B12 Deficiency in Runners

running nutrition

What is the role of B12 in the body?

B12 is responsible for making red blood cells. It also plays an important role in nerve function, DNA, cognition and memory. More broadly speaking, B vitamins play a key role in metabolism, i.e. how efficiently your body converts energy (i.e. food) into fuel, which is key in endurance sports, of course.

What is the B12 daily recommended intake? Is it different for endurance athletes?

The recommended daily intake (RDI) of B12 in adults ranges from 2.4-2.8 micrograms. B12 can’t be made by the body, so we need to get it from food. This essential vitamin is found in animal products, but not in plants. That means that if you follow a plant-based diet, you need to supplement with B12. While some foods like cereals and mock meats are fortified with B12, a supplementing is the most accurate way to ensure you’re meeting your needs.

Some research has suggested that regular endurance training is associated with increased nutrient requirements, including vitamin B12 and folate. It’s unclear exactly how much more you should get and that depends on the intensity, duration, and frequency of your training.

Because vitamin B12 is a water-soluble vitamin, meaning that it doesn’t get stored in the body and any excess is excreted via urine, the risk of toxicity is very low, so it’s overall safe to supplement at higher levels.

What are the possible causes of B12 deficiency?

There are two possible causes of B12 deficiency: insufficient intake (via food or supplement) or inadequate absorption in the digestive system.

What are the symptoms of B12 deficiency?

  • anemia

  • fatigue

  • memory loss or difficulty thinking

  • dizziness and loss of balance

  • ‘pins and needles’ in your extremities or numbness

  • a painful/swollen tongue

I don’t have any of those symptoms. Could I still be deficient?

Yes. Because B12 is stored in the liver and can ‘keep you going’ for a while without symptoms, you may be getting insufficient B12 or not absorbing it properly and developing a deficiency without actually experiencing any symptoms yet.

The most accurate way to find out if you are B12 deficient is with a blood test. The blood test should measures two things: your B12 levels and your MMA levels. MMA (methymalonic acid) levels become elevated when B12 levels are deficient. Increased MMA levels can point to a B12 deficiency, even when B12 levels are still ‘normal’. Note that what is considered ‘normal’ ranges, so you may be on the low end of normal levels and heading toward a deficiency, which increased MMA levels can point to.


Should I supplement with B12?

If you follow a plant-based diet, yes. You should take a B12 supplement daily to ensure you meet your requirements. If you consume animal products, your levels may be sufficient, but since absorption plays as much of a role in nutrient levels as dietary intake, it’s a good idea to get a blood test and double check.

As mentioned above, if you’re a runner or endurance athlete, you may benefit from a higher dose of B12. Supplementing with a B-complex (a formulation that provides a balance dosage of all B-vitamins) may also support performance by increasing energy and endurance. Speak to your healthcare provider or nutritionist to find out what the best option is for your needs.

Should I get B12 shots?

I would only consider a B12 shot if you have an absorption issue, i.e. your intake is sufficient, but your digestive system is not absorbing the B12 as it should. However, not all B12 shots are created equal, so speak to your healthcare provider or nutritionist beforehand. Getting your B12 in a shot isn’t getting at the root of the problem though. We need to identify the cause of the absorption issue and address digestion as a whole to get your body absorbing B12 (and other nutrients) appropriately.

I hope you found this blog post helpful. If you have any questions, don’t hesitate to reach out to me via email at sabrina@handfulofgrapes.com or DM me on Instagram, @handfulofgrapes. :)


Sabrina AlberghiComment