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Previous Volume 342:1531-1532 May 18, 2000 Number 20 Next

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To the Editor: In their analysis of the energy expended in chewing gum (Dec. 30 issue),¹ Levine et al. instructed subjects to chew gum "at a frequency of precisely 100 Hz (a value that approximates chewing frequency at our institution) with the aid of a metronome." I am curious about the use of hertz, the Système International unit of frequency measured in cycles per second.^2,3 As defined, a value of 1.0 Hz rather than 100 Hz would be more plausible. Alternatively, if the experimental protocol had called for a setting of 100 on a standard metronome, as might be inferred from the quoted text, the unit of measurement that should have been used is Maelzel's metronome (MM), which indicates oscillations per minute.⁴ A measurement of MM 100 is consistent with calculations based on my own informal observations of gum chewing.

David A. Florman, J.D.
575 Madison Ave.
New York, NY 10022-2585

References

1. Levine J, Baukol P, Pavlidis I. The energy expended in chewing gum. N Engl J Med 1999;341:2100-2100. [Free Full Text]
2. National Institute of Standards and Technology Web site. (See http://physics.nist.gov/cuu/units/units.html.)
3. "Hertz." In: Encyclopedia Britannica Web site. (See http://www. britannica.com/bcom/eb/article/0/0,5716,41115+1+40251,00.html.)
4. Apel W. Harvard dictionary of music. 2nd ed. rev. Cambridge, Mass.: Belknap Press, 1972:523.

To the Editor: Mr. Florman is correct: we did use erroneous units to describe the normal chewing rate at our institution. We should have used chews per minute rather than hertz. The rate of 100 chews per minute at our institution indeed approximates that calculated by Mr. Florman in New York City. The rate varies according to body size. In quadripeds, the chewing rate relates to body mass to the –0.128 power, a relation that relates primarily to jaw mechanics rather than to metabolic needs.¹ Hence, larger organisms chew with greater thermal efficiency than smaller organisms, and I would not want to mislead readers of the Journal regarding any inefficiency at our institution.

James Levine, M.D., Ph.D.
Mayo Clinic
Rochester, MN 55905

References

1. Druzinsky RE. The time allometry of mammalian chewing movements: chewing frequency scales with body mass in mammals. J Theor Biol 1993;160:427-440. [CrossRef][Medline]

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Related Letters:

The Energy Expended in Chewing Gum
Levine J., Baukol P., Pavlidis I.
Extract | Full Text  
N Engl J Med 1999; 341:2100, Dec 30, 1999. Correspondence

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