While the food distribution system in the United States and Canada ensures a mix of plant and animal foods from the broad range of soil selenium conditions (see Chapter 7), local foods (e.g., from farmers' markets) may vary considerably from the mean values in food composition databases. However, the variation in selenium content of food sources does not appear to exceed that for many other nutrients. For example, the variation in β-carotene content of

Box 9-1 Uses of Dietary Reference Intakes for Healthy Individuals and Groups

Type of Use

For the Individual

For a Group

Assessment

EARa: use to examine the possibility of inadequacy of reported intake.

EARb: use to estimate the prevalence of inadequate intakes within a group.

 

AIa: intakes at this level have a low probability of inadequacy.

AIb: mean intake at this level implies a low prevalence of inadequate intakes.

 

ULa: intake above this level has a risk of adverse effects.

ULb: use to estimate the prevalence of intakes that may be at risk of adverse effects.

Planning

RDA: aim for this intake.

EAR: use in conjunction with a measure of variability of the group's intake to set goals for the median intake of a specific population.

 

AI: aim for this intake.

 
 

UL: use as a guide to limit intake; chronic intake of higher amounts may increase risk of adverse effects.

 

EAR = Estimated Average Requirement RDA = Recommended Dietary Allowance AI = Adequate Intake UL = Tolerable Upper Intake Level

a Requires accurate measure of usual intake. Evaluation of true status requires clinical, biochemical, and anthropometric data.

b Requires statistically valid approximation of usual intake.



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