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Why use % for Vit A, C, calcium and iron when the RDA depends on age and gender?

crux2019crux2019 Posts: 3Member Member Posts: 3Member Member
It seems to me one of the greatest sources of error in the data base are the % of the title nutrients. When scanning the bar code of a food I've found examples of mg of calcium and iron reported on the packing being directly numerically converted into %. E.g., A food can show 97.5 mg of calcium and 2.6 mg of iron per serving on the packaging, but when scanned and ported over into MFP it literally becomes 97.5% of calcium and 2.6% of iron. The food is then flagged as a high source of calcium within the app. However, the RDA for men aged 19 - 70 by the NIH (N=USA) is 1000 mg of calcium. So, in fact, this food is only 9.8% of the RDA for men aged 19-70 and women aged 19 - 50, and less at 8.1% for women aged 51 - 70 (RDA for women in this age group is 1200 mg of calcium). The error in the iron is worse. At 2.6 mg of iron per serving, this amounts to fully 32.5% of the RDA for men aged 19+, but significantly less for women aged 19-50 at 14.4%. In fact the food, while a decent source of Ca, is an excellent source of Fe (ignoring the bioavailability).

Why use %'s at all? Why not just use mg or micrograms as required? What does it mean in MFP when it tells me the % RDA of a nutrient? Has it taken my age and gender into account? When I "report a food" and come to add in the correct % for nutrients, what age and gender do I use?


  • MikePTYMikePTY Posts: 2,970Member, Premium Member Posts: 2,970Member, Premium Member
    MFP database uses standard food labeling values as provided in the United States. Food labels only require a percentage for vitamins, not an actual measurement to be listed. That is why MFP uses percentages. The percentages are based off of the RDA as set by the FDA. You can Google specific vitamins to see what the FDA considers to be the daily value of that vitamin and how it compares to your own personal recommendations.
  • crux2019crux2019 Posts: 3Member Member Posts: 3Member Member
    Thanks Mike! I get it now. I was using the National Institute of Health’s facts sheets, which are more finer grained than the FDA’s Nutrition Facts Labeling Requirements.

    It still doesn’t solve the issue of incorrect percentages being ported into MFP when reading bar codes. I guess MFP assumes numbers are percentages even if they are actual masses being reported on the label instead of percentages. Anyway, at least I can correct those now, but the kJ to kcal bug needs fixing.
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