Overlapping Vitamin A Interventions with Provitamin A Carotenoids and Preformed Vitamin A Cause Excessive Liver Retinol Stores in Male Mongolian Gerbils.

BACKGROUND: Vitamin A (VA) deficiency is a public health problem in some countries. Fortification, supplementation, and increased provitamin A consumption through biofortification are efficacious, but monitoring is needed due to risk of excessive VA intake when interventions overlap. OBJECTIVES: Two studies in 28-36-d-old male Mongolian gerbils simulated exposure to multiple VA interventions to determine the effects of provitamin A carotenoid consumption from biofortified maize and carrots and preformed VA fortificant on status. METHODS: Study 1 was a 2 × 2 × 2 factorial design (n = 85) with high-ß-carotene maize, orange carrots, and VA fortification at 50% estimated gerbil needs, compared with white maize and white carrot controls. Study 2 was a 2 × 3 factorial design (n = 66) evaluating orange carrot and VA consumption through fortification at 100% and 200% estimated needs. Both studies utilized 2-wk VA depletion, baseline evaluation, 9-wk treatments, and liver VA stores by HPLC. Intestinal scavenger receptor class B member 1 (Scarb1), ß-carotene 15,15'-dioxygenase (Bco1), ß-carotene 9',10'-oxygenase (Bco2), intestine-specific homeobox (Isx), and cytochrome P450 26A1 isoform α1 (Cyp26a1) expression was analyzed by qRT-PCR in study 2. RESULTS: In study 1, liver VA concentrations were significantly higher in orange carrot (0.69 ± 0.12 µmol/g) and orange maize groups (0.52 ± 0.21 µmol/g) compared with baseline (0.23 ± 0.069 µmol/g) and controls. Liver VA concentrations from VA fortificant alone (0.11 ± 0.053 µmol/g) did not differ from negative control. In study 2, orange carrot significantly enhanced liver VA concentrations (0.85 ± 0.24 µmol/g) relative to baseline (0.43 ± 0.14 µmol/g), but VA fortificant alone (0.42 ± 0.21 µmol/g) did not. Intestinal Scarb1 and Bco1 were negatively correlated with increasing liver VA concentrations (P < 0.01, r2 = 0.25-0.27). Serum retinol concentrations did not differ. CONCLUSIONS: Biofortified carrots and maize without fortification prevented VA deficiency in gerbils. During adequate provitamin A dietary intake, preformed VA intake resulted in excessive liver stores in gerbils, despite downregulation of carotenoid absorption and cleavage gene expression.

Carotenoid and Tocochromanol Profiles during Kernel Development Make Consumption of Biofortified "Fresh" Maize an Option to Improve Micronutrient Nutrition.

Biofortification is a strategy to reduce micronutrient malnutrition. The aim of this study was to investigate whether consumption of biofortified fresh maize can supply nutritionally meaningful amounts of provitamin A carotenoids (PVA), zinc, lysine, and tryptophan. The accumulation patterns for PVA and tocochromanol compounds in developing grain of 23 PVA hybrids was studied, and nutritionally meaningful amounts of those compounds were found in grain by milk stage, when fresh maize is eaten. The highest PVA and tocochromanol accumulation occurred by physiological maturity. The percent apparent retention in boiled fresh maize was 92%, 117%, 99%, and 66% for PVA, zinc, lysine, and tryptophan, respectively. Consumption of 0.5 to 2 ears of fresh maize daily could supply 33-62.2%, 11-24% and more than 85% of the estimated average requirement of PVA, tryptophan, and zinc, respectively. The results indicate that eating biofortified fresh maize can contribute to improved micronutrient nutrition.

The research and implementation continuum of biofortified sweet potato and maize in Africa.

The enhancement of sweet potato and maize with provitamin A carotenoids has been part of HarvestPlus's research continuum since the formation of the biofortification project. This review includes case studies of biofortification strategies used for sweet potato in Uganda and orange maize in Zambia. The current status of the science and release of biofortified varieties was reviewed by three scientists who were part of the HarvestPlus program for more than a decade with input from a scientist who experienced orange maize dissemination in Zambia. High ß-carotene varieties of sweet potato were introduced into South Africa and Mozambique, and efficacy and effectiveness studies, respectively, showed promise to improve vitamin A status, followed by dissemination efforts in Uganda. A randomized, controlled effectiveness trial tested extension models to promote sweet potato and assessed vitamin A intake among Ugandans. Orange maize breeding was initially a challenge, but considering that the carotenoid biosynthetic pathway was present in maize germplasm, breeders quickly bred higher amounts of provitamin A into the maize that was ultimately released in Zambia. Initial resistance occurred because orange maize was associated with yellow maize, which had negative connotations associated with food aid and animal feed, and consumers preferred white maize. Currently, both orange crops are available on the market.

Maize Milling Method Affects Growth and Zinc Status but Not Provitamin A Carotenoid Bioefficacy in Male Mongolian Gerbils.

Background: Vitamin A (VA) and zinc deficiencies are prevalent. Maize is a common staple, and milling affects nutrient and nutrient-modifier profiles.Objective: We investigated the interaction of maize milling methods (i.e., whole grain compared with refined) in male Mongolian gerbils aged 29-35 d with conventionally bred provitamin A-biofortified (orange) or white maize on VA and zinc status.Methods: Study 1 (n = 67) was a 2 × 3 milling (whole compared with refined) by VA [no-vitamin A placebo group (VA-), orange, and VA-supplemented group (VA+)] design, with 4 wk of VA depletion followed by six 4-wk treatments (n = 10/treatment). Study 2 (n = 33) was a 2 × 2 milling-by-zinc [no-zinc placebo group (Zn-) compared with zinc-supplemented group (Zn+)] design, including 2 wk of VA depletion followed by four 3-wk treatments (n = 8-9/treatment). For study 1, positive and negative control groups were given supplemental VA at equimolar amounts to ß-carotene equivalents consumed by the orange groups (74 ± 5 nmol/d) or placebo, respectively. For study 2, positive and negative control groups were given 152 µg Zn/d or placebo, respectively.Results: Milling significantly affected zinc concentration, providing 44-45% (whole grain) or 9-14% (refined) NRC requirements. In study 1, orange maize improved liver VA concentrations (mean ± SD: 0.28 ± 0.08 µmol/g) compared with the white maize groups (0.072 ± 0.054 µmol/g). Provitamin A bioefficacy was similar. In study 2, neither zinc nor milling influenced liver retinol. Refined Zn- gerbils weighed less than others by day 14 (46.6 ± 7.1 compared with 56.5 ± 3.5 g, respectively; P < 0.0001). Milling affected pancreas zinc concentrations (refined Zn-: 21.1 ± 1.8 µg Zn/g; whole Zn-: 32.5 ± 5.8 µg Zn/g).Conclusions: Whole-grain intake improved zinc and did not affect provitamin A bioefficacy. Other factors affected by milling (e.g., shelf life, preference, aflatoxin fractioning) need to be considered to maximize health.

13C Natural Abundance of Serum Retinol Is a Novel Biomarker for Evaluating Provitamin A Carotenoid-Biofortified Maize Consumption in Male Mongolian Gerbils.

BACKGROUND: Crops such as maize, sorghum, and millet are being biofortified with provitamin A carotenoids to ensure adequate vitamin A (VA) intakes. VA assessment can be challenging because serum retinol concentrations are homeostatically controlled and more sensitive techniques are resource-intensive. OBJECTIVES: We investigated changes in serum retinol relative differences of isotope amount ratios of (13)C/(12)C (δ(13)C) caused by natural (13)C fractionation in C3 compared with C4 plants as a biomarker to detect provitamin A efficacy from biofortified (orange) maize and high-carotene carrots. METHODS: The design was a 2 × 2 × 2 maize (orange compared with white) by carrot (orange compared with white) by a VA fortificant (VA+ compared with VA-) in weanling male Mongolian gerbils (n = 55), which included a 14-d VA depletion period and a 62-d treatment period (1 baseline and 8 treatment groups; n = 5-7/group). Liver VA and serum retinol were quantified, purified by HPLC, and analyzed by GC combustion isotope ratio mass spectrometry for (13)C. RESULTS: Treatments affected liver VA concentrations (0.048 ± 0.039 to 0.79 ± 0.24 µmol/g; P < 0.0001) but not overall serum retinol concentrations (1.38 ± 0.22 µmol/L). Serum retinol and liver VA δ(13)C were significantly correlated (R(2) = 0.92; P < 0.0001). Serum retinol δ(13)C differentiated control groups that consumed white maize and white carrots (-27.1 ± 1.2 δ(13)C‰) from treated groups that consumed orange maize and white carrots (-21.6 ± 1.4 δ(13)C‰ P < 0.0001) and white maize and orange carrots (-30.6 ± 0.7 δ(13)C‰ P < 0.0001). A prediction model demonstrated the relative contribution of orange maize to total dietary VA for groups that consumed VA from mixed sources. CONCLUSIONS: Provitamin A efficacy and quantitative estimation of the relative contribution to dietary VA were demonstrated with the use of serum retinol δ(13)C. This method could be used for maize efficacy or effectiveness studies and with other C4 crops biofortified with provitamin A carotenoids (e.g., millet, sorghum). Advantages include no extrinsic tracer dose, 1 blood sample, and higher sensitivity than serum retinol concentrations alone.

Maize genotype and food matrix affect the provitamin A carotenoid bioefficacy from staple and carrot-fortified feeds in Mongolian gerbils (Meriones unguiculatus).

Biofortification to increase provitamin A carotenoids is an agronomic approach to alleviate vitamin A deficiency. Two studies compared biofortified foods using in vitro and in vivo methods. Study 1 screened maize genotypes (n = 44) using in vitro analysis, which demonstrated decreasing micellarization with increasing provitamin A. Thereafter, seven 50% biofortified maize feeds that hypothesized a one-to-one equivalency between ß-cryptoxanthin and ß-carotene were fed to Mongolian gerbils. Total liver retinol differed among the maize groups (P = 0.0043). Study 2 assessed provitamin A bioefficacy from 0.5% high-carotene carrots added to 60% staple-food feeds, followed by in vitro screening. Liver retinol was highest in the potato and banana groups, maize group retinol did not differ from baseline, and all treatments differed from control (P < 0.0001). In conclusion, ß-cryptoxanthin and ß-carotene have similar bioefficacy; meal matrix effects influence provitamin A absorption from carrot; and in vitro micellarization does not predict bioefficacy.

Provitamin a carotenoid bioavailability:what really matters?

Micronutrient malnutrition, or “hidden hunger,” afflicts a large part of the world’s population, with vitamin A deficiency among the most prevalent public health problems. Provitamin A carotenoids in plant foods are a source of vitamin A for humans; however, several factors, including species of carotenoids, host status, and effectors of absorption can negatively, positively, or in yet undetermined ways affect the bioavailability of these compounds. Staple foods biofortified with provitamin A carotenoids have shown more efficient bioconversion to retinol than generally observed for vegetables (e. g., 3 - 6 versus 10 - 80 beta-carotene to 1 µg retinol). Staple foods such as maize, rice, and cassava, are generally more accessible than meat or vegetable sources of retinol or provitamin A carotenoids to poor consumers, who are most likely to suffer micronutrient malnutrition. Interdisciplinary teamwork, including plant breeders, nutritionists, government and local agencies, seed companies, and communities, is needed to avail biofortified crops to needy populations. Key steps include developing, validating the nutritional effects of, providing nutrition education concerning, and promoting the use of biofortified crops. Provitamin A carotenoid biofortification of sweet potato, maize, cassava, and rice are at different stages along this continuum. Close linkages between agriculture, nutrition, and health, are essential in the quest to eradicate hunger among the poor.