Why Is Vitamin B12 So Important?

by | January 10, 2018

B12 seems to be the main vitamin that causes vegans a lot of worry.

Non-vegans too, now I think of it, as over the last year or two B12 seems to have become the vitamin of the moment. But it is rather important, because it is used by the body in the production of red blood cells, and it plays a vital role in maintaining the myelin sheath around nerves. Let me tell you a little more about what this all means.

Firstly, B12 is used by our bodies in the production of red blood cells. These are the cells responsible for transporting oxygen, and when we are short on them, this is called anaemia. Anaemia shows itself on blood tests as a low haemaglobin (Hb) level. Haemaglobin is the protein found in red blood cells which picks up oxygen in the lungs and carries it around the body. Now, Hb can be reduced for several reasons, including a low iron store and other medical conditions. When your B12 levels are very low, your bone marrow struggles to make as many red blood cells as required. As a result, your cells get bigger to compensate (macrocytosis) as the number of cells reduces, and the Hb levels goes down too.

B12’s role in the nervous system, is that it is used in the process of myelination of nerves. Put in simple terms, it helps the body to wrap the nerves in a protective cover. Imagine your nerves as thin wires, down which electrical impulses pass (this isn’t far off the real scenario, actually). If your wire isn’t insulated, you will discharge some of that electrical impulse along the way, so the full impulse won’t reach the other end. This is exactly what happens with nerves, with a protein cover acting as the insulating plastic you see on wires. B12 is used in laying down this insulating layer, and in maintaining it. If nerves aren’t adequately myelinated, then signals are not transmitted properly, leading to symptoms of tingling, numbness, and occasionally pains in the limbs. Rarely, there are more serious effects from chronic B12 deficiency, which can involve the spinal cord, and there are some studies linking low B12 levels to dementia.

As you can now see, B12 really is a vital nutrient, but unfortunately it is only found in animal derived foods, other than small doses in fortified foods. This means that all vegans should be taking a daily supplement. It’s role in nervous system health also impacts on pregnancy, because along with folate, it also helps to form a healthy spine in the fetus, and deficiency can lead to defects like Spina Bifida or Anencephaly. The recommended daily intake of B12 is 1-2μg/day, with pregnant and breastfeeding women requiring a little more. Supplements which can be bought contain much higher levels than the recommended dose. This is because we don’t absorb all B12 that passes through our gut.

If you are concerned that you may already be deficient in B12, you should see a doctor to have your blood level checked.

Symptoms of B12 deficiency include:
  • Anaemia
    • Tiredness, shortness of breath, headaches
  • Tingling, numbness or weakness in the legs
  • Cracked, red skin at the corners of the mouth or a sore swollen tongue
  • Difficulties conceiving (there are many causes of this but B12 deficiency can result in infertility)
  • Visual disturbances
  • Memory problems and depression

If you are found to be B12 deficient, you will probably need a bigger dose than the shop bought supplements contain. You may even need an injection. Due to the potential serious side effects of B12 deficiency, and accepting that we are, as vegans, at higher risk of it, I would recommend that you see your doctor if you are worried about B12 deficiency.

Thanks for reading,

The Vegan Doctor

The Vegan Doctor is a UK GP, a practicing vegan and health writer. She is a medical advocate for the vegan lifestyle, breaking down barriers between vegans and the medical profession. You can find her on her website, Facebook or Instagram @the_vegan_doc


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