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

Use of the Paired Retinol Isotope Dilution Test, but with a Single Isotope Dose, to Assess the Impact of a Vitamin A Intervention on Vitamin A Stores in Theoretical Children with Low Stores

BACKGROUND

As currently applied, the paired retinol isotope dilution (RID) test, which is used to assess the impact of a vitamin A intervention on vitamin A total body stores (TBS), requires 2 doses of stable isotope-labeled vitamin A.

OBJECTIVES

The objectives of this study were to evaluate use of a single isotope dose (4 μmol) to assess TBS by RID before and after intervention in theoretical children with low/moderate TBS.

METHODS

We selected 6 theoretical children with assigned values for TBS ranging from 82 to 281 μmol. Using Simulation, Analysis and Modeling software, we simulated the variable [plasma retinol specific activity (SAp)] and coefficients (Fa and S) used in the RID equation TBS (μmol) = FaS × 1/SAp in both the unsupplemented steady state at day 14 postdosing and during the subsequent 4 mo without or with vitamin A supplementation [2.8 μmol retinol/d (801 μg retinol activity equivalents/d)].

RESULTS

Fraction of dose in plasma on day 150 compared with day 14 was similar in the unsupplemented and supplemented conditions [geometric mean, 32% (range, 20%-48%) and 30% (20%-48%), respectively] and simulated values for FaS were similar under the 2 conditions. After 2 and 4 mo of daily vitamin A supplementation with 2.8 μmol/d, TBS was 78% and 128% higher, respectively, than without supplementation.

CONCLUSIONS

Results indicate that the paired RID method can successfully be done using a single 4 μmol dose of stable isotope. Furthermore, because values for the RID coefficient FaS were similar in the unsupplemented and vitamin A-supplemented conditions, these results in theoretical children indicate that FaS determined by population ("super-subject") modeling of steady state vitamin A kinetic data could be used to predict TBS by RID after a vitamin A intervention in individuals from the same or a similar group.

Heart rate variability behavior in young men after short-term carotenoid-containing supplementation

Background

Heart rate variability can reflect the risk of developing cardiovascular disease (CVD), while carotenoids are good for CVD prevention. However, the acute effect of short-term carotenoid-containing supplementation on heart rate variability in young men is unclear.

Methods

Thirty young men between 20 and 29 years of age without personal or family history of cardiovascular diseases were randomly divided into control and experimental groups. The anthropometric data, physiological parameters, and serum biochemical data were acquired, which were without significant difference between the two groups, at the beginning of trial. The participants in the experimental group consumed one pack of compound nutritional supplements in the morning (e.g., 10 AM) and another pack at night (e.g., 7 PM) each day. Heart rate variability was measured again once a month. Repeated measures analysis of variance with Roy's largest root test and Bonferroni post hoc test were applied for primary outcomes.

Results

Repeated measures analysis of variance indicated a significant time interaction effect for the estimated marginal means of percussion entropy index scale (T1 versus T3, T1 versus T4, and T2 versus T4 with p = 0.009, 0.005, and 0.032, respectively). Roy's largest root test indicates there were significant differences between the means of the index after the intervention between two groups only on T3 and T4 (p = 0.007, η ² = 0.232 and p = 0.028, η ² = 0.162, respectively).

Conclusion

Short-term carotenoid-containing supplementation could help young men by increasing heart rate variability capacity compared to controls over three months.

Prevalence of vitamin A deficiency and dietary inadequacy in Indian school-age children and adolescents

PURPOSE

There are no representative estimates of vitamin A deficiency (VAD) and risk of vitamin A (VA) dietary inadequacy in Indian children and adolescents. To evaluate, from national surveys, the prevalence of VAD measured by serum retinol concentrations (< 0.7 µmol/L or < 20 µg/dL), and the risk of VA dietary inadequacy and excess intake beyond the tolerable upper limit (TUL).

METHODS

National and state-level VAD prevalence adjusted for inflammation was estimated in school-age children (5-9 years: 10,298) and adolescents (10-19 years: 9824) from the Comprehensive National Nutrition Survey (CNNS 2016-18). The risk of dietary inadequacy against age-specific average VA requirements, and excess intake against the TUL, was assessed from the National Sample Survey Office (NSSO 2014) data.

RESULTS

Serum retinol concentrations increased with age (5-19 years) in both genders and were significantly lower in school-age children (1.02 µmol/L, CI: 1.01-1.03) compared to adolescents (1.13 µmol/L, CI 1.12-1.15). The inflammation-adjusted prevalence of VAD in school-age children and adolescents was 19.3% (CI 18.8-19.9) and 14.4% (CI 13.9-14.9) respectively, and this was > 20% in seven and four states for children and adolescents, respectively. The prevalence of VAD was significantly higher among children with lower socio-economic status. The risk of dietary VA inadequacy, from the NSSO survey, was 69 and 78% in children and adolescents, respectively. This risk reduced to 6 and 17% with VA fortified oil and milk intake, while the proportion of intakes exceeding the TUL became 6 and 0.5% in children and adolescents, respectively.

CONCLUSIONS

The national prevalence of VAD in school-age children and adolescents in India was just less than 20%. The risk of dietary VA deficiency is likely to decline substantially with VA fortified food intake, but a risk of excessive intake also begins to appear; therefore, a careful assessment of the risk of hypervitaminosis A is required at these ages.

Biological evidence to define a vitamin A deficiency cutoff using total liver vitamin A reserves

Vitamin A is a fat-soluble vitamin involved in essential functions including growth, immunity, reproduction, and vision. The vitamin A Dietary Reference Intakes (DRIs) for North Americans suggested that a minimally acceptable total liver vitamin A reserve (TLR) is 0.07 µmol/g, which is not explicitly expressed as a vitamin A deficiency cutoff. The Biomarkers of Nutrition for Development panel set the TLR cutoff for vitamin A deficiency at 0.1 µmol/g based on changes in biological response of several physiological parameters at or above this cutoff. The criteria used to formulate the DRIs include clinical ophthalmic signs of vitamin A deficiency, circulating plasma retinol concentrations, excretion of vitamin A metabolites in the bile, and long-term storage of vitamin A as protection against vitamin A deficiency during times of low dietary intake. This review examines the biological responses that occur as TLRs are depleted. In consideration of all of the DRI criteria, the review concludes that induced biliary excretion and long-term vitamin A storage do not occur until TLRs are >0.10 µmol/g. If long-term storage is to continue to be part of the DRI criteria, vitamin A deficiency should be set at a minimum cutoff of 0.10 µmol/g and should be set higher during times of enhanced requirements where TLRs can be rapidly depleted, such as during lactation or in areas with high infection burden. In population-based surveys, cutoffs are important when using biomarkers of micronutrient status to define the prevalence of deficiency and sufficiency to inform public health interventions. Considering the increasing use of quantitative biomarkers of vitamin A status that indirectly assess TLRs, i.e. the modified-relative-dose response and retinol-isotope dilution tests, setting a TLR as a vitamin A deficiency cutoff is important for users of these techniques to estimate vitamin A deficiency prevalence. Future researchers and policymakers may suggest that DRIs should be set with regard to optimal health and not merely to prevent a micronutrient deficiency.

Breast Milk-Derived Retinol Is a Potential Surrogate for Serum in the 13C-Retinol Isotope Dilution Test in Zambian Lactating Women with Vitamin A Deficient and Adequate Status

BACKGROUND

Vitamin A (VA) deficiency (VAD) affects ∼19 million pregnant women worldwide. The extent of VAD in Zambian women of reproductive age is unknown owing to lack of survey inclusion or the use of static serum retinol concentrations, a low-sensitivity biomarker.

OBJECTIVES

This cross-sectional study employed isotopic techniques to determine VA status with serum and milk among women aged 18-49 y (n = 197) either lactating with infants aged 0-24 mo or nonlactating with or without infants.

METHODS

Assistants were trained and piloted data collection. Demographic data, anthropometry, and relevant histories were obtained including malaria and anemia. For retinol isotope dilution (RID), baseline fasting blood and casual breast milk samples were collected before administration of 2.0 μmol 13C2-retinyl acetate and 24-h dietary recalls. On day 14, blood (n = 144) and milk (n = 66) were collected. Prevalence of total liver VA reserves (TLR) ≤0.10 μmol/g was defined as VAD with comparison to the DRI assumption of 0.07 μmol/g as minimally acceptable for North Americans.

RESULTS

When a 20% adjustment for dose lost to milk was made in the RID equation for lactation, mean total body VA stores (TBS) for lactating women were 25% lower than for nonlactating women (P < 0.01), which was not the case without adjustment (P = 0.3). Mean ± SD TLR for all women were 0.15 ± 0.11 μmol/g liver. Using retinol purified from breast milk instead of serum for RID analysis yielded similar TBS and TLR, which were highly correlated between methods (P < 0.0001). Serum retinol ≤0.70 μmol/L had 0% sensitivity using either VAD liver cutoff and milk retinol ≤1.0 μmol/L had 42% sensitivity for VAD at 0.10 μmol/g.

CONCLUSIONS

Determining accurate VA status among women of reproductive age, especially lactating women, forms a basis for extrapolation to the general population and informing policy development and program implementation.