Findings in 3 clinical trials challenge the accuracy of the Institute of Medicine's estimated average requirements for vitamin A in children and women.

Background: Vitamin A (VA) estimated average requirements (EARs) for women and children are extrapolated from rats and adult males. The retinol isotope dilution (RID) test can sensitively characterize VA status and intake requirements.

Objectives: These studies evaluated current EARs for children 4-8 y and women 19-30 y old.

Duration of Retinol Isotope Dilution Studies with Compartmental Modeling Affects Model Complexity, Kinetic Parameters, and Calculated Vitamin A Stores in US Women.

Background: Retinol isotope dilution (RID) indirectly estimates vitamin A (VA) status. Multicompartment modeling of RID data is used to refine study designs and equations to calculate VA stores. Previous studies suggest that VA in slowly turning over pools is not traced if follow-up is not long enough; however, shorter RID studies are being investigated.

Serum carotenoid interactions in premenopausal women reveal α-carotene is negatively impacted by body fat.

Increasing body mass indices (BMIs) across the globe reflect pandemic shifts towards habitual positive energy imbalances. Excess body fat in individuals is often associated with high-energy and high-fat diets scanty in fresh produce. Carotenoids are fat-soluble pigments plentiful in many fruits and vegetables.

Vitamin A isotope dilution predicts liver stores in line with long-term vitamin A intake above the current Recommended Dietary Allowance for young adult women.

Background: The Estimated Average Requirement (EAR) and Recommended Dietary Allowance (RDA) for vitamin A are 1.7 and 2.4 μmol/d (500 and 700 μg retinol activity equivalents/d), respectively, for nonpregnant, nonlactating women aged >19 y.

Strategies to increase vegetable or reduce energy and fat intake induce weight loss in adults.

For obese individuals seeking to optimize health and well-being, healthy dietary strategies are important. Vegetables and fruits contribute to a healthy diet, and increased consumption may cause weight reduction by displacing foods high in energy and fat. The objective of this study was to determine if advising high vegetable (8 servings) and moderate fruit (2-3 servings) consumption would result in weight reduction in obese individuals.

13C natural abundance in serum retinol acts as a biomarker for increases in dietary provitamin A.

The natural isotopic composition of 13C and 12C in tissues is largely determined by the diet. Sources of provitamin A carotenoids (e.g.

One-time graded doses of vitamin A to weanling piglets enhance hepatic retinol but do not always prevent vitamin A deficiency.

Background: Vitamin A supplements are administered to infants in developing countries at immunization contacts; doses of 50000 IU vitamin A are recommended. Doses of 100000 IU are given to children aged 0.5-1 y.

One-time vitamin A supplementation of lactating sows enhances hepatic retinol in their offspring independent of dose size.

Background: Single megadoses of vitamin A between 200,000 and 400,000 IU have been administered to lactating mothers to improve the vitamin A status of both mothers and breastfeeding infants. However, the most beneficial dosing regimen is not known.

Objective: The effect of megadoses of vitamin A supplements given to lactating sows on hepatic vitamin A concentrations in their nursing offspring was examined.

Adjustments to the modified relative dose response (MRDR) test for assessment of vitamin A status minimize the blood volume used in piglets.

The modified relative dose response (MRDR) test is widely used in public health research to assess vitamin A (VA) status of populations and individuals. However, method adjustments intended to make the test more useful in large field studies and/or less invasive have not been systematically verified. To compare the similarity between modified tests and the standard MRDR test, and validate both modified and standard tests against liver reserves of VA, we used a piglet model.

A theoretical increase in infants' hepatic vitamin a is realized using a supplemented lactating sow model.

Vitamin A deficiency (VAD) is a public health problem affecting millions in developing nations. Supplementation for lactating women, whose needs are high, involves large oral doses of the preformed vitamin. The safety and efficacy of these doses has been inadequately studied.