Why is there such a big fuss around vitamin B12 in veganism and plant-based diets? Because it is the only nutrient that seems to be obligatorily obtained through animal-based foods. B12 is, therefore, often used as the decisive argument against the legitimacy of plant-based diets. However, when we look at the full picture – including ecological factors related to the issue – we find that under optimal conditions, humans do not need B12 from animal-based foods. While this is not easy to achieve, it definitely reinforces the idea, that our species could be plant-based.
“Anthropoids, including all great apes, take most of their diet from plants, and there is a general consensus that humans come from a strongly herbivorous ancestry. Though gut proportions differ, overall gut anatomy and the pattern of digestive kinetics of extant apes and humans are very similar.”K. Milton, 1999
For quick readers:
Re-evaluating the vegan B12 paradigm is overdue
The need for B12 supplementation in vegans is often used as reasoning against the concept that humans are a naturally plant-based species. It suggests that we need animal-based foods, to obtain the essential substance and that plant-based diets are unhealthy and not biologically appropriate for our species. However, this is not necessarily true, as today’s toxic world impairs our B12-producing microbiome and its colonization of the B12-absorbing parts of the intestines. We need the full picture to re-evaluate!
The antibiotics and pesticides are an attack on our ability to obtain B12 from the microbiome, and a suboptimal diet prevents the right condition to absorb B12.
If humans still lived in their natural habitat as the tropical frugivorous species that we are, the odds are high that we would not need B12 from food, or supplement but obtain it from an optimally healthy microbiome. That this is indeed a real scenario has been shown in a nature-published study and backed up by anecdotal evidence of long-term high-fruit vegans.
This biological, holistic view could be a starting point for possibly shifting the dogma that the natural human diet cannot be fully plant-based! And indeed, there is evidence for this case, which we will discuss in this article.
But let’s start by understanding B12 better and the role it plays in the understanding of the natural human diet:
Can our microbiome provide sufficient B12?
Humans seem to depend on animal-based foods for B12, because the cobalamins found in some plants (i.e., seaweeds), are not a reliable or suitable source of B12 for humans. The microbiome produces B12 in both, frugivores (including humans) and herbivores (read more here). But can we get enough B12 from our microbiome? Or do we obligatorily need animal-based foods for B12?
That the intestinal microbiome produces B12 is nothing new. However, there are still doubts that in humans, this suffices to get enough B12 – or get B12 at all:
“…whether microbially produced B12 in the gut is used by the host is not yet known.”Kundra et al., 2022
This was just one more study was not able to answer the fundamental unsolved question: can the microbiome production of B12 sustain the human body?
But how come we don’t know? When it comes to the microbiome as a source of intestinal B12, there seems to be a critical anatomical problem in non-ruminant mammals, like apes and humans: Vitamin B12 is synthesized in the intestines, but it is excreted without being absorbed, resulting in feces that contain vitamin B12.
“It has long been assumed that B12 is produced by bacteria in the large intestine (aka the colon), but since B12 is produced below the ileum (where B12 is absorbed), it is not available for absorption.”veganhealth.org
“Human faeces contain appreciable quantities of vitamin B12 or vitamin B12-like material presumably produced by bacteria in the colon, but this is unavailable to the non-coprophagic (non-faeces-eating) individual.”Albert et al., 1980
Nor do we get B12 from our microbiome… or do we??? Is this weird anatomical “quirk” really true? After all, there are long-term vegans that get along fine without B12 supplementation. And if we just dig deep enough we find that there seems to be an overlooked underlying root cause, an environmental problem that affects our own B12 production and absorption:
Vitamin B12 is actually produced and absorbed by a perfectly healthy gut
Is vitamin B12 really excreted without being absorbed? It usually is – due to living in the modern Western environment that impedes healthy microbiome colonization! But it might be possible that B12 of our microbiome is absorbed in the right places under better conditions:
Not convinced yet? Let’s explore the evidence:
The B12 issue is caused by an unnatural habitat, not by a faulty anatomy
The microbiome and gut colonization is largely determined by environmental influences rather than genetics. For example, Humans have been shown to have a nearly identical microbiome to wild (frugivorous) chimpanzees when living in a natural environment (Gomez et al., 2019). What changes our microbiome is a “modern” polluted environment and diet (Sharma et al., 2020).
Therefore, it is likely that humans potentially can obtain vitamin B12 directly from the microbiome when the microbiome is restored to its natural state, similarly to other apes:
And in biology, it would only make sense that the symbiotic bacteria are on the right spot and not have evolution make us eat “un-swallowable” poop with utter disgust, right? After all, nature has solved uncountable anatomically and biochemically much more complex issues than that – and, indeed, that is what we found when digging deeper:
A study published in the science journal Nature called “Vitamin B12 synthesis by human small intestinal bacteria” found that intestinal vitamin B12 was more available to people living in tropical India than living in a Western country (England).
The study emphasizes that the small intestine, where B12 is absorbed, does actually contain a significant microbial community capable of producing the vitamin – but this healthy microbiome condition is “more extensive” in non-westerner individuals living in tropical India than when the same people live in a Western country facing cold climate. After all. we are a tropical species and do not thrive in non-tropical climates.
“… It is possible that in India, these individuals have a bacterial flora in the small intestine which provides a significant proportion of their daily requirements of vitamin B12, but when they move to a more protected environment, the bacterial flora reverts to that characteristic of subjects living in western countries with little or no resident flora in the upper small bowel3, the individuals lose their endogenous source of vitamin B12 and therefore become more prone to develop overt vitamin B12 deficiency.” (Albert et al., 1980)
This finding is backed up by anecdotal evidence from people that are long-term fruit-based vegans that their B12 levels are in a healthy range, without supplementations. And while this is not the case for everyone, it does show that it is possible!
It seems that living in our natural habitat – the tropics (in this case, India) enables vitamin B12 absorption of our own microbiome possible. Factors might be:
- Better access to ripe, high-quality tropical fruits, which affects the microbiome
- Tropical warm and moist climates with adequate sunshine (vitamin D affects the microbiome)
- A less sterile, less antimicrobial environment than in Western countries (in this case, England), enables a natural exchange of beneficial microorganisms between individuals, as well as from the environment to individuals
B12 is not a vegan problem, it’s an antibiotic problem!
Our extreme use of chemicals against microorganisms (antibiotics and pesticides found in food, water etc.) is not only fighting pathogens and pests – it is also an attack on our microbiome and our B12-producing bacteria! This is one reason why farmed animals and non-vegans regularly experience B12 deficiency, too, and thus need to supplement.
In a perfect world – or let’s say in a perfect gut – B12 is produced by some of our friendly mutualistic bacteria and potentially can be absorbed. Unfortunately, human microbiomes are severely disrupted by antibiotics, pesticides, and pollutants we find in our modern and toxic world. Additionally, most diets we eat today are not the natural diet of our species, which prevents the intestines from being a sufficient source of B12.
The dogma that veganism is not natural for the human species is partly based on the “B12 misconception,” – while the real reason is that we live in a toxic world with unhealthy biomes. We live outside the tropics, our natural habitat, which causes us not to have access to our natural foods and eat our species-appropriate, fruit-based diet.
Supplement B12 on a plant-based diet
What we have learned so far indicates that the supplementation of B12 is helpful until the microbiome is restored to the point it can provide us with the vitamin.
Can you benefit from supplementing vitamin B12? My educated guess is, that you benefit if
- your microbiome is unbalanced and pre-damaged
- you had antibiotics in your lifetime
- you are exposed to chemical pollution (agriculture or urban life)
- If your foods do not contain enough cobalt
What type of supplement
The quality of vitamin B12 supplements matters: generally, methylcobalamin is being favored over the commercially most easily available cyanocobalamin: methylcobalamin is the natural and active form found in foods (read more here on different types of B12). It also has been shown to have more positive outcomes for the microbiome (Xu et al.; 2018).
Conclusion: An optimal diet and natural environment might enable us to obtain B12 from our microbiome!
The microbiome’s contribution to B12 production in individuals adhering to plant-based diets highlights the intricate relationship between our dietary choices, gut bacteria, and nutrient synthesis. While the microbiome has the potential to produce B12, the challenge lies in ensuring efficient absorption of the vitamin in the small intestine. By consuming a species-specific human diet that supports a healthy microbiome, individuals can optimize their chances of B12 absorption from microbial sources.
The B12 issue has wrongly been used as an argument against plant-based diets. However, if we stick to our species-specific, topical, high-fruit diet, we provide the conditions for a microbiome to be healthy and functional enough to produce B12 on the right location within our intestines.
Want to know more about adopting a frugivore diet yourself? Check out our guide:
Go to How to do the Frugivore Diet
Check out our supplement guide here!
- Niklewicz, A. et al. (2022) ‘The importance of vitamin B12 for individuals choosing plant-based diets’, European Journal of Nutrition, 62(3), pp. 1551–1559. doi:10.1007/s00394-022-03025-4.
- Vitamin B12 in Plant Foods (no date) VeganHealth.org. Available at: https://veganhealth.org/vitamin-b12/vitamin-b12-plant-foods/ (Accessed: 28 May 2023).
- Albert, M.J., Mathan, V.I. and Baker, S.J. (1980a) ‘Vitamin B12 synthesis by human small intestinal bacteria’, Nature, 283(5749), pp. 781–782. doi:10.1038/283781a0.
- Kundra, P. et al. (2022) ‘Healthy adult gut microbiota sustains its own vitamin B12 requirement in an in vitro batch fermentation model’, Frontiers in Nutrition, 9. doi:10.3389/fnut.2022.1070155.
- Intestinal bacteria as a vitamin B12 source (no date) VeganHealth.org. Available at: https://veganhealth.org/vitamin-b12/intestinal-bacteria-as-b12-source/ (Accessed: April 5, 2023).
- Hills, R. et al. (2019) Gut microbiome: Profound implications for diet and disease. Nutrients, 11(7), p. 1613. doi:10.3390/nu11071613.
- A. Gomez et al., Plasticity in the human gut microbiome defies evolutionary constraints. mSphere. 4 (2019), doi:10.1128/msphere.00271-19.
- A. K. Sharma et al., Traditional human populations and nonhuman primates show parallel gut microbiome adaptations to analogous ecological conditions. mSystems. 5 (2020), doi:10.1128/msystems.00815-20.
- Zimmermann, J. (2022a) Formen von Cobalamin (vitamin B12) IM überblick: Kanyo®, Vital und Gesund. Available at: https://www.vital-und-gesund.de/b12/cobalamin/ (Accessed: 28 May 2023).
- Xu, Y. et al. (2018a) ‘Cobalamin (vitamin B12) induced a shift in microbial composition and metabolic activity in an in vitro colon simulation’, Frontiers in Microbiology, 9. doi:10.3389/fmicb.2018.02780.