The lowdown on Vitamin B12

Jun 11, 2014

By Karen Sherwood, Nutritionist at Sports Club/LA - Boston

If you’re experiencing fatigue, muscle weakness, dizziness, heart palpitations, bleeding gums, shortness of breath or nausea, you may have a deficiency in this very important vitamin. What is B12? More importantly, why do we need it and how do we get it?


Vitamin B12 (cyanocobalamin) is a water-soluble B vitamin that’s essential for the human body as it plays a huge role in several metabolic processes. Like all vitamins in the B family, it helps support adrenals and regulates the nervous system. In particular, vitamin B12 aids in the production of DNA and RNA, and the development of red blood cells, nerve cells and myelination (layer covering the nerves). Other benefits include:

  • Enhances energy and mood
  • Promotes immune function
  • Supports metabolism of carbohydrates and fats
  • Helps prevent anemia
  • Promote cardiovascular function by boosting homocysteine levels


How much do we need?

According to the National Institutes of Health (NIH), the average daily allowance is:

  • 2.4 micrograms (mcg) for people age 14 and older
  • 2.6 mcg for adult and adolescent pregnant females
  • 2.8 mcg for adult and adolescent lactating females

The best food sources of B12 are red meat, organic dairy products, fish and shellfish, eggs and poultry. That’s why vegetarians and vegans, as well as folks over 50, should regularly take a whole-food-based vitamin B12 supplement, (approximately 25-100 mcg per day) as part of a B-complex that contains the full spectrum of B vitamins (thiamine, biotin, riboflavin, niacin and B6). I often recommend my clients take it under the tongue in an oral spray or tablet for better absorption.  

What can deplete B12?

  • Excessive alcohol
  • Smoking
  • Frequent use of antibiotics
  • Frequent use of stomach-acid controlling drugs (i.e., proton pump inhibitors)
  • Diabetes medications (i.e., metformin)

A diet high in sugar and/or processed food can contribute to overall vitamin deficiencies, so it’s important to eat a variety of whole foods like vegetables, fruits, lean proteins and healthy fats. And make sure to stay away from packages with ingredients you can’t pronounce!