Taking a Vitamin B12 Supplement? You Need to Know This.
Last year, in an effort to ward off a vitamin B12 deficiency, I turned to vitamin B12 supplements. Because animal products (both meat, especially shellfish and organ meat, and dairy) are the only foods containing naturally occurring vitamin B12, vegetarians and vegans often struggle to get enough vitamin B12 and are therefore at risk for vitamin B12 deficiencies. Plants don't contain vitamin D— they can't produce it. Period.
While I’m neither vegetarian nor vegan, I am heavily plant-based. For me, that means that I very rarely eat meat and my consumption of dairy is limited to maybe once per day. I also don’t eat fortified cereals (or other factory-fortified foods), which have been manufactured to contain added nutrients such as B vitamins.
So, in order to avoid becoming deficient in vitamin B12, I started taking a B-complex/B12 supplement. I’d also heard that vitamin B12 was excellent for increasing your energy levels. Who doesn’t want more energy? I’ve got a job, a toddler (also a job), and sleep problems. I’m searching high and low for some extra vroom.
Role of Vitamin B12 in Our Bodies
According to the MayoClinic, vitamin B12 “plays essential roles in red blood cell formation, cell metabolism, nerve function and the production of DNA.” In a nutshell, vitamin B12 is critical for optimal health and, well, life.
Symptoms of Low Vitamin B12 Levels
As mentioned, vegetarians and especially vegans are at a greater risk of having a vitamin B12 deficiency compared to the general population. Harvard Health also notes that people who have had weight-loss surgery are more likely to experience low levels of vitamin B12 as their bodies often become less capable of extracting B12 from food. Celiac and Crohn’s disease suffers may have lower levels of vitamin B12, since these conditions can interfere with a person’s ability to absorb nutrients. There are other risk categories, too; older adults, for example, often have difficulty absorbing B12.
The symptoms of a vitamin b12 deficiency are wide-ranging and can include:
- Fatigue
- Weakness
- Neurological changes, including numbness, tingling, or other sensations in your hands and feet
- Brain fog and difficultly thinking
- Megaloblastic anemia
But this is just the tip of the iceberg. A vitamin B12 deficiency is associated with a whole host of symptoms.
How Much Vitamin B12 Should I Take?
For the average adult, the recommended daily intake (RDI) for vitamin B12 is 2.4 micrograms (mcg). That gets bumped up to 2.6 micrograms if you’re pregnant and 2.8 micrograms if you’re breastfeeding.
Vitamin B12 is water-soluble (as are B vitamins in general), meaning it’s easily absorbed and metabolized. As a result, if consumed in excess quantities, the body can usually excrete it (via your pee), no problemo.
(Fat-soluble vitamins — such as vitamin A, D, E, and K — on the other hand, don’t exit the body as quickly and are instead stored in the liver and fatty tissue. There’s therefore more of a chance for these vitamins to build up, sometimes to toxic levels.)
Still, you don’t want to go overboard on Vitamin B12 or any other water-soluble vitamin. Instead, unless your doctor recommends otherwise, stick to the recommended daily dose and take about 2.4 micrograms of vitamin B12 daily.
What You Need to Know: Check What's in Your Supplement
Vitamin deficiencies are no joke, and we’ve established that Vitamin B12 is involved in regulating certain critical bodily functions. When you eat a largely plant-based diet like I do, you have to be mindful that you're getting enough vitamin B12. So I picked up a B12 supplement to take along with my daily multivitamin. Can't hurt, right?
At first, I felt great. Or at least I thought I did. To be honest, I’m not sure if I actually felt any better or more energized. I’m wondering now if my reaction was a result of the placebo effect. I was taking this thing that was supposedly good for me, so it could only make me feel good, right?
Also, my pee was bright, bright yellow. That there was evidence that something was going on. Bright yellow pee must be a sign that, inside, I was also bright, vivid, bursting with health.
A few weeks later, I noticed that my sleep was really deteriorating. I wasn’t struggling to fall asleep, although it could take me 30 or so minutes to get there. My biggest issue was that I was waking up in the middle of the night and staying awake. For hours.
At first I attributed my insomnia to the heightened anxiety I’d been experiencing. Thanks to an explosive mix of work-, finances-, and parenting-related pressures, I could not turn my brain off at night. I’d lie in bed ruminating on things both big and small, catastrophizing my way to sleeplessness.
One morning as I was standing over the sink and taking my vitamins, I casually turned the B-complex vitamin bottle around to look more closely at the label.
What I saw shocked me.
Each capsule contained 250 micrograms of vitamin B12 as adenosylcobalamin... and 250 micrograms of vitamin B12 as methylcobalamin.
A note on B12. B12’s chemical name is “cobalamin.” There are several different forms of B12, but the active coenzyme forms of B12 are adenosylcobalamin (active in our cells) and methylcobalamin (active in our mitochondria) and are found in meat and dairy products.
OK, let me remind you that the recommended RDI for the average adult is 2.5 micrograms. I was taking a total of 500 micrograms (more if you count what I was getting from food) — that’s 20,000% of the recommended daily intake.
I was horrified.
I was also furious with myself. How could I have been such a blind, unthinking consumer? I was usually so careful about what I put in my body, especially when it came to supplements. When I got pregnant with my son a few years earlier, I'd spent hours comparing different prenatal multivitamins and DHA supplements.
With my foray into vitmain B12, I'd dropped the ball. The product was by a well-known and reputable brand, and I’d plucked it right off the shelf at my local Whole Foods. I just assumed this was a no-brainer and went on my way.
Vitamin B12 Supplements Contain A LOT of B12
What shocked me even more was that the amount of B12 my supplement contained was on the low end of the spectrum compared to other supplements.
I took a look at a few different manufacturers and discovered that some were even selling products that contained over 200,000% of the RDI.
- Kirkland: 5000 mcg (208,330% RDI)
- Nature’s Bounty: 500 mcg (20,833% RDI) and 1000 mcg (41,667% RDI)
- Nature’s Made: 1000 mcg (41,667% RDI)
- Natrol: 5000 mcg (208,330% RDI)
- Vitafusion: 3000 mcg (125,000% RDI)
I’m not going to disclose the brand I took, largely because it’s not the brand’s fault that I was taking such an inane dose but rather my own. This was a case of user error. That said, I am pretty shocked that something this potent can be purchased over the counter.
Vitamin B12 Overdose? Is That a Thing?
Back to that moment at the kitchen sink when I realized just how much B12 I'd been taking. I frantically Googled “vitamin B12 overdose” as you do, fully prepared for imminent death. Thankfully, because of Vitamin B12’s aforementioned water-solubility, I learned that I probably was not going to suffer from any toxic build-up.
Still, there are side effects associated with consuming too much vitamin B12. And I’d been taking 500 micrograms (oh God, facepalm) every day or every other day for a few months.
High doses of vitamin B12 can lead to dizziness, headache, anxiety, and nausea/vomiting, etc. These symptoms can be although are not necessarily an indication of an “overdose,” especially if you’re using it for therapeutic reasons under a doctor’s supervision.
I put “overdose” in scare quotes because overdosing on vitamin B12 is technically not possible. No “upper tolerable limit” for B12 has been established, in part because the body doesn’t absorb the full dosage. The National Institutes of Health maintains that “only about 10 mcg of a 500 mcg oral supplement is actually absorbed in healthy people.” Furthermore, according to the National Institute of Medicine, “no adverse effects have been associated with excess vitamin B12 intake from food and supplements in healthy individuals.”
Well, that's a relief.
The Relationship Between Vitamin B12 and Sleep
As I mentioned earlier, my sleep had been really suffering during the period I'd been supplementing with vitamin B12. I only put two-and-two together when I discovered I'd been taking 20,000% of the RDI.
First: The relationship between B12 and sleep is inconclusive. There are two small studies from thirty years ago that show that vitamin B12 can improve sleep-wake rhythm disorders due to its impact on the hormone responsible for regulating sleep: melatonin. Interestingly, the subjects in the studies didn’t have B12 deficiencies. (People with sleep-wake rhythm disorders often have irregular sleeping patterns, including a lot of naps throughout a 24-hr period, abnormal sleep times, abnormal total sleep time for their age, difficulty sleeping and/or staying awake.)
In general though, there just aren’t that many clinical studies out there on the relationship between sleep and vitamin B12 specifically, and certainly none that are broad in scale. That said, I did encounter references to studies suggesting that too much B12 has been linked to sleep disturbances by promoting wakefulness.
Then there’s the anecdotal evidence connecting B12 (and B vitamins in general) to sleep problems; a quick Google search turns up tons of self-reported stories. And while these claims aren’t backed up by robust clinical evidence, they’re pretty compelling. Some sceptics might argue that this is just the placebo effect at work. Not so, says New York Times health writer Tara Parker-Pope in an article on multivitamins and sleep interference — it’s quite likely much more than a placebo effect.
Note: If you're suffering from stress- or anxiety-related insomnia, check out my post on this topic to learn more.
High Doses: My Takeaways
If vitamin B12 can affect a person’s melatonin levels, and if you don’t suffer from a sleep-wake rhythm disorder (which B12 can in theory “treat”), then B12 could very well be behind your sleep problems. Said another way, B12 seems to help people who suffer from a certain narrow subset of sleep disorders while potentially creating sleep issues for others. In my case, the impact of B12 on my melatonin levels was potentially dysregulating.
Also, if high doses of vitamin B12 are associated with anxiety, and if anxiety can negatively impact sleep (in my case, I know it does), then B12 can in theory fuel insomnia.
I stopped taking B12 the very same day I read the label of my B-complex. And, wouldn’t you know it, my sleep improved that very night. I still struggle with sleep, but I’m confident that that particular rough patch I experience was vitamin B12-induced.
What About Vitamin B12 and Increased Energy and Endurance?
I'm afraid this is a marketing ploy, the placebo effect, or both. Manufacturers, brands, and entrepreneurs claim that vitamin B12 can boost your energy levels and endurance because of B12's role in energy metabolism.
However, according to science, unless a person is deficient in vitamin B12, supplementation is likely not going to have a beneficial effect on one's energy and endurance.
The Moral of the Story
- Check your supplement labels carefully. Be a conscious consumer. Do not make assumptions about what a product is or what is can do for you, no matter how benign you think it might be.
- If you don’t have a known vitamin B12 deficiency and/or your doctor hasn’t recommended that you take B12, then you probably don’t need to be taking supplemental B12 beyond what’s already in your multivitamin (and you certainly don’t need to be taking mega-high doses).
- If you’re struggling to sleep and you’re taking high doses of vitamin B12, consider if there’s a link
- Prioritize food sources of vitamin B12 over supplements (if possible!).
- If you’re vegan, vegetarian, or in a group at risk of a vitamin deficiency, consult your doctor; your doctor’s advice overrides anything you read on the interwebs!
