Oat kernels are processed in a variety of ways, and the amount they are processed has everything to do with the impact on blood sugar. In general, the less the cooking time the oats require, the more glycemic the oats will be:
- Groats - Whole oat kernels are called "groats". They can be cooked and eaten, but are sometimes difficult to obtain. They aren't as popular as other forms because they take a fairly long time to cook (soaking overnight helps). They have the least impact on blood glucose.
- Steel-Cut Oats (also called coarse-cut oats, Irish oats, or Scotch oats)- In steel-cut oats (such as McCann's brand), the kernels are cut into two or three pieces, making them cook faster than groats (about 10-15 minutes).
- Rolled Oats - Rolled oats are what we usually think of as "oatmeal". The whole oat kernel is steamed, rolled flat(ish), steamed again, and toasted. This process means that the integrity of the grain is diminished, and the oats are partially cooked. Because of this they cause a faster and higher blood sugar rise.
- Quick-Cooking Oats - Quick-cooking oats similar to rolled oats, but broken up into smaller pieces so they will cook faster.
- Instant Oatmeal - Usually purchased in individual serving packets, the rolled oats are pre-cooked, and then dried. Usually flavorings and sugar are added. It's best to stay far away from instant oatmeal.
- Ready to Eat Cereals (Cheerios, etc) - Yes, they are technically "whole grain", but they have been processed to the point where the starch in them turns to sugar very quickly.
Carbohydrate and Fiber Counts for Oats
- ½ cup cooked oatmeal: 14 grams effective (net) carbohydrate plus 2 grams fiber, 3 grams protein, and 83 calories
- ¼ cup uncooked oatmeal: 12 grams effective (net) carbohydrate plus 2 grams fiber, 3 grams protein, and 74 calories
- ¼ cup uncooked steel-cut oats: 24 grams effective (net) carbohydrate plus 3 grams fiber, 4 grams protein, and 150 calories
- ½ cup cooked oat bran: 10 grams effective (net) carbohydrate plus 3 grams fiber, 3 grams protein, and 44 calories
- ¼ uncooked oat bran: 12 grams effective (net) carbohydrate plus 4 grams fiber, 4 grams protein, and 58 calories
Glycemic Index for OatsThe glycemic index (GI) of cooked steel-cut oats is in the range of 42-50. The GI of oatmeal made from rolled oats is 51-63, with an average of 55. Instant oatmeal has a GI of 82.
Glycemic Load of Oats
- ½ cup cooked oatmeal: 7
- ½ cup cooked steel-cut oats: 6
- 1 packet instant oatmeal, unsweetened: 18
- ¼ cup uncooked oatmeal: 7
Health Benefits of OatsOats are a very good source of manganese. In addition to the 1.5 grams of soluble fiber discussed above, a half-cup serving provides about 8% of the daily requirement of magnesium, zinc, and selenium.
More Information About Oats at Calorie Count.
More Carb Profiles:
Leroux, Marcus, Foster-Powell, Kaye, Holt, Susanna and Brand-Miller, Janette. "International table of glycemic index and glycemic load values: 2002." American Journal of Clinical Nutrition. Vol. 76, No. 1, 5-56, (2002).
Liu L, Zubik L, Collins FW, Marko M, Meydani M. The antiatherogenic potential of oat phenolic compounds. Atherosclerosis. 2004 Jul;175(1):39-49. 2004.
USDA National Nutrient Database for Standard Reference, Release 21.