I was reading the nutrition information on a box of Kellog’s cereal.
For vitamin B12( and for a few more like vitamin B6 etc.)the listing says that Vitamin B12 is zero with cereal but 35% of DV(Daily Value) with 250 ml of milk:
What does this imply? Zero B12 in the cereal itself but 35% of Daily Value when taken with milk? Where does the B12 come from if it is zero in the cereal?
The wiki page on milk suggests 100g has 18% of the RDA of B[sub]12[/sub], so a typical “serving” with cereal (250ml, if I recall correctly) is in the neighborhood of 35%.
There probably isn’t any calcium, magnesium or Vitamin A in the cereal either, until you add the milk.
Exactly what cereal box are you looking at in your OP?
Fortified cereals like All-Bran, Special K and Total all have 100%, and most of the Kellog cereals I looked at online showed at least 25% for B[sub]12[/sub] for cereal alone.
I would suspect that: (a) People eat cereal for other reasons than to gain their B-6 and B-12 RDA – for example, milk is a terrible source of dietary fibre, while cereals, particularly bran and whole grain ones, are a fair to outstandingly good source of fibre.
(b) The reason for the two nutritional-value tables is that typically people eat cereals with milk on them, not dry (and yes, there are a few exceptions). Ergo, a person interested in what proportion of his RDAs is being filled by his dish of breakfast cereal is not interested in taking the figure for one serving of dry cereal + [the figure for one serving (one glass) of milk / what fraction of a serving is normally put on cereal] – what he wants is what one serving of cereal with the normal amount of milk on it adds up to, in one easy-to-read place. Should he choose to eat it dry, or with vodka or durian juice in place of milk, he can use the dry-serving figure. If he’s in the overwhelming majority who eat cereal with milk, he’ll use the cereal-with-milk figure.
Of minor note is the cereal packets we get with army field rations. They consist, usually, of oatmeal mixed with powdered milk. The package helpfully suggests adding water or, if you prefer, eat it dry.