B12 - still confused

butterfly

What I want to know is how much is the basic recommended amount__ per week.__ If I multiply the daily amount x7 will that tell me? Where on the internet do you find basic requirements? B12 seems to have many different amounts suggested by various people and sites.

At the moment I haven't had any meat for almost a year. I'm on and off dairy - not by desire but I get scared due to weight loss - that's another story. I realize dairy doesn't give me b12. I have recently been eating - just a few times a small amount of salmon. A doctor online told me eating that once a week would be plenty for b12.

But on Cronometer when I changed the daily amount to seven times that (just to see how much salmon would fulfill that) one cup was only filled 1/2 the required amount (for a week) on Cronometer. So then that doctor was wrong and I'd have to eat it twice a week.

I hope some of that made sense.

I've searched online to find out how much you need per week but the sites like nutrition.org jumps up to a massive amount for a week compared to the daily amount. But he is saying that it's hard to absorb so if you take a supplement once a week you need to take a WAY higher amount. Is there an RDA for B12? Is there a site that just shows all the basic RDA or any countries recommended amounts for vitamins and minerals? I'm probably deficient - a really nice person on here gave me great suggestions for how to take it in supplement form, which I'm going to try (I get sick from b12 supplements) but I haven't yet. I feel a little bit like the doctor I chatted with online wasn't really being specific with me. I had to pay for that but he kind of gave me a not satisfactory response. He was like, yeah yeah that should be fine. (

Susan_RD_101

Hello!

There is an RDA for B12 and for healthy adults, it's 2.4 mcg per day. This level of B12 was set to maintain blood values and normal functioning. B12 does not have a current upper limit, as no adverse reactions have been seen with higher levels of intake.

Some vitamin B12 is lost by the body through bile, stool, urine, etc. but a lot is recycled, which is why requirements aren't very high. However, if you a plant-based diet and aren't replenishing stores, you can run out of vitamin B12.

In general, the higher the dose of vitamin B12 you take, the less often you need to take it. If you wanted to supplement daily, taking a smaller dose like 50 mcg should be sufficient. If you wanted to supplement weekly, you would only need to take ~1000 mcg 1-2 x per week.

Regular bloodwork (every 6-12 months) is important to ensure that you are taking the correct dose of B12. Some people lack stomach acid or something called intrinsic factor, which is needed to absorb B12 well. In this case, monthly B12 injections, which bypass the gut, are used.

Hope this helps!

Pryme

Between my multi and my B complex I'm at 118mcg per day. I have been meat free for 2mo now and ate fish once in that time, I know fish is meat but anyway. I usually only hit 2 or 3% of my B12 without my vitamins. Same with D. Those are the 2 I've needed with vitamins. Everything else I hit without.

Susan_RD_101

@Pryme

Great work meeting those targets!

butterfly

Hi Susan,

Sorry, I have a lot of distracting stuff in my life lately and I read this before and basically understood it but reading it again a have a few more questions. Sorry. Don't mean to be a pita but I'd really like to understand this well so I can feel more confident about my choices.

The 2.4 mcg RDA is to maintain a basic level. Why then is it necessary to take 50 mcg a day? Is it because meat eaters are having extra intake and then it just stays in their systems more so they only need 2.4 mcg but vegans don't get any extra so require 50 mcg a day? Is the 50 mcg to compensate for the loss through urine, etc? Or because it's assumed the body will only absorb a small proportion of the 50 mcg? (Assuming you don't have the intrinsic factor issue). Or is it thought that 2.4 is the bare minimum and we really do better with more?

If you take a lot more than 2.4 mcg does your blood/body still maintain certain parameters of B12, like Vit C or do your blood levels just keep going up? I understand you're saying that there are no know adverse affects from having more, which I get, but I was just wondering if that's because the body just takes what it needs and gets rid of the rest or if it's fine to have higher levels actually staying in your body.

Also, why is the weekly value best at 1000 or more mcg instead of 50 x 7 (350 mcg)? Is it because at any one time when you take it that you will only absorb a small percent? This is what also confused me on Nutrition.org. The weekly amount was much higher than the daily amount x7.

So it sounds like once B12 is in your system a lot stays in your system for awhile as you say by recycling, but it's still necessary to take more regularly because we also lose some regularly and if vegan not consuming any.

Pryme,
That's sounds great. Thanks for sharing that.

Susan_RD_101

@butterfly

No worries! I’m here to answer your questions. 😊

To be honest, there isn’t a solid reason why we recommend that vegans take such large doses of B12 when the RDA is only 2.4 mcg. The best answer I can tell you is that we want to create a safety margin since the damage caused by a B12 deficiency can be permanent. Also, there are many factors that can impact absorption (such as decreased stomach acid, the use of metformin, aging, etc.), so a higher dose is a safer dose.

B12 levels will increase with a chronic high intake, but only a small amount of this is being absorbed with the remainder being lost in the urine. Given this low risk for toxicity, an upper limit was never established.

You do not need to take a large dose of B12 as often (e.g. 1000+ mcg 1-2 x per week) since you are absorbing a larger percentage of the nutrient. With lower doses, you absorb less and need to take them more often.

When most people go vegan, they are starting out with pretty high levels. Over time, these levels can deplete, especially if no B12 is being consumed from diet. I’ve found that vegans can have good levels for 1-2 years (although there is huge variation here). However, given the risk of deficiency and the permanent damage that can occur, I don’t want to wait for stores to deplete before supplementing.

Hope this clears things up!

Kind regards,

hobo

@butterfly

The 2.4 mcg RDA is to maintain a basic level.
Why then is it necessary to take 50 mcg a day?
Also, why is the weekly value best at 1000 or more mcg instead of 50 x 7 (350 mcg)?

See these videos for an explanation:

https://nutritionfacts.org/video/vitamin-b12-recommendation-change/
https://nutritionfacts.org/video/cheapest-source-of-vitamin-b12/
https://nutritionfacts.org/video/daily-source-of-vitamin-b12/
https://en.wikipedia.org/wiki/Vitamin_B12#Absorption_and_distribution

They say that when we take in B12 we absorb 1.5 mcg and 1% of the remainder and that the 2.4mcg RDA has been updated to 4-7mcg RDA.

For daily supplements

Dr Greger recommended 250mcg /day.

If you take a 250 mcg supplement then the formula says 1.5 mcg is absorbed and 1% of the remaining 248.5mcg is absorbed by diffusion so 1.5 + 2.485 = 3.985mcg ~ 4mcg.

Similarly, if you take a 550 mcg supplement then again 1.5 + 5.485 = 6.985 ~ 7mcg is absorbed.

So a daily RDA of 4-7mcg would suggest daily supplements of 250-550mcg.

Some supplements are timed release (or slow release) so perhaps more will be absorbed because the 1.5mcg limit is every few hours?

For weekly supplements

Dr Greger recommended 2500mcg /week.

A weekly 2500mcg supplement should give 1.5 + 25 = 26.5mcg absorbed averaging at 3.87 mcg/day.

Note: I'm just explaining the math and not making recommendations.

See also:
https://nutritionfacts.org/topics/b12/
https://veganhealth.org/vitamin-b12/

hobo

How should large B12 supplements be logged in Cronometer?

If a large supplement is taken with other foods then the 1.5mcg may already have been taken up (and logged) leaving just 1% of the supplement absorbed.

For example, if a 2500mcg B12 supplement is taken then should 2500mcg or 25mcg be recorded in Cronometer?

I think it depends on whether you view the B12 data as absorbed or consumed.

For foods with B12 levels <1.5mcg per meal they are probably the same thing.
For large supplements, they aren't (according to the formula).

I would be inclined to record a 2500mcg supplement as 25mcg and view the data in the Trends Nutrition Report as an indication of B12 absorbed per day.

Would that make sense?

Wm_Wy1ONE

OUCH, my brain hurts I'll have to read this a few more times.

Susan_RD_101

@Wm_Wy1ONE

Nutrition can certainly be confusing! Let me know if there is anything in particular I can help you with.

Kind regards,