The glycemic index is a measure of how a carbohydrate-containing food affects blood sugar. A glycemic index is assigned based on comparison of blood sugar changes in relation to a reference food, such as glucose or white bread. According to the American Diabetes Association, high GI foods cause a higher spike in blood glucose than foods with lower indexes. A glycemic index of 70 or greater is considered high, while a glycemic index below 55 is low. The ADA indicates that the glycemic index does not provide a complete picture of a food's nutritional value. For the most benefit, you should consider the glycemic index of foods in conjunction with an overall healthy diet and exercise plan.
Grains
While whole grains contain the entire grain kernel, refined grains have the bran and germ removed. Whole-grain breads and cereals will not raise blood sugar as much as their refined counterparts. Breads such as rye, barley and whole wheat have a low glycemic index. According to the International Table of Glycemic Index and Glycemic Load Values, rye bread has a glycemic index of 40, and barley bread has a GI of 34. The GI of whole-wheat bread is 53.
Refined grains are white breads, pastas and crackers. White breads have a higher glycemic index than whole grains. For example, the glycemic index of a white bagel is 72, and the GI of a baguette is 95. Among refined cereals, cornflakes and corn pops have glycemic indexes of about 80. Whenever possible, choose whole grains instead of refined grains for more nutrients and fiber at a lower glycemic index.
Vegetables
Vegetables are available in non-starchy and starchy varieties. Tomatoes, peppers, greens, okra and cucumbers are all non-starchy vegetables with low GI, while parsnips, corn and sweet and white potatoes are starchy. The U.S. Department of Agriculture food pyramid recommends 2 1/2 to 3 cups of vegetables daily for adults including 2 1/2 to 6 cups of starchy vegetables per week. The ADA recommends choosing non-starchy vegetables often because they are low in calories and have low glycemic indexes. A medium baked potato has a glycemic index of 76, while a sweet potato has a GI of 61. Parsnips have a glycemic index of 97. When deciding on vegetables, choose fresh vegetables that are in season. Canned or frozen vegetables are also good as long as they do not contain added sodium, sugars or sauces.
Fruit
Fruit is a mainstay of a healthy diet. Although fruits have a wide range of glycemic indexes, it is always a healthier choice for a sweet snack than candy or sweetened drinks. According to MyPyramid.gov, adults should aim for 1 1/2 to 2 cups of fruit each day. Apples are a convenient choice because they require no preparation, and they have a low glycemic index of 38. Cherries and grapefruit are low GI fruits as well, with indexes of 22 and 25, respectively. Fruits with higher glycemic index include watermelon, pineapples, raisins and dates. Watermelon has a glycemic index of 72, and pineapples have a GI of 59. The glycemic index of raisins is 64, while the glycemic index of dried dates is 103. Although some fruits have a high glycemic index, do not discount them completely as they are still full of vitamins, minerals and antioxidants.
References
- MyPyramid.gov: Inside the Pyramid
- American Diabetes Association: Glycemic Index and Diabetes
- Oregon State University Linus Pauling Institute: Glycemic Index and Glycemic Load
- "American Journal of Clinical Nutrition": International Table of Glycemic Index and Glycemic Load Values
- Kansas State University Research and Extension: Glycemic Index and Glycemic Load
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