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reflects a usual intake below the UL. In this example, only the 7 days of intake data provide levels of confidence of 85 to 90 percent for concluding that this woman's usual intake is below the UL given her observed mean intake.

Since this test would be conducted only in cases where the observed mean intake for the individual is high enough to suggest a problem, the SD of daily intake as calculated in CSFII or the National Health and Nutrition Examination Survey may underestimate the individual's true SD of daily intake. This is because there is some evidence that the SD of daily intake increases as the mean intake increases (Nusser et al., 1996). Using a SD of daily intake that is too small may lead to the conclusion that usual intake is below the UL when in reality it is not (at a given level of assurance).

As described previously, this test can be performed when daily intakes can be assumed to approximate a normal distribution. An indication that daily intakes are not normally distributed is a high CV of intake. From Appendix Table B-2, Table B-3, Table B-4 through Table B-5, it can be seen that for several nutrients the CV of daily intake is above 60 to 70 percent. In those cases, this test approach is not recommended, and one should make a qualitative assessment of the individual's intake. Table 3-5 presents qualitative interpretations of an individual's intake in relation to the UL. The impact of within-person variation at high intake levels (e.g., levels approaching the UL) has not been studied extensively.

When using the proposed method it is important to note that the pooled estimates of the within-person standard deviation of intakes in Table B-2, Table B-3, Table B-4 to Table B-5 are based on data on nutrients from food only, not food plus supplements. This suggests the need for caution in using these estimates in assessing individual intakes relative to the UL. For some nutrients, ULs are defined on the basis of total intake (food plus supplements), and the estimates of the within-person

TABLE 3-5 Qualitative Interpretation of Intakes Relative to the Tolerable Upper Intake Level (UL)

Intake relative to the UL

Suggested Qualitative Interpretation

Greater than or equal to the UL

Potential risk of adverse effects if observed over a large number of days

Less than the UL

Intake is likely safe if observed over a large number of days

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