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| Certain people who report problems with consuming lactose are not actually lactose intolerant. In a study of 323 Sicilian adults, Carroccio et al. (1998) found only 4% were both lactose intolerant and lactose maldigesters, while 32.2% were lactose maldigesters but did not test as lactose intolerant. However, Burgio et al. (1984) found that 72% of 100 Sicilians were lactose intolerant in their study and 106 of 208 northern Italians (i.e., 51%) were lactose intolerant. | | Certain people who report problems with consuming lactose are not actually lactose intolerant. In a study of 323 Sicilian adults, Carroccio et al. (1998) found only 4% were both lactose intolerant and lactose maldigesters, while 32.2% were lactose maldigesters but did not test as lactose intolerant. However, Burgio et al. (1984) found that 72% of 100 Sicilians were lactose intolerant in their study and 106 of 208 northern Italians (i.e., 51%) were lactose intolerant. |
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| ==Lactose intolerance by group==
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| [[Image:LacIntol-World2.png|left|thumb|200px|Lactose Intolerance by Region (African countries are only a rough guess)]]
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| Most Japanese can consume 200 ml (8 fl oz) of milk without severe symptoms (McGee 2004; Swagerty et al, 2002).<ref name="Yoshida">[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1234085&dopt=Abstract ''Studies on the etiology of milk intolerance in Japanese adults'', Yoshida Y, Sasaki G, Goto S, Yanagiya S, Takashina K, Gastroenterol Jpn.;10(1):29–34, 1975]</ref>
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| {| class="wikitable"
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| | '''Human groups'''
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| | '''Individuals Examined'''
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| | '''Percent Intolerant'''
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| | '''[[Allele frequency]]'''
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| |Dutch || N/A || 1%<ref name=AdvHG>''Genetics of lactose digestion in humans.'', Flatz, G. , Advances in Human Genetics, 1987</ref> || N/A
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| |Swedes || N/A || 2%<ref name=SA>''Lactose and Lactase'', Norman Kretchmer, Scientific American, October, 1972</ref> || 0.14
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| ||Europeans in Australia ||160 || 4%<ref name=SA/> || 0.20
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| |White people of Northern European and Scandinavian descent||N/A||5%<ref name=variant/><ref name=UCD/>||N/A
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| |Danes || N/A || 5%<ref>[[Anne Charlotte Jäger]], [http://www.dskb.dk/index.jsp?id=7353&gr=7446 "Laktose-intolerans: Gentest for laktose-intolerans - hurtig og billig diagnostik"], [[DSKB-NYT]], no. 1, February 2006.</ref> || N/A
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| |Demographics of the United Kingdom|British||5–15%<ref name=probiotic>[[Michael de Vrese]], Anna Stegelmann, Bernd Richter, Susanne Fenselau, Christiane Laue and Jürgen Schrezenmeir,[http://www.ajcn.org/cgi/content/full/73/2/421S "Probiotics—compensation for lactase insufficiency"], ''[[American Journal of Clinical Nutrition]]'', Vol. 73, No. 2, 421S-429s, February 2001.</ref> ||N/A
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| |Swiss || N/A || 10%<ref name=SA/> || 0.316
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| |White Americans || 245 || 12%<ref name=SA/> || 0.346
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| |Tuareg || N/A || 13%<ref name=probiotic/> || N/A
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| | Germans || N/A || 15%<ref name=probiotic/> || N/A
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| | Austrians || N/A || 15–20%<ref name=probiotic/> || N/A
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| |Eastern Slavs (Russians, Belarusians, Ukrainians) || N/A || 15%<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15991859&dopt=Abstract Prevalence of the lactase deficiency among the population of the northwestern region of Russia]</ref> || N/A
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| |-
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| |Northern French||N/A||17%<ref name=probiotic/> ||N/A
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| |Finns || 134 || 18%<ref name=SA/> || 0.424
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| |Central Italians|| 65 || 19%<ref name=Italian/> ||N/A
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| |Indian Children||N/A||20%<ref name=variant>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11788828&query_hl=14&itool=pubmed_docsum ''Identification of a variant associated with adult-type hypolactasia'', Enattah NS, Sahi T, Savilahti E, Terwilliger JD, Peltonen L, Jarvela I, Nat Genet. 2002 Feb;30(2):233–7]</ref><ref name=UCD>[http://nutrigenomics.ucdavis.edu/nutrigenomics/index.cfm?objectid=968814F6-65B3-C1E7-0C7007B71CC9959A ''Lactose Intolerance: The Molecular Explanation'', UC Davis Nutritional Genomics website]</ref>
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| ||N/A
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| |African Tutsi || N/A || 20%<ref name=SA/> || 0.447
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| |African Fulani || N/A || 23%<ref name=SA/> || 0.48
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| |Bedouins || N/A||25%<ref name=probiotic/> ||N/A
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| |Northern Indians ||N/A||27%<ref name=Indian>''Lactose intolerance in North and South Indians'', Tandon RK, Joshi YK, Singh DS, Narendranathan M, Balakrishnan V, Lal K., Am J Clin Nutr 1981;35:943–6, 1981.</ref>||N/A
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| |African American Children||N/A||45%<ref name=variant/>||N/A
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| |Indian Adults||150||50%<ref name=variant/><ref name=UCD/><ref>[http://www.indianjgastro.com/article.asp?issn=0254-8860;year=2004;volume=23;issue=2;spage=78;epage=78;aulast=Rana ''Lactose malabsorption in apparently healthy adults in northern India, assessed using lactose hydrogen breath test'', Rana SV, Bhasin DK, Naik N, Indian Journal of Gastroenterology, Volume 23, Issue 2, p. 78, 2004]</ref>||N/A
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| |Southern Italians|| 51 || 41%<ref name=Italian/> || N/A
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| |Saami (in Russia and Finland) || N/A || 25–60%<ref>A. Kozlov, D. Lisitsyn, "Hypolactasia in Saami subpopulations of Russia and Finland", ''[[Anthropologischer Anzeiger]]'', 55(3-4):281–287, 1997.</ref> || N/A
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| |Northern Italians|| 89 || 52%<ref name=Italian>[http://www.ajcn.org/cgi/content/abstract/45/4/748''Primary adult lactose malabsorption in Italy: regional differences in prevalence and relationship to lactose intolerance and milk consumption'', LT Cavalli-Sforza, A Strata, A Barone and L Cucurachi, American Journal of Clinical Nutrition, Vol 45, 748–754, 1987]</ref> || N/A
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| |North American Hispanics ||N/A||53%<ref name=probiotic/> ||N/A
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| |Balkans|| N/A||55%<ref name=probiotic/> ||N/A
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| |Mexican American Males||N/A||55%<ref name=variant/><ref name=UCD/>||N/A
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| |Cretans||N/A||56%<ref name=variant/>||N/A
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| |African Maasai || 21 || 62%<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=581925&dopt=Abstract ''Lactose malabsorption among Masai children of East Africa'', RT Jackson, MC Latham, Am J Clin Nutr. 1979 Apr;32(4):779–82.]</ref>
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| || N/A
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| | Southern French||N/A||65%<ref name=probiotic/> ||N/A
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| |Greek Cypriots||N/A||66%<ref name=variant/><ref name=UCD/>||N/A
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| |North American Jews||N/A||68.8%<ref name=variant/><ref name=UCD/>||N/A
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| |Southern Indians ||N/A||70%<ref name=Indian/>||N/A
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| |Sicilians ||100||71%<ref name=Burgio>[http://www.ajcn.org/cgi/reprint/39/1/100.pdf ''Prevalence of primary adult lactose malabsorption and awareness of milk intolerance in Italy'', G Roberto Burgio, Gebhard Flatz, Cristiana Barbera, Rosario Patan, Attilio Boner, Cinzia Cajozzo, and Sibylle D Flaiz, The American Journal of Clinical Nutrition 39: pp 100–104, January 1984.]</ref><ref>[http://www.jacn.org/cgi/content/full/19/suppl_2/165S ''Lactose Intolerance'', Tuula H. Vesa, Philippe Marteau, and Riitta Korpela, Journal of the American College of Nutrition, Vol. 19, No. 90002, 165S-175S (2000)]</ref>||N/A
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| |South Americans||N/A||65–75%<ref name=probiotic/> ||N/A
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| |Rural Mexicans||N/A||73.8%<ref name=variant/><ref name=UCD/>||N/A
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| |African Americans || 20 || 75%<ref name=SA/> || 0.87
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| |Kazakhs from northwest Xinjiang || 195 || 76.4% <ref name=China/>||
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| |Lebanese||75||78%<ref>[http://www.ajcn.org/cgi/reprint/32/10/1994.pdf ''Lactose intolerance in the Lebanese population and in “Mediterranean lymphoma”'', Salah M. Nasrallah, The American Journal of Clinical Nutrition 32 , pp. 1994–1996, October, 1979.]</ref>||N/A
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| |Central Asians||N/A||80%<ref name=probiotic/> ||N/A
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| |Alaskan Eskimo||N/A||80%<ref name=variant/><ref name=UCD/>||N/A
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| |Australian Aborigines || 44 || 85%<ref name=SA/> || 0.922
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| |Inner Mongolians||198||87.9%<ref name=China>[http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=6235167&dopt=Abstract''Prevalence of primary adult lactose malabsorption in three populations of northern China''], Wang YG, Yan YS, Xu JJ, Du RF, Flatz SD, Kühnau W, Flatz G., Hum Genet. 1984;67(1):103-6.</ref>||
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| |African Bantu || 59 || 89%<ref name=SA/> || 0.943
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| |Asian Americans||N/A||90%<ref name=variant/><ref name=UCD/>||N/A
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| |Northeastern Han Chinese || 248 || 92.3%<ref name=China/>||
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| |Chinese || 71 || 93%<ref name=SA/> || 0.964
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| |Southeast Asians||N/A||98%<ref name=variant/><ref name=UCD/>||N/A
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| |Thais || 134 || 98%<ref name=SA/> || 0.99
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| |Native Americans || 24 || 100%<ref name=SA/> || 1.00
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| |}
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| The [[statistical significance]] varies greatly depending on number of people sampled.
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| Lactose intolerance levels also increase with age. At ages 2 - 3 yrs., 6 yrs., and 9 - 10 yrs., the amount of lactose intolerance is, respectively:
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| * 6% to 15% in white Americans and northern Europeans
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| * 18%, 30%, and 47% in Mexican Americans
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| * 25%, 45%, and 60% in black South Africans
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| * approximately 30%, 80%, and 85% in Chinese and Japanese
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| * 30–55%, 90%, and >90% in Mestizos of Peru<ref name=Sahi> ''Genetics and epidemiology of adult-type hypolactasia'', Sahi T., Scand J Gastroenterol Suppl ;29:202:7–20, 1994</ref><ref>[http://www.ajcn.org/cgi/content/abstract/29/1/19?ijkey=10c44e0ee3932cb3ee9d514dd65488c8284bc803&keytype2=tf_ipsecsha ''Lactose malabsorption in Mexican-American children'', Woteki CE, Weser E, Young EA, Am J Clin Nutr;29:19–24, 1976]</ref>
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| Chinese and Japanese populations typically lose between 80 and 90 percent of their ability to digest lactose within three to four years of weaning.
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| Ashkenazi Jews can keep 20 - 30 percent of their ability to digest lactose for many years.<ref name=Sahi/><ref>''Genetics of lactose digestion in humans'', Flatz G., Adv Hum Genet ;16:1 - 77, 1987</ref><ref>''Genetics of lactase persistence and lactose intolerance'', Swallow DM., Annu Rev Genet ;37:197 - 219, 2003.</ref> Of the 10% of the Northern European population that develops lactose intolerance, the development of lactose intolerance is a gradual process spread out over as many as 20 years.<ref>[http://pmj.bmj.com/cgi/content/full/81/953/167 ''Systemic lactose intolerance: a new perspective on an old problem'', S B Matthews, J P Waud, A G Roberts and A K Campbell, Postgraduate Medical Journal;81:167 - 173, 2005.]</ref>
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| ==References== | | ==References== |