|
Page: History of Genetic Prevalence
Main article
| Home > Nutrition > History of Genetic Prevalence |
Lactose intolerance has been studied as an aid in understanding ancient diets and population movement in prehistoric societies. Milking an animal vastly increases the efficiency of raising it in regards to the calories that can be extracted compared to consumption of its meat alone. It is not surprising then, that consuming milk products became an important part of the agricultural way of life in the Neolithic. Given that at this time the majority of the population of all areas was lactose intolerant, it is believed that most of the milk was used to make mature cheeses, in which most of the lactose can be safe to eat.
However, cheese takes a long time to produce and one of the theories for the prevalence of lactose tolerance in northern Europe and certain parts of the near east is that, at a time of famine, it became advantageous to consume the milk directly, without having to wait for it to mature. A small number of others believe that the practical advantages of the mutation have been over emphasised and that it is no more than chance that this gene was allowed to flourish in certain societies.
In Europe, Roman sources attest that milk was often used as a purgative (to induce vomiting and diarrhea), and horse milk is suggested as the best, with goat's milk as the worst. This corresponds to the amount of lactose in the milk; horse milk has a great deal of lactose, and goat's milk not very much. Roman authors also remark that the people of northern Europe, particularly Britain and Germany drank unprocessed milk (as opposed to the Romans who made cheese). This corresponds very closely with modern European distributions of lactose intolerance, where the people of Britain, Germany and Scandinavia have a good tolerance, and those of southern Europe, especially Italy, have a poorer tolerance.
In east Asia, historical sources also attest that the Chinese did not consume milk, whereas the nomads that lived on the borders did. Again, this reflects modern distributions of intolerance. China is particularly notable as a place of poor tolerance, whereas in Mongolia and the Asian steppes horse milk is drunk regularly. Here they even make an alcoholic beverage, called Kumis, from horse milk (although the fermentation process reduces the amount of lactose present). This tolerance is thought to be advantageous as the nomads do not settle down long enough to process mature cheese or may find themselves regularly going through brief periods of starvation; and given that their prime source of income is generated through horses, to ignore their milk as a source of calories would be greatly detrimental.
The African Fulani have a nomadic origin and their culture once completely revolved around cow, goat, and sheep herding. Dairy products were once a large source of nutrition for them. As might be expected if lactase persistence evolved in response to dairy product consumption, they are particularly tolerant to lactose (about 77% of the population). Many Fulani still live in Guinea-Conakry, Burkina Faso, Mali, Nigeria, Niger, Cameroon, and Chad.
A thorough scientific overview of genetic polymorphisms of intestinal lactase activity in adult hypolactasia, is in chapter 76 of OMMBID. A noncoding variation in the MCM6 gene has been strongly associated with adult type hypolactasia.
|
Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
qualified health provider with any questions you may have regarding a medical condition.
|