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Series H, Episode 13: Holidays

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Ian Dunn
767067.  Tue Dec 14, 2010 6:43 am Reply with quote

Here is the preview.

767704.  Fri Dec 17, 2010 5:22 pm Reply with quote

So, how much excrement does a human pass in a year?

I'm imagining eggshaped in the booth when that was being recorded, furiously Googling for a figure which looked authoritative enough to pass to Stephen - and not finding one.

Many trivia websites and "answers" websites have addressed the matter, but since their answers vary between three ounces per day and 5.7 pounds per day, I rather suspect all these figures of being made up. And I can't immediately find any serious scientific discussions of the question.


767720.  Fri Dec 17, 2010 6:37 pm Reply with quote

I don't know where they got their numbers exactly, but The Human Footprint (2007) reckons the average person will produce 2,865 kg of excreta over a lifetime (which I believe they place at 78.5 years).

Not sure how best to break that into per year as I would assume the amount varies considerably between infancy, adulthood, etc.

767725.  Fri Dec 17, 2010 6:45 pm Reply with quote

349gą131g an average of 1.5 times a day

Determination of the Mean Daily Stool Weight, Frequency of Defecation and Bowel Transit Time: Assessment of 1000 Healthy Subjects
Seyed Mohammad Kazem Hosseini Asl MD, Seyed Davood Hosseini MD


The average weight of stools of 115 individuals is 123.6 Gm., with a standard deviation of 40.2 and a standard error of 3.74.

Robert C. Rendtorff and Mark Kashgarian
Volume 10, Number 3, 222-228, DOI: 10.1007/BF02617184


Low fecal weight and slow bowel transit time are thought to be associated with bowel cancer risk, but few published data defining bowel habits in different communities exist. Therefore, data on stool weight were collected from 20 populations in 12 countries to define this risk more accurately, and the relationship between stool weight and dietary intake of nonstarch polysaccharides (NSP) (dietary fiber) was quantified. In 220 healthy U.K. adults undertaking careful fecal collections, median daily stool weight was 106 g/day (men, 104 g/day; women, 99 g/day; P = 0.02) and whole-gut transit time was 60 hours (men, 55 hours; women, 72 hours; P = 0.05); 17% of women, but only 1% of men, passed < 50 g stool/day. Data from other populations of the world show average stool weight to vary from 72 to 470 g/day and to be inversely related to colon cancer risk (r = -0.78). Meta-analysis of 11 studies in which daily fecal weight was measured accurately in 26 groups of people (n = 206) on controlled diets of known NSP content shows a significant correlation between fiber intake and mean daily stool weight (r = 0.84). Stool weight in many Westernized populations is low (80-120 g/day), and this is associated with increased colon cancer risk. Fecal output is increased by dietary NSP. Diets characterized by high NSP intake (approximately 18 g/day) are associated with stool weights of 150 g/day and should reduce the risk of bowel cancer.

Fecal weight, colon cancer risk, and dietary intake of nonstarch polysaccharides (dietary fiber)
Cummings JH, Bingham SA, Heaton KW, Eastwood MA.
Gastroenterology. 1992 Dec;103(6):1964-7.


Abstract;This study investigates the relation of fecal production and dietary habits and life-styles in four 21 to 22 year-old healthy female students. The survey was conducted over 30 days and was repeated twice. All feces that were discharged were collected and weighed. The subjects performed very little physical exercise. The fecal weight, the number of defecations per day, gastrointestinal symptoms, feeling of incomplete defecation and of abdominal distention were recorded. The fecal weight was converted to autocorrelation, and the day-by-day variation was examined by a time series analysis(correlogram). Free access to foods was allowed. The weight of each food item was weighed for nutritional evaluation. The daily number of steps walked and sleeping hours were taken as indicators of life-style. The average fecal weight ranged from 96.8g/day to 127.8g/day, with a grand mean for the four subjects of 94.1g/day. The average number of times of defecation during the 60 days period was 53 to 72, or 0-3 a day. The subjects tended to have feeling of incomplete defecation when the stool was hard and fecal weight was less than 100g per day, whereas the subjects felt incomplete defecation less frequently when the stool was well-formed or pasty. The time series analysis by correlogram indicates that the variation in fecal weight formed a 3-4 day cycle and that the cycle was irrelevant to fecal weight. This survey shows that there was no apparent correlation among the fecal weight and nutrient intake, the number of meals per day, the number of steps walked or sleeping hours per day. It also indicates that defecation factors differ from individual to individual. (author abst.)

Weight of feces and its daily fluctuation in young women. Part 1. Asurvey of the relation fecal weight and dietary habits and life styles.
Japanese Journal of Public Health

The consensus seems to be about 110g/day or 40.15Kg a year. 2865kg/78.5years = 36.5Kg/years so that's a broadly similar estimate. As regards the parrot fish we should remember that sand is quite heavy, particularly wet sand.

And with that I wash my hands of the matter.

767730.  Fri Dec 17, 2010 6:59 pm Reply with quote

Good work, you two. So the amount of excrement passed by a human in a lifetime is of the order of three tons.

Accordingly, it's quite remarkable that the parrot fish - a fish which is typically around 18 inches in length - produces one ton per year. But the elves' source for this was a learned book by an eminent geologist, so I do not doubt it.

767736.  Fri Dec 17, 2010 7:24 pm Reply with quote

Though if we had to chew through rocks to get to our food...
The bottom would probably fall out of the cement industry (or should that be the other way around).

767737.  Fri Dec 17, 2010 7:24 pm Reply with quote

I have to admit I still have doubts as to the amount of excrement a parrot fish will pass in a year.

For one ton to pass in one year you'd need an average of 3 kilos per day, which seems incredible for an animal that size, especially as I'd expect the sand to be part of the excrement and not all of it.

A quick look around found a book called "Marine Biology" by Herbert H. Webber and Harold V. Thurman, and in chapter 12, page 310, it states "By eating coral (and corraline red algae) a single parrot fish may produce up to 90 kg of sand per year".

Ian Dunn
767781.  Sat Dec 18, 2010 7:15 am Reply with quote

I think that last night's QI was once of the best episodes in a while. I especailly liked the holiday homework. It made a nice change with the panel presenting interesting information with Stephen not needing to do much work.

767927.  Sat Dec 18, 2010 5:16 pm Reply with quote

Not that Bhutan isn't fascinating but, well, it doesn't begin with H does it? That got skipped over I feel. Was there, in fact, a reason why Bill went to Bhutan?

Spud McLaren
767929.  Sat Dec 18, 2010 5:20 pm Reply with quote

Celebaelin wrote:
Not that Bhutan isn't fascinating but, well, it doesn't begin with H does it? That got skipped over I feel. Was there, in fact, a reason why Bill went to Bhutan?
Is it to do with the Himalayas?

767960.  Sat Dec 18, 2010 6:22 pm Reply with quote

Indeed, I believe Stephen put an early emphasis on the Himalayas. Then the emphasis sort of went away.

Nonetheless, I was glad to hear about Bhutan. The largest contingent of refugees I work with is the Bhutanese contingent. They're an interesting bunch (and mean that very kindly).

767965.  Sat Dec 18, 2010 6:33 pm Reply with quote

The largest contingent of refugees I work with is the Bhutanese contingent.

Refugees from what?

767974.  Sat Dec 18, 2010 7:01 pm Reply with quote

Most of the refugees in our program seem to refugees because of political persecution. I try not to ask too many questions about why they had to leave their homelands as I know it is quite painful for most of them to talk about. The Bhutanese we have all speak Nepali. Nepali speakers don't have a good time of it in Bhutan, to say the least. I know several of them are of Gurung ethnicity, but I'm not sure how that plays into their being refugees, if at all.

767975.  Sat Dec 18, 2010 7:06 pm Reply with quote

I only ask because on the programme Bhutan got quite a glowing reference - measuring wealth in terms of popular happiness for instance.

767979.  Sat Dec 18, 2010 7:15 pm Reply with quote

I know. Before I worked with these refugees, I was under the impression that Bhutan was some great haven of Himalayan happiness.

This might shine some light on the plight of the Nepali: --Lhotshampa being the Bhutanese (Dzongkha language) name for the Nepali speaking population that have been made to leave Bhutan.

They are, by and large, a hard-working group and they study very hard at home to improve their English. We have between 15 and 20 Bhutanese refugees in our program.


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