I’ve been studying nutritional controversies for about 3 decades. While there may be several reasons why they persist, I think the big problem is the tendency of most nutrition experts to rely on consensus of opinion or authority rather than scientific data. Consider, for example, the “calorie is a calorie” debate. Perhaps the matter would be resolved if scientists just paid more attention to what the gut microbes do with the food we eat.

The digestive tract contains about 2 kilograms of gut microbes. In addition, it’s estimated that 500 to a thousand different kinds of gut microbes inhabit various ecological niches from the mouth to colon.

They eat what the host eats and most of the calories processed by gut microbes do not get absorbed into the bloodstream. In fact, one can keep the caloric total constant and vary the nutrient mix in ways that cause more or less calories to get absorbed into the bloodstream. If you read the Prologue to “Good Calories, Bad Calories” you may have noticed this comment on page xvi:

“…the less carbohydrates in their diets, the greater their weight loss, even though all her subjects were eating equivalent amounts of calories and protein. ‘No adequate explanation could be given,’ Young reported, implying that further scientific research might be important to clarify this issue.”

About two months ago I began looking for data on heat energy produced by gut microbes as they multiply. I needed that information to calculate daily gut microbe energy consumption.

As I mentioned earlier, the calories consumed by gut microbes as they multiply do not get absorbed into the bloodstream. They are, however, accounted for in metabolic chamber measurements because the heat released diffuses into the body.

I’d probably still be searching except that Gary Tivendale found a document for me entitled “Basics of Fermentation” (1). Page 5 of the document begins with, “A universal product of microbial growth is heat. The heat of combustion of microorganisms is fairly constant with a typical value of 5 kcal/g.”

Researchers have determined that the weight of dry bacterial cells excreted daily ranges from 5.34 to 8.54 grams (2). Using these figures, the average daily heat generated by gut biota ranges from about 27 kcal to 43 kcal. Since microbial heat energy diffuses into the body, it probably ought to be considered an essential part of the body’s temperature regulating mechanism (3).

When subjects of normal weight attempt to gain weight by overeating, quite often excess body heat is generated which researchers routinely ascribe to an increase in metabolic rate (4). I suspect fermentation taking place in the digestive tract may contribute substantially to the sensation of being overheated. It’s also likely that extra microbial activity takes place when extra food is consumed but only if the nutrient content is adequate to support microbial reproductive activity. Pure sugars and fats do not meet that criteria. So on a high junk food diet, gut microbe activity is curtailed and energy absorption into the bloodstream increases.

For more on this, I suggest you visit Gary Tivendale’s collection of documents at http://www.scribd.com/people/view/3737769-gary-tiv

Regards,
David Brown
1925 Belmar Dr
Kalispell, MT 59901
Ph/406-257-5123
Nutrition Education Project

1. http://rothfus.cheme.cmu.edu/tlab/ferm/projects/t6_s99/t6_s99_manual.PDF

2. http://books.google.com/books?id=hiUbAAAAYAAJ&pg=PA653&lpg=PA653&dq=Dry+Weight+of+Fecal+Bacteria&source=bl&ots=_lkqMog4Zl&sig=8I_0h9sJWynTJP6AAMNU8aRq3AA&hl=en&ei=gsBKSqf7BYPklAfHuOwo&sa=X&oi=book_result&ct=result&resnum=10

3. http://www.anapsid.org/tracydigestion.html

4. http://books.google.com/books?id=iVqZdRh6ICoC&pg=PA128&lpg=PA128&dq=Further+research,+at+Rockefeller+University,+discovered+a+raising&source=bl&ots=hJQmBXwFLM&sig=LuGkgoFjeM_RoBHZjEeBCyKzx1I&hl=en&ei=cOVSSqq2JIHusQOGkNCKBw&sa=X&oi=book_result&ct=result&resnum=1