Dietary intakes of retinol equivalents, a-tocopherol equivalents, vitamin D and phylloquinone were estimated from three sets of 4-d weighed diet records and compared to three corresponding fasting plasma concentrations of retinol, 25-hydroxyvitamin D, a-tocopherol, and phylloquinone measured in 34 healthy adults over 20 wk. The magnitude of the correlation between dietary vitamin intake and its corresponding biochemical measure is in part determined by the reproducibility of each of the

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... , so within-to-between subject variance ratios were calculated for both dietary intakes and plasma concentrations. Phylloquinone was the only fat-soluble vitamin with a significant correlation between dietary intake and fasting plasma concentration (r Å 0.51, P Å 0.004). This correlation improved with an increase in both the number of independent diet records and independent plasma measures. Of the dietary intake measures, all the fat-soluble vitamins had greater within than between subject variance, with the highest measured for phylloquinone (6.86:1). Of the plasma measures, only phylloquinone had a within-to-between subject variance ratio greater than one (5.36:1). Comparisons across age and sex for dietary intake and plasma concentrations differed in pattern among the fat-soluble vitamins. J. Nutr. 127: 587-592, 1997. 1 The contents of this publication do not necessarily reflect the views of the US Department of Agriculture, nor does mention of trade names, commercial of the fat-soluble vitamins. products, or organizations imply endorsement of the US Government. 2 The costs of publication of this article were defrayed in part by the payment METHODS of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact. Subjects. Subjects were recruited from the New England region 3