Dietary vitamin A has both chronic and acute effects on vitamin A indices in lactating rats and their offspring

To further investigate the effect of dietary vitamin A (VA) intake on milk VA concentrations and pup VA status, female rats were fed 2 concentrations of VA [0 (n = 9) or 50 micromol/kg diet (n = 10)] during pregnancy and lactation. Plasma retinol concentrations were significantly higher (30-40%) during lactation than before pregnancy or after weaning but were not influenced by dietary VA. In rats fed VA, VA concentrations during lactation were significantly higher in milk (1.5-3 times), mammary tissue (>100%), liver (4 times), pup plasma (20-40%), and pup liver (1.1-6.7 times). In Expt. 2, when VA intake was switched on d 7 of lactation from 0 to 50 micromol/kg, milk VA concentrations (2.24 +/- 0.42 micromol/L; mean +/- SD, n = 6) increased significantly (1.7 times) by d 9 to the same level as in rats administered 50 micromol/kg (6.04 +/- 0.60 micromol/L; n = 6). When VA was removed from the diet on d 7, concentrations declined significantly (by 50%) and by d 11 were the same as those in rats given 0 micromol/kg. We conclude that the rapid effect of changes in dietary VA intake are attributable to changes in the delivery of chylomicron VA to mammary tissue and milk.     

Vitamin A during lactation: relationship of maternal diet to milk vitamin A content and to the vitamin A status of lactating rats and their pups

We have investigated the effects of maternal vitamin A intake during pregnancy and lactation or during lactation alone on the concentration of vitamin A in rat's milk and on vitamin A levels in plasma and liver of dams and their pups. Groups of Sprague-Dawley rats were fed diets having either a high vitamin A content [15 retinol equivalents (R.E.)/g diet] or a low vitamin A content (0.6 R.E./g) for 42 d, including 7-8 d prior to pregnancy, pregnancy, and for 14 d of lactation. The concentration of vitamin A in milk on d 14 of lactation was significantly greater on the high vitamin A diets [114 +/- 16 micrograms/dl (mean +/- SEM; n = 8) versus 52 +/- 7.3 micrograms/dl (n = 11), P less than 0.005]. However, milk vitamin A concentration on d 1 of lactation did not vary with maternal vitamin A intake during pregnancy. In a second study in which supplementation with vitamin A (30 R.E./g diet) was begun on d 1 postpartum, the milk vitamin A content increased progressively with duration of lactation. Maternal plasma vitamin A concentrations did not differ between rats fed the higher or lower vitamin A diets. However, liver vitamin A concentrations both of dams and of their 14-d-old pups were significantly higher when dams were fed the higher vitamin A diets during pregnancy and/or lactation. The results of these studies indicate that the transfer of vitamin A from mother to offspring by milk and the vitamin A status of dams and their suckling neonates is influenced by maternal vitamin A intake during lactation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Vitamin A intake affects the contribution of chylomicrons vs. retinol-binding protein to milk vitamin A in lactating rats

To investigate the influence of vitamin A intake on the contribution of chylomicrons vs. holo retinol-binding protein to milk vitamin A, female rats were fed diets containing either 10 (n = 6) or 50 micromol vitamin A/kg body (n = 4) during pregnancy and through d 13 of lactation. [3H]Vitamin A was incorporated into each diet beginning on d 6 of lactation. Vitamin A concentrations on d 13 were significantly higher in dam liver (x 3), pup liver (x 2.6), milk (x 2.5) and mammary tissue (x 1.3) in rats consuming the higher level of vitamin A. In both groups, vitamin A specific activities in plasma and milk reached apparent plateaus by 2.33 d after addition of [3H]vitamin A to the diets. Vitamin A specific activity in milk was higher than in plasma at all times in both groups. The estimated minimum contribution of chylomicrons to milk vitamin A was 32 +/- 3% in rats fed the lower level of vitamin A vs. 52 +/- 10% at the higher level (P = 0.014). We concluded that dietary vitamin A, like triglycerides, may be directed to mammary tissue during lactation for preferential secretion into milk; thus, increasing vitamin A intakes will increase the contribution of dietary vitamin A to milk. In contrast to milk, mammary tissue vitamin A turns over very slowly.     

Vitamin A concentrations in piglet extrahepatic tissues respond differently ten days after vitamin A treatment

Periodic supplementation to infants and young children is encouraged in developing countries by the WHO. We investigated vitamin A (VA) in extrahepatic tissues of piglets after supplementation with retinyl acetate to determine long-term storage. 3, 4-Didehydroretinyl acetate (DRA) as a tracer was used to evaluate uptake from chylomicra in 4 h. Sows were fed a VA-depleted diet throughout pregnancy and lactation. Male castrated piglets (n = 28, 11.6 +/- 0.5 d) from these sows were weaned onto a VA-free diet for 1 wk, assigned to 4 groups, and dosed orally with 0, 26.2, 52.4, or 105 micromol VA. After 10 d, 5.3 micromol DRA was administered to determine short-term uptake of 3, 4-didehydroretinol (DR). Four hours later, piglets were killed; adrenal glands, kidney, lung, and spleen were collected and analyzed for retinol and DR. Retinol concentrations of kidney and adrenal gland were higher than control, but treated groups did not differ. Retinol concentration was highest in kidney (1.70-2.52 nmol/g), followed by adrenal gland (0.30-0.48 nmol/g), lung (0.15-0.21 nmol/g), and spleen (0.11-0.15 nmol/g). Total retinol in kidney and spleen was different among the groups (P < 0.05). Unesterified retinol was the major VA form; the percent retinol of total VA was lowest in adrenal glands. DR did not differ among the groups. In 4 h, the minimum estimated chylomicron contribution to tissue DR was 63-280% higher than the maximum DR exposure from retinol-binding protein. Constant dietary intake may be important in maintaining VA concentrations in extrahepatic tissues.     

Kinetic analysis shows that iron deficiency decreases liver vitamin A mobilization in rats

In view of evidence that nutritional status of iron and vitamin A may affect the other nutrient's metabolism, we used model-based compartmental analysis to examine effects of iron deficiency on whole-body vitamin A dynamics in rats. Weanling male Sprague-Dawley rats were fed the AIN93G diet with 2.5 nmol retinyl palmitate/g and either 45 [control (CN)] or 4 microg/g Fe [iron-deficient (ID)] for 8 wk. ID rats consumed food ad libitum; CN rats were food-restricted so that their body weights were the same as ID rats. Two rats/group were killed; liver vitamin A was determined and used for vitamin A balance calculations. [(3)H]Retinol-labeled plasma was administered intravenously to remaining rats, and 27 serial blood samples were collected for 7 wk. At killing, plasma vitamin A was 0.52+/-0.12 (ID, n = 5) vs. 1.34+/-0.12 micromol/L (CN, n = 6; P<0.001), and liver vitamin A was 809+/-94 (ID) vs. 112+/-24 nmol (CN, P<0.001). Plasma tracer data were fit to a three- or four-compartment model using the Simulation, Analysis and Modeling computer program and kinetic parameters were calculated. Vitamin A transfer rate between the retinyl ester storage pool [14+/-3 (ID) vs. 24+/-4 nmol/d (CN), P<0.05] and plasma was lower in ID rats. Vitamin A remained longer in the body [44+/-11 (ID) vs. 22+/-3 d (CN), P<0.05]. Adjusted mean disposal rate was lower in ID (10.0) than CN rats (19.9 nmol/d), as was estimated vitamin A absorption efficiency [58% (ID) vs. 76% (CN)]. Our results suggest that iron deficiency inhibits mobilization of vitamin A stores and may decrease the absorption and irreversible utilization of vitamin A.     

Zinc transporters in the rat mammary gland respond to marginal zinc and vitamin A intakes during lactation

Marginal intake of zinc and vitamin A is common during lactation and a deficiency of one micronutrient can result in a secondary deficiency of the other. However, the resistance of milk zinc (Zn) concentration to changes in dietary Zn or vitamin A indicates tight regulation of mammary gland Zn transport. Although several mammalian proteins have been identified and implicated in Zn transport, the mechanisms responsible for mammary gland Zn transport and their regulation by dietary Zn and vitamin A are unknown. In this study, we identified mammary gland Zn transporters and determined effects of marginal Zn and vitamin A intakes on their levels. Rats were fed a control [25 mg Zn/kg, 4 retinol equivalents (RE)/g], a low Zn (10 mg Zn/kg), a low vitamin A (0.4 RE/g), or a low Zn (10 mg Zn/kg) and vitamin A (0.4 RE/g) diet throughout lactation. ZnT-1, ZnT-2 and ZnT-4 were identified in the mammary gland and localized to the serosal membrane (ZnT-1) or intracellularly (ZnT-2 and ZnT-4) by immunostaining. Rats fed a low Zn or low vitamin A diet had lower ZnT-1 protein and higher ZnT-4 mRNA expression and protein levels compared with controls. There was a significant interaction between dietary Zn and vitamin A on zinc transporter mRNA expression and protein levels. Although total mammary gland Zn was not affected, mammary gland metallothionein levels were lower in rats fed low Zn and higher in rats fed low vitamin A, suggesting different mechanisms regulating zinc transporter levels. These results indicate that milk Zn level is maintained through coordinated regulation of mammary gland zinc transporters and documents an effect of vitamin A on zinc homeostasis at the molecular level during lactation.     

Low intensity exercise and varying proportions of dietary glucose and fat modify milk and mammary gland compositions and pup growth.

Exercise during pregnancy or lactation may create a competition for glucose between the exercising muscle and either the developing fetus or the lactating mammary gland. To test these two hypotheses, pregnant rats were randomly assigned to isoenergetic diets with varying levels of glucose (20, 40 or 60% by weight) and fat (30, 22 or 14%, respectively, by weight) and were rested (R) or exercised (E) on a motorized treadmill at 20 m/min, 60 min/d (low intensity), 7 d/wk throughout pregnancy and lactation. Main effects and selected interactions of diet and exercise during pregnancy and diet, exercise and litter size during lactation were tested using 3 x 2 and 3 x 2 x 2 factorial designs, respectively. Neither diet nor exercise affected pregnancy outcomes. In contrast, during lactation, milk and mammary gland compositions and pup growth were altered. Exercise produced higher milk protein concentrations (40% glucose diet) and lower milk lactose concentrations (20% glucose diet). Exercise also lowered mammary gland fat content and produced higher milk fat concentrations. The 60% glucose diet resulted in the highest milk fat concentrations, but pups of dams fed the 40% diet were heavier on lactation d 15 than pups of dams fed the 60% diet. Taken together, these results support the claim of decreased availability of glucose to the mammary gland for lactose synthesis during chronic low intensity exercise. Additionally, the best lactation performance was not supported by a high carbohydrate (60% glucose), lower fat (14%) intake. A more moderate carbohydrate (40% glucose), higher fat (22%) intake promoted greater pup weights at weaning, suggesting an overlooked role for macronutrient composition in optimizing lactation performance.     

Wheat gluten during pregnancy and lactation: effects on mammary gland development and pup viability

Diets containing 13% protein supplied by wheat gluten (WG), wheat gluten + lysine + threonine (WGLT), or casein + methionine (CM) were fed to pregnant rats from conception through day 15 of lactation. A crossover design was used with combinations of WG, WGLT, and CM during pregnancy and lactation. Out of six dams fed WG during both pregnancy and lactation and nursing a total of 48 pups on day 1 of lactation, only two pups were still alive on day 15 of lactation. In contrast, CM dams still were nursing 47 pups at this time. Differences in the weight and composition of mammary tissue were directionally similar to and consistent with pup viability. The data obtained confirm the importance of protein quality in the lactation diet and also demonstrate that deficits in mammary gland development occurring during pregnancy may not necessarily be overcome by a nutritionally adequate diet consumed during lactation.     

Carotenoid-biofortified maize maintains adequate vitamin a status in Mongolian gerbils

Efforts to biofortify maize with provitamin A carotenoids have been successful, but the impact on vitamin A (VA) status has not been determined. We conducted two studies that investigated the bioefficacy of provitamin A carotenoids from maize and compared maize percentage and carotenoid concentrations on VA status in VA-depleted Mongolian gerbils (Meriones unguiculatus). Gerbils (n = 40/study) were fed a white maize diet 4 wk prior to treatment. In study 1, treatments (n = 10/group) included oil control, 60% high-beta-carotene maize, and beta-carotene or VA supplements (matched to high-beta-carotene maize). In study 2, gerbils were fed 30 or 60% orange or yellow maize diets. Gerbils were killed after 4 wk. In study 1, liver VA concentrations, compared with the high-beta-carotene maize group (0.25 +/- 0.15 micromol/g), were higher in the VA group (0.56 +/- 0.15 micromol/g, P < 0.05), lower in the control (0.10 +/- 0.04 micromol/g, P < 0.05), and did not differ in the beta-carotene group (0.25 +/- 0.08 micromol/g). Bioconversion was approximately 3 microg beta-carotene to 1 mug retinol (1.5 mol beta-carotene to 1 mol retinol). The liver beta-carotene content was greater in the high-beta-carotene maize group (26.4 +/- 6.0 nmol) than in the beta-carotene supplement group (14.1 +/- 6.0 nmol; P < 0.05). In study 2, the gerbils' VA status improved with increasing dietary beta-carotene. Liver VA in gerbils fed orange maize was greater than in those fed yellow maize, regardless of maize percentage (P < 0.05). Biofortified maize adequately maintained VA status in Mongolian gerbils and was as efficacious as beta-carotene supplementation. In populations consuming maize as a staple food, using orange instead of white maize could dramatically affect VA status.     

Effect of dietary protein and energy on protein synthesis during lactation in rats

A series of experiments was carried out in which effects of dietary protein and energy on protein synthesis during lactation were evaluated. Purified diets were fed to female rats from conception until d 15 of lactation. Protein supplied by wheat gluten, gluten + lysine + threonine or casein + methionine was fed at 20 or 25% in the diet. Protein synthesis in mammary gland and liver was measured with a large dose of L-[4-3H]phenylalanine. As lactation proceeded, protein absolute synthesis rates (ASRs) in casein-fed dams increased from 1056 to 2246 mg/d in mammary gland but remained unchanged in liver. In contrast, ASRs in wheat gluten-fed dams remained unchanged in both tissues. Feeding a protein-free diet or starving dams for 3 d reduced ASR in mammary gland 59 and 72%, respectively, when measured on d 15 of lactation. The corresponding reductions in liver ASR were 41 and 46%. A 20% restriction of dietary energy at a constant protein intake reduced protein synthesis in mammary glands 34, 55 and 28% in dams fed gluten, gluten + lysine + threonine or casein, respectively. In summary, protein synthesis during lactation was reduced less in liver than in mammary gland in response to dietary restriction of protein or energy.     

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. DESIGN: Lactating sows were given a high (2.1 mmol), low (1.05 mmol), or control (0 mmol) dose of retinyl acetate in oil (n=3 sows per treatment). Piglets nursed for 3 or 14 d, consumed a vitamin A-free diet for the next 4 d, and were then killed. Liver and serum samples were analyzed for vitamin A. RESULTS: After 3 d, piglets of the control, low-dose, and high-dose sows had different (P=0.034) hepatic vitamin A concentrations, ie, 0.078+/-0.004, 0.14+/-0.053, and 0.13+/-0.026 micromol/g, respectively. Liver vitamin A concentrations on day 18 were 0.069+/-0.004, 0.14+/-0.044, and 0.11+/-0.026 micromol/g in the control, low-dose, and high-dose piglets, respectively (P=0.017). Liver vitamin A concentrations in piglets of the low- and high-dose sows were not significantly different (day 3: P=0.97; day 18: P=0.59). Serum retinol concentrations were higher (P=0.02) at early kill (0.95+/-0.22 micromol/L) than at late kill (0.76+/-0.24 micromol/L) but were not significantly different between groups. CONCLUSIONS: Maternal vitamin A supplementation enhances liver vitamin A concentrations in offspring. Larger one-time doses are not more effective than are smaller doses. Additional research is needed to determine the most effective maternal dosing regimens for improving infant vitamin A status.     

Marginal maternal Zn intake in rats alters mammary gland Cu transporter levels and milk Cu concentration and affects neonatal Cu metabolism

Marginal zinc intake is common and leaves women particularly vulnerable to Zn deficiency due to increased demand for Zn as a consequence of reproduction. Zn deficiency during pregnancy and lactation has been associated with secondary affects on copper metabolism in the offspring; however, the underlying mechanisms are unknown. The effects of marginal maternal Zn intake on maternal and neonatal Cu metabolism were determined in rats. Plasma, milk and tissue Cu and Zn concentrations and plasma and milk ceruloplasmin (Cp) activity were measured in dams fed a control (CON, 25 mg Zn/kg diet) or a marginal Zn diet (ZD, 10 mg Zn/kg diet) and their suckling pups. There was no effect on maternal tissue Cu or Zn or milk Zn concentration; however, plasma Cp activity was higher in dams fed ZD, suggesting that Cp activity may be a useful marker for identifying marginal Zn status. Rats fed ZD had high mammary gland Ctr1, Atp7A and Atp7B levels, milk Cp activity and Cu concentration. Immunostaining and differential centrifugation indicated that ZD also altered Ctr1 and Atp7A localization in the mammary gland. Pups from dams fed ZD had higher small intestine Cu and lower plasma Cu than CON pups. These results suggest that marginal maternal Zn intake during pregnancy and lactation increase mammary gland Cu transporter levels and alter their localization, resulting in high milk Cu levels, possibly in response to transiently elevated plasma Cu levels. The combination of high milk Cu concentration and immature neonatal Cu transport exposes the suckling neonate to excess Cu; however, whether this occurs in humans is not yet known.     

Twice the amount of alpha-carotene isolated from carrots is as effective as beta-carotene in maintaining the vitamin A status of Mongolian gerbils

The vitamin A (VA) value of carotenoids from fruits and vegetables is affected by many factors. This study determined the VA value of alpha-carotene isolated from carrots compared with beta-carotene and retinyl acetate supplements fed to Mongolian gerbils (Meriones unguiculatus). Gerbils (n = 38) were fed a VA-free diet for 4 wk. At baseline, 6 gerbils were killed to determine liver VA. Gerbils were divided into 3 treatment groups (n = 9/group) and given 35, 35, or 17.5 nmol retinyl acetate, alpha-carotene or beta-carotene, respectively, in 2 divided doses 5 h apart each day. The remaining 5 gerbils received oil vehicle. Gerbils were killed after 3 wk of supplementation. Serum samples and livers were collected and analyzed for VA. Liver extracts were subsequently saponified to quantify alpha-retinol. Serum retinol concentrations did not differ among the groups. Liver retinyl palmitate concentrations were significantly higher in the retinyl acetate treatment group (0.198 +/- 0.051 micromol/g; P < 0.05) than in all other groups. The alpha- and beta-carotene treatments resulted in similar retinyl palmitate concentrations, i.e., 0.110 +/- 0.026 and 0.109 +/- 0.051 micromol/g, respectively, which did not differ from the concentrations in gerbils killed at baseline (0.123 +/- 0.024 micromol/g). The oil group had significantly less retinyl palmitate (0.061 +/- 0.029 micromol/g; P < 0.05) than all other groups. alpha-Retinol was detected in livers of the alpha-carotene group (0.062 +/- 0.013 micromol/g). Thus, twice the amount of purified alpha-carotene maintained VA status as well as beta-carotene in VA-depleted gerbils. Conversion factors were approximately 5.5 microg alpha-carotene or approximately 2.8 mug beta-carotene to 1 microg retinol.     

Weekly vitamin A and iron supplementation during pregnancy increases vitamin A concentration of breast milk but not iron status in Indonesian lactating women

Studies on the effect of vitamin A and iron supplementation during pregnancy on maternal iron and vitamin A status postpartum are scarce. We investigated whether retinol and iron variables in breast milk and in serum postpartum were enhanced more with weekly vitamin A and iron supplementation during pregnancy than with weekly iron supplementation. During pregnancy, subjects were randomly allocated to two groups and received either (n = 88) a weekly supplement of iron (120 mg Fe as FeSO(4)) and folic acid (500 microg) or (n = 82) the same amount of iron and folic acid plus vitamin A [4800 retinol equivalents (RE)]. Transitional milk (4-7 d postpartum) had higher (P < 0.001) concentrations of retinol and iron than mature milk (3 mo postpartum). Compared with the weekly iron group, the weekly vitamin A and iron group had a greater (P < 0.05) concentration of retinol in transitional milk (as micromol/L) and in mature milk (as micromol/g fat). Although serum retinol concentrations approximately 4 mo postpartum did not differ significantly, the weekly vitamin A and iron group had significantly fewer (P < 0.01) subjects with serum retinol concentrations < or = 0.70 micromol/L than the weekly iron group. Iron status and concentrations of iron in transitional and mature milk did not differ between groups. We have shown that weekly vitamin A and iron supplementation during pregnancy enhanced concentrations of retinol in breast milk although not in serum by approximately 4 mo postpartum. However, no positive effects were observed on iron status and iron concentration in breast milk.     

Low arachidonic acid rather than alpha-tocopherol is responsible for the delayed postnatal development in offspring of rats fed fish oil instead of olive oil during pregnancy and lactation

This study was designed to compare in rats the effects of dietary fish oil and olive oil during pregnancy and lactation on offspring development, fatty acid profile and vitamin E concentration. From d 0 of pregnancy, female Sprague-Dawley rats were divided into two groups that were fed purified diets that differed only in their nonvitamin lipid components. One diet contained 10 g fish oil/100 g diet (FOD), whereas the other contained 10 g olive oil/100 g diet (OOD). At d 20 of gestation, maternal adipose tissue fatty acid profile did not differ between rats fed the two diets, whereas both maternal and fetal plasma and liver arachidonic acid (AA) contents were proportionally lower and eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid contents were higher in the FOD group than in the OOD group. alpha-Tocopherol concentration was lower in maternal and fetal plasma, liver and brain in the FOD group than in the OOD group. The postnatal increase in body weight and length was less and body and psychomotor maturation indices were delayed in pups from FOD-fed dams compared with those from OOD-fed dams. This difference was maintained when pups were cross-fostered at birth, with the delay in postnatal development present in the pups suckling dams fed FOD during lactation. At age 21 d, pups suckling dams fed FOD had lower AA and higher EPA and DHA concentrations in brain phospholipids. Although alpha-tocopherol in plasma and liver was lower in pups suckling dams fed FOD rather than OOD, brain alpha-tocopherol concentrations did not differ. Milk yield and milk alpha-tocopherol and AA concentrations were lower and EPA and DHA were higher in the milk of dams fed FOD compared with those fed OOD. Postnatal development indices and the proportion of plasma, liver and brain AA concentrations, although not plasma, liver and brain alpha-tocopherol concentrations, recovered to the values found in dams fed OOD when the FOD was supplemented with gamma-linolenic acid. However, postnatal development indices were not recovered when the FOD was supplemented with sufficient exogenous vitamin E to increase plasma and liver alpha-tocopherol concentrations above those in dams fed OOD. Thus, although feeding FOD during pregnancy and lactation decreases both alpha-tocopherol and AA concentrations, the latter deficiency rather than the former seems to be responsible for delayed postnatal development of rat pups.     

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.     

Evaluation of vitamin B-6 status and function of rats fed excess pyridoxine

We compared the vitamin B-6 status of 12-wk-old rats (n = 12) fed excess (1400 mg/kg diet) or the recommended level (7 mg/kg diet, control) of pyridoxine (PN) hydrochloride to test if excess vitamin B-6 would cause tissue depletion of pyridoxal phosphate (PLP), the active coenzyme form of vitamin B-6. Plasma PLP, tryptophan-load test results, food intake, and tissue and body weights were not different at wk 6. Red blood cell endogenous alanine aminotransferase activity and PLP concentration were elevated (P less than 0.01) in rats fed 1400 mg PN.HCl/kg diet. In contrast, PLP concentration in muscle was significantly lower (P = 0.01) in rats fed excess vitamin B-6 (9.7 +/- 0.8 nmol/g, mean +/- SEM) than in controls (14.9 +/- 1.4). PLP concentration in other tissues, including plasma, was not affected. In rats fed excess vitamin B-6, pyridoxal was increased in all tissues examined (P less than 0.05), and total vitamin B-6 was increased in plasma, red blood cells and kidneys (P less than 0.05). Total glycogen phosphorylase (a + b) activity in the gastrocnemius was not affected, but phosphorylase a activity was increased in rats fed excess vitamin B-6 (P = 0.025). Concentrations of dopamine and metabolites in the caudate nucleus of the basal ganglia were not affected. A transient, but significant, elevation in acoustic startle response, a central nervous system reflex, was observed in rats fed excess vitamin B-6. The depletion in muscle PLP could not hae been predicted by either plasma or red blood cell PLP concentration, although the latter did reflect vitamin B-6 intake.(ABSTRACT TRUNCATED AT 250 WORDS)     

Vitamin E supplementation decreases basal levels of F(2)-isoprostanes and prostaglandin f(2alpha) in rats

Lipid peroxidation is thought to be an important factor in the pathophysiology of a number of diseases and in the process of aging. We investigated the effects of supplementation with vitamin E on lipid peroxidation in rats. Both free radical-induced nonenzymatic- and cyclooxygenase-catalyzed enzymatic lipid peroxidation were investigated by measuring the levels of F(2)-isoprostanes (8-iso-PGF(2alpha)) and PGF(2alpha)-metabolite (15-K-DH-PGF(2alpha)), respectively, in blood, urine and liver. Samples were collected from control rats (n = 6) and from rats supplemented with vitamin E in the diet for 3 wk (n = 8, 20 g/kg diet of DL-alpha-tocopherol hydrogen succinate). Plasma alpha-tocopherol concentration and antioxidative capacity were greater in the vitamin E-supplemented rats than in the control rats (17.9 +/- 1.7 vs. 50.4 +/- 10.4 micromol/L, P < 0.001 and 181 +/- 6 vs. 275 +/- 27 micromol/L trolox equivalents, P < 0.001). Urine 8-iso-PGF(2alpha) tended to be lower in the vitamin E-supplemented rats (0.72 +/- 0.40 vs. 0.34 +/- 0.19 nmol/mmol creatinine, P = 0.056). Urine 15-K-DH-PGF(2alpha) was lower due to vitamin E supplementation (0.97 +/- 0.38 vs. 0.56 +/- 0. 21 nmol/mmol creatinine, P < 0.05), as was liver-free 8-iso-PGF(2alpha) concentration (0.47 +/- 0.11 vs. 0.18 +/- 0.04 nmol/g, P < 0.001). Supplementation with vitamin E did not affect plasma 8-iso-PGF(2alpha) or 15-K-DH-PGF(2alpha) concentrations, liver total 8-iso-PGF(2alpha) or plasma malondialdehyde levels. Thus, vitamin E supplementation reduced urine basal levels of biomarkers of both nonenzymatic and enzymatic lipid peroxidation. In liver, vitamin E reduced the basal level of free 8-iso-PGF(2alpha) but not total 8-iso-PGF(2alpha).     

Efficacy of daily and monthly high-dose calciferol in vitamin D-deficient nulliparous and lactating women

BACKGROUND: We previously found a high prevalence of vitamin D deficiency and low medication regimen compliance in Arab and East Indian women residing in the United Arab Emirates (UAE). The appropriate dosing regimen for improving vitamin D status in this population is not known. OBJECTIVE: We aimed to determine the efficacy of daily and monthly supplementation with vitamin D2, the only high-dose calciferol available in the UAE, in lactating and nulliparous women. DESIGN: Healthy lactating (n = 90) and nulliparous (n = 88) women were randomly assigned to consume 2000 IU vitamin D2/d or 60,000 IU vitamin D2/mo for 3 mo. Serum 25-hydroxyvitamin D [25(OH)D] concentrations were measured by radioimmunoassay at baseline and every month. RESULTS: Most women had vitamin D deficiency [ie, 25(OH)D < 50 nmol/L] at study entry. Mean +/- SD 25(OH)D concentrations at 3 mo were significantly higher than baseline in both lactating (39.8 +/- 12.4 and 25.2 +/- 10.7 nmol/L, respectively) and nulliparous (40.4 +/- 23.4 and 19.3 +/- 12.2 nmol/L, respectively) women (P < 0.001 for both). In total, vitamin D supplementation was effective in achieving serum 25(OH)D concentrations of >or=50 nmol/L in 21 (30%) of 71 women at endpoint. CONCLUSIONS: Oral vitamin D2 supplementation with 2000 IU/d or 60,000 IU/mo for 3 mo was safe, and it increased serum 25(OH)D concentrations significantly; however, only a small proportion of the women studied achieved concentrations of >or=50 nmol/L. This suggests that, when sunlight exposure is limited, doses of vitamin D2 higher than those currently studied may be needed. Monthly dosing appears to be a safe and effective alternative to daily dosing.     

Increased risk of vitamin B-12 and iron deficiency in infants on macrobiotic diets

The blood iron, vitamin B-12, and folate status of the 1985 birth cohort of Dutch infants aged 10.1-20.4 mo fed macrobiotic diets (n = 50) and matched omnivorous control infants (n = 57) was measured. Fe deficiency (combination of Hb less than 120 g/L, ferritin less than 12 micrograms/L, and FEP greater than 1.77 mumol/L) was observed in 15% of the macrobiotic group but not in the control group (p = 0.003). Plasma vitamin B-12 concentrations in the macrobiotic group were far below those of the control group (geometrical mean: 149 and 404 pmol/L, respectively, p less than 0.001). Plasma folate concentrations were higher in the macrobiotic group (31.6 +/- 11.7 nmol/L) than in the control group (21.1 +/- 8.8 nmol/L, p less than 0.001). In the macrobiotic group mean corpuscular volume, mean corpuscular hemoglobin mass, and mean corpuscular hemoglobin concentration were higher and hematocrit and red blood cells were lower (all p less than 0.05) than in the control group. It is advised to incorporate regular servings of animal foods into the macrobiotic diet to obtain an adequate amount of vitamin B-12.