March 6, 2009

When 100% Isn't Really 100%

The new boxes of Total cereal proudly exclaim:

"NOW! The most calcium and Vitamin D of any leading cereal!"

(Although I couldn't find a photograph of these boxes, the slightly outdated one on the left boasts the 100% calcium claim).

A cup of this retooled version provides a day's worth of calcium (1,000 milligrams) -- too bad our bodies can only metabolize approximately 500 milligrams at a time.

In other words, that bowl of cereal actually provides, at most, half a day's worth of calcium.

Not bad by any means, but not quite what the food label says.

I am also concerned about a cereal that attempts to provide a day's worth of iron and calcium in the same serving, since high amounts of calcium (anything above 300 milligrams, per the research literature) are known to interfere with the absorption of non-heme iron.

2 comments:

christine said...

hi andy,

just a quick question - is this the reason that a lot of supplements tend to only have 10% the dv for calcium, but 50% or more the dv for iron? as a vegan, should i be looking into supplementing on top of my multivitamin with some calcium? it seems like that's harder to get, whereas many things are fortified with iron or contain a lot of it: broccoli, fortified cereals and pastas, etc.

christine said...

sorry andy, what i meant to ask was why supplements chose a low calcium/high iron d.v. ratio over a high calcium/low iron one. pretty obvious that having high calcium/high iron would be a bad idea since the ions would be competing to be oxidized (right? or is it reduced? i forget which way it goes)