Toward a comprehensive approach to the collection and analysis of pica substances, with emphasis on geophagic materials.
BACKGROUND
Pica, the craving and subsequent consumption of non-food substances such as earth, charcoal, and raw starch, has been an enigma for more than 2000 years. Currently, there are little available data for testing major hypotheses about pica because of methodological limitations and lack of attention to the problem.


METHODS
In this paper we critically review procedures and guidelines for interviews and sample collection that are appropriate for a wide variety of pica substances. In addition, we outline methodologies for the physical, mineralogical, and chemical characterization of these substances, with particular focus on geophagic soils and clays. Many of these methods are standard procedures in anthropological, soil, or nutritional sciences, but have rarely or never been applied to the study of pica.


RESULTS
Physical properties of geophagic materials including color, particle size distribution, consistency and dispersion/flocculation (coagulation) should be assessed by appropriate methods. Quantitative mineralogical analyses by X-ray diffraction should be made on bulk material as well as on separated clay fractions, and the various clay minerals should be characterized by a variety of supplementary tests. Concentrations of minerals should be determined using X-ray fluorescence for non-food substances and inductively coupled plasma-atomic emission spectroscopy for food-like substances. pH, salt content, cation exchange capacity, organic carbon content and labile forms of iron oxide should also be determined. Finally, analyses relating to biological interactions are recommended, including determination of the bioavailability of nutrients and other bioactive components from pica substances, as well as their detoxification capacities and parasitological profiles.


CONCLUSIONS
This is the first review of appropriate methodologies for the study of human pica. The comprehensive and multi-disciplinary approach to the collection and analysis of pica substances detailed here is a necessary preliminary step to understanding the nutritional enigma of non-food consumption.
Young
Sera L
SL
School of Public Health, University of California, Berkeley, California, United States of America.
Wilson
M Jeffrey
MJ
Miller
Dennis
D
Hillier
Stephen
S
D000538:Aluminum Silicates; D000740:Anemia / Q000150:complications; D002623:Chemistry Techniques, Analytical / Q000379:methods*; D000077215:Clay; D005247:Feeding Behavior; D015438:Health Behavior; D006801:Humans; D010842:Pica / Q000175:diagnosis* / Q000209:etiology; D012107:Research Design; D012987:Soil / Q000032:analysis; D013048:Specimen Handling
D000538:Aluminum Silicates; D012987:Soil; D000077215:Clay
Obstet Gynecol. 1967 Apr;29(4):581-4
5227624
Gastroenterol Clin Biol. 1994;18(6-7):609-16
7533109
Ann Gastroenterol Hepatol (Paris). 1988 May-Jun;24(3):133-8
3041907
Med Anthropol. 1992 Jan;13(4):337-51
1545692
Endocrinol Metab Clin North Am. 1995 Mar;24(1):187-205
7781626
J Trop Pediatr. 1993 Oct;39(5):318-9
8271348
J Nutr. 1998 Sep;128(9):1555-61
9732319
J Am Diet Assoc. 1959 Aug;35(8):810-5
13664469
Gastroenterol Clin Biol. 1989 Jan;13(1):18-24
2647564
J Nutr. 1970 Aug;100(8):973-80
5495850
Q Rev Biol. 2000 Jun;75(2):113-48
10858967
Am J Dis Child. 1985 May;139(5):456-9
3984968
Science. 1970 Sep 25;169(3952):1334-6
5271640
Soc Sci Med. 1999 Apr;48(8):1069-79
10390045
Br J Haematol. 1977 Jun;36(2):298
559513
Sci Total Environ. 2004 Oct 15;333(1-3):75-87
15364520
J Trop Med Hyg. 1982 Aug;85(4):159-63
6292443
J Nutr. 1977 Nov;107(11):2020-5
561832
Gut. 1993 Jan;34(1):51-5
8432452
J Transcult Nurs. 1999 Jan;10(1):65-8
10476154
J Pharm Belg. 1990 Jul-Aug;45(4):268-73
2290122
J Natl Med Assoc. 1983 Sep;75(9):895-902
6631996
Am J Clin Nutr. 1979 Oct;32(10):2129-35
484531
Trans R Soc Trop Med Hyg. 2007 Aug;101(8):766-72
17568644
South Med J. 1995 Dec;88(12):1236-40
7502117
J Nutr. 2004 Oct;134(10):2717-21
15465772
J Toxicol Clin Toxicol. 1982 Oct;19(8):807-19
7182509
Mt Sinai J Med. 1975 Sep-Oct;42(5):410-4
1081190
N Engl J Med. 1976 Nov 4;295(19):1034-7
972657
Am J Clin Nutr. 1981 Oct;34(10):2248-56
6794346
J Exp Biol. 2004 Jan;207(Pt 2):319-24
14668315
Gastroenterol Clin Biol. 1985;9(12 Pt 2):9-12
3869119
Appl Environ Microbiol. 1993 Sep;59(9):3123-5
16349051
Gastroenterology. 1976 Dec;71(6):1028-32
11141
J Pharm Sci. 1966 Nov;55(11):1215-20
4381893
Curr Anthropol. 2002 Feb;43(1):19-61
14992226
Experientia. 1971 Jul;27(7):847-8
5167803
J Nutr. 1994 Jun;124(6 Suppl):954S-962S
8201446
Am J Clin Nutr. 1968 Dec;21(12):1384-93
4881679
Birth. 1995 Sep;22(3):129-37
7575860
South Med J. 2002 Oct;95(10):1228-9
12425520
Trans R Soc Trop Med Hyg. 1988;82(4):621-5
2855678
Curr Med Res Opin. 1982;8(4):233-41
6759058
Arch Fr Pediatr. 1992 Nov;49(9):779-83
1300965
Acta Haematol. 1978;60(2):76-84
98953
Histochem J. 1987 Dec;19(12):665-70
3443559
Br J Haematol. 1977 Mar;35(3):476-7
557984
Physiol Behav. 1976 Oct;17(4):691-7
1034944
J Nutr. 2006 Dec;136(12):3033-8
17116716
Nutrition. 2001 Jul-Aug;17(7-8):685-7
11448605
Am J Clin Nutr. 1968 Jan;21(1):78-86
5237295
South Med J. 1999 Feb;92(2):190-2
10071665
J Chem Ecol. 2003 Jul;29(7):1525-47
12921434
Geogr Rev. 1984;74(2):157-69
11614511
Am J Clin Nutr. 1991 Feb;53(2):448-56
1989412
Curr Opin Gastroenterol. 2007 Nov;23(6):595-601
17906434
Appl Environ Microbiol. 1983 Sep;46(3):673-82
6639022
Int J Artif Organs. 1983 Jul;6(4):207-13
6629527
West J Med. 2000 Jul;173(1):20-4; discussion 25
10903283
Br J Pharmacol. 2004 Mar;141(6):951-60
14993105
J Chem Ecol. 1986 Mar;12(3):635-46
24306904
Am J Obstet Gynecol. 1970 Sep 15;108(2):262-7
4952579
World J Biol Psychiatry. 2009;10(4 Pt 3):936-8
17853279
Int J Epidemiol. 1999 Feb;28(1):169-74
10195684
J Chem Ecol. 2003 Jul;29(7):1503-23
12921433
J Pharm Sci. 1975 Sep;64(9):1566-8
1185581
J Natl Med Assoc. 1981 Feb;73(2):163-4
7205979
J Ren Nutr. 1999 Jan;9(1):14-20
9861097
Trop Med Int Health. 1997 Jul;2(7):624-30
9270730
Am J Obstet Gynecol. 1988 Dec;159(6):1456-60
3207124
Clin Pediatr (Phila). 1981 Dec;20(12):783-5
7307412
Annu Rev Nutr. 1982;2:303-22
6764733
Proc Soc Exp Biol Med. 1967 Oct;126(1):304-8
5988011
Am J Obstet Gynecol. 2002 May;186(5 Suppl Understanding):S190-7
12011885
J Agric Food Chem. 2006 Oct 18;54(21):8362-8
17032052
Trans R Soc Trop Med Hyg. 2004 Dec;98(12):734-41
15485704
Boll Chim Farm. 1999 Jun;138(6):239-42
10464971
Am J Trop Med Hyg. 2007 Apr;76(4):725-31
17426179
J Nutr. 1992 Feb;122(2):327-32
1732473
Med J Aust. 1978 Mar 25;1 Suppl 1:1-3
661724
N Engl J Med. 1982 Apr 29;306(17):1056-7
7063004