What having a vitamin B12 deficiency taught me about behavioural science

Photo by Diana Polekhina on Unsplash

I’ve never really been a supplement person. I know many people are, religiously taking their multivitamin every day, maybe their vitamin C or iron – my mum has an array of supplements she takes every morning without fail.

I guess I’m a big believer that having a healthy diet should be enough to get everything that your body needs. That, and the fact that no one needs 200% of their recommended RDA on top of their diet every day. And the fact that there’s been numerous articles detailing why most supplements are pointless (eg here, here, here, here, here).

So when my annual blood test (yes, I come from a family that passionately believes in annual check-ups) revealed a vitamin D deficiency, I reluctantly purchased a bottle of vitamin D pills (alongside some probiotics, because why not?). After all, you can’t really get vitamin D from food, and due to my melanoma history I have to be very careful in the sun.

I am the nightmare patient all health behaviour experts dread

That same bottle of pills is still in my cupboard. It’s been there for at least a year (possibly even more). For a while it lived on the kitchen counter, as I tried to make it more salient and remind myself to take it. I tried to create a habit and always take it at lunch, so that as soon as I have lunch I would be primed to take it.

None of it worked. Why?

Although changing the environment to make habit formation easier is a key part of behaviour change (especially behavioural design and behavioural economics), there was clearly something missing here – belief.

  • I have already said that I am not a big believer in supplements. When people tell me about the supplements they take I ask them why, and when people ask me whether to take supplements I usually suggest that they check their diet first.
  • I wasn’t really feeling unwell in any way, and my levels were low but likely comparable to the rest of the country given the lack of sunlight.
  • How was this supplement really going to be improve my life anyway?

Unless you create really clever ways to change the environment that bypass these issues, belief is a big barrier. Belief changes everything. And belief means that the bottle of vitamin D is still in my cupboard, half-full. After all, it’s so much easier to keep doing what you were doing before than changing your behaviour.

Fast forward a year later

My annual blood test, again. Vitamin D levels, low again. But this time, something was different. My vitamin B12 levels were dangerously low. They were in the red zone. They were so low, the doctor left a note saying they recommended urgently going to see my GP to discuss B12 injections. That I could be suffering from an autoimmune disease called pernicious anaemia, which means not being able to absorb B12.

Obviously, here the tone was slightly different. And so was the outcome.

Here comes my behavioural science lesson

I bought my B12 supplements and have been taking them every day without fail for the past 2 months.

I created a habit

As with the vitamin D bottle, I tried to prime myself and create a habit. I placed the bottle of pills on the kitchen counter and aimed to form a habit of taking them every day after lunch.

I had a clear goal

I decided there was a need for an experiment. I could have gone to the doctor straight away, but instead, ever the scientist, I wanted to see if indeed I was suffering from pernicious anaemia or whether I wasn’t actually eating enough B12-rich food (which a daily supplement would solve with no problem).

So I decided to take a supplement every day for 2 months and then have another blood test to see if my levels were better. My goal was to understand what was actually going on so I could take appropriate action. That meant taking the supplement every day, otherwise the experiment would be void.

I was shit-scared of what might happen if I don’t take them

Crucially, in this case there was belief. A lot of it. The situation was dire. The levels were red. The doctor urged immediate action.

I was scared into taking action.

I believed that if I didn’t take action, there would be consequences – bad things would happen. I believed that taking action was important for my health.

So do you have to scare yourself to change behaviour?

Not necessarily. If there is a behaviour you want to change (eg maybe sticking to your yoga self-practice?), you can experiment with creating a habit (eg picking the same time to practice every day) and priming yourself to do it (eg leaving your mat out at night so you see it when you wake up in the morning) – I’ve written about this already here.

But it’s also important to ask yourself why you want to adopt this new behaviour; what will it offer you, how will it make your life better. If you can’t convince yourself that your life will be better or that it’s important to do this then you fall back to habit, and sometimes that just doesn’t work.

And in case you’re wondering

My experiment worked. My vitamin B12 levels are now back to normal. My behaviour change has been reinforced by the results of the blood test, so I continue to take my supplement every day.

What does this have to do with yoga?

Not much really. I got asked to write a post about supplements. I wrote this instead. Perhaps it will be more useful it generally adopting new (and healthy) behaviours. Maybe even a yoga-related behaviour.


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