You need vitamin B12 in order to produce and maintain your red blood cells, nerves, and DNA. Getting too little B12 can lead to anemia, a deficiency of red blood cells, which is a condition that can cause you to feel tired and weak. When you don’t absorb enough B12 from your food to make red blood cells, your body’s oxygen capacity decreases, along with your endurance.
In addition, vitamin B12 deficiency can increase your chances of having skin numbness and tingling (in your hands and feet), poor mental health, as well as decreased cognitive function, and poor coordination. Some research suggests that athletes with poor or marginal nutritional status for vitamin B12 may have decreased ability to perform high intensity exercise. In women specifically, higher B12 levels correlate with enhanced athletic performance. This is likely due to B12’s role in the synthesis of new cells, such as red blood cells, and to its role in the repair of damaged cells as the body rebuilds tissues. Also, women who are on any form of birth control are at the risk of B12 depletion.