Archive for the ‘Vitamin B12’ Category

B12 and Lung Cancer

Tuesday, September 5th, 2017

A recently-released study from the University of Washington found an increase in lung cancer among male smokers with a vitamin B12 intake of 55 µg per day or more (3). There was no increase in lung cancer among women, women smokers, or non-smoking men.

Because this study raises concern about vitamin B12 supplements for smokers, I’ve updated the article, Smokers and Cyanocobalamin. The article is short, so I’ve reproduced it here:

Because smokers receive cyanide from smoking, and vitamin B12 can actually be used to detoxify cyanide due to its strong affinity for the cyanide molecule, there’s a concern that perhaps cyanocobalamin will not be effective for smokers.

For example, hydroxocobalamin injections decreased blood cyanide levels by 59% in smokers (1.5-3 packs/day) and cyanide was eliminated in the urine as cyanocobalamin (1). In another study, smokers were found to excrete 35% more B12 than nonsmokers (2). But in another, serum B12 of smokers didn’t differ from nonsmokers, and the Institute of Medicine concluded that “The effect of smoking on the B12 requirement thus appears to be negligible (2).”

But most smokers have an intake of hydroxocobalamin, and other non-cyanocobalamin forms of B12, through animal foods, while vegan smokers do not have a non-cyanocobalamin source of B12 unless they seek out a supplement. There’s no research on B12 and vegan smokers, but I’m not aware of any who have had trouble warding off B12 deficiency.

Additionally, one prospective study found an increase in lung cancer with B12 supplements among male smokers for the highest intake group of 55–275 µg/day (3). Other research has not found an association with vitamin B12 in cancer, but it hasn’t been studied thoroughly among male smokers. However, an arguably better piece of evidence comes from a randomized, clinical trial that did not find an increase in cancer with increasing serum B12 levels (from 400 µg/day) in a population with a high rate of smoking (4).

At this time, there doesn’t seem to be enough evidence to warrant separate vitamin B12 recommendations for smokers.


1. Forsyth JC, Mueller PD, Becker CE, Osterloh J, Benowitz NL, Rumack BH, Hall AH. Hydroxocobalamin as a cyanide antidote: safety, efficacy and pharmacokinetics in heavily smoking normal volunteers. J Toxicol Clin Toxicol. 1993;31(2):277-94.

2. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 2000.

3. Brasky TM, White E, Chen CL. Long-Term, Supplemental, One-Carbon Metabolism-Related Vitamin B Use in Relation to Lung Cancer Risk in the Vitamins and Lifestyle (VITAL) Cohort. J Clin Oncol. 2017 Aug 22:JCO2017727735.

4. Ebbing M, Bønaa KH, Nygård O, Arnesen E, Ueland PM, Nordrehaug JE, Rasmussen K, Njølstad I, Refsum H, Nilsen DW, Tverdal A, Meyer K, Vollset SE. Cancer incidence and mortality after treatment with folic acid and vitamin B12. JAMA. 2009 Nov 18;302(19):2119-26.

Methylcobalamin & Adenosylcobalamin: Consolidated

Wednesday, November 11th, 2015

It’s raining B12!

I have consolidated all the information from my blog and regarding the benefits and drawbacks of supplementing with the co-enzyme forms, methylcobalamin and adenosylcobalamin, over cyanocobalamin.

Click here: Methylcobalamin & Adenosylcobalamin


If you like my posts, please like my posts! Or share them!

I am very grateful for donations of any amount (click here).

Purchase anything through these links and JackNorrisRD gets a percentage:

Pangea – The Vegan Store
Vegan for Life by Jack Norris & Ginny Messina

Thank you!

Two B12 Deficiency Cases

Wednesday, November 11th, 2015

I have updated the page, Individual Cases of Deficiency, with two recent cases below. In the past, readers have asked me to post these when they come out, so I will continue to do so.

Biyani S, Jha SK, Pandey S, Shukla R. Acute bilateral useless hand syndrome: a rare presenting manifestation of vitamin B12 deficiency. BMJ Case Rep. 2015 Oct 16;2015. | link

A 38-year-old man, “strict vegetarian,” developed “useless hand syndrome.” Laboratory tests showed vitamin B12 deficiency. He was given B12 injection and after 8 weeks was free of symptoms.

Førland ES, Lindberg MJ. [Severe macrocytic anaemia and secondary hyperparathyroidism in a vegan]. Ugeskr Laeger. 2015 Aug 10;177(33). | link

“In this case report we present a 39-year-old male vegan with severe macrocytic anaemia due to vitamin B12 deficiency as well as secondary hyperparathyroidism due to severe vitamin D deficiency.”

Vegan Health & Fitness Magazine: Vegans Need B12

Sunday, November 8th, 2015

Over the past couple of years a number of readers and colleagues have contacted me about the apparent stance of Vegan Health & Fitness Magazine (VHFM) that vegans do not need to supplement with vitamin B12. People have contacted the magazine about this issue but they have not modified their position.

Currently, VHFM has an article, The Science is in: B12, by Brian Acree, which has been available for some time (no publication date is listed).

Despite the name of the article, Acree suggests that the science is actually not in. He argues that we have no definitive answers, but that if vegans eat a variety of plant foods, including foods like seaweed, we’ll be fine.

Acree bases his argument mostly on research from the Watanabe group, research that I detail in B12 in Plant Foods.

Acree says, “Of particular interest is the fact that Watanabe cited two studies that showed that vegans who consumed nori and/or chlorella (the green substance in all green vegetables) had serum vitamin B-12 concentrations ‘twice as high as those not consuming these algae.'”

Acree appears to be mistaking the algae, chlorella, for the molecule chlorophyll and, because of this mistake, seems to be suggesting that all green vegetables contain B12. But in reality, chlorophyll has nothing to do with vitamin B12.

Readers of this blog probably remember that just a couple weeks ago, and after this article by Acree was published, the first study came out indicating that chlorella has B12 activity (see Chlorella Shown to Have B12 Activity in Humans—Caution Warranted).

As for nori, in the one study looking at nori’s B12 activity in humans, it didn’t have any (more info).

In 2014, VHFM ran an article by Deobrah Nasmyth that pointed out that the editor of VHFM, Brenda Carey, doesn’t take B12 supplements or eat fortified foods and hasn’t developed B12 deficiency. Acree also uses his own personal lack of B12 deficiency symptoms as evidence that vegans don’t need to supplement with B12.

The problem with this reasoning is that unless you’re getting your methylmalonic acid and homocysteine levels checked, there’s no way for someone to know they don’t have B12 deficiency.

The study on chlorella mentioned above shows that many vegans come down with vitamin B12 deficiency due to a lack of vitamin B12 in the diet. Long periods of mild B12 deficiency are linked with dementia, and poor bone health in vegans.

And even if some vegans don’t develop vitamin B12 deficiency or obvious symptoms, too many vegans do develop them and sometimes with horrible consequences (see the Background section of Vitamin B12: Are You Getting It).

It’s not worth risking people’s health in order to make a philosophical statement and I hope to see Vegan Health & Fitness take a more responsible position regarding vitamin B12.

Chlorella Shown to Have B12 Activity in Humans—Caution Warranted

Wednesday, October 28th, 2015

I have updated the article B12 in Plant Foods with a new study on B12 activity in Chlorella:

In a 2015 (USA) study, Merchant et al. fed 17 B12-deficient vegans and vegetarians a Chlorella pyrenoidosa supplement for 60 days (1). Average serum MMA levels decreased from 441 nmol/L at baseline to 301 nmol/L at 30 days and 297 nmol/L at 60 days. Average serum homocysteine levels decreased from 10.0 µm/L at baseline to 9.5 µmol/L at 30 days and 9.0 µmol/L at 60 days. No adverse effects were noted from the chlorella regimen.

Some caveats:

• Average serum MMA levels appeared to stabilize on this regimen at above recommended levels. B12 deficiency is generally defined as serum MMA levels above 270 nmol/L, the same standard used in this study by Merchant et al.

• The study was funded by Sun Chlorella Corporation of Japan and the lead author of the study is a paid consultant.

• A daily regimen of 45 Sun Chlorella A tablets (totaling 9 g) were used in this study. That amount of tablets would be quite costly. While it might require fewer than 45 tablets to achieve the same results, we can’t tell from this study.

In summary, it appears that at least some batches of chlorella have vitamin B12 activity, but it’s too soon to know how much chlorella vegans would require for optimal B12 status.


If you like my posts, please like my posts! Or share them!

I am very grateful for donations of any amount (click here).

Purchase anything through these links and JackNorrisRD gets a percentage:

Pangea – The Vegan Store
Vegan for Life by Jack Norris & Ginny Messina

Thank you!


1. Merchant RE, Phillips TW, Udani J. Nutritional Supplementation with Chlorella pyrenoidosa Lowers Serum Methylmalonic Acid in Vegans and Vegetarians with a Suspected Vitamin B(12) Deficiency. J Med Food. 2015 Oct 20. [Epub ahead of print] | link

Methyl vs. Cyano B12

Sunday, October 25th, 2015

Special note: A study was just released suggesting that the algae chlorella has vitamin B12 activity. I will be reporting on that as soon as I get the paper.

A paper was published in the July edition of Molecular Nutrition and Food Research reviewing the four different forms of vitamin B12 (1). The four forms are cyanocobalamin (CNCbl), hydroxocobalamin (HOCbl), methylcobalamin (MeCbl), and adenosylcobalamin (AdoCbl).

A quick summary is that MeCbl and AdoCbl are the two forms of vitamin B12 that are co-enzymes–the body actually uses these forms and needs both of them. But CNCbl is the form most commonly found in supplements and fortified foods while HOCbl is the form usually contained in B12 shots.

There has been a debate for about the last 10 years as to whether supplementing with the co-enzyme forms is better than supplementing with CNCbl or HOCbl. The paper by Obeid et al. suggests that people do not benefit more from the co-enzyme forms. Even for people with genetic defects of vitamin B12 metabolism, injections with HOCbl are preferable to supplementing with the co-enzyme forms.


Currently, we do not have sufficient evidence to suggest that the benefits of using MeCbl or AdoCbl override that of using CNCbl or HOCbl in terms of bioavailability, biochemical effects, or clinical efficacy. There is uncertainty regarding the claimed superior role of Cbl coenzyme forms for prevention and treatment of Cbl deficiency. However, HOCbl may be an advantageous precursor of the cofactors, particularly in the inherited disorders of metabolic Cbl processing. CNCbl is a more stable and inexpensive form that appears to be best suited for oral supplementation and parenteral [intravenous] treatment as well.



If you like my posts, please like my posts! Or share them!

I am very grateful for donations of any amount (click here).

Purchase anything through these links and JackNorrisRD gets a percentage:

Pangea – The Vegan Store
Vegan for Life by Jack Norris & Ginny Messina

Thank you!


1. Obeid R, Fedosov SN, Nexo E. Cobalamin coenzyme forms are not likely to be superior to cyano- and hydroxyl-cobalamin in prevention or treatment of cobalamin deficiency. Mol Nutr Food Res. 2015 Jul;59(7):1364-72. | link

Absorption of Various Forms of B12

Thursday, August 13th, 2015

Breaking news from 1971 for vitamin B12 junkies!

A reader alerted me to a 1971 study comparing absorption rates of cyanocobalamin, hydroxocobalamin, methylcobalamin, and adenosylcobalamin (1).

They found that at doses of 1 µg, 5 µg, and 25 µg, all forms were absorbed at about the same rate for practical purposes.

However, the researches suggested, based on other research, that at higher doses, cyanocobalamin is better absorbed. They theorized that this could be because absorption of methylcobalamin by way of intrinsic factor is efficient while cyanocobalamin is better absorbed through passive diffusion.

Based on this study, I’ve cleaned up the page Methylcobalamin & Adenosylcobalamin where you can also see a table of the absorption rates from this 1971 study.


If you like my posts, please like my posts! Or share them. Thank you!

I greatly appreciate donations of any amount (click here).

Purchase anything through these links and JackNorrisRD gets a percentage:


1. Adams JF, Ross SK, Mervyn L, Boddy K, King P. Absorption of cyanocobalamin, coenzyme B 12 , methylcobalamin, and hydroxocobalamin at different dose levels. Scand J Gastroenterol. 1971;6(3):249-52. | link

B12 Status of Whole Foods Vegans Consuming Nori and Mushrooms

Wednesday, February 11th, 2015
Summary A German study suggests that whole foods vegans who do not supplement with vitamin B12 have subpar vitamin B12 status and that nori and dried mushrooms do not improve B12 status.

In a 2014 study from Germany (1), a group of 10 whole foods vegans, who did not take supplements, were found to have methylmalonic acid (MMA) levels of almost 400 nmol/l. MMA is the most specific way to measure vitamin B12 status, with healthy levels being 270 nmol/l or less.

A second group of vegans who supplemented – it’s not clear with how much but it seems to have been at least 2 doses of 1,000 µg/week of B12 on average – had MMA levels of just above 200 nmol/l.

The whole foods-only vegans were given a minimum of 12 g/week of nori and 15 g/week of sun dried mushrooms, which the researchers calculated to contain an average of 3.1 µg/day of vitamin B12; the RDA is 2.4 µg. Their MMA levels were measured every 2 months for 8 months and they did not dip much below 350 nmol/l.

The vegans who took supplements were given more B12 than normal (though it’s not clear how much), and their MMA levels steadily decreased to about 150 nmol/l at 6 months, but then back up to 200 nmol/l at 8 months.

This research indicates that at the amounts given, nori and sun dried mushrooms do not improve vitamin B12 status.

I have updated the article B12 in Plant Foods with this information.


If you like my posts, please like my posts! Or share them. Thank you!

Purchase anything through these links and JackNorrisRD gets a percentage:


1. Schwarz J, Dschietzig T, Schwarz J, Dura A, Nelle E, Watanabe F, Wintgens KF, Reich M, Armbruster FP. The influence of a whole food vegan diet with Nori algae and wild mushrooms on selected blood parameters. Clin Lab. 2014;60(12):2039-50. | link

Vitamin B12 in Nori

Saturday, August 30th, 2014
Summary A review paper by the Watanabe group suggests that vegans can rely on nori for vitamin B12. I strongly advise against this.

There is a group of researchers in Japan who regularly publish papers in scientific journals about plant sources of vitamin B12. Fumio Watanabe is often the lead researcher, so I refer to them as the “Watanabe group.”

Some of their papers analyze the B12 in foods such as mushrooms, algae, and black tea, while other papers are just review articles of previous research. The latter is the case with their latest paper, Vitamin B12-containing Plant Food Sources for Vegetarians, published in the May 5, 2014 issue of Nutrients (1). A free version can be obtained at the link.

When the Watanabe group analyzes a food for B12, they often find molecules that they believe to be the vitamin. But a complication with simply finding B12 in food is that the food might also contain inactive B12 analogues that interfere with active B12. The Watanabe group is well aware of this and often analyzes the food for some of the typical inactive B12 analogues. Sometimes they feed the food to rats to see if it lowers the rats’ methylmalonic acid (MMA) levels, the prime indicator of B12 activity. Based on how much active B12 and inactive analogues they find, and any results with rats, they make recommendations as to whether a food can provide B12 for vegans.

In their latest review, based on the results of their various experiments combined with a study in which six vegan children stayed healthy eating large amounts of seaweed (my analysis here), they suggest that nori is a “suitable” source of B12 for vegans.

The biggest flaw in this theory is that there is a study that tested raw and dried nori using the gold standard of lowering MMA levels in humans (2), and although the authors of this study were optimistic about raw nori, the fact was that both dried and raw nori reduced B12 status in their subjects.

I often hear from people who say they have been vegan for some time, have not supplemented with B12, and are not B12 deficient. They take this to mean that vegans don’t need a supplemental source of B12. In most cases they do not know whether, in fact, they are B12 deficient or not, because they haven’t been appropriately tested for deficiency. And once you go vegan without a source of B12, you never know when deficiency symptoms might kick in – someone can be fine for years and then one day they start to feel tingling in their fingers or toes or they become severely fatigued. You don’t want to end up like any of the vegans listed in the Individual Cases of Deficiency.

There is also the problem of subclinical B12 deficiency where someone doesn’t feel any symptoms but has mild deficiency for years that can possibly develop into dementia or a stroke. As the Watanabe group says in their latest paper:

“However, Vitamin B12 deficiency may go undetected in vegetarians because their diets are rich in folic acid, which may mask vitamin B12 deficiency until severe health problems occur. Vitamin B12 deficiency contributes to the development of hyperhomocysteinemia, which is recognized as a risk factor for atherothrombotic and neuropsychiatric disorders, thereby negating the beneficial health effects of a vegetarian lifestyle.”

This does not mean that vegans need to get tested for B12 deficiency. On the contrary, I don’t see any need for that unless you decide not to supplement with B12 according to the recommendations here or you are supplementing but experiencing symptoms of B12 deficiency.

Whenever I post about B12, it is inevitable that someone, I suspect an internet troll in many cases, will pipe in to say that cyanocobalamin is not a good source of B12 but that methylcobalamin is. Except in very rare cases, this is not true (see Methylcobalamin & Adenosylcobalamin for more information). If you decide to rely on methylcobalamin, I recommend at least 1,000 µg per day.

If this post interested you, you might also want to read my August 2013 post about the Watanabe group, B12 in Plants and Algae Update.

In conclusion, there is no new evidence to suggest that nori is a reliable source of B12 for vegans and I advise against relying on it.


If you like my posts, please like my posts! Or share them. Thank you!

Purchase anything through these links and JackNorrisRD gets a percentage:


1. Watanabe F, Yabuta Y, Bito T, Teng F. Vitamin B12-containing plant food sources for vegetarians. Nutrients. 2014 May 5;6(5):1861-73. | link

2. Yamada K, Yamada Y, Fukuda M, Yamada S. Bioavailability of dried asakusanori (porphyra tenera) as a source of Cobalamin (Vitamin B12). Int J Vitam Nutr Res. 1999 Nov;69(6):412-8. | link

Clinical Trial of Methylcobalamin

Tuesday, January 28th, 2014

I’m taking another break from vitamin K2 to report on a study that a reader passed on regarding methylcobalamin (1).

There has been very little testing of methylcobalamin and so I normally recommend taking cyanocobalamin because it is a more stable form of vitamin B12 and there are anecdotal reports of people needing large doses of methylcobalamin to achieve results.

A 2011 clinical trial from Korea sheds some light on this issue. The study was done with people who had their stomachs removed (gastrectomy) due to cancer. Patients who have had a gastrectomy can no longer produce intrinsic factor, a molecule required for efficient B12 absorption, and they are typically given B12 injections.

In this trial, patients took 1,500 µg of methylcobalamin each day.

At baseline, their B12 levels were an average of 170 pg/ml and 24 out of 30 had tingling in their hands and feet, the traditional sign of vitamin B12 deficiency. Many had other indicators as well, including elevated homocysteine (an average of 17.5 µg/l). Over the course of the 3 month trial, vitamin B12 levels steadily increased to an average of 810 pg/ml, homocysteine steadily decreased to 11.4 µg/l, 28 patients experienced symptom relief, and 16 patients were free of all symptoms.

A drawback to this trial is that it did not have a placebo group; all the patients knew they were receiving vitamin B12. But these results are, in my opinion, too impressive to be due simply to placebo and based on the homocysteine and symptom improvement, it appears safe to say that 1,500 µg per day of methylcobalamin should be enough for just about anyone.

I have added a paragraph about this study to the Methylcobalamin & Adenosylcobalamin page at


If you like my posts, please like my posts! Or share them. Thanks!

I greatly appreciate donations of any amount and it allows me to spend more time on nutrition (click here).

Purchase anything through these links and JackNorrisRD gets a percentage: Gift Cards – E-mail Delivery

Vegan for Life: Everything You Need to Know to Be Healthy and Fit on a Plant-Based Diet from


1. Kim HI, Hyung WJ, Song KJ, Choi SH, Kim CB, Noh SH. Oral vitamin B12 replacement: an effective treatment for vitamin B12 deficiency after total gastrectomy in gastric cancer patients. Ann Surg Oncol. 2011 Dec;18(13):3711-7. | link