Dear all:
Sometimes I am astounded at the lack of common sense that is employed when people encounter a "rule".  The reason why there is a recommendation to start solids "AROUND" six months -- is mainly because about 30% of infants will become iron deficient between six to nine months without additional iron.  There are two problems with "diagnosing" iron deficiency.

Problem 1) Iron deficiency occurs BEFORE you have a low hemoglobin value.  So, by the time an infant has iron deficiency severe enough to lead to a hemoglobin value designated as "anemic" the infant may already have suffered cognitive delays.  The other tests for iron deficiency are far more invasive requiring serum samples rather than finger sticks.

Problem 2) Hemoglobin, like any biochemical indicator has a range.  Each individual has a different range of what is normal for them.  When a population is NOT iron deficiency, you get a nice bell shaped curve.  When you have an iron deficient population you get a curve with a skew in it, due to the iron deficient individuals in that population.  When you apply a cut-off value to that curve, you will automatically end up with some false positives and some false negatives.  There is one technique that I only saw employed once at a lactation conference where you plot a receiver operating characteristic curve to pick the best cutoff that leads to the fewest false positives and negatives.  So, this means that with iron deficiency and any other nutritional deficiency -- some people will be perfectly healthy below a cutoff value and others will not be healthy even if they are above that value.

Research on nutrition indicators was used to finally PROVE that you don't need to introduce solids before six months of age.  Every single one of those indicators have cutoff values and every single one of those cutoff values are subject to false positives and negatives.

A "BEHAVIOR"  such as continued exclusive breastfeeding doesn't even make it to the level of an indicator!  It is merely a behavior not a diagnosis.  The behavior might increase the risk of a particular condition, but it does not DIAGNOSE that condition.

The reason why the recommendation for iron starts at six months is because of the risk of cognitive development from iron deficiency and the inability to really detect it before it happens -- but you can readily see from the numbers that there will always be some infants who will be quite fine and won't have iron deficiency.  

Keep in mind, I haven't worked on micronutrient deficiencies in 10 years, so perhaps some new research will have provided different proportions of deficiency.

Best, Susan Burger

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