B12: Water-Soluble Vitamin Deficiency & Toxicity Symptoms

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  • 0:44 Intrinsic Factor
  • 1:32 Deficiency
  • 2:27 Vegan Diets
  • 3:06 Atrophic Gastritis
  • 4:30 Toxicity
  • 5:16 Lesson Summary
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Vitamin B12 (cobalamin) is a water-soluble vitamin found naturally in animal products, but also available in fortified plant foods. Learn how pernicious anemia and atrophic gastritis impact B12 absorption and the symptoms of deficiency and toxicity.

B12 and Pernicious Anemia

You probably already know that 'eating an apple a day will keep the doctor away,' but do you know what eating a plateful of liver a day will keep away? I bet you can come up with some interesting answers, but the correct answer is pernicious anemia, which is a type of anemia in which the body cannot absorb adequate vitamin B12 due to a lack of intrinsic factor.

Liver, by the way, is very high in vitamin B12, also known as cobalamin, so eating a lot of it helps overcome this absorption problem. In this lesson, we will learn about symptoms that arise when you can't get enough vitamin B12, and also take a look at what might happen if you take in too much of this vitamin.

Intrinsic Factor

Now, before we change gears here, I want to reassure you that if you do get diagnosed with pernicious anemia, your doctor will not make you eat platefuls of liver. While this was the original cure for this condition, today, pernicious anemia is controlled through megadoses of injectable vitamin B12.

The megadoses are needed to treat pernicious anemia because as we learned from the definition, a person with this condition is lacking intrinsic factor. This is a protein from the stomach that enhances B12 absorption. It helps out absorption by grabbing ahold of B12 and guiding it through the digestive tract wall. Some B12 can absorb on its own, but when it's attached to intrinsic factor it's like having a VIP pass, and its absorption goes through much easier.


One of the functions of vitamin B12 is that it helps in the formation of red blood cells. Because of this, having a vitamin B12 deficiency, which means you do not get enough B12, can result in anemia, which is a general term that describes a condition in which there are not enough healthy red blood cells to transport oxygen around your body.

Another of the functions of vitamin B12 is that it helps maintain healthy nerve cells. We know that your nervous system is your body's command center, consisting of your brain, spinal cord, and nerves. It coordinates your movements and enables you to comprehend the world around you. So, if you think about it, if your nervous system is out-of-whack due to a vitamin B12 deficiency, it is reasonable to think that you would experience symptoms such as weakness, numbness and tingling in your hands and feet, loss of balance, depression, and confusion.

Vegan Diets

So, how hard is it to get enough B12 into your body? Well, that might depend on your diet. First, of all, vitamin B12 is only found in animal products, such as organ meats, which includes liver; red meat; poultry; eggs; and dairy products, like milk. This can create a problem for a person who chooses to follow a strict vegan diet plan, which does not include any animal products. To make sure they're getting adequate B12, vegans must consume a supplement that contains the vitamin or eat grains that are fortified with B12. You're likely to find these in the breakfast cereal aisle.

Atrophic Gastritis

B12 is the only one of the eight B-complex vitamins that's only found in animals. This is because B12 exists best when bound to protein inside of the animal. When a person eats the animal-based food, the B12 stays bound to the protein. This explains why vegans would not naturally get B12 in their diet, and it is also why B12 deficiency can be a problem for older adults suffering from atrophic gastritis. This condition is characterized by an inflammation of the stomach lining that interferes with secretions of stomach acids and enzymes.

This term is easy to recall if you remember that 'atrophic' means to atrophy, or waste away, and 'gastritis' refers to stomach, so in this condition the stomach is atrophying and not able to produce its normal secretions. Sufficient amounts of these stomach secretions are needed to break the bond between B12 and the protein.

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