I once heard a story to the effect that Walter Raleigh made a bet with Queen Elizabeth that he could find the weight of the smoke in a pipeful of tobacco. When she accepted his challenge, he weighed a pipeful of tobacco, then gave it to Her Majesty to smoke. After the smoke cleared, he weighed the ashes, and argued that the loss of weight could only be attributed to the weight of the smoke.
What about feces? Could you (or a researcher with a high threshhold for dealing with disgusting substances - let’s say a forensic pathologist, or a technician at the Center for Science in the Public Interest ) place a sample of feces in a bomb calorimeter, and calculate the number of calories per gram in the stool? Has it ever been done (and recorded in published research)?
Could this type of experiment/data collection yield useful information regarding the weight control implications of certain specific food choices?
Well, in both examples, there is no way to seperate smoke from steam. I would think that you should first dry the feces then determine the calorie density of the dried feces.
I also think that the number would vary so greatly from person to person and day to day that the results would be relatively useless.
This isn’t true though. Weight of the smoke is equal to the weight of fuel consumed plus weight of oxygen taken from the air.
It’s a similar situation, I think. Stool contains undigested food plus waste products from your body. You can’t distinguish between the two with a bomb calorimeter.
I’m probably going to get myself into a crapload of trouble here, but I think by definition stool contains only digested matter… it has passed thru the entire digestive system, and therefore cannot be called “undigested”… it is all “waste products” at that point.
Not entirely true. There’s quite a bit of cellulose in there, and some of it is even recognizable as the food you ate. There is also some usable protein, because the human gut is not terribly efficient. We wouldn’t want to eat our own poop, but flies and some dogs will gladly gulp it down.
Don’t forget that about 12% of the total weight of the stool is dead bacteria, that didn’t come directly from the food you ate (though they did eat it).
Well… the fact that it went thru the digestive tract to its conclusion, would qualify it as ‘Digested’… even if not fully ‘utilized’ or if done in a wasteful manner… food in the stomach could be qualified as “undigested”, but once its in the crapper, it’s done… atleast as done as our system can do - re-eating it would likely not change that fact… (as opposed to rabbits/herbivores or animals that can and do recycle)
Digestion really has only one meaning when it comes to our intestines. In digestion fats, proteins, and sugars are broken down, i.e. digested, usually by enzymes, to their smallest components - fatty acids, amino acids, and simple sugars. Vitamins and minerals, which are already small enough to be directly absorbed without further breakdown, can also be included in digestion.
Any food that is not broken down in this fashion is undigested in every meaningful sense. Cellulose and other fibers are the largest part of these undigested substances but any foods can potentially contribute. Lactose intolerance is defined, for example, as the condition in which undigested lactose reaches the colon. A condition called “rapid transit” can also push foods through the intestines so quickly that they are not properly digested. Numbers of other food-related conditions also produce undigested remains in the colon and feces.
So, digestion has a very specific meaning. Just arriving at the colon is not only not part of that definition, but the very opposite of it. And that’s a fruitful distinction.
To answer the OP, fecal analysis is a quite standard method in biology. Feces may be analyzed in various ways, but they are often dried and then subjected to bomb calorimetry.
Feces contain undigested matter from ingestion (both matter that is largely undigestable such as cellulose, as well as usable nutrients that escaped absorption in the digestive tract), some bodily waste products, particularly from the bile ducts, and bacteria from the gut flora. But useful information on digestive efficiency can still be obtained from analysis.
Most biologists have a “higher threshold for dealing with disgusting substances” than average. Feces are par for the course.
Do any of you know what the moisture content of average human feces is…or do I have to do the research myself? How about the calorie content? I never thought about it before, but now enquiring minds want to know!
If your digestive tract is working properly, then the calorie content of feces is essentially zero. As I wrote above, all the nutrients have been digested earlier.
I don’t see how that could be correct. I have observed food (sweet corn kernels, for example) that have passed thru my digestiive system essentially unchanged. They appear just like uneaten corn kernels, and would presumably contain the same food value & calories.
Are you claiming that my digestive system is not “working properly” just because some food passes thru undigested? That seems to be a common condition; I have seen stories of archaeologists using this to determine the diet of prehistoric cultures.
No, that’s not correct. Feces have a significant caloric content. Not all of the digestible material has necessarily been broken down, and not all of the nutrients resulting from that breakdown have necessarily been absorbed.
This study, for one, examined the relative energy content of feces depending on different diets.
As they say, 500 billion flies can’t be wrong. And it’s not just flies that eat human feces; pigs and dogs will do so too, because they have significant energy content.
There are entire food chains consisting of coprophages. One of my colleagues did a study on the relative energy content of the feces of different fish.
Well, Doug, you did open a thread about feces, after all.
I don’t know exactly how bomb calorimetry is done, but I’m pretty sure cellulose (called fiber by the food industry) will burn. We humans can’t break down and use those cellulose calories*, so I’ll grant that measuring them would be meaningless. However, there is still useful protein in human dung. In a dreadful emergency :eek: one could probably survive by eating it. The traditional insult, “Eat shit and die!” is not a cause-and-effect thing. If necessary, one could eat shit and survive. If Doug is still reading, he’ll need another gallon of brain bleach, I suppose. Maybe, after opening another dozen fecal threads, he’ll be less easily grossed out. Let’s see, a gross is 144, is there a term for 12 gross?
Perhaps folks who routinely eat termites can digest cellulose, with the aid of the bacteria in the termites’ guts. That would be some delightful research, eh? Maybe the producers of Fear Factor could be persuaded to fund it.
The digestive system begins with the mouth. The teeth start the process of grinding food into smaller bits and the saliva contains enzymes that start the process of digestion. The stomach continues the mostly mechanical grinding process, but also adds hydrochloric acid and other chemicals to further the physical breakdown of foods.
Literally hundreds of thousands of enzymes attack the chyme - the soft slurry - in the small intestine.
These must reach their chemical targets to work, however; if foods are not properly chewed the enzymes can’t digest. Foods with hard shells, like corn and peas, especially require the mechanical action to break the coating so that the enzymes can do their work.
Your mother was right: you do need to chew your food properly. Colibri, I’ll admit that “essentially zero” calories was a little strong. But I don’t think I need to back off too far. Certainly, the interaction of types of foods will affect digestibility. And floating feces because of high fat content is often a sign that a problem is occurring. Even so, most of the nutritional value of feces will come from the fiber that is excreted and not from nutrients left undigested. Even those flies you mention require extremely enzyme-rich saliva to break down fiber to get nutrition out of shit.
If you eat right and chew well, what comes out of you has almost all of the nutrition that humans can process removed. We’re just not designed to make use of the dead bacteria or the fiber that makes up most of the bulk. Maybe other species can, but that’s not the question I was answering.
I went to a reflexologist once, and she told me that, with proper diet and drinking vinegar, my poop would have no odor. Until that moment, I thought it was just locker room folklore that some women thought their shit didn’t stink. That was not what I expected to learn in that appointment.
“Things will happen that you won’t be ready for.” --Jackson Browne