This should be very close to what you are looking for:

Nakamura,K.; Schoeller,D.A.; Winkler,F.J.; Schmidt,H.L. (1982):
Geographical variations in the carbon isotope composition of the diet 
and hair in contemporary man. Biomedical Mass Spectrometry, 9, 390-
394.

Cheers

Rudi

E-mail: [log in to unmask]

Dr. Rudi Schäufele
Chair of Grassland Science
Technische Universität München-Weihenstephan
Am Hochanger 1
D-85350 Freising-Weihenstephan
Tel.: ++49 8161 715265
Fax : ++49 8161 713243