Have you ever wondered what it means to be lactose intolerant? Sure, most of us realize that it means you can not eat dairy products, and you may even know that it means you can not digest the sugar lactose. But did you realize that lactose intolerance is not something that you are born with, it is something that develops later in life. If those who are lactose intolerant were born with the disorder then they would be unable to digest milk as a child, which for our ancestors was the primary way of feeding an infant. In fact as a newborn we are all capable of digesting milk because our body produces the necessary enzyme, lactase. This enzyme cleaves the lactose into glucose and galactose, which the body can then absorb and use for energy. However, between the ages of two and five most infants are weaned off of milk and as a result the body down regulates the production of lactase as a means of saving energy. Without production of the enzyme the body can no longer digest lactose through its own means, but why can many adults still consume lactose and others can not?
As you may know, the body gets quite a bit of help digesting everything we put into it, and many times that help can come from other organisms living inside us. Bacteria that line our intestines have the gene that is capable of producing lactase, and this is how adults continue to digest milk later in life. This is called a mutualistic relationship because both parties receive a benefit from being in the relationship. The bacteria get a source of lactose, which they break down, and then both the bacteria and the host can use the glucose and galactose for energy.
Even lactose intolerant people have some of this bacteria lining their intestines, but not enough to digest the lactose quick enough. As a result the "milk sugar" just sits there and can cause nausea, diarrhea, and cramps. The severity of this disorder depends on many factors: first how much lactase your body produces, second is how much bacteria you have in your gut, and third is how much lactose you consume. Some lactose intolerant people can only drink a glass of milk, while others can have two. But it is important to realize that we are all lactose intolerant to some point because eventually the amount of lactose we ingest will out number the bacteria's capacity for digesting lactose. This is the reason for that ridiculous challenge of drinking a gallon of whole milk in thirty minutes without vomiting.
Lastly, I wanted to note that I did read some articles saying that lactose intolerance has evolved into a genetically transmitted disorder. Theories as to why this has occurred state that since the human race has left its hunter gatherer era traditional needs for digesting milk have declined. Since the inability to digest milk is no longer a health concern genetic mutations in the lactase gene have been able to be passed on generation to generation, which is the reason certain ethnic groups are experiencing high percentages of intolerance or predisposition to lactose intolerance.
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For the most part, I already knew that lactose intolerance is something that develops later in life and is something people are not born with. It makes complete sense from an evolutionary standpoint that lactase would be needed less and less as an infant grows and becomes less dependant on milk. What I did not know is that there are bacteria lining the stomach that are responsible for the decomposition of lactose in adults. I always assumed that people who are not lactose intolerant retain the lactase enzyme for life. It was very interesting to read that everybody looses this enzyme and what really controls whether an individual is lactose intolerance is the amount of bacteria lining the stomach. It just goes to show that bacteria really are everywhere. Life most certainly would not be the same without them.
I am glad you made a post about this because I have never been able to drink a glass of milk by itself. My memories from my time in India also indicate this as I used to try to avoid drinking milk by adding things to it and making excuses. I can only drink milk through cereal when it is flavored or with Nestle mixes. The same occurs for cheese as I have never been a fan of string cheese. I wonder if this qualifies for lactose intolerance as I know of many people with the same conditions but they all can eat deserts, which have milk but are flavored.
My aunt was never lactose intolerant until she got pregnant with my cousin. She couldn't eat cheese, or eat bread as that contained milk. If she had any sort of milk based foods, she would develop a fever and break out in hives all over her body. My cousin was born lactose intolerant too. He reaction to lactose was not as bad as my aunts. He has had therapy and is now fine and gets to eat chocolate like all the other kids.
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