Nutrition
Do fortified cereals replace a B12 supplement?
Short answer
No — in practice fortified breakfast cereals should not replace a dedicated vitamin B12 supplement. Treat them only as a welcome extra in a plant-based diet, not as its main, foundational source.
Why cereal alone is not enough?
How B12 is absorbed: The digestive system takes up vitamin B12 in two ways — via intrinsic factor (at most about 1.5–2 µg at a time) and via passive diffusion (about 1% of the dose at high concentrations). To cover daily needs from fortified foods alone, you would need to eat those products two or three times a day, several hours apart. A single bowl of cereal in the morning is not enough.
Very low doses per serving: One serving of cereal typically provides 0.4 µg to 1 µg of B12. Because of how absorption works, your body will take up only a fraction of what you need from that.
Unhealthy extras: Vitamin-fortified breakfast cereals often contain a lot of sugar, glucose-fructose syrup and processed carbohydrates. Eating large amounts every day just for B12 is inefficient and unhealthy.
Lack of consistency: It is hard to keep up a routine of eating exactly the same amount of fortified foods every day. A dedicated supplement guarantees a steady, controlled dose.