If there were a vote for the nutrient plant-based eaters need to pay the most attention to, vitamin B12 would win by a landslide.

You've probably heard: "B12 only exists in animal products" or "Animal foods contain natural vitamin B12."

But the truth is, B12 is synthesized by microorganisms.

B12 Is Made by Microorganisms

In ancient times, humans gathered food from the earth, and fruits and vegetables were often lightly coated in soil — which contains abundant microorganisms, some of which produce vitamin B12. Since the body needs very little (the recommended daily intake for adults is about 2.4 mcg), obtaining B12 in past environments wasn't difficult.

However, modern agriculture and urbanization have changed soil ecology. Produce must now be thoroughly washed before reaching the table to eliminate pathogens and contaminants. Natural contact between humans and soil microorganisms has diminished — and with it, natural B12 acquisition.

Modern animal farming deliberately adds vitamin B12 to animal feed, so the B12 obtained from animal products is actually a secondhand synthetic source.

What Does B12 Do?

Vitamin B12 is primarily involved in red blood cell formation, nervous system function, and DNA synthesis. Though the body needs only small amounts, its importance is significant.

Early B12 deficiency may appear as fatigue, low energy, difficulty concentrating, and memory problems — easily mistaken for overwork or poor sleep, making it hard to detect.

Long-term deficiency can lead to megaloblastic anemia, numbness in hands and feet, poor balance, and nerve damage. Because the body can store B12 for several years, many who newly adopt a plant-based diet may not experience symptoms until years later.

Importantly, B12 isn't only a concern for plant-based eaters. Older adults, those with low stomach acid, and long-term users of antacids may develop deficiency even on an omnivorous diet. The Institute of Medicine (IOM) recommends that people over 50, regardless of diet, should rely on supplements or B12-fortified foods to meet their needs.

How to Get B12 ?

The most reliable B12 sources currently include vitamin B12 supplements, B12-fortified plant milks, fortified breakfast cereals, and B12-containing nutritional yeast. For plant-based eaters, directly supplementing B12 is simpler, safer, and more effective than relying on uncertain natural sources.

Some research discusses obtaining B12 through nori, nutritional yeast, or fermented foods, but the evidence is not yet sufficient to rely on these alone.

In a broader sense, this reflects our relationship with the environment. Every era has its own way of living. Since modern life already offers convenient, stable, and environmentally lighter ways to obtain vitamin B12, perhaps the more worthwhile question is not "do I have to get B12 from meat?" but "how can I care for my health, the animals, and the planet in a way that fits today's world?"

Supplementing B12 isn't a weakness of a plant-based diet — it's simply a new health habit for modern life.