Micronutrient Series: Vitamin B12
Written by Emily Pomfrey Wells & fact checked by Holley Samuel MEd, RD, LD, CPT
Introduction
Runners often want to know how the foods they eat impact their overall health and performance. All foods contain both macro and micronutrients. Macronutrients include carbohydrates, fat, protein and alcohol and make up the calories, or energy portion, of our food. Micronutrients often refer to vitamins and minerals, which are important for health, optimizing running and training abilities, and various functions throughout the body.
What is Vitamin B12 and where does it come from?
The micronutrient vitamin B12, also known as cyanocobalamin or methylcobalamin, is an essential water soluble vitamin, meaning that the body can’t make this vitamin on its own. In order to get the recommended amounts, we must consume foods or supplements that contain Vitamin B12. Vitamin B12 is found in animal products like meat, fish, poultry and eggs, and in fortified nutritional yeast and cereals, and supplements.1 Nutritional yeast is a great popcorn addition; it adds a nutty cheesy flavor and can be especially beneficial for vegan and vegetarian runners who may be at an increased risk for B12 deficiency because they don’t consume as many animal products as omnivore athletes. Even runners who incorporate animal products can be at risk for a B12 deficiency because running puts additional stress on the body and increases energy and micronutrient needs. Runners may have increased needs for B12 because of its role in red blood cell (cells that deliver oxygen to our body) formation. All those foot strikes pounding the pavement during running can accelerate the breakdown of red blood cells, and adequate intake of B12 can help replenish these important cells at an acceptable rate.
What does a vitamin B12 deficiency look like?
Runners experiencing vitamin B12 deficiency may experience extra fatigue throughout the day and poor performance outcomes. Other symptoms of vitamin B12 deficiency may include cramping, tingling or numbness in the extremities, and the inability to get through normal training cycles. Vitamin B12 deficiencies can be tested by looking at B12 serum or plasma levels and/or serum methylmalonic acid (MMA), which is a B12 metabolite. If you have a B12 deficiency, it needs to be corrected and can often be fixed by increasing animal product consumption or through supplementation.
How much do I need?
The recommended daily amount for males and females who are not pregnant or breastfeeding over the age of fourteen is 2.4 micrograms per/day. Symptoms of B12 deficiency can take years to develop and certain individuals may need B12 injections or supplements containing up to 1000mcg per day to correct their vitamin B12 deficiency. Since dosing and method of supplementation varies quite a bit, it is best to test your blood prior to blindly taking supplements to get the best results.
The body does not store excess amounts of vitamin B12 because it is a water soluble vitamin, however over supplementation is still possible and can lead to negative outcomes. Working with a qualified health professional like a registered dietitian can help to ensure that runners are on the right track and meeting their needs.
References:
National Institute of Health. Vitamin B12 Fact Sheet. Updated March 9, 2022. Accessed March 16, 2022.
Nebl J, Schuchardt JP, Ströhle A, Wasserfurth P, et al. Micronutrient status of recreational runners with vegetarian or non-vegetarian dietary patterns. Nutrients. 2019 May 22;11(5):1146. doi: 10.3390/nu11051146. PMID: 31121930; PMCID: PMC6566694.