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01.08.2016


Algae and mushrooms not a full alternative for vitamin B12 supplements

In theory vegans don't need supplements to maintain their vitamin B12 levels. Vitamin B12 is found in foods such as nori seaweed and shiitake mushrooms. But theory and practice are not the same thing, German researchers discovered when they studied vegans' blood for eight months. They published their findings in Clinical Laboratory.

Vitamin B12
Vitamin B12 is vital for the functioning of the central nervous system and for the synthesis of DNA. The vitamin is found above all in meat, but also in other animal products such as dairy and eggs. If you eat protein-rich animal products you are unlikely to suffer from a vitamin B12 deficiency. But if you don't eat animal products, it's another matter...

Researchers thought at one time that chlorella and spirulina contain vitamin B12. And indeed, the products contain substances that do resemble the vitamin B12 analogues in animal products but these do not function as vitamins. Researchers call these substances pseudovitamin B12. [J Agric Food Chem. 1999 Nov;47(11):4736-41.]

Below left: vitamin B12; below right: pseudovitamin B12.


Algae and mushrooms not a full alternative for vitamin B12 supplements


There are a couple of plant-based sources of vitamin B12. [Nutrients. 2014 May 5;6(5):1861-73.] Some algae Porphyra yezoensis, Porphyra tenera and Plerochrysis carterae produce vitamin B12 analogues in large quantities. The Japanese food product nori consists of dried Porphyra yezoensis algae. And mushrooms like shiitake also contain vitamin B12 analogues.

Study
The researchers wondered whether vegans who eat nori and shiitake daily consume sufficient amounts of vitamin B12. Of course you only know for sure if you try it out, so the Germans did an eight-month long experiment with 75 people.

The researchers analysed the blood of ten vegans who ate 12 g nori and 15 g dried mushrooms every week. They did this on five different occasions throughout the experiment. The amount of nori the participants ate provided them with 2.4 mcg vitamin B12 daily and the mushrooms provided another 0.7 mcg per day. Nutritionists in the US advise healthy adults to consume 2.4 mcg vitamin B12 daily, so the vegans should have been getting enough vitamin B12 in the experiment.

The researchers also studied the blood of a number of vegans who took dietary supplements containing synthetic vitamin B12, the blood of a group of vegetarians (who ate no meat, but did eat dairy and eggs) and the blood of a group of meat eaters.

Results

The figure below shows that the blood of the vegans who ate mushrooms and nori contained approximately enough vitamin B12 as a whole and in particular holotranscobalomin. Holotranscobalomin is an active form of vitamin B12. The concentrations of this were on the low side in the vegans, but not low enough to be regarded as a deficiency.


Algae and mushrooms not a full alternative for vitamin B12 supplements


Algae and mushrooms not a full alternative for vitamin B12 supplements
Vitamin B12 metabolism is complex. It's possible to have enough vitamin B12 in your blood and still have a deficiency. So the researchers also measured the concentration of methylmalonic acid in the blood of their test subjects. If the concentration of this substance is higher than 300 nanomol per litre, then there is a B12 deficiency. And hey presto...


Algae and mushrooms not a full alternative for vitamin B12 supplements


Conclusion
It's not that the researchers dismiss plant-based vitamin B12 sources, but they warn vegans that they shouldn't rely solely on these sources.

"Overall, vegans following a whole food, unrefined, organic diet were able to maintain a borderline supply of vitamin B12 over a period of eight months reflected by increased methylmalonic acid, but otherwise normal or at least greyzone measures of B12", they wrote. "A regular check on vitamin B12 is therefore recommended."

"Those vegans taking additional dietary supplements demonstrated satisfactory overall results."

Source:
Clin Lab. 2014;60(12):2039-50.

More:
Vitamin B12 inhibits mental decline in the elderly 17.08.2014
Combination of arginine, ornithine and vitamin B12 has anabolic effect on power lifters 16.04.2010

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