The one vitamin you now can't get enough from plants
It is often said that a vegan diet is not healthy because of the lack of certain nutrients. This is just not true. There is only one vitamin that we can’t get enough from plants, vitamin B12 or also known, cobalamin. Before, though, we could. The problem is over-farming and washing vegetables too much (I will explain as we go).
Foods That Contain Vitamin B12
Found mainly in animal products (fish, shellfish, meat, eggs and dairy)1 and in some algae species (nori).2
Why Is Mostly Found In Animals?
B12 is produced by microorganisms (bacteria and archaea) found in the soil, which live in symbiotic relationships with roots plants.3 These microorganisms need the mineral cobalt in order to produce B12. We even know which enzyme is used to create B12, the BluB protein.4, 5 Fun fact! Most plants don't even require B12. However, a B12 deficiency inhibits plant growth under nitrogen-limited conditions. So they really benefit from a symbiosis relationship with B12-producing microorganisms.6
B12 is also produced by bacteria found in the stomach of ruminants, as well as bacteria in symbiosis with phytoplankton (green algae and cyanobacteria), which then will be the source of energy for fish.7
Moreover, vitamin B12 is also produced by bacteria found in the large intestine of humans. However, it is not bioavailable for us because the receptors necessary for absorbing the vitamin are found in the small intestine, upstream of the site of production. The vitamin B12 that we produce is excreted through faeces.3
Technically, we could obtain vitamin B12 accidentally from plants which are in contact with B12-producing bacteria in the soil. That is how animals, such as gorillas, get vitamin B12 (apart from eating their own faeces). Unfortunately, due to excessive agriculture, the soil is deficient in cobalt and, because our vegetables are very washed, we can’t get enough vitamin B12 through eating just plants. Indeed, epidemiological studies have shown that vegans and vegetarians tend to have lower levels of vitamin B12 compared to the general population.8, 9, 10
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Vitamin B12 Deficiency
Vitamin B12 is crucial for the normal function of the brain and the nervous system. It is also involved in the formation of red blood cells and DNA.
Because the human body can store vitamin B12 for up to 4 years, symptoms of a deficiency can take several years to appear.
When vitamin B12 levels are low, neurological difficulties can appear (depression, memory problems, fatigue and confusion), as well as anaemia.11
Recommended Dosage And Supplementation
People over 14 years old are advised to take 2.4 micrograms (µg) of vitamin B12 daily. Pregnant women and lactating women should aim for 2.6 µg and 2.8 µg, respectively.
For vegetarians and vegans, it is advised to supplement with B12. There are no side effects reported of taking too much vitamin B12; any excess will be excreted in the urine.11, 12 But still, you don’t want to over-supplement in any case.
B12 can appear in 4 different forms:
- Methylcobalamin: active form of B12 in the human body.
- Adenosylcobalamin: active form of B12 as well.13
- Hydroxycobalamin: intermediate form.14
- Cyanocobalamin: synthetic form.15
Which Form Of B12 Should You Choose?
Research is mixed regarding which form is best absorbed by the body, and we have to keep in mind that each person absorbs it differently (based on age and genetics).
Some research suggests that supplementing with any of the nature bioidentical forms (methylcobalamin, adenosylcobalamin or hydroxycobalamin) is preferred instead of the use of cyanocobalamin, due to they are more bioavailable and safe. 13 However, other research did not show an advantage of taking methylcobalamin and adenosylcobalamin compared to cyanocobalamin.14
One important point is that when cyanocobalamin is ingested, it can be converted into the active forms (methylcobalamin and adenosylcobalamin). On the contrary, methylcobalamin does not increase levels of adenosylcobalamin.15
Thus, based on the current research, there are two possible good options: a supplement containing cyanocobalamin, or one that combines methylcobalamin and adenosylcobalamin.16
Note: don’t buy a multivitamin that includes vitamin B12 in the cyanocobalamin form. This form can be degraded in the presence of vitamin C and copper.
While sublingual supplements are often promoted as being more efficiently absorbed, there is no evidence to show that this form of supplement is superior to regular oral vitamin B12.17 Also, just to mention, fortified foods with vitamin B12 have also been proven to be highly bioavailable.1
Some Recommendations Based On Dosage And B12 Form
- Vitamin B12 cyanocobalamin 1000 µg: take 1 pill every 3 days.
- Vitamin B12 all 3 forms 3000 µg: take 1 pill per week.