10. Mood
One interesting symptom of vitamin B12 deficiency is that it can lead to mood swings. There are many studies that show a link between B12 and mood and this makes sense seeing as the brain is a key part of the nervous system.
The link is explained by the theory that as levels of B12 go down, levels of something called homocysteine go up. This is what is known as the ‘homocysteine hypothesis of depression’. This substance can negatively impact the brain tissue, thereby interfering with signals that get sent to and from the brain. The result is mood changes.
Likewise, any form of lethargy can often be linked with depression. You might find that you feel depressed but likewise, you may feel easily angered and find your temper is shortened. Either way, these symptoms seem to respond well to B12 supplementation.