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brendanhill

Why do nutrient database not factor in bioavailability?

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I was compiling some data about vegan sources of calcium and thought I had formed a reasonable spreadsheet. Then I came across the following page, describing how variable the bioavailability of calcium across various sources really is:

 

http://plenteousveg.com/vegan-sources-calcium/

 

For example, without factoring in bioavailability we would think that 1 cup of Chinese cabbage would meet ~70% of our calcium requirements. When factoring in bioavailability, it is closer to ~20%. Conversely, a cup of collard greens go from ~27% to ~50%. These are significant differences when trying to formulate a nutritionally complete diet and yet all nutrition databases I have seen online seem to ignore this difference.

 

Is the description of calcium bioavailability in the link above accurate?

 

If so, is there any point using standard online nutrition databases to evaluate calcium sources?

 

Is this degree of variability in bioavailability across various sources the case for many other vitamins eg. B12, iron etc?

 

Regards,

-Brendan

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Brendan,

 

Great profile picture by the way! Which one are you?  :)xyz

 

Regarding bioavailable - yes, its really difficult to gauge, and does appear to vary dramatically based on foods themselves, not to mention what else you eat with them (e.g. coffee, tea and phytates inhibit mineral absorption, vitamin C enhances iron absorption, black pepper potentiates curcumin's effects, etc.).

 

Mostly we (try to) avoid obsessing over such things (with varying degrees of success :)xyz), get as much nutrition from diet as we can, and supplement when we suspect deficiencies, especially if backed up by blood tests suggesting we in fact are deficient.

 

See my answers to your other set of questions here for some more details.

 

--Dean

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Thanks Dean, I discovered your posts shortly after posting and I appreciate the time you've taken to lay out your own plan. It will be a helpful reference for me.

 

Regards,

-Brendan

 

P.S. The little one on my shoulders is now 3 and in a couple of weeks will have a baby brother. How time flies.

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