Mineral deficiencies are more common than vitamin deficiencies, statistics shows that one in four adults deals with lack of vitamin B12. In this article we will cover the symptoms and causes of vitamin B12 deficiency, plus you will get a few easy tips on how to regulate that.
In the published research, one plant food, chlorella, has been shown to have vitamin B12 activity in humans; there are caveats that you should be aware of before relying on it (see below). The only other plant food that has been tested is nori, which did not have B12 activity.
A number of foods, arguably, warrant further attention. But unless these foods are shown consistently to correct B12 deficiency, vegans should not rely on them for vitamin B12.
It cannot be emphasized enough that until a particular food, obtained from multiple regions, consistently improves vitamin B12 status (by lowering MMA levels), it should not be relied upon as a source of vitamin B12.
It could be a boon to the vegan movement to find a source of vitamin B12 that naturally and reliably exists in a vegan food. In their zeal to find such a source, some vegan advocates recommend foods whose ability to provide vitamin B12 is sketchy at best. Because of the harm that can come to someone relying on such foods for vitamin B12, I review the published scientific research below with a skeptical view.
There has been a long history of misconceptions about which, if any, plant foods are sources of B12. Much of this stems from the methods of measuring B12 analogues. Other confusion stems from bacterial contamination that occurs in some foods but not others. Please see Measuring B12 in Plant Foods: Why the Confusion? for an explanation of the methods for for measuring B12 analogues in plant foods.
Unlike animals, most, if not all, plants have no B12 requirement for any function, and therefore have no active mechanisms to produce or store B12. When B12 is found in them it can be due to contamination which is not reliable.
Many seaweeds have been shown to have B12 analogues. Most seaweeds are macroalgae, which are technically not plants. Some macroalgae contain an enzyme that can use cobalamin, but also have an enzyme with the same function that does not require cobalamin in case it is not present. These macroalgae do not make their own cobalamin, but rather have a symbiotic relationship with cobalamin-producing bacteria (1). Note that I am purposefully using the term “cobalamin” rather than “vitamin B12” because it is not clear if these cobalamins are active vitamin B12 in humans.
During the 1970s, two enzymes in plants (potatoes and bean seedlings) were found to respond to the addition of adenosylcobalamin (2, 3), a co-enzyme form of B12. One explanation is that adenosylcobalamin provides some factor that is usable by these enzymes, but that adenosylcobalamin is not required by these plants for growth. Thus far, these plants have not been shown to counteract B12 deficiency symptoms (though I am not aware of any well-designed attempts as it is assumed that they do not contain B12). It is probably safe to assume that many vegans who have developed severe B12 deficiency ate potatoes and beans.
There are some rumors, though no evidence of which I am aware, that if you let organic produce, such as carrots, sit at room temperature for a few hours, bacteria on the surface of the carrots will produce B12. For this to happen, specific species of bacteria would be required, as would cobalt, on the surface of these foods. Until there is research showing that such a method can lower MMA levels, such produce should not be considered to provide B12.
Many of the studies below analyze the vitamin B12 analogues in various foods to determine if the food contains vitamin B12, rather than feeding various batches obtained in typical food markets, to people to see if it improves their vitamin B12 status. There are significant problems with this approach because:
Even if you find some molecules that seem to be vitamin B12, you don’t know how it will interact with other inactive B12 molecules inevitably also prevalent in these foods.
We do not know how the B12 got there: whether the plant made it (unlikely), whether it has come from symbiotic bacteria, or whether it came from fecal or insect contamination. Thus, we do not know how reliable it would be in other batches of that food throughout the world.
The packaging, storage, transportation, and preparation methods can differ greatly between the careful laboratory methods used in these reports and the versions someone might buy in a grocery store.
It cannot be emphasized enough that until a particular food, obtained from multiple regions, consistently improves vitamin B12 status (via lowering MMA levels), it should not be relied upon as a source of vitamin B12.
If you want to see more about the research visit Vegan Health