CopperLine wrote:phoenix wrote:CopperLine wrote:TCs / Turks are more likely to be lactose intolerant than Europeans
If this is claiming that lactose intolerance has a genetic basis the your conclusion that TCs/Turks are more likely to belactose intolerant than Europeans is clear baloney since TCs/Turks and Europeans are not genetic categories nor display genetic differences as TCs/Turks and Europeans. The description TC/Turk and European are political categories and descriptions and as such TCs/Turks are simply a sub-set of a political set called Europeans.
From "Matching Grants":
D-876
Turkey - Izmir
Lactose Deficiency
$40,000
The community to be served in this project is the children and their families and the relatives , who live in Izmir and suburbs. The ''PREVELANCE OF LACTOSE DEFICIENCY'' is seen in Turkish children and it is costly to recover from this condition. Because the management and therapy of the growth retardation and bone weakness which are the complications of lactose deficiency are all expensive for the families.
We aim to determine the prevelance of lactose deficiency among healthy children and to describe their clinical characteristics. One of the primary future goals of this study is to develope effective strategies identifies and follow up children with lactose deficiency. To identitfy children with lactose intolerance will help to prevent malnutrition, growth retardation, and bone weakness, unnecessary avoidance of dairy products.
We believe that this study will allow us to give appropriate support to children with lactose deficiency. Another primary future goal of this study is to develop effective strategy (with informing the families about the results of this study through the "Family doctorship" at least in Eagean Region in Turkey.) to identify and follow up children with lactose deficiency. . . .
Is that it
Phoenix ? Is that the basis for your claim ? Holy moly ! So the fact that this is
not a comparative study, the fact that its
doesn't mention genetics, the fact that it speaks about prevalence and lactose
deficiency, the fact that it makes
no mention of Europeans, leads you to post an item which says
TCs / Turks are more likely to be lactose intolerant than Europeans
Your source material said nothing of the sort - and you claim to be a scientist ?
If you don't approve of my conclusion, you can peruse these, and draw your own . . .
BTW why you are so defensive about my statement?
source for ref.1
http://www.cambridge.org/us/books/kiple/lactose.htm
Distribution of Lactase Persistence
Several authors have compiled the results of regional studies (Flatz 1987; Kretchmer 1993; Sahi 1994). Some of the major findings are summarized here in Table IV.E.6.1.
It should be noted that data for northern India and Pakistan are suspect and that figures for Finno-Ugrian groups in northern Russia and western Siberia (Khanty, Mansi, Mari, Mordva, Nentsy) are based on small, possibly unrepresentative, samples and older methods (Valenkevich and Yakhontova 1991; Kozlov, Sheremeteva, and Kondik 1992). There is little hard information for the Balkan or Iberian peninsulas, Slavic territories east of Poland, Siberia, central Asia, or the Indian subcontinent. It would also be interesting to have more data on East African pastoralists, such as the Maasai, and on Baggara Arab and other cattle-keeping groups of the West African Sahel.
A high proportion of lactase persisters was noted in northwestern Europe in the early 1970s, and there were similar reports from northern India, from Bedouin and other pastoral populations in the Middle East and northern Africa, and from the Tutsi pastoralists of the Uganda-Rwanda region of East Africa. Very low rates were found among eastern, and most southern, Asians, most Africans, and native populations of the Americas and the Pacific, and only modest rates were found in southern and eastern Europe. In North and South America, Australia, and New Zealand, adult lactase ability is closely linked to place of origin; for example, white Australians resemble their European counterparts in lactase persistence, whereas Aborigines are almost entirely lactose intolerant. Varying degrees of Spanish and Indian ancestry may explain regional differences in Mexico (Rosado et al. 1994). Similarly, a higher than expected prevalence of lactase persistence among Buryat Mongols of Russia’s Lake Baikal region may be due to gene flow from European Russians (Kozlov et al. 1992).
Adult lactase capability appears to have evolved in two, and possibly three, geographic areas. The case is clearest and best documented for northern Europe, where there are very high percentages around the Baltic and North Seas. High levels of lactase persistence seem closely linked to Germanic and Finnic groups. Scandinavia, northern Germany, and Britain have high levels, as do the Finns and Estonians, the Finnic Izhorians west of St. Petersburg, the Mari of the middle Volga basin, and, to a lesser extent, their more distant relations, the Hungarians.
There is a general north—south gradient in Europe, which is evident within Germany, France, Italy, and perhaps Greece. As noted, more information is needed for Spain, Portugal, and eastern Europe, but there may be something of a west—east gradient in the Slavic lands. Varying frequencies of the LAC*P allele among Lapp groups may be related to differing lengths of historical use of reindeer and cow’s milk and to admixture with other Scandinavians (Sahi 1994).
The second center of adult lactase persistence lies in the arid lands of Arabia, the Sahara, and eastern Sudan. There, lactase persistence characterizes only nomadic populations heavily dependent on camels and cattle, such as the Bedouin Arabs, the Tuareg of the Sahara, the Fulani of the West African Sahel, and the Beja and Kabbabish of Sudan. Lower rates among Nigerian Fulani may indicate a higher degree of genetic mixing with other peoples than among the Fulani of Senegal.
In contrast, surrounding urban and agricultural populations, whether Arab, Turkish, Iranian, or African, have very low rates. It is interesting to note that the Somali sample also had a low frequency of the LAC*P allele. Possibly, pastoral Somali have higher prevalences than their urban compatriots.
A third center of adult lactase persistence has been suggested among the Tutsi population of the Uganda-Rwanda area of the East African interior. The Tutsi are an aristocratic cattle-herding caste of Nilotic descent who have traditionally ruled over agricultural Bantu-speakers. Table IV.E.6.1 shows that only 7 percent of a sample of 65 Tutsi adults were lactase deficient, but the data are old, there certainly has been some mixture with Bantu-speakers, and the study should be replicated. The Nilotic peoples of the southern Sudan, whence the Tutsi originated a few centuries ago, do not display this trait. Unless the Tutsi result can be confirmed, and the Maasai and other East African Nilotic groups can be tested, this third center of the LAC*P allele must be considered doubtful. If it does exist, it probably arose as a fairly recent mutation, as there are no obvious historical mechanisms to account for gene flow between the Tutsi and desert dwellers farther north.
Evolution of Lactase Persistence
Frederick J. Simoons (1969, 1970) has advanced the thesis that lactase persistence is closely linked to dairying. His culture-evolution hypothesis is that groups that kept cattle and other milk animals would gain a selective advantage if adults retained the ability to use milk and milk products as food.
A mutation like LAC*P would be nutritionally beneficial, and the growing number of milk-using adults would then be encouraged to devote more effort toward livestock raising. In general, the distribution of adult lactase persistence and dairy ing shows a positive relationship. In areas with
no dairying tradition, such as China, Oceania, Pre-Columbian America, or tropical Africa, few adults can digest lactose.
Northern Europe presents the opposite case. More data around the periphery of the two postulated centers would be highly desirable, and we know little about most of the stock-raising societies of central Asia. Still, although the correspondence is not perfect, and gene flow through population mixing complicates the picture, the association seems strong. Given the origins of cattle keeping about 4000 to 3500 B.C. in northern Europe, and even earlier in the Middle East, there probably has been enough time for modest selective pressures to have produced observed LAC*P rates (Sahi 1994).
Other selective forces may also have been at work. Flatz (1987) has suggested that calcium absorption was such a factor in northern Europe. Lactose is known to facilitate calcium absorption in the intestine. The cold, cloudy climate frequently discouraged skin exposure to sunlight, thereby reducing the body’s production of vitamin D. Relatively little dietary vitamin D was available, and so in its absence, calcium was poorly absorbed. Northern populations were thus vulnerable to rickets and osteomalacia. Pelvic deformities made births more difficult. The gradual extinction of the Greenland Viking colony is an example; skeletal evidence shows that such bone diseases were common among this moribund population. A mutant LAC*P allele would not only allow adults to use an excellent source of calcium, but the lactose would also facilitate its absorption. While not proven, this hypothesis has attracted much attention. It would complement the theory that the pale skin of northern Europeans is a genetic trait maximizing the utility of sunlight in vitamin D production and, hence, calcium absorption.
Similarly, other selective pressures facilitating the survival of mutant LAC*P alleles have been postulated for the Sahara—Arabian Peninsula desert region. There is a high degree of dependency on milk among many groups of desert pastoralists, and so a positive link between lactase persistence and milking seems very plausible. In addition, it has been argued (Cook 1978) that the simple fact that milk is a liquid would give adults who could consume it in large quantities a powerful selective advantage. The theory, while unproven, certainly seems plausible. G. C. Cook’s suggestion that lactase persistence conveyed some resistance to gastrointestinal diseases has attracted much less support. At least for cholera, his claim must be rejected, based on what we know of the historical geography of the disease. Cholera seems to have been restricted to the Indian subcontinent until very recent times.
Finally, it seems most likely that the European and Arabia-Sahara centers of LAC*P prevalence, and the Uganda-Rwanda center (if it in fact exists), arose independently. Population movement and gene flow can be very extensive and, no doubt, have played a substantial role around the centers. Despite the efforts of some authors to find a common origin in the ancient Middle East, it is simpler to suggest independent origins than to postulate gene flow from the Middle East to Scandinavia and to the interior of East Africa. The problem might be resolved in the future if gene sequencing could show that the LAC*P alleles in Sweden and Saudi Arabia are, in fact, the same or are distinct forms of the gene with a similar function.
Conclusions
Lactose malabsorption is the normal condition of most adults. Many suffer the clinical symptoms of lactose intolerance if they consume milk, especially in large amounts. In two, or possibly three, places, genetic mutations have arisen that allow adults to gain the nutritional and culinary benefits of milk and many other dairy products. This ability has evolved along with cultural developments with profound implications for livelihood, including, in the northern European case, the development of mixed farming. East Asian, African, Oceanic, and Amerindian peoples, of course, thrived without this genetic trait and its cultural consequences. Their infants and young children enjoyed the nutritional advantages of milk; adults ate other things, including fermented milk products. Milk can be consumed by most lactose-intolerant older children in moderate amounts, and so milk can be a valuable nutrient for the undernourished or famine stricken. Modern commercial lactase products allow most lactose-intolerant adults to consume dairy products; thus, pizza and ice cream need not be forbidden foods.
1: Am J Hum Genet. 2004 Jun;74(6):1111-20. Epub 2004 Apr 26. Links
Genetic signatures of strong recent positive selection at the lactase gene.Bersaglieri T, Sabeti PC, Patterson N, Vanderploeg T, Schaffner SF, Drake JA, Rhodes M, Reich DE, Hirschhorn JN.
Divisions of Genetics and Endocrinology, Harvard Medical School, Boston, MA 02115, USA.
In most human populations, the ability to digest lactose contained in milk usually disappears in childhood, but in European-derived populations, lactase activity frequently persists into adulthood (Scrimshaw and Murray 1988). It has been suggested (Cavalli-Sforza 1973; Hollox et al. 2001; Enattah et al. 2002; Poulter et al. 2003) that a selective advantage based on additional nutrition from dairy explains these genetically determined population differences (Simoons 1970; Kretchmer 1971; Scrimshaw and Murray 1988; Enattah et al. 2002), but formal population-genetics-based evidence of selection has not yet been provided. To assess the population-genetics evidence for selection, we typed 101 single-nucleotide polymorphisms covering 3.2 Mb around the lactase gene. In northern European-derived populations, two alleles that are tightly associated with lactase persistence (Enattah et al. 2002) uniquely mark a common (~77%) haplotype that extends largely undisrupted for >1 Mb. We provide two new lines of genetic evidence that this long, common haplotype arose rapidly due to recent selection: (1) by use of the traditional F(ST) measure and a novel test based on p(excess), we demonstrate large frequency differences among populations for the persistence-associated markers and for flanking markers throughout the haplotype, and (2) we show that the haplotype is unusually long, given its high frequency--a hallmark of recent selection. We estimate that strong selection occurred within the past 5,000-10,000 years, consistent with an advantage to lactase persistence in the setting of dairy farming; the signals of selection we observe are among the strongest yet seen for any gene in the genome.
PMID: 15114531 [PubMed - indexed for MEDLINE]
1: PLoS Genet. 2006 Sep 15;2(9):e143. Epub 2006 Jul 25. Links
European population substructure: clustering of northern and southern populations.Seldin MF, Shigeta R, Villoslada P, Selmi C, Tuomilehto J, Silva G, Belmont JW, Klareskog L, Gregersen PK.
Rowe Program in Human Genetics, Departments of Biological Chemistry and Medicine, University of California Davis, Davis, California, United States of America.
[email protected]
Using a genome-wide single nucleotide polymorphism (SNP) panel, we observed population structure in a diverse group of Europeans and European Americans. Under a variety of conditions and tests, there is a consistent and reproducible distinction between "northern" and "southern" European population groups: most individual participants with southern European ancestry (Italian, Spanish, Portuguese, and Greek) have >85% membership in the "southern" population; and most northern, western, eastern, and central Europeans have >90% in the "northern" population group. Ashkenazi Jewish as well as Sephardic Jewish origin also showed >85% membership in the "southern" population, consistent with a later Mediterranean origin of these ethnic groups. Based on this work, we have developed a core set of informative SNP markers that can control for this partition in European population structure in a variety of clinical and genetic studies.
PMID: 17044734 [PubMed - indexed for MEDLINE]
1: Proc Natl Acad Sci U S A. 2007 Mar 6;104(10):3736-41. Epub 2007 Feb 28. Links
Absence of the lactase-persistence-associated allele in early Neolithic Europeans.Burger J, Kirchner M, Bramanti B, Haak W, Thomas MG.
Johannes Gutenberg University, Institute of Anthropology, Saarstrasse 21, D-55099 Mainz, Germany.
[email protected]
Lactase persistence (LP), the dominant Mendelian trait conferring the ability to digest the milk sugar lactose in adults, has risen to high frequency in central and northern Europeans in the last 20,000 years. This trait is likely to have conferred a selective advantage in individuals who consume appreciable amounts of unfermented milk. Some have argued for the "culture-historical hypothesis," whereby LP alleles were rare until the advent of dairying early in the Neolithic but then rose rapidly in frequency under natural selection. Others favor the "reverse cause hypothesis," whereby dairying was adopted in populations with preadaptive high LP allele frequencies. Analysis based on the conservation of lactase gene haplotypes indicates a recent origin and high selection coefficients for LP, although it has not been possible to say whether early Neolithic European populations were lactase persistent at appreciable frequencies. We developed a stepwise strategy for obtaining reliable nuclear ancient DNA from ancient skeletons, based on (i) the selection of skeletons from archaeological sites that showed excellent biomolecular preservation, (ii) obtaining highly reproducible human mitochondrial DNA sequences, and (iii) reliable short tandem repeat (STR) genotypes from the same specimens. By applying this experimental strategy, we have obtained high-confidence LP-associated genotypes from eight Neolithic and one Mesolithic human remains, using a range of strict criteria for ancient DNA work. We did not observe the allele most commonly associated with LP in Europeans, thus providing evidence for the culture-historical hypothesis, and indicating that LP was rare in early European farmers.
PMID: 17360422 [PubMed - indexed for MEDLINE]
1: Ann Hum Genet. 1998 May;62(Pt 3):215-23. Links
Lactase haplotype frequencies in Caucasians: association with the lactase persistence/non-persistence polymorphism.Harvey CB, Hollox EJ, Poulter M, Wang Y, Rossi M, Auricchio S, Iqbal TH, Cooper BT, Barton R, Sarner M, Korpela R, Swallow DM.
MRC Human Biochemical Genetics Unit, University College London, UK.
A genetic polymorphism is responsible for determining that some humans express lactase at high levels throughout their lives and are thus lactose tolerant, while others lose lactase expression during childhood and are lactose intolerant. We have previously shown that this polymorphism is controlled by an element or elements which act in cis to the lactase gene. We have also reported that 7 polymorphisms in the lactase gene are highly associated and lead to only 3 common haplotypes (A, B and C) in individuals of European extraction. Here we report the frequencies of these polymorphisms in Caucasians from north and south Europe and also from the Indian sub-continent, and show that the alleles differ in frequency, the B and C haplotypes being much more common in southern Europe and India. Allelic association studies with lactase persistence and non-persistence phenotypes show suggestive evidence of association of lactase persistence with certain alleles. This association was rather more clear in the analysis of small families, where haplotypes could be determined. Furthermore haplotype and RNA transcript analysis of 11 unrelated lactase persistent individuals shows that the persistence (highly expressed) allele is almost always on the A haplotype background. Non-persistence is found on a variety of haplotypes including A. Thus it appears that lactase persistence arose more recently than the DNA marker polymorphisms used here to define the main Caucasian haplotypes, possibly as a single mutation on the A haplotype background. The high frequency of the A haplotype in northern Europeans is consistent with the high frequency of lactase persistence.
PMID: 9803265 [PubMed - indexed for MEDLINE]
1: Am J Hum Genet. 2001 Jan;68(1):160-172. Epub 2000 Nov 28. Links
Lactase haplotype diversity in the Old World.Hollox EJ, Poulter M, Zvarik M, Ferak V, Krause A, Jenkins T, Saha N, Kozlov AI, Swallow DM.
MRC Human Biochemical Genetics Unit, Galton Laboratory, Department of Biology, University College London, London NW1 2HE, United Kingdom.
Lactase persistence, the genetic trait in which intestinal lactase activity persists at childhood levels into adulthood, varies in frequency in different human populations, being most frequent in northern Europeans and certain African and Arabian nomadic tribes, who have a history of drinking fresh milk. Selection is likely to have played an important role in establishing these different frequencies since the development of agricultural pastoralism approximately 9,000 years ago. We have previously shown that the element responsible for the lactase persistence/nonpersistence polymorphism in humans is cis-acting to the lactase gene and that lactase persistence is associated, in Europeans, with the most common 70-kb lactase haplotype, A. We report here a study of the 11-site haplotype in 1,338 chromosomes from 11 populations that differ in lactase persistence frequency. Our data show that haplotype diversity was generated both by point mutations and recombinations. The four globally common haplotypes (A, B, C, and U) are not closely related and have different distributions; the A haplotype is at high frequencies only in northern Europeans, where lactase persistence is common; and the U haplotype is virtually absent from Indo-European populations. Much more diversity is seen in sub-Saharan Africans than in non-Africans, consistent with an "Out of Africa" model for peopling of the Old World. Analysis of recent recombinant haplotypes by allele-specific PCR, along with deduction of the root haplotype from chimpanzee sequence, allowed construction of a haplotype network that assisted in evaluation of the relative roles of drift and selection in establishing the haplotype frequencies in the different populations. We suggest that genetic drift was important in shaping the general pattern of non-African haplotype diversity, with recent directional selection in northern Europeans for the haplotype associated with lactase persistence.
PMID: 11095994 [PubMed - indexed for MEDLINE]
1: Am J Hum Genet. 2004 Jun;74(6):1111-20. Epub 2004 Apr 26. Links
Genetic signatures of strong recent positive selection at the lactase gene.Bersaglieri T, Sabeti PC, Patterson N, Vanderploeg T, Schaffner SF, Drake JA, Rhodes M, Reich DE, Hirschhorn JN.
Divisions of Genetics and Endocrinology, Harvard Medical School, Boston, MA 02115, USA.
In most human populations, the ability to digest lactose contained in milk usually disappears in childhood, but in European-derived populations, lactase activity frequently persists into adulthood (Scrimshaw and Murray 1988). It has been suggested (Cavalli-Sforza 1973; Hollox et al. 2001; Enattah et al. 2002; Poulter et al. 2003) that a selective advantage based on additional nutrition from dairy explains these genetically determined population differences (Simoons 1970; Kretchmer 1971; Scrimshaw and Murray 1988; Enattah et al. 2002), but formal population-genetics-based evidence of selection has not yet been provided. To assess the population-genetics evidence for selection, we typed 101 single-nucleotide polymorphisms covering 3.2 Mb around the lactase gene. In northern European-derived populations, two alleles that are tightly associated with lactase persistence (Enattah et al. 2002) uniquely mark a common (~77%) haplotype that extends largely undisrupted for >1 Mb. We provide two new lines of genetic evidence that this long, common haplotype arose rapidly due to recent selection: (1) by use of the traditional F(ST) measure and a novel test based on p(excess), we demonstrate large frequency differences among populations for the persistence-associated markers and for flanking markers throughout the haplotype, and (2) we show that the haplotype is unusually long, given its high frequency--a hallmark of recent selection. We estimate that strong selection occurred within the past 5,000-10,000 years, consistent with an advantage to lactase persistence in the setting of dairy farming; the signals of selection we observe are among the strongest yet seen for any gene in the genome.
PMID: 15114531 [PubMed - indexed for MEDLINE]
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Lactose intolerance (LI) is a common disorder that affects a quarter of the US population and may affect as many as 75% of the world population. The prevalence varies by race and ethnicity. It is more common among African-Americans, Hispanics and oriental population. In India, for example, it is seen in 25% of north Indian and 70% of south Indian population.
