Is Cyanocobalamin Really Made From Human Waste?

Cyanocobalamin, the form of vitamin B12 found in most supplements and fortified foods, is not made from human waste. It is produced through microbial fermentation, a controlled industrial process in which specific strains of bacteria synthesize the vitamin in large bioreactors. The claim that it comes from sewage or human feces has a thin thread of historical connection to real science, but the thread snaps long before it reaches the supplement bottle on your shelf.

Where the Myth Comes From

The rumor did not appear out of nowhere. Vitamin B12 can only be made by certain bacteria and archaea, not by plants, animals, or chemical synthesis in any practical sense. Those B12-producing bacteria live in many environments, including soil, animal guts, and yes, sewage. In the early decades of B12 research, scientists studied the vitamin wherever they could find it in high concentrations, and sewage sludge happened to be one of those places. A 1987 study, for example, isolated two previously unknown B12-related compounds from sewage sludge as part of basic biochemistry research.¹ That kind of work was about understanding B12’s chemistry, not about manufacturing supplements.

This distinction matters. The fact that researchers once studied B12 in sewage does not mean the supplement industry harvests vitamin B12 from wastewater treatment plants. Researchers also study bacteria in hot springs, ocean vents, and Antarctic ice cores without those environments becoming manufacturing sites. But the sewage connection was vivid enough to stick in public memory, and it has been recycled through social media and alternative health communities ever since. Nutritional misinformation thrives on exactly this kind of half-truth, where a real scientific detail is stripped of context and presented as a shocking revelation.²

How Cyanocobalamin Is Actually Manufactured

The industrial production of vitamin B12 relies on microbial fermentation, and it has for decades. The process is conceptually similar to how beer, yogurt, or insulin is made: you grow a specific microorganism under controlled conditions and collect the compound it produces. The two bacterial workhorses of the B12 industry are strains of Propionibacterium freudenreichii (sometimes classified under its older name P. shermanii) and strains related to Pseudomonas denitrificans.³ These bacteria are grown in steel fermentation tanks filled with carefully formulated nutrient media, typically containing sugars, amino acids, and trace minerals like cobalt, which is an essential part of the B12 molecule.

Chemical synthesis of B12 is theoretically possible. The molecule was famously synthesized in a laboratory in the 1970s, but that synthesis required about 70 chemical steps and is completely impractical for commercial production. The complexity of the B12 molecule, one of the largest and most structurally intricate vitamins, makes fermentation the only viable production route.⁴ This is not a corner-cutting shortcut by supplement manufacturers. There is genuinely no other way to make it at scale.

The fermentation broth is harvested, and the B12 is extracted and purified through several stages of filtration, chromatography, and crystallization. The final product is a highly purified crystalline powder. Cyanocobalamin specifically is formed during the purification process when a cyanide group (from activated charcoal used in purification or added deliberately in trace amounts) binds to the cobalt center of the molecule. This gives cyanocobalamin its remarkable chemical stability, which is one reason it became the dominant supplement form: it holds up well in storage, in fortified foods, and on pharmacy shelves.

The Bacterial Monopoly on B12

One reason this myth gains traction is that people are surprised to learn no plant, animal, or fungus can make vitamin B12 from scratch. The vitamin is synthesized exclusively by certain bacteria and archaea.² Every bit of B12 in a steak, a glass of milk, or an egg got there because bacteria somewhere in the food chain produced it first. In ruminant animals like cows, bacteria in the rumen (a specialized stomach compartment) synthesize B12 as long as the animal’s diet supplies enough cobalt.⁵ The animal absorbs the vitamin, and it accumulates in tissues like liver and muscle, which is how it enters the human diet through meat and dairy.

Humans have B12-producing bacteria in their own large intestine, too. A systematic review examining the relationship between vitamin B12 and the gut microbiome found that B12 is both synthesized and utilized by bacteria in the human gut.⁶ The catch is that B12 absorption in humans happens primarily in the small intestine, upstream of where most of these bacteria live. So the B12 your gut bacteria make mostly passes through you without being absorbed. This biological quirk is why humans need dietary B12, whether from animal foods, fortified products, or supplements, and it is also why the presence of B12 in feces does not mean feces are a sensible raw material for supplement production.

When someone online says “B12 comes from bacteria, and bacteria live in poop, so B12 supplements come from poop,” they are stringing together individually true statements into a conclusion that does not follow. Bacteria live in many places. The ones used for supplement manufacturing are pure, well-characterized laboratory strains grown in sterile or near-sterile conditions, not wild colonies scraped out of a sewer.

What Your Body Does With Cyanocobalamin

A common follow-up question is whether cyanocobalamin is even a “natural” form of B12. Strictly speaking, it is not the form you would find in food. The B12 in meat and dairy comes primarily as methylcobalamin and adenosylcobalamin, the two coenzyme forms your cells actually use. Cyanocobalamin is a synthetic but stable form that your body readily converts into those active forms.

After you swallow a cyanocobalamin supplement, your body strips off the cyanide group using a protein called MMACHC (also known as CblC). This yields a partially reduced form of B12 that is then delivered to the two enzymes in human cells that require the vitamin: methionine synthase, which operates in the cell’s main compartment, and methylmalonyl-CoA mutase, which works inside mitochondria. Those enzymes rebuild the coenzyme forms they need from this intermediate.⁷

The trace amount of cyanide released during this conversion is genuinely tiny, well within what the body handles routinely from other dietary sources. For perspective, a single almond contains more cyanide-generating compounds than a B12 supplement. Some people prefer methylcobalamin or hydroxocobalamin supplements on the grounds that these forms skip the cyanide removal step, and there is nothing wrong with that choice, but the evidence does not suggest that cyanocobalamin is harmful or meaningfully less effective for most people.

Why the Myth Keeps Spreading

Nutritional misinformation tends to follow a predictable pattern: take a real but obscure scientific detail, present it without context, and attach it to something people already feel uneasy about. Supplements are a prime target because many people already have vague anxieties about what goes into pills they cannot inspect. The sewage claim hits multiple psychological buttons at once: disgust, distrust of “Big Pharma,” and the appeal of feeling like you know something most people do not.

The claim also benefits from the fact that the real manufacturing process, microbial fermentation, sounds vaguely industrial and unfamiliar. Most people do not realize that fermentation is the same basic process behind bread, cheese, and wine. When someone hears “bacteria make it in a factory,” they do not picture a cheese wheel. They picture something ominous. The gap between public perception of fermentation and the reality of it is wide enough for misinformation to thrive in.

Researchers studying nutritional myths have noted that misleading claims about food and supplements often succeed because they offer simple, emotionally compelling narratives that are harder to dislodge with nuanced explanations.² “Your supplement comes from sewage” is a punchier story than “your supplement comes from a well-characterized strain of Pseudomonas denitrificans grown in a controlled bioreactor with defined nutrient media and then purified through multiple chromatographic steps.” The truth is boring. That is, unfortunately, one of its defining features.

Quality Control in B12 Supplements

If the worry behind the sewage myth is really about purity, that concern is worth addressing on its own terms. Finished B12 supplements do undergo quality testing, and researchers have developed validated analytical methods to quantify the four bioactive forms of B12 (adenosylcobalamin, cyanocobalamin, hydroxocobalamin, and methylcobalamin) in dietary ingredients and supplements, with high precision and accuracy.⁸

A separate concern is contamination with heavy metals, which can affect any supplement regardless of its active ingredient. Recent analytical work has assessed vitamin B12 supplements for the presence of cadmium, mercury, and lead, metals that can appear in trace amounts in pharmaceutical products and should be monitored.⁹ These are legitimate quality concerns, but they have nothing to do with the raw material being sewage. Heavy metal contamination in supplements usually traces back to soil conditions where plant-derived ingredients were grown, processing equipment, or excipients (the inactive fillers and binders in a tablet), not to the B12 molecule itself.

If you want to be cautious about supplement quality, the most practical step is to look for products that carry third-party testing seals from organizations like USP, NSF International, or ConsumerLab. These organizations verify that the product contains what the label claims and screen for common contaminants. This addresses the real-world purity question far more usefully than worrying about whether bacteria in a fermentation tank are somehow connected to sewage.

B12 for People Who Avoid Animal Products

The sewage myth has an especially unfortunate impact on people who depend on B12 supplements most: vegans and strict vegetarians. Because no plant naturally produces B12, people who avoid all animal products need supplementation or fortified foods to maintain adequate B12 levels.² Data from a large US nutrition survey found that about 3.6% of American adults had measurable B12 deficiency, with the rate being roughly twice as high among people who did not take B12 supplements compared to those who did.¹⁰

For these individuals, the “made from sewage” claim can create a real barrier to taking a supplement they genuinely need. B12 deficiency is not a trivial issue. It can lead to megaloblastic anemia, nerve damage, cognitive difficulties, and in severe cases, irreversible neurological harm. The irony of the myth is that it sometimes convinces the people who most need B12 supplements to avoid them, based on a misunderstanding of how those supplements are produced.

Some emerging research is exploring whether microbial fermentation can be used to enrich plant-based foods directly with B12, essentially letting the same kinds of bacteria that make supplement-grade B12 do their work inside tempeh, fermented vegetables, or other plant matrices. This approach could eventually make it easier for plant-based eaters to get B12 from food rather than pills, but it remains an area of active development rather than a current commercial reality for most consumers.

The Cobalt Connection and Ruminant Biology

An interesting side note that occasionally gets tangled into the myth involves livestock. Cattle and sheep get their B12 from bacteria in their own rumens, and the efficiency of that bacterial production depends heavily on cobalt availability in the animal’s diet. When researchers supplemented dairy cows with a B12 precursor called 5,6-dimethylbenzimidazole, the apparent rate of B12 synthesis by rumen bacteria increased by about a third.⁵ This finding matters for animal nutrition but sometimes gets garbled in popular accounts into the idea that B12 in meat is “synthetic” or “supplemented,” which then loops into broader suspicion about the vitamin.

What is actually happening is straightforward: the cow’s gut bacteria make B12, and the cow absorbs it. Giving the bacteria more of a specific building block helps them make more B12. The animal is not being “injected with synthetic vitamins” in the way the myth implies. The bacteria are doing what bacteria do. The same fundamental biology, microbes synthesizing a complex molecule that larger organisms cannot make for themselves, underlies both the B12 in a steak and the B12 in a supplement. The difference is that in one case the bacteria live in a cow’s stomach, and in the other they live in a stainless steel tank. Neither involves sewage.

Gut bacteria in humans are performing the same trick, just in the wrong location. The B12 they produce in the colon cannot be efficiently absorbed because the absorption machinery sits higher up in the digestive tract.⁶ Some animals, like rabbits, solve this problem through coprophagy, eating their own feces to recapture nutrients produced in the hindgut. Humans, for understandable reasons, do not take this approach, which is precisely why we need dietary or supplemental sources of B12 in the first place.