Lactose Intolerance

I am lactose intolerant and there are many misconception about people with lactose intolerant not being able to drink milk. Well technically yes we can't consume lactose, but depending on each individual, we can consume a little bit of lactose every day (and thus enjoy ice cream, yogurt, cheese, etc.).

What is lactose intolerance?

From WordNet Search, lactose intolerance is a "congenital disorder consisting of an inability to digest milk and milk products; absence or deficiency of lactase results in an inability to hydrolyze lactose."

Lactose intolerance affects a large population of people from all over the world. In the Caucasian population, approximately 1 in 20 people is lactose intolerant. This figure increases when you move from to South America to Africa and then to Asia. In Asia, some 50-100% of the people in Asian countries are lactose intolerant, as shown in the lactase hotspots map below (I know it's missing America):

picture credit: Archaeology: The milk revolution

What causes lactose intolerance?

People who do not produce enough lactase enzyme or do not product it at all, problems such as diarrhea, abdominal pain, etc. can occur if too much lactose is consumed. When there is insufficient lactase to break down the lactose ingested, the lactose remains undigested undergoes fermentation, which means that it is broken down by other bacteria in out body for their nutrition. This process will causes the symptoms commonly experience by those who are lactose intolerant.

You can become lactose intolerant as you grow older

Young children almost universally produce lactase and can digest the lactose in their mother's milk as well as cow's milk. But as they mature, most switch off the lactase gene. Only 35% of the human population can digest lactose beyond the age of about seven or eight. Especially if you consume lesser milk as you grow older, your body might determine that you no longer need lactase and hence produce less lactase.

A number of people who are lactose intolerance actually are able to consume small amounts of lactose and still not have symptoms.

Depending on the person, often they are able to take about 1/3 to one cup of milk per day spread throughout the day (and not at one shot).  They can usually also take cheese and yogurt. By fermenting milk to cheese and yogurt, the lactose level is actually reduced.

Full-fat milk is better tolerated than skim milk because the fat in the milk slows down the travel time of the lactose, allowing any lactase enzymes more time to break down the lactose. It is also recommended to spread consumption of milk products evenly throughout the day and consume them with other non-dairy products to improve tolerance.

Sources:
Archaeology: The milk revolution (I find this a very good read)
RX For Readers: Lactose intolerant?
The evolution of lactase persistence in Europe. A synthesis of archaeological and genetic evidence