nutrient decline in vegetables and fruit

[Haydu, Suzanne (DHS-MCH)]

Here are some other refreshing perspectives that I have heard.  I think we
need a USDA perspective next.



"The situation with chromium may be instructive here.  As analytical 
tecniques improved, Cr content of tissues, plasma, etc. declined 
by some orders of magnitude over the years.

Past RDA values were also probably higher because committees, 
realizing their level of ignorance, wished to err more on the side of 
safety.  As nutrient requirements became better known, 
nutritionists felt more comfortable about cutting their margin of 
error."




"I'm certain that analytical sensitivity is a major factor here. Early
methods, especially from the 1930's, for every analyte were quite crude and
nonspecific, and not very sensitive.  If one also looks at earlier RDA's,
especially from the 1940's, they are far higher for most nutrients, again,
because the early food composition tables overestimated nutrient content.
With time, improved data on intake as well as other factors, have resulted
in lower estimates for requirements for virtually
every nutrient. Unfortunately, because there are no standard reference
materials for food analysis, we are unable to quantify the extent to which
improved analytical methodology accounts for these findings, which are not
surprising.  Our colleagues at USDA  may wish to review the publication
and offer an informed perspective."