Thursday, March 18, 2010
Is It True That Fiber Has Negative Calories?
This question is very similar to the question about celery taking more energy to chew than it provides in kilocalories.
There are two different types of fiber; the soluble type like the fiber found in oatmeal and insoluble type as is found in celery. Both are technically carbohydrates which mean they should have 4 kcal/gram. But, since the body is unable to fully digest fiber, researchers have suggested that a value of 2 kcal/gram be used to calculate their caloric value. This recommendation is based on what is called a "mixed" diet which means that along with the fiber you are also eating other carbohydrates, fats, and proteins.
FYI: The nutrition information on celery indicates that 1 cup contains almost 4 grams of fiber and has 19 calories. This discrepancy indicates a gap in research and practice because according to Guenther and Jensen, this cup of celery should contain only 8 calories.
Source: Guenther, P.M. & Jensen, H.H. (2000).Estimating energy contributed by fiber using a general factor of 2 vs 4 kcal/g. Journal of the American Dietetic Association. 100(8).