Neurotransmitters control how nerve cells throughout your body communicate with each other, and all of them require vitamin B-12. B-12 fights sluggishness, fatigue, and brain fog. It’s crucial for producing red blood cells. Converting nutrients into glucose requires healthy levels of B-12, and you need plenty of B-12 to produce mood-managing neurotransmitters in the brain. B-12 also helps produce and maintain the insulation of nerve cells in your brain and spine.