視頻（維生素B12）的英文文本，

Vitamin B12, also known as cobalamin, is an essential water-soluble micronutrient that our body cannot synthesize on its own.

So, we must take it through the diet.

Vitamin B12 is essentially required to maintain the normal function of the brain and nerves.

It is also required for the production and maturation of red blood cells.

In addition, vitamin B12 plays a role in fatty acid synthesis and energy release within the cells.

Vitamin B12 is absorbed into the body with the help of a protein called intrinsic factor, which is secreted by the stomach.

This substance binds to the vitamin B12 molecule and facilitates its absorption.

Excess vitamin B12 is stored in the liver for future use.

Deficiency of vitamin B12 causes certain neurologic manifestations.

In addition, it can lead to a specific type of anemia called megaloblastic anemia.

In megaloblastic anemia, the red blood cells are immature, and they are bigger than the normal ones.

These red blood cells are very fragile, and they have a shorter lifespan than the normal ones.

Vitamin B12 deficiency can occur due to many reasons.

One of the major causes is dietary deficiency, meaning that you eat a less amount of foods containing vitamin B12.

Another cause is reduced intrinsic factor secretion by the stomach.

This can occur when the stomach epithelium is damaged, like in gastritis.

People with gastric bypass surgery will also have the same problem.

Sometimes, the absorption of vitamin B12 by the intestine is reduced, especially in conditions like Crohn’s disease.

Some common signs and symptoms of vitamin B12 deficiency include the following.

Extreme tiredness.

Shortness of breath.

Faintishness and pale skin, all of which are signs of anemia.

In addition, individuals may also have loss of appetite and loss of weight, a noticeable heartbeat, also known as palpitations.

A sore and red tongue, known as glossitis.

Mouth ulcers.

Pins and needles sensation, also known as paresthesia.

Vision problems.

Irritability.

Depression.

And behavioral and mental status changes.