Transcription
Hey, this is America's perfection analyst. Let's talk about vitamin B12 absorption.
In a previous video, I've talked about B12 deficiency anemia, but this is just a focused video on B12 absorption. So please pay attention. First, you eat vitamin B12 in the form of cobalamin from your diet, preferably from animal protein. That doesn't mean that there are no other sources of B12, but animal protein is the best—such as eggs, meat, dairy products.
But when you eat this vitamin B12, it's not free; it's bound to the animal protein. We have to break this bond between them. How? Well, amylase from your salivary gland, as well as your gastric secretions, does that. So, as you know, hydrochloric acid in your stomach will convert pepsinogen into pepsin. Pepsin will sever this bond between the cobalamin and the animal protein. Okay. Now this cobalamin will be bound to another protein from your salivary gland—why? To protect it from your gastric acid. Fine. So we have now the cobalamin and the R protein. Also note that gastric secretion is a source of R protein, as well as your biliary system; all of them offer R protein. Okay. Also, your nice, amazing stomach will produce intrinsic factor, which will help in the absorption of vitamin B12 at the terminal ileum.
But now let's go back to the stomach. We have B12 plus R protein. Let's go through the duodenum. The pancreas will secrete protease—no, sorry, protease. The pancreas will secrete protease enzymes to sever this bond between the B12 and the R protein, and it will make this R protein bind the intrinsic factor that was made in the stomach. So intrinsic factor is made in the stomach, but it's bound to the B12 in the intestine. Fine. Then let's go together: B12 and the intrinsic factor—what a love story—until the terminal ileum will divorce them. It will absorb this B12 with the intrinsic factor, separate the intrinsic factor from the cobalamin to give it to the amazing bride, the transcobalamin. The transcobalamin is a transporter that will transport the cobalamin through the bloodstream.
After cobalamin is absorbed, it has two destinations: either to go to your body cells and get utilized, or to go to the liver to be stored for years. On the other hand, folic acid is only stored for months; vitamin B12 for years. It's more easy to get folate deficiency than it is to get B12 deficiency, because the liver's storage lasts years. So if you have a problem with any of this, you will get B12 deficiency. All of these problems will be discussed in my video, "B12 Deficiency." You can check this out.
Also, let's mention something called bacteria. You have nice bugs living in your small intestine. In cases of bacterial overgrowth, they will interfere with the absorption of vitamin B12. Why? Because they literally eat the B12 to use it in their own metabolism; they are competing with you, these nasty bacteria. So bacterial overgrowth can be a cause of vitamin B12 deficiency.
This is vitamin B12 absorption in brief. So: your salivary glands—created both amylase and the R protein; stomach—you have the pepsinogen severing the bond, R protein and intrinsic factor facilitating absorption; bile—R protein; pancreas—protease; what else? The ileum will destroy this relationship and form a new relationship with the transcobalamin. Transcobalamin will transport it to your cells, as well as deliver it to be stored. The B12 that's not bound to transcobalamin will end up in the urine. Goodbye, B12. Okay, that was B12 absorption. I'll see you in the next video.