Amount of dietary fat and type of soluble fiber independently modulate postabsorptive conversion of beta-carotene to vitamin A in mongolian gerbils

Porcine bile acids promote the utilization of fat and vitamin A under low-fat diets

Fat-soluble vitamin malabsorption may occur due to low dietary fat content, even in the presence of an adequate supply of fat-soluble vitamins. Bile acids (BAs) have been confirmed as emulsifiers to promote fat absorption in high-fat diets. However, there are no direct evidence of exogenous BAs promoting the utilization of fat-soluble vitamins associated with fat absorption in vitro and in vivo. Therefore, we chose laying hens as model animals, as their diet usually does not contain much fat, to expand the study of BAs. BAs were investigated in vitro for emulsification, simulated intestinal digestion, and release rate of fat-soluble vitamins. Subsequently, a total of 450 healthy 45-week-old Hy-Line Gray laying hens were chosen for an 84-day feeding trial. They were divided into five treatments, feeding diets supplemented with 0, 30, 60, 90, and 120 mg/kg BAs, respectively. No extra fat was added to the basic diet (crude fat was 3.23%). In vitro, BAs effectively emulsified the water-oil interface. Moreover, BAs promoted the hydrolysis of fat by lipase to release more fatty acids. Although BAs increased the release rates of vitamins A, D, and E from vegetable oils, BAs improved for the digestion of vitamin A more effectively. Dietary supplementation of 60 mg/kg BAs in laying hens markedly improved the laying performance. The total number of follicles in ovaries increased in 30 and 60 mg/kg BAs groups. Both the crude fat and total energy utilization rates of BAs groups were improved. Lipase and lipoprotein lipase activities were enhanced in the small intestine in 60, 90, and 120 mg/kg BAs groups. Furthermore, we observed an increase in vitamin A content in the liver and serum of laying hens in the 60, 90, and 120 mg/kg BAs groups. The serum IgA content in the 90 and 120 mg/kg BAs groups was significantly improved. A decrease in serum malondialdehyde levels and an increase in glutathione peroxidase activity were also observed in BAs groups. The present study concluded that BAs promoted the absorption of vitamin A by promoting the absorption of fat even under low-fat diets, thereupon improving the reproduction and health of model animals.

Improving the bioavailability of oil-soluble vitamins by optimizing food matrix effects: A review

The potency of oil-soluble vitamins (vitamins A, D, E and K) in fortified foods can be improved by understanding how food matrices impact their bioavailability. In this review, the major food matrix effects influencing the bioavailability of oil-soluble vitamins are highlighted: oil content, oil composition, particle size, interfacial properties, and food additives. Droplet size and aggregation state in the human gut impact vitamin bioavailability by modulating lipid digestion, vitamin release, and vitamin solubilization. Vitamins in small isolated oil droplets typically have a higher bioavailability than those in large or aggregated ones. Emulsifiers, stabilizers, or texture modifiers can therefore affect bioavailability by influencing droplet size or aggregation. The dimensions of the hydrophobic domains in mixed micelles depends on lipid type: if the domains are too small, vitamin bioavailability is low. Overall, this review highlights the importance of carefully designing food matrices to improve vitamin bioavailability.

Factors affecting the fate of β-carotene in the human gastrointestinal tract: A narrative review

Carotenoids and their metabolites play crucial roles in human health such as in immunity, cell differentiation, embryonic development, maintenance of plasma membrane integrity, and gastrointestinal functions, in addition to counteracting night blindness and other eye-related diseases. However, carotenoid bioavailability is highly variable and often low. The bioavailability of β-carotene, among the most frequently consumed carotenoid from the diet, is determined by food matrix related factors such as carotenoid dose, its location in food the matrix, the physical state in food, the presence of other food compounds in the matrix such as dietary fiber, dietary lipids, other micronutrients present such as minerals, and food processing, influencing also the size of food particles, and the presence of absorption inhibitors (fat replacers and anti-obesity drugs) or enhancers (nano-/micro-formulations). However, also host-related factors such as physiochemical interactions by gastrointestinal secretions (enzyme and salts) and other host-related factors such as surgery, age, disease, obesity, and genetic variations have shown to play a role. This review contributes to the knowledge regarding factors affecting the bioavailability of β-carotene (food and host-relegated), as well as highlights in vitro models employed to evaluate β-carotene bioavailability aspects.

Newly formulated, protein quality-enhanced, extruded sorghum-, cowpea-, corn-, soya-, sugar- and oil-containing fortified-blended foods lead to adequate vitamin A and iron outcomes and improved growth compared with non-extruded CSB+ in rats

Corn and soyabean micronutrient-fortified-blended foods (FBF) are commonly used for food aid. Sorghum and cowpeas have been suggested as alternative commodities because they are drought tolerant, can be grown in many localities, and are not genetically modified. Change in formulation of blends may improve protein quality, vitamin A and Fe availability of FBF. The primary objective of this study was to compare protein efficiency, Fe and vitamin A availability of newly formulated extruded sorghum-, cowpea-, soya- and corn-based FBF, along with a current, non-extruded United States Agency for International Development (USAID) corn and soya blend FBF (CSB+). A second objective was to compare protein efficiency of whey protein concentrate (WPC) and soya protein isolate (SPI) containing FBF to determine whether WPC inclusion improved outcomes. Eight groups of growing rats (n 10) consumed two white and one red sorghum–cowpea (WSC1 + WPC, WSC2 + WPC, RSC + WPC), white sorghum–soya (WSS + WPC) and corn–soya (CSB14 + WPC) extruded WPC-containing FBF, an extruded white sorghum–cowpea with SPI (WSC1 + SPI), non-extruded CSB+, and American Institute of Nutrition (AIN)-93G, a weanling rat diet, for 4 weeks. There were no significant differences in protein efficiency, Fe or vitamin A outcomes between WPC FBF groups. The CSB+ group consumed significantly less food, gained significantly less weight, and had significantly lower energy efficiency, protein efficiency and length, compared with all other groups. Compared with WSC1 + WPC, the WSC1 + SPI FBF group had significantly lower energy efficiency, protein efficiency and weight gain. These results suggest that a variety of commodities can be used in the formulation of FBF, and that newly formulated extruded FBF are of better nutritional quality than non-extruded CSB+.

Carotenoid deposition in plant and animal foods and its impact on bioavailability

Over the past decades, an enormous body of literature dealing with the natural deposition of carotenoids in plant- and animal-based foods has accumulated. Prominent examples are the large solid-crystalline aggregates in carrots and tomatoes or the lipid-dissolved forms in dairy products and egg yolk. Latest research has identified lipid-dissolved forms in a rare number of plant foods, such as tangerine tomatoes and peach palm fruit (Bactris gasipaes Kunth). In addition, liquid-crystalline forms were assumed in so-called tubular chromoplasts of numerous fruits, e.g., in papaya, mango, and bell pepper. The bioavailability of carotenoids from fresh and processed foods strongly depends on their genuine deposition form, since their effective absorption to the human organism requires their liberation from the food matrix and subsequent solubilization into mixed micelles in the small intestine. Consequently, a broad overview about the natural array of carotenoid deposition forms should be helpful to better understand and modulate their bioavailability from foods. Furthermore, naturally highly bioavailable forms may provide biomimetic models for the improved formulation of carotenoids in food supplements. Therefore, this review paper presents scientific evidence from human intervention studies associating carotenoid deposition forms with their bioavailability, thus suggesting novel technological and dietary strategies for their enhanced absorption.

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 β-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.

Meeting the Vitamin A Requirement: The Efficacy and Importance of β-Carotene in Animal Species

Vitamin A is essential for life in all vertebrate animals. Vitamin A requirement can be met from dietary preformed vitamin A or provitamin A carotenoids, the most important of which is β-carotene. The metabolism of β-carotene, including its intestinal absorption, accumulation in tissues, and conversion to vitamin A, varies widely across animal species and determines the role that β-carotene plays in meeting vitamin A requirement. This review begins with a brief discussion of vitamin A, with an emphasis on species differences in metabolism. A more detailed discussion of β-carotene follows, with a focus on factors impacting bioavailability and its conversion to vitamin A. Finally, the literature on how animals utilize β-carotene is reviewed individually for several species and classes of animals. We conclude that β-carotene conversion to vitamin A is variable and dependent on a number of factors, which are important to consider in the formulation and assessment of diets. Omnivores and herbivores are more efficient at converting β-carotene to vitamin A than carnivores. Absorption and accumulation of β-carotene in tissues vary with species and are poorly understood. More comparative and mechanistic studies are required in this area to improve the understanding of β-carotene metabolism.

Effect of Thermal Treatment on the Antioxidant Activity and Content of Carotenoids and Phenolic Compounds of Cactus Pear Cladodes (Opuntia ficus-indica)

Cactus pears (Opuntia ficus-indica) are draught resistant plants originated in Mexico. Their flattened stem segments, called cladodes, have moisture, protein and fibre contents of 92, 1-2 and 4-6% respectively, and a pectin content in the range of 0.8-3.3% depending on the species. They also contain certain concentration of carotenoids which are of special interest because of their antioxidant activity. This work is aimed to identify and quantify the main carotenoids present in the stems and to evaluate the effect of thermal treatments on the antioxidant activity and concentration of carotenoids and phenolic compounds. The carotenoids -cryptoxanthin, -carotene and lutein were identified in the cladodes, the latter having the highest concentration. Thermal treatments increased the extractability of these pigments and the antioxidant activity was related to the carotenoids concentration. Total phenolic content decreased after the thermal treatments; however this result had little effect on the antioxidant activity. Mucilage present in the stems decreased the extractability of the carotenoids.

Effects of high-fat diet on neuronal damage, gliosis, inflammatory process and oxidative stress in the hippocampus induced by transient cerebral ischemia

In this study, we investigated the effects of a normal diet (ND) and high-fat diet (HFD) on delayed neuronal death in the gerbil hippocampal CA1 region after transient cerebral ischemia. In the HFD-fed gerbils, ischemia-induced hyperactivity was significantly increased and neuronal damage was represented more severely compared to the ND-fed gerbils. Ischemia-induced glial activation was accelerated in the HFD-fed gerbils. Cytokines including interleukin-2 and -4 were more sensitive in the hippocampal CA1 region of the HFD-fed gerbils after ischemia-reperfusion. Additionally, we found that decreased 4-HNE and SODs immunoreactivity and protein levels in the hippocampal CA1 region of the HFD-fed gerbils after ischemia-reperfusion. These results indicate that HFD may lead to the exacerbated effects on ischemia-induced neuronal death in the hippocampal CA1 region after ischemia-reperfusion. These effects of HFD may be associated with more accelerated activations of glial cells and imbalance of pro- and anti-inflammatory cytokines and/or antioxidants after transient cerebral ischemia.

Accelerated and exacerbated effects of high dietary fat on neuronal damage induced by transient cerebral ischemia in the gerbil septum

BACKGROUND

Obesity induced by high-fat diet (HFD) is one of the most widespread metabolic disorders in current society. However, there has been little research regarding the effects of HFD-induced obesity in the septa of animal models of cerebral ischemia. Therefore, in the present study, we investigated septal effects of HFD on neuronal damage and gliosis induced by transient cerebral ischemia.

METHODS

Body weight, blood glucose levels and serum lipid profiles levels were measured both in the normal diet (ND) and HFD-group. We also investigated the effects of ND and HFD on neuronal damage and gliosis in the septum after transient cerebral ischemia using immunohistochemistry.

RESULTS

The levels of blood glucose, serum triglyceride, and total cholesterol were significantly increased in the HFD-fed gerbils compared with the ND-fed gerbils, although body weight was not significantly changed after HFD feeding. In the ND-fed gerbils, ischemia-induced neuronal damage was found in the septohippocampal nucleus (SHN) of the septum 7 days after ischemia. In the HFD-fed gerbils, ischemia-induced neuronal damage in the SHN was much more severe compared with that of the ND-fed gerbils 4 and 7 days after ischemia. In addition, we found that ischemia-induced glial activation including astrocytes and microglia was accelerated and exacerbated in the HFD-fed gerbils compared with that in the ND-fed gerbils.

CONCLUSION

These results indicate that HFD can lead to much more severe effects in ischemia-induced neuronal damage/death in the septum after ischemia-reperfusion, and that it may be associated with accelerated change in glial activation.

Avocado consumption enhances human postprandial provitamin A absorption and conversion from a novel high-β-carotene tomato sauce and from carrots

Dietary lipids have been shown to increase bioavailability of provitamin A carotenoids from a single meal, but the effects of dietary lipids on conversion to vitamin A during absorption are essentially unknown. Based on previous animal studies, we hypothesized that the consumption of provitamin A carotenoids with dietary lipid would enhance conversion to vitamin A during absorption compared with the consumption of provitamin A carotenoids alone. Two separate sets of 12 healthy men and women were recruited for 2 randomized, 2-way crossover studies. One meal was served with fresh avocado (Persea americana Mill), cultivated variety Hass (delivering 23 g of lipid), and a second meal was served without avocado. In study 1, the source of provitamin A carotenoids was a tomato sauce made from a novel, high-β-carotene variety of tomatoes (delivering 33.7 mg of β-carotene). In study 2, the source of provitamin A carotenoids was raw carrots (delivering 27.3 mg of β-carotene and 18.7 mg of α-carotene). Postprandial blood samples were taken over 12 h, and provitamin A carotenoids and vitamin A were quantified in triglyceride-rich lipoprotein fractions to determine baseline-corrected area under the concentration-vs.-time curve. Consumption of lipid-rich avocado enhanced the absorption of β-carotene from study 1 by 2.4-fold (P < 0.0001). In study 2, the absorption of β-carotene and α-carotene increased by 6.6- and 4.8-fold, respectively (P < 0.0001 for both). Most notably, consumption of avocado enhanced the efficiency of conversion to vitamin A (as measured by retinyl esters) by 4.6-fold in study 1 (P < 0.0001) and 12.6-fold in study 2 (P = 0.0013). These observations highlight the importance of provitamin A carotenoid consumption with a lipid-rich food such as avocado for maximum absorption and conversion to vitamin A, especially in populations in which vitamin A deficiency is prevalent. This trial was registered at clinicaltrials.gov as NCT01432210.

Importance of β,β-carotene 15,15'-monooxygenase 1 (BCMO1) and β,β-carotene 9',10'-dioxygenase 2 (BCDO2) in nutrition and health

In humans, varying amounts of absorbed β-carotene are oxidatively cleaved by the enzyme β,β-carotene 15,15'-monooxygenase 1 (BCMO1) into two molecules of all-trans-retinal. The other carotenoid cleavage enzyme β,β-carotene 9',10'-dioxygenase (BCDO2) cleaves β-carotene at the 9',10' double bond forming β-apo-10'-carotenal and β-ionone. Although the contribution of BCDO2 to vitamin A formation has long been debated, BCMO1 is currently considered the key enzyme for retinoid metabolism. Furthermore, BCMO1 has limited enzyme activity towards carotenoids other than provitamin A carotenoids, whereas BCDO2 exhibits a broader specificity. Both enzymes are located at different sites within the cell, with BCMO1 being a cytosolic protein and BCDO2 being located in the mitochondria. Expression of BCMO1 in tissues other than the intestine has recently revealed its function for tissue-specific retinoid metabolism with importance in embryogenesis and lipid metabolism. On the other hand, biological activity of BCDO2 metabolites has been shown to be important in protecting against carotenoid-induced mitochondrial dysfunction. Single-nucleotide polymorphisms (SNPs) such as R267S and A379V in BCMO1 can partly explain inter-individual variations observed in carotenoid metabolism. Advancing knowledge about the physiological role of these two enzymes will contribute to understanding the importance of carotenoids in health and disease.

Yellow maize with high β-carotene is an effective source of vitamin A in healthy Zimbabwean men

BACKGROUND

The bioconversion efficiency of yellow maize β-carotene to retinol in humans is unknown.

OBJECTIVE

The objective of this study was to determine the vitamin A value of yellow maize β-carotene in humans.

DESIGN

High β-carotene-containing yellow maize was grown in a hydroponic medium with 23 atom% (2)H(2)O during grain development. Yellow maize β-carotene showed the highest abundance of enrichment as [(2)H(9)]β-carotene. Eight healthy Zimbabwean men volunteered for the study. On day 1 after a fasting blood draw, subjects consumed 300 g yellow maize porridge containing 1.2 mg β-carotene, 20 g butter, and a 0.5-g corn oil capsule. On day 8, fasting blood was drawn, and subjects consumed 1 mg [(13)C(10)]retinyl acetate in a 0.5-g corn oil capsule and 300 g white maize porridge with 20 g butter. Thirty-six blood samples were collected from each subject over 36 d. Concentrations and enrichments of retinol and β-carotene in labeled doses and serum were determined with the use of HPLC, gas chromatography-mass spectrometry, and liquid chromatography-mass spectrometry.

RESULTS

The area under the curve (AUC) of retinol from 1.2 mg yellow maize β-carotene was 72.9 nmol · d, and the AUC of retinol from 1 mg retinyl acetate (13)C(10) was 161.1 nmol · d. The conversion factor of yellow maize β-carotene to retinol by weight was 3.2 ± 1.5 to 1.

CONCLUSION

In 8 healthy Zimbabwean men, 300 g cooked yellow maize containing 1.2 mg β-carotene that was consumed with 20.5 g fat showed the same vitamin A activity as 0.38 mg retinol and provided 40-50% of the adult vitamin A Recommended Dietary Allowance. This trial was registered at clinicaltrials.gov as NCT00636038.

Development of novel microsatellite DNA markers by cross-amplification and analysis of genetic variation in gerbils

The objectives of this study are to establish microsatellite loci for the Mongolian gerbil based on mouse microsatellite DNA sequences and to investigate genetic variation in the laboratory gerbil (Capital Medical University, CMU) and 2 wild gerbil populations (from Yin Chuan city [YIN] and the Hohehot Municipality [HOH]). In total, 536 mouse microsatellite markers were chosen to identify polymorphic dinucleotide repeat loci in the gerbil by cross-amplification. Of these markers, 313 (58.39%) have been discretely amplified from the CMU laboratory gerbil and been sequenced. Of the 313 sequenced markers, 130 were confirmed as simple sequence repeat (SSR) loci in the gerbil. In total, 6 of those newly identified loci plus 6 identified in previous reports were used to estimate the genetic polymorphism for 30 laboratory gerbils and 54 wild gerbils (27 each of the HOH and YIN groups). A total of 29 alleles were observed in the 3 populations, and 11 of 12 loci (91.67%) are polymorphic markers. Nei's standard genetic distances of 0.0592 (CMU vs. HOH) and 0.1033 (CMU vs. YIN) were observed. The averages of observed versus expected heterozygosity are 0.5231/0.4008, 0.5051/0.3882, and 0.4825/0.3665 for the YIN, HOH, and CMU populations, respectively. These results show that cross-amplification using mouse microsatellite primers is an efficient way to identify gerbil SSR loci. By using these 12 selected markers, we have demonstrated that genetic variation level within the CMU population is higher than that has been reported previously and are comparable with the levels found in 2 wild populations.

Anthocyanins in purple-orange carrots (Daucus carota L.) do not influence the bioavailability of beta-carotene in young women

Purple carrots contain anthocyanins in addition to the provitamin A carotenoids in typical orange carrots. Simultaneous consumption of these phytochemicals in carrots may affect the bioavailability of carotenoids. The bioavailability of beta-carotene in humans was assessed from an acute feeding of orange (OC) and purple (PC) carrots with white (WC) as a control. Carrot smoothies were served to female subjects (n = 5, aged 21-26 years) for breakfast after 1 week on a low carotenoid diet and overnight fast. OC and PC smoothies were equalized to 10.3 mg of all-trans beta-carotene. Plasma beta-carotene was measured for 144 h following treatments. Peak plasma concentrations of OC and PC treatments did not differ. The PC treatment 0-144 h area-under-the-curve for beta-carotene was 76% of the OC treatment (P < 0.05). However, when the first 24 h were compared, OC and PC treatments did not differ, suggesting that anthocyanins in purple carrots do not affect the absorption of beta-carotene postprandially.

In vitro bioaccessibility of beta-carotene in orange fleshed sweet potato (Ipomoea batatas, Lam.)

Substitution of white with orange fleshed varieties of sweet potatoes (OFSP) was recently shown to alleviate vitamin A deficiency in children in Africa. However, the relationship between beta-carotene (BC) content of different cultivars of OFSP and its bioavailability is unknown. Here, we used the three phase (oral, gastric and small intestinal) in vitro digestion procedure to examine the bioaccessibility of BC from eight cultivars of boiled OFSP. All-trans BC (all-E-BC) was the only isomer of BC detected in raw roots for cultivars of OFSP with amounts ranging from 112 to 281 microg/g. Boiling OFSP decreased all-E-BC content by 11% with conversion to 13-cis BC (13-Z-BC). The efficiency of BC micellarization during simulated digestion of boiled OFSP was only 0.6-3%. Addition of soybean oil (2% vol/wt) to boiled OFSP prior to in vitro digestion more than doubled partitioning of all-E-BC in the micelle fraction for all cultivars. The relatively poor bioaccessibility of all-E-BC was not a limitation of the in vitro model as micellarization was proportional to amount of OFSP digested from 0.5 to 3.0 g and minimally altered by increasing bile salt content during small intestinal digestion. Moreover, micellarization of all-E-BC from boiled fresh OFSP and commercially processed OFSP was significantly less than from carrots processed identically. These results indicate the need for further efforts to elucidate the basis for relatively poor bioaccessibility of BC from OFSP.

Nutriomic analysis of fresh and processed fruit products. 2. During in vitro simultaneous molecular passages using Caco-2 cell monolayers

Many studies have used Caco-2 cell monolayers as human intestinal absorption models. However, only a few studied digested foods, instead of pure standard compounds. Moreover, beneficial and nutritional molecules (nutriome) have not been investigated simultaneously. The present study explored nutriome passages from digest solution of fresh, dried, and juiced tomato, mango, and papaya using Caco-2 cell monolayers in apical-->basolateral directions. A validation method using complementary TEER and P(app) values or internal standard caffeine is recommended because physiologically passive diffusion is unlikely to happen. Sugars were transported into basolateral sides, resulting in potential glucose equivalent bioavailability of 2.26-75 mg h(-1)/100 g (WB). Using sugar passage rates (DB) of juices as 100% references, the rate order was tomato (49.8% dried; 89.5% fresh) > mango (56.8% dried; 22.8% fresh) > papaya (18.7% dried; 36.7% fresh). Major indications that phytochemical absorption does not occur in the small intestine were obtained from the bioassay condition selected. Apical organic acid levels decreased, which occasionally were transported into basolateral sides, whereas the disappearances of apical carotenoids and phenolics were not. Pectin substances were predicted to be responsible for the disappearances of bioactive compounds in those pectin-rich fruits. Further investigations on the role of pectin substances in intestinal passages are recommended.

Sweet potato beta-carotene bioefficacy is enhanced by dietary fat and not reduced by soluble fiber intake in Mongolian gerbils

Orange-fleshed sweet potato (OFSP) is an important source of beta-carotene (betaC). Provitamin A bioefficacy from plant foods is influenced by dietary fat and fiber. We fed 3% OFSP powder diets with varying amounts of fat and soluble fiber to vitamin A (VA)-depleted Mongolian gerbils (n = 85) for 3 wk (8 groups, n = 10/group; control, n = 9) following a baseline kill (n = 6). OFSP diets differing in fat (3, 6, and 12%) contained 0.24% soluble fiber. Two additional 3% OFSP diets contained 6% fat and 3 or 9% white-fleshed sweet potato (WFSP) powder with soluble fiber contents of 0.42 and 0.80%, respectively. Control, VA-, and betaC-supplemented groups were included. Simulated digestion experiments compared the bioaccessibility of betaC from boiled vs. oil stir-fried OFSP. All OFSP diets maintained VA status and 12% fat and WFSP-added diets improved VA status above baseline (P < 0.05). Bioefficacy, as bioconversion factors, in gerbils fed 12% fat (3.5 +/- 1.4 microg betaC:1 microg VA) was improved over the 3% fat and betaC groups (6.5 +/- 3.7 and 6.7 +/- 3.7 microg betaC:1 microg VA, respectively) (P < 0.05) but did not differ from WFSP-added groups or the 6% fat group with no WFSP. Stir-frying doubled the efficiency of betaC incorporation into micelles during small intestinal digestion in support of the stimulatory effect of dietary fat on bioefficacy in vivo. Soluble fiber intake derived from WFSP did not influence bioefficacy. Replacing WFSP with OFSP will affect VA status if adopted by target groups.

Intestinal absorption of dietary carotenoids

The assessment of carotenoid bioavailability has long been hampered by the limited knowledge of their absorption mechanisms. However, recent reports have elucidated important aspects of carotenoid digestion and absorption. Disruption of food matrix and increasing amounts of fat seem to enhance the absorption of carotenes to a larger extent than that of xanthophylls. Comparing different carotenoid species, xanthophylls seem to be more easily released from the food matrix and more efficiently micellized than the carotenes. On the other hand, carotenes are more efficiently taken up by the enterocytes. However, carotenoid emulsification and micellization steps are largely affected by the food matrix and dietary components, being the main determinant of carotenoid bioavailability from foodstuffs. Although the intestinal uptake of carotenoids has been thought to occur by simple diffusion, recent studies reported the existence of receptor-mediated transport of carotenoids in enterocytes. Comparisons between the intestinal absorption of a wide array of carotenoids would be useful to elucidate the absorption mechanism of each carotenoid species, in view of the recent indications that intestinal carotenoid uptake may involve the scavenger receptor class B type I and possibly other epithelial transporters. The unraveling of the whole mechanism underlying the absorption of carotenoids will be the challenge for future studies.

Bioavailability of beta-carotene (betaC) from purple carrots is the same as typical orange carrots while high-betaC carrots increase betaC stores in Mongolian gerbils (Meriones unguiculatus)

Vitamin A (VA) deficiency is a worldwide public health problem. Biofortifying existing sources of beta-carotene (betaC) and increasing dietary betaC could help combat the issue. Two studies were performed to investigate the relative betaC bioavailability of a betaC supplement to purple, high-betaC orange, and typical orange carrots using Mongolian gerbils (Meriones unguiculatus). In study 1, which used a traditional bioavailability design, gerbils (n 32) received a diet containing orange, purple, or white carrot powder, or white carrot powder +a betaC supplement. In study 2, which included betaC-biofortified carrots, gerbils (n 39) received orange, high-betaC orange, purple, or white carrot powder in their diet. Both studies lasted 21 d and the gerbils were killed to determine the effect of carrot type or supplement on serum and liver betaC, alpha-carotene, and VA concentrations. Liver stores of betaC or VA in the gerbils did not differ between orange and purple carrot diets when equal amounts of betaC from each of the diets were consumed (P>0.05). Both the orange and purple carrot diet resulted in higher liver VA compared with the supplement (P<0.05). High-betaC carrots resulted in more than 2-fold higher betaC and 1.1 times greater VA liver stores compared with typical orange carrots (P<0.05). These results suggest that high-betaC carrots may be an alternative source of VA to typical carrots in areas of VA deficiency. Second, phenolics including anthocyanins and phenolic acids in purple carrot do not interfere with the bioavailability of betaC from purple carrots.

Vitamin A prevents high fat diet-induced ACF development and modifies the pattern of expression of peroxisome proliferator and retinoic acid receptor m-RNA

Some dietary compounds, among them fats, are modulators of colon cancer risk. This study reports the modulating effects of n-6, with or without vitamin A, on promotion of colon preneoplasic lesions induced by 1,2-dimethylhydrazine (DMH) and on the expression of nuclear receptors (PPARgamma, RXRalpha, and RARbeta). One group of male Fisher rats was fed a basic diet (5% safflower oil) and two groups were fed a high-fat diet (HFD, 25% safflower oil). Of these, one was supplemented with 200 IU vitamin A for 5 mo. The safflower oil contained polyunsaturated fatty acids, mainly linoleic acid (73%). The data showed an increasing effect of safflower oil-enriched diet on aberrant crypt foci occurrence and multiplicity. This effect was impaired by vitamin A supplementation. In addition, an HFD-related up-regulation of PPARgamma and a concomitant down-regulation of RARbeta mRNA expression were observed with or without chemical initiation and were prevented by vitamin A. Moreover, when treated with DMH, HFD rats exhibited a dramatically decreased expression of RXRalpha mRNA (-49%). It was hypothesized that HFD, leading to hyperexpression of PPARgamma, would produce an alteration of retinoic acid signaling and, in this way, create a background modulating colon cancer risk.

Dietary vitamin A intakes of Filipino elders with adequate or low liver vitamin A concentrations as assessed by the deuterated-retinol-dilution method: implications for dietary requirements

BACKGROUND

The vitamin A requirements of elderly humans have not been studied.

OBJECTIVE

In a cross-sectional study of 60-88-y-old men (n = 31) and women (n = 31) in rural Philippines, we assessed the dietary intakes of elders with adequate (> or = 0.07 micromol/g) or low (< 0.07 micromol/g) liver vitamin A concentrations to estimate vitamin A requirements for this age group.

DESIGN

Total-body vitamin A was assessed by the deuterated-retinol-dilution technique; liver vitamin A concentrations were assessed by assuming that liver weight is 2.4% of body weight and that, in this marginally nourished population, 70% of total-body vitamin A is in the liver; serum retinol was measured by HPLC; and dietary intakes were assessed with 3 nonconsecutive 24-h dietary recalls. The mean vitamin A intake + 2 SDs of subjects with adequate liver vitamin A concentrations was used to estimate an acceptable or sufficient vitamin A intake value for elders.

RESULTS

The mean (+/- SD) vitamin A intakes of the men and women with adequate vitamin A in liver were 135 +/- 86 and 134 +/- 104 microg retinol activity equivalents (RAE)/d, respectively; intakes of the men and women with low vitamin A in liver were 75 +/- 53 and 60 +/- 27 microg RAE/d, respectively. Total-body vitamin A or liver vitamin A but not serum retinol correlated with dietary RAE, preformed vitamin A, beta-carotene, fat, and protein. An estimated acceptable or sufficient dietary vitamin A intake associated with adequate liver vitamin A concentrations in elders is 6.45 microg RAE/kg body wt; for a reference 76-kg man and a 61-kg woman, these values are approximately 500 and 400 microg RAE/d, respectively.

CONCLUSION

The dietary vitamin A intakes of elders with adequate or low liver vitamin A concentrations as estimated by use of the deuterated-retinol-dilution technique are useful for assessing vitamin A requirements.

Bioavailability of all-trans and cis-isomers of lycopene

Lycopene, the predominant carotenoid in tomatoes, is among the major carotenoids in serum and tissues of Americans. Although about 90% of the lycopene in dietary sources is found in the linear, all-trans conformation, human tissues contain mainly cis-isomers. Several research groups have suggested that cis-isomers of lycopene are better absorbed than the all-trans form because of the shorter length of the cis-isomer, the greater solubility of cis-isomers in mixed micelles, and/or as a result of the lower tendency of cis-isomers to aggregate. Work with ferrets, a species that absorbs carotenoids intact, has demonstrated that whereas a lycopene dose, stomach, and intestinal contents contained 6-18% cis-lycopene, the mesenteric lymph secretions contained 77%-cis isomers. The ferret studies support the hypotheses that cis-isomers are substantially more bioavailable then all-trans lycopene. In vitro studies suggest that cis-isomers are more soluble in bile acid micelles and may be preferentially incorporated into chylomicrons. The implications of these findings are not yet clear. Rats appear to accumulate lycopene in tissues within the ranges reported for humans, suggesting that they can be used to study effects of lycopene isomers on disease processes. Investigations are underway to determine whether there are biological differences between all-trans and various cis-isomers of lycopene regarding its antioxidant properties or other biological functions.

All-trans beta-carotene appears to be more bioavailable than 9-cis or 13-cis beta-carotene in gerbils given single oral doses of each isomer

Male gerbils (28 d old) were used to investigate the beta-carotene (betaC) isomer pattern in the intestine and tissues 6 h after ingestion of three betaC isomers. After a 49- to 52-d period of consuming the AIN93G diet without vitamin A (VA) or betaC, three groups (n = 7) were gavaged with crystalline all-trans (at)betaC, 9-cis (9c)betaC or 13-cis (13c)betaC solubilized in oil and a control group (n = 5) with oil alone. Total betaC per dose for gerbils in the atbetaC, 9cbetaC and 13cbetaC groups was 384 +/- 3, 391 +/- 2 and 386 +/- 2 nmol, respectively. After 6 h, gerbils were killed and serum, stomach contents, small intestinal contents (SIC), small intestinal mucosal scrapings (SIM) and liver were collected. betaC and VA in tissues were quantified using HPLC. Nonspecific isomerization of betaC occurred in the digestive tracts of gerbils administered betaC; the greatest effect was in the SIC of the 13cbetaC (50:50 cis:trans) and 9cbetaC (70:30 cis:trans) groups. Concentrations of total betaC in the SIM of gerbils administered at betaC were greater than those intubated with 9cbetaC and 13cbetaC (P < 0.05). Gerbils that received atbetaC had greater total betaC concentrations in serum (P < 0.05) and total betaC stores in liver (P < 0.01) compared with those administered 9cbetaC and 13cbetaC. Gerbils intubated with 9cbetaC had higher levels of total betaC in serum (P = 0.05) and liver (P < 0.01) compared with those intubated with 13cbetaC. Because of its preferential uptake, transport and tissue accumulation, atbetaC appears to be a more bioavailable isomer than 9cbetaC or 13cbetaC in gerbils.

Alpha- and beta-carotene from a commercial puree are more bioavailable to humans than from boiled-mashed carrots, as determined using an extrinsic stable isotope reference method

The extent to which processing affects the carotene or vitamin A value of foods is poorly understood. An extrinsic reference method was used to estimate the mass of carotenes and vitamin A derived from various preparations made from the same lot of carrots. Using a repeated-measures design, nine healthy adult subjects consumed test meals of either carrot puree (commercial baby food) or boiled-mashed carrots on separate days; six of the subjects also consumed a test meal of raw-grated carrot. Test meals supplied 34.7 micromol (18.6 mg) carrot beta-carotene (beta C), plus 6 micromol deuterium-labeled retinyl acetate (d(4)-RA) in oil solution. Baseline-adjusted carotene and retinyl ester (R-ester) area-under-curve (AUC) responses in the triacylglycerol-rich lipoprotein (TRL) fraction (0-8.5 h) were determined using HPLC and gas chromatography-mass spectrometry. The masses of absorbed beta C, alpha-carotene (alpha C) and R-ester were estimated by comparing their AUC values with that of deuterium-labeled retinyl ester (d(4)-R-ester), assuming the latter represented 80% of the d(4)-RA reference dose. Absorption of beta C and alpha C was approximately twofold greater from carrot puree than from boiled-mashed carrots, whereas the retinol yield was only marginally (P = 0.11) influenced by treatment. Carotene and R-ester absorption from raw-grated carrot was intermediate to, and did not differ significantly from the cooked preparations. The vitamin A yield (puree, 0.53 mg; boiled-mashed, 0.44 mg) of cooked carrot containing 18.6 mg beta C was substantially less than that predicted by current convention and limited primarily by intestinal carotene uptake. Processing can therefore significantly improve bioavailability of carrot carotenes, and in some cases influence the carotene value more than the intrinsic vitamin A value.