Sex Sleep Eat Drink Dream (33 page)

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Inside the tooth and in its sockets:
The following information on teeth is from Peter W. Lucas,
Dental Functional Morphology: How Teeth Work
(New York: Cambridge University Press, 2004), 4.
By animal standards, human teeth:
Peter W. Lucas, "The origins of the modern human diet," paper presented at the American Association for the Advancement of Science, February 19, 2005.
When Lieberman fed a soft diet:
Interview with Dan Lieberman, February 26, 2005; D. E. Lieberman et al., "Etfects of food processing on masticatory strain and craniofacial growth in a retrognathic face,"
Journal of Human Evolution
46, 655–77 (2004).

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Two hormones, CCK and PYY:
Stephen R. Bloom et al., "Inhibition of food intake in obese subjects by peptide YY
_3–36
)"
New England Journal of Medicine
349, 941–48 (2003).

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Give people an infusion:
Badman and Flier, "The gut and energy balance."
people injected with PYY:
Bloom et al., "Inhibition of food intake in obese subjects."
Those rich in fiber, which move more slowly:
R. L. Batterham et al., "Gut hormone PYY
_3–36
physiologically inhibits food intake,"
Nature
418, 650–54 (2002).
David Cummings and his team have shown:
J. Overduin et al., "Role of the duodenum and macronutrient type in ghrelin regulation,"
Endocrinology
146:2, 845–50 (2005).

5. POST-LUNCH

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Some observers have even credited walking:
Osip Mandelstam,
The Noise of Time and Other Prose Pieces
(London: Quartet Books, 1988), quoted in Bruce Chatwin,
The Songlines
(New York: Penguin, 1987), 230.
55 
Around 4.2 feet per second:
R. McNeill Alexander, "Walking made simple,"
Science
308, 58–59 (2005).
Canadian scientists asked athletes:
A. K. Gutmann et al., "Constrained optimization in human running,"
Journal of Experimental Biology
209, 622–32 (2006).

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Not long ago, biochemists ... discovered:
A. J. Lipton et al., "S-nitrosothi-ols signal the ventilatory response to hypoxia,"
Nature
413, 171–74 (2001).
Brushing is not a simple matter:
Kevin R. Foster, "Hamiltonian medicine: why the social lives of pathogens matter,"
Science
308, 1269–70 (2005); personal communication with Kevin Foster.
That the maw is neighborhood:
Clifford Dobell, ed.,
Antony van Leeuwenhoek and His Little Animals
(New York: Harcourt Brace, 1922), 239–40.
Only lately have we learned:
Paul B. Eckburg et al., "Diversity of the human intestinal microbial flora,"
Science
308, 1635—38 (2005).
The ... oral occupants are not:
S. S. Socransky and A. D. Haffajee, "Dental biofilms: difficult therapeutic targets,"
Periodontology
28, 12–55 (2002).

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Brushing disrupts these social relationships:
Foster, "Hamiltonian medicine."
bad breath is mainly the result:
Mel Rosenberg, "The science of bad breath,"
Scientific American,
April 2002, 72–79; personal communication with Mel Rosenberg, July 28, 2006; "The sweet smell of Mel's success,"
www.taucac.org/site/News2?JServSessionIdr006=xwwa961jq1.app5b&abbr=record
, retrieved July 29, 2006.

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The clandestine events of digestion:
William Beaumont,
Experiments and Observations on the Gastric Juice and the Physiology of Digestion
(New York: Dover Publications, 1959, reprint of 1833 edition).
a talent it owes to its inner walls:
Mark Dunleavy, "Gut feeling," www.
newscientist.com/lastword.

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The production of these juices:
M. Bouchouca et al., "Day-night patterns of gastroesophageal reflux,"
Chronobiology International
12, 267–77 (1995).
That we can digest our meals without taxing:
Quotes and explanations in the following text are from Michael Gershon,
The Second Brain
(New York: HarperCollins, 1998); M. Gershon, "The enteric nervous system: a second brain," in
Hospital Practice,
www.hosppract.com/issues/1999/07/gershon.htm.

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Your resident bacteria play:
The following discussion of intestinal microbes comes from: F. Backhed et al., "Host-bacterial mutualism in the human intestine,"
Science
307, 1915–19 (2005); L. V. Hooper and J. I. Gordon, "Commensal host-bacterial relationships in the gut,"
Science
292, 1115–18 (2001); D. R. Relman, "The human body as microbial observatory,"
Nature Genetics
30, 131–33 (2002); J.-P Kraehenbuhl and M. Corbett,"Keeping the gut microflora at bay," Science 303, 1624–25 (2004); Edward Ruby et al., "We get by with a little help from our (little) friends,"
Science
303, 1305–7 (2004); L.V. Hooper et al., "Molecular analysis of commensal host-microbial relationships in the intestine,"
Science
291, 881–84 (2001); and from personal communications with Jeffrey Gordon, February 20, 2005.
In 2005, scientists for the first time:
The following description of microbial flora is from R B. Eckburg et al., "Diversity of the human intestinal microbial flora,"
Science
308, 1635–38 (2005).

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Scientists at Yale discovered:
Ruslan Medzhitov, "Recognition of commensal microflora by toll-like receptors is required for intestinal homeostasis,"
Cell
118:6, 671–74 (2004); "Good bacteria trigger proteins to protect the gut,"
www.hhmi.org/news/medzhitov.html.

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germ-free mice can eat:
B. S. Samuel and J. L. Gordon, "A humanized gnotobiotic mouse model of host-archaeal-bacterial mutualism,"
Proceedings of the National Academy of Sciences
103:26, 10011–16 (2006); F. Backhed et al., "The gut microbiota as an environmental factor that regulates fat storage,"
Proceedings of the National Academy of Sciences
101:44, 15718–23 (2004).
Gordon and his lab mates:
R. E. Ley et al., "Human gut microbes associated with obesity,"
Nature
444, 1022–23 (2006); R J. Turnbaugh et al., "An obesity-associated gut microbiome with increased capacity for energy harvest,"
Nature
444, 1027–31 (2006).

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How long it takes for bowel, bugs, and brain:
R. H. Goo et al., "Circadian variation in gastric emptying of meals in man,"
Gastroenterology
93, 513–18 (1987).
Franz Halberg ... determined:
Franz Halberg et al., "Chronomics: circadian and circaseptan timing of radiotherapy, drugs, calories, perhaps nutriceuticals and beyond,"
Journal of Experimental Therapeutics and Oncology
3:5, 223 (2003).
some of those peripheral clocks:
Karl-Arne Stokkan et al., "Entrainment of the circadian clock in the liver by feeding,"
Science
291, 490–93 (2001).

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One recent study showed:
Ueli Schibler et al., "Peripheral circadian oscillators in mammals: time and food,"
Journal of Biological Rhythms
18:3, 250–60 (2003); J. Rutter et al., "Regulation of clock and NPAS
₂
DNA binding by the redox state of NAD cofactors,"
Science
293, 510–14 (2001).

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gastroenterologists hurdled the obstacles:
C.S.J. Probert et al., "Some determinants of whole-gut transit time: a population-based study,"
Quarterly Journal of Medicine
88, 311–15 (1995).
"
A meal is typically a mixture":
R. Bowen, "Gastrointestinal transit: how long does it take?,"
www.vivo.colostate.edu/hbooks/pathphys/digestion/basics/transit.html
, retrieved September 29, 2006; personal communication with Richard Bowen, October 2006.

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Feces ... are made mostly of:
Ralph A. Lewin,
Merde: Excursions in Scientific, Cultural, and Socio-Historical Coprology
(New York: Random House, 1999); Backhed, "Host-bacterial mutualism in the human intestine," 1917.
The stink in feces:
Bill Rathmell, "No Bull,"
www.newscientist.com
.
the compound is said to be used:
K. G. Friedeck, "Soy protein fortification of a low-fat dairy-based ice cream,"
Journal of Food Science
68, 2651 (2003).
Scientists investigated the phenomenon:
Michael D. Levitt et al., "Evaluation of an extremely flatulent patient,"
American Journal of Gastroenterology
93:11, 2276–81 (1998).

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Just by living, by keeping your heart beating:
The following discussion of metabolism comes from Eric Ravussin, "A neat way to control weight?,"
Science
307, 530–31 (2005); personal communication with Eric Ravussin, August 8, 2006.

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unless they're pregnant or nursing:
Jean Mayer,
Human Nutrition
(Springfield, 111.: Charles C. Thomas, 1979), 21–24.
Scientists at Harvard have shown:
Eric'S. Bachman, "EAR signaling required for diet-induced thermogenesis and obesity resistance,"
Science
297. 843–45 (2002).
One of the genes responsible:
Bradford B. Lowell and Bruce M. Spiegel-man, "Towards a molecular understanding of adaptive thermogenesis,"
Nature
404, 652–60 (2000).

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In one two-month study, scientists at the Mayo Clinic:
J. A. Levine et al., "Role of nonexercise activity thermogenesis in resistance to fat gain in humans,"
Science
283, 212–14 (1999); James Levine and Michael Jensen, response to "A fidgeter's calculation,"
Science
284, 1123 (2000).
the Mayo Clinic team set out to pinpoint:
J. A. Levine et al., "Interindivid-ual variation in posture allocation: possible role in human obesity,"
Science 307,
584–86 (2005).

6. THE DOLDRUMS

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It's the doldrums:
Norton Juster,
The Phantom Tollbooth
(New York: Random House/Bullseye Books, 1988), 24.

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This and other questions of weariness:
Eighth annual meeting of the Society for Research on Biological Rhythms, Amelia Island, Florida, 2002 (hereafter, SRBR meeting, 2002).
Soon to speak was Mary Carskadon:
Mary Carskadon, "Guidelines for the Multiple Sleep Latency Test (MSLT): a standard measure of sleepiness,"
Sleep
9, 519–24 (1986); Mary Carskadon and William Dement, "Daytime sleepiness: quantification of a behavioral state,"
Neuroscience Biobehavioral Review
11, 307–17 (1987).
On the 7-point Stanford Sleepiness Scale:
E. Hoddes et al., "Qualification of sleepiness: a new approach,"
Psychophysiology
10, 431–36 (1973).
According to neuroscientists, a yawn:
A. Argiolas and M. R. Melis, "The neuropharmacology of yawning,"
European Journal of Pharmacology
343:1, 1–16 (1998).

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But when Robert Provine ... tested this theory:
R. Provine, "Yawning: no effect of 3–5% CO
₂
, 100% 02, and exercise,"
Behavioral Neural Biology
48:3, 382–93 (1987).
As Dr. Seuss said: Dr. Seuss's Sleep Book
(New York: Random House, 1962).
To probe the nature of contagious yawning:
S. M. Platek et al., "Contagious yawning: the role of self-awareness and mental state attribution,"
Cognitive Brain Research
17, 223–27 (2003).
A follow-up fMRI study:
S. Platek et al., "Contagious yawning and the brain,"
Cognitive Brain Research
23, 448–52 (2005); personal communication with Platek, September 7, 2006.

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A deep seasonal rhythm largely ignored:
N. E. Rosenthal,
Winter Blues: Seasonal Affective Disorder
(New York: Guilford Press, 1998), 287 f.

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"
Gastric stretch" is thought to have:
S. Schacter et al., "Vagus nerve stimulation,"
Epilepsia
39, 677–86 (1998); A. Yamanaka et al., "Hypothalamic orexin neurons regulate arousal according to energy balance in mice,"
Neuron
38, 701–13 (2003).
In cats, the mere act of gently stimulating:
T. Kukorelli and G. Juhasz, "Sleep induced by intestinal stimulation in cats,"
Physiology and Behavior
19, 355–58 (1977).
A big meal rich in fat:
A. Wells et al., "Influence of fat and carbohydrate on postprandial sleepiness, mood, and hormones,"
Physiology and Behavior
61:5, 679–86 (1997).
When scientists compared midafternoon:
Gary Zammit et al., "Postprandial sleep in healthy men,"
Sleep
18:4, 229–31 (1995).
The work of Carskadon and others:
M. A. Carskadon and C. Acebo, "Regulation of sleepiness in adolescents: update, insights, and speculation,"
Sleep
25:6, 606–14 (2002); M. Carskadon, "The rhythm of human sleep and wakefulness," presentation at SRBR meeting, 2002; W. Dement and C. Vaughan,
The Promise of Sleep
(New York: Dell, 2000), 79–84.
Peretz Lavie confirmed this:
Peretz Lavie,
The Enchanted World of Sleep
(New Haven: Yale University Press, 1996), 51; personal communication with Lavie, February 14, 2005.

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Dale Edgar ... verified the location:
D. M. Edgar et al., "Effect of SCN lesions on sleep in squirrel monkeys: evidence for opponent processes in sleep-wake regulation,"
Journal of Neuroscience
13, 1065–79 (1993); Dement and Vaughan,
The Promise of Sleep,
78–81. personal communication with Dement, March 5, 2005.
Just how severely you suffer:
M. Carskadon, "The rhythm of human sleep and wakefulness."