Fiber digestibility and calorie balance

Question
I've recently read your answer to Ruby regarding getting some calories from dietary fiber supplements due to their fermentation in the intestines. When you say that "1 cup of ground Psyllium husks (96.5 g fiber) has 67 calories", can this be taken as a general reference value? I am asking because you also mentioned that fermentation also depends on  other factors such as the types of food eaten and the presence of certain bacteria. Doesn't this mean that the amount calories provided from dietary fibers varies from one individual to the other? If it is the case, then how do I know how much calories I am truly getting from fibers from a dietary fiber supplement? Is there a way to figure out exactly how much calories I am getting from the fibers of a dietary fiber supplement? Are you able to give me info/references on some of the scientific literature where you found the nutritional info about ground Psyllium husks? Thank you.

Answer
Dear Mayly,

The seeds of Psyllium (Plantago afra) contain about 19 percent fiber, 18.8 percent protein, and 10-20 percent triglycerides, the husk is the covering of seeds and is almost all-fiber.

Dietary fiber, which exists mainly as polysaccharides, may be digested after microbial fermentation in large intestine and colon. The end products of colonic fermentation are mostly fats, which contributes to the positive energy balance (short-chain fatty acids) and heat, which contributes to the negative calorie balance since it adds to calorie dissipation through the process of thermoregulation.

Digestibility of insoluble dietary fiber is about 80 percent but this is true for a low-fiber food or meal; for higher-fiber foods the digestibility decreases, so you have to not only know your fiber supplement values but also the values of your meal.

Which one -- positive or negative balance -- prevails, depends on too many factors to allow for individual consideration. This leads us to your other question, that of individual calorie counting so the answer is: you cant really know  how many calories you are  truly getting from fibers in a dietary supplement.

What's more, you cant truly know how much energy (calories) you are getting with anything at all. please read these articles for explanation:

Calorie Controversies
http://atkinszone-exercise.blogspot.com/2008/03/calorie-controversies.html

Calorie = calorie = calorie?
http://atkinszone-exercise.blogspot.com/2008/03/calorie-calorie-calorie.html

1. Finally, regarding 'references on some of the scientific literature' here's SOME of it.

2. Rosado, P Lopez, M Morales and LH Allen  Fiber digestibility and breath-hydrogen excretion in subjects consuming rural and urban Mexican diets. American Journal of Clinical Nutrition, Vol 53, 55-60,

3. Cummings JH, Englyst HN. Fermentation in the human large intestine and available substrates. Am I Clin Nutr l987;45: 1243-55.

4. Rubinstein R, Howard AV, Wrong OM. In vivo dialysis of faeces as a method of stool analysis. The organic anion component. Clin Sci 1969; 37:549-64.

5. Cummings JH, Hill Mi, Bone ES, Branch Wi, Jenkins DJA. The effect of meat protein and dietary fiber on colonic function and metabolism. Part II. Bacterial metabolites in feces and urine. Am I Clin Nutr l979;32:2094-lOl.

6. Ruppin H, Bar Meir S. Soergel KH, Wood CM, Schmitt MG. Absorption of short chain fatty acids by the colon. Gastroenterology 1980; 78:1500-7.

7. Roediger WEW. Role ofanaerobic bacteria in the metabolic welfare of the colonic mucosa in man. Gut 1980;21:793-8.

8. JOANNE L. SLAVIN, PAULA M. BRAUER AND JUDITH A. MARLETT. Neutral Detergent Fiber, Hemicellulose and Cellulose Digestibility in Human Subjects. Journal of Nutrition, published online June 01, 2008

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