upper aero-digestive tract (2-10).

However, don't get bogged down in the specifics of the glycemic index and glycemic load of every food. You will drive yourself crazy trying to check these numbers for all of the foods you eat. Just remember, that your total pattern of diet is what matters. Eating one or two foods with a higher glycemic index is NOT important. If your overall diet is healthy, and the overall glycemic load of your diet is low, having a sweet treat now and then is not a problem. Also remember, glycemic index can be misleading. Carrots have a high glycemic index, but a LOW glycemic load. And, if you eat one food with a high glycemic index, but combine it with some low glycemic index foods, then the total glycemic load of your meal or snack will be lower. In summary, do not get concerned with each specific glycemic index or glycemic load number. Rather, focus your eating on a healthy dietary pattern with a low-glycemic load.

In general, WHOLE plant foods, such as vegetables, fruits, whole grains, and especially legumes (beans) have a LOW glycemic load. If you base your choices around these foods, you will do well to keep your glycemic load low. In addition to this, there is plenty of research that tells us that plant foods, especially fruits and vegetables, can reduce risk of many types of cancer (11). Therefore, if you focus your diet around WHOLE plant foods, you will both eat a diet with a low glycemic load AND you will be including the cancer fighting nutrients found in plant foods.

What about the Atkins' Diet?

The Atkins' Diet is a very popular weight loss diet. The Atkins' Diet focuses on low glycemic index foods and has a low glycemic load overall. Why isn't this diet a good one to follow?

The Atkins' Diet does have a low glycemic load, which can be a good thing. However, the downside of this diet is the LACK of healthy cancer fighting foods! The Atkins' Diet requires you to cut out most of the VERY FOODS that we know fight cancer the best - vegetables and fruits (11). Many health experts now feel that when it comes to beating cancer, what is missing from your diet (cancer fighting plant foods) may be more important than what is in your diet! In other words, not eating cancer fighting foods may increase your risk of cancer as much as eating the 'wrong' foods. For this reason, the Atkins' diet is not ideal for people who want to reduce risk of cancer.

In addition to this, the Atkins' diet can be loaded with saturated fat. Numerous studies tell us that saturated fat may increase risk of many types of cancer as well as heart disease, the two biggest killers in the United States (12). As well, heart disease is the number 1 or 2 cause of death in people diagnosed with breast or prostate cancer (13). For all of these reasons, a plant-based diet that contains plenty of vegetables, whole grains, legumes, and fruit appears to be the much better choice for people who are concerned about their risk of cancer. This type of diet will have a low glycemic load AND unlike the typical Atkins' diet, will contain thousands of healthy cancer-fighting phytochemicals .

Tips For Eating a High Plant Food, Low Glycemic Load Diet

  • Do not drink soda pop anymore.
  • Let me say that again. Do not drink soda pop anymore. Regular soda pop is nothing but PURE sugar. Worse yet, it is liquid sugar, which means it affects your body quicker than sugar in foods. It raises insulin and other hormones faster than sugar in food.
  • When you switch from regular soda pop to water, decrease the amount of soda pop you drink slowly. This will help prevent symptoms of caffeine withdrawal, such as headaches.
  • If you do not like plain water, try carbonated water that does not contain sugar. Look at the label. If the water contains calories, put it back on the shelf. Instead pick a brand that does not contain calories. Plain, flavored or carbonated water will not contain calories. If the water contains calories, then it contains sugar. Water with sugar is no better than soda pop. There are several brands of carbonated, NON-sugar, flavored waters from which to chose.
  • Chose WHOLE fruit over fruit juice. There are three nutrients that slow down the absorption of sugar in food. These are fiber, fat, and protein. WHOLE fruit contains fiber while fruit juice does NOT contain fiber. A piece of whole fruit is almost always a better choice than juice.
  • Sprinkle ground flax seeds into your cereal, yogurt, fruit smoothies, and salads. This will add protein & fat to the meal or snack. This slows sugar absorption for a healthier effect on the body. Adding flax seeds to another food will lower the overall Glycemic Load of the snack or meal.
  • Sprinkle nuts (walnuts, almonds, etc.) into salads and stir fry dishes. Again, this adds healthy fat to the meal to help balance your diet. Adding nuts to another food will lower the overall Glycemic Load of the snack or meal.
  • Replace store bought salad dressings with your own balsamic or apple cider vinegar and olive oil mixtures. Store bought dressings can contain a lot of sugar.
  • If you are too busy to prepare you own salad dressing, try a 'healthy' brand such as Annie's Naturals, Chelton House, Earthbound Farm, Elena's, New Organics, Newman's Own, Up Country Naturals, Walden Farms, Whole Foods or Seeds of Change. These are just a few examples of healthy salad dressings. There are many good ones available. These dressings can be found in the health food section of your grocery store.
  • To pick a healthy salad dressing, look for a dressing that contains no sugar, no corn syrup, and no hydrogenated fats. If you read the ingredient list and see the words 'sugar', 'corn syrup', 'high fructose corn syrup', 'hydrogenated' or 'partially hydrogenated', this dressing is less healthy. Try a different brand.
  • Start basing your diet around UNPROCESSED whole plant foods including vegetables, fruit, whole grains, and legumes. Do this instead of basing your food choices around fast food, microwave meals, or 'instant dinner' trays. These often contain sugar. They also contain unhealthy fats and too many calories. Plus, they do not contain the healthy cancer-fighting phytochemicals of whole plant foods.
  • Instead of pretzels or chips, have a small handful of nuts as a snack. Watch portion size, because nuts are high in calories. But, remember, those calories come from HEALTHY fats. Most snack foods such as pretzels contain no healthy nutrients and may contain simple sugar.
  • Replace snack foods with WHOLE vegetables & fruits. Try baby carrots and hummus as a quick, easy and tasty snack.
  • For a great snack, try one piece of fruit with a small handful of nuts or a spoonful of nut butter. The nuts add protein and healthy fat to your diet. The nuts will lower the overall Glycemic Load of the snack.
  • When you buy bread products, read the label. If you see the word 'enriched', then the product is NOT a whole grain. Instead look for words such as 'whole grain' , 'stone ground', 'whole ground', 'whole wheat flour', 'whole oat flour', or 'whole barley flour'. These are tips that tell you that this food IS a whole grain! Remember, these contain more protein and fiber and are healthier for you. Usually, they contain less simple sugar as well! Pure whole grains have a LOWER glycemic index and glycemic load than refined grains or 'white flour' products.
  • Try to eat foods that are as close to their 'natural form' as possible. For example, a corn chip is made of corn, but it's NOT a whole food. To make a corn chip, first the corn is picked, then ground and crushed. Next the fiber portion of the corn is thrown out. Then the corn is fried in processed fat (hydrogenated fat). Next it is treated with artificial flavors, dyes, and preservatives. This hardly looks like corn anymore!
  • Now think of corn on the cob. It is picked, shipped, and ends up on your dinner table! It is not processed. It is a WHOLE food. The less processing that a food undergoes before you eat it, the better it is for you. Less processing means a lower glycemic index and a lower glycemic load!
  • Make dessert an OCCASSIONAL treat. There is nothing wrong with having a sweet treat now and then. Just make sure 'now and then' only means a few times per week, at the most.
  • Cut out desserts and sugary foods that you do not care about. For example, if you absolutely cannot live without chocolate, make sure that when you do enjoy a sweet treat, you save it for those chocolate treats that you really love. Don't waste your treats on foods that you can live without.
  • Say the statement, "I absolutely cannot live without _______." Insert the name of your favorite sweet treat. Then, when you eat a sweet treat, MAKE SURE it is your special treat, not something you only enjoy a little bit.

NOTE: If you are in cancer treatment, these diet changes may not be right for you. Please discuss your nutrition needs with your health care team. Also, see our section on Treatment Symptom Management to help with these issues.

For additional information and ideas on this topic, please see our article Does Sugar 'Feed' Cancer? 

Recipes to Help You Eat a Low Glycemic Load Diet

Great Greens

Hearty Sweet Potato Stew

Baked Alaskan Salmon

White Bean Soup

1. Willett, W. Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating. Simon & Schuster. 2001.

2. Augustin LS, Gallus S, Franceschi S, Negri E, Jenkins DJ, Kendall CW, Dal Maso L, Talamini R, La Vecchia C. Glycemic index and load and risk of upper aero-digestive tract neoplasms (Italy). Cancer Causes Control. 2003;14(7):657-662.

3. Augustin LS, Gallus S, Bosetti C, Levi F, Negri E, Franceschi S, Dal Maso L, Jenkins DJ, Kendall CW, La Vecchia C. Glycemic index and glycemic load in endometrial cancer. Int J Cancer. 2003;105(3):404-407.

4. McCann SE, Freudenheim JL, Marshall JR, Graham S. Dietary glycemic index, glycemic load and ovarian cancer risk: a case-control study in Italy. Ann Oncol. 2003;14(1):78-84.

5. Michaud DS, Liu S, Giovannucci E, Willett WC, Colditz GA, Fuchs CS. Dietary sugar, glycemic load, and pancreatic cancer risk in a prospective study. J Natl Cancer Inst. 2002;94(17):1293-300.

6. Augustin LS, Dal Maso L, La Vecchia C, Parpinel M, Negri E, Vaccarella S, Kendall CW, Jenkins DJ, Francesch S. Dietary glycemic index and glycemic load, and breast cancer risk: A case-control study. Ann Oncol. 2001;12 (11):1533-1538.

7. Franceschi S, Dal Maso L, Augustin L, Negri E, Parpinel M, Boyle P, Jenkins DJ, La Vecchia C. Dietary glycemic load and colorectal cancer risk. Ann Oncol. 2001;12(2):173-78.

8. Singh PN, Fraser GE. Dietary risk factors for colon cancer in a low-risk population. Am J Epidemiol. 1998;148(8):761-74.

9. De Stefani E, Deneo-Pellegrini H, Mendilaharsu M, Ronco A, Carzoglio JC. Dietary sugar and lung cancer: a case-control study in Uruguay. Nutr Cancer. 1998;31(2):132-37.

10. Slattery ML, Benson J, Berry TD, Duncan D, Edwards SL, Caan BJ, Potter JD. Dietary sugar and colon cancer. Cancer Epidemiol Biomarkers Prev. 1997;6(9):677-85.

11. World Cancer Research Fund. Food, Nutrition and the Prevention of Cancer: a global perspective. Washington, DC: American Institute for Cancer Research; 1997.

12. Weisburger JH. Lifestyle, health and disease prevention: the underlying mechanisms. Eur J Cancer Prev. 2002;11(Suppl 2):S1-S7.

13. Moyad MA. Dietary fat reduction to reduce prostate cancer risk: controlled enthusiasm, learning a lesson from breast or other cancers, and the big picture. Urology. 2002;59(4 Suppl 1):51-62.

This content was last reviewed August 15, 2010 by Dr. Reshma L. Mahtani.
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