Effect of a single oral dose of ascorbic acid on body temperature and trace mineral fluxes in healthy men and women

Several metabolic changes characteristic of the acute-phase response were examined in healthy men and women following a single 1 g dose of ascorbic acid. Utilizing a placebo-controlled, double-blind protocol, oral body temperatures were recorded in rested, fasted subjects (0900 hr) prior to the consumption of 1 g L-ascorbic acid or placebo (n = 10/group). Temperatures were recorded hourly for the next 8 hours, and again the next morning in the rested, fasted state (0900 hr). Blood samples, collected at 0, 4, and 24 hours post-dose, were analyzed for plasma ascorbate, iron, and zinc. Mean oral body temperature was significantly elevated 2 hours post-dose in the experimental subjects compared to controls (+0.7 degrees F, p = 0.03). In the vitamin-dosed subjects, mean plasma ascorbate rose 32% over the control value after 4 hours (1.11 +/- 0.08 and 0.84 +/- 0.06 mg/100 ml, ns). Serum iron levels were similar in the two groups at 0 and 4 hours post-dose, but at 24 hours post-dose mean serum iron of the vitamin-dosed subjects fell to 73% of that recorded for the control subjects (77 +/- 8 and 105 +/- 10 micrograms/100 ml, p = 0.04). Plasma zinc levels were similar for both groups at 0, 4, and 24 hours post-dose. These data indicate that ascorbate administration, at a level commonly supplemented in the US diet, elicits several host metabolic responses similar to those observed following exposure to infectious or inflammatory agents. These metabolic changes are most likely due to the reducing potential of the vitamin and may factor in the reported prophylactic success of vitamin C supplementation.     

Effects of acute starvation on vitamin A status in rats.

Maintenance of vitamin A stores in the body is dependent on a number of basic metabolic processes. These processes, such as protein and carbohydrate metabolism, are disrupted in acute starvation, and, as a result, alterations in vitamin A status may result. We investigated this possibility in 8-week-old Sprague-Dawley male rats. The rats were starved for 24, 48, and 72 hr but had free access to water. At 24 hours of starvation, the plasma retinol concentration was depressed, but not significantly so. After 48 and 72 hours of starvation, however, the plasma retinol concentration decreased to less than half of the control values (61 +/? 4 vs 124 +/? 12 nmol/dl at 72 hours, mean +/? SEM, (p less than 0.005). The hepatic retinoid (retinyl esters + retinol) concentration (nmol/g liver) was increased at 24 and 48 hours of starvation compared to controls (p less than 0.05), and by 72 hours the concentration was 56% greater in starved rats than in fed controls (p less than 0.001). The total hepatic retinoid content (mumol/total liver) was decreased moderately at all periods of starvation compared to controls (p less than 0.05). In both starved and fed animals, the total hepatic content per 100 g body weight, a measure of total vitamin A reserves, was statistically the same. These results demonstrate that acute starvation in rats alters the vitamin A equilibrium between the plasma and hepatic stores without affecting the overall vitamin A reserves.(ABSTRACT TRUNCATED AT 250 WORDS)     

Postnatal changes in serum osteocalcin and parathyroid hormone concentrations.

Cord clamping at birth leads to interruption of calcium (Ca) supply to the fetus. After birth, neonatal parathyroid hormone (PTH) secretion appears stimulated by hypocalcemia, with serum PTH increasing after birth and peaking at 24 hours of age. This rise in PTH presumably leads to bone resorption and Ca release. We theorize that bone formation may also be affected and that a serum marker of bone formation, serum osteocalcin (OC) concentrations, will decrease postnatally. OC is synthesized by osteoblasts and its serum concentrations are believed to reflect bone formation. We measured serum ionized Ca (iCa), PTH, and OC in cord blood and at 2 and 24 hours in 26 neonates born after uncomplicated pregnancies, labors, and deliveries. Serum iCa (mg/dl) decreased from 5.79 +/? 0.06 (cord, means +/? SEM) to 5.31 +/? 0.05 (2 hr), then to 4.89 +/? 0.05 (24 hr) (p less than 0.05). Serum PTH (microliter Eq/ml) increased from 35.9 +/? 4.3 (cord) to 41.7 +/? 4.0 (2 hr) (p = 0.1), and to 50.3 +/? 4.6 (24 hr) (p less than 0.01). Serum OC (ng/ml) decreased from 55.1 +/? 10.6 (cord), to 12.4 +/? 4.3 (2 hr) (p less than 0.01), then remained stable at 12.7 +/? 1.9 (24 hr). The change (cord minus 24 hr) in OC correlated inversely with the change in PTH over the first 24 hours of age (r = -0.42. p = 0.03). Therefore, there is a sudden decrease in an index of bone formation (i.e., serum OC) in the first 24 hours of life in which rising serum PTH may have had an impact.(ABSTRACT TRUNCATED AT 250 WORDS)     

Zinc tolerance test in uremia: effect of calcitriol supplementation.

The effect of 1,25(OH)2D3 on zinc absorption was indirectly determined in hemodialysis patients using the oral zinc tolerance test. The increment in plasma zinc and the area under the curve following an oral zinc load of 25 mg were studied in seven patients, before and after 6 weeks of therapy with 1 microgram/day of 1,25(OH)2D3 [Rocaltrol(R)]. Before therapy, fasting plasma zinc, 2 hour plasma zinc, and the area under the curve (AUC) were subnormal (hemodialysis patients vs normals: 96 +/? 2 vs 105 +/? 3 micrograms/dl, p less than 0.05, 161 +/? 8 vs 222 +/? 16 micrograms/dl, p less than 0.025, and 188 +/? 25 vs 302 +/? 33 micrograms hr/dl, p less than 0.025, respectively). Following Rocaltrol, serum calcium level increased (8.9 +/? .12 to 9.8 +/? .4 mg/dl, p less than 0.05), parathyroid hormone levels decreased (20.4 +/? 8.9 to 13.6 +/? 7.2 ng/ml, p less than 0.05), but there was no significant change in fasting plasma zinc, 2 hour plasma zinc, or AUC (89 +/? 3 micrograms/dl, 149 micrograms/dl, and 176 +/? 18 micrograms hr/dl, respectively). These results suggest that short-term 1,25(OH)2D3 therapy had no significant impact on zinc absorption or plasma zinc level in uremics.     

Plasma zinc and copper levels of infants fed different milk formulas.

The plasma zinc and copper levels of 32 full-term healthy infants, aged 3-4 months, using different infant formulas, were measured. The plasma zinc levels of infants using soy formula (45.1 +/? 19.1 micrograms/dl) and iron-fortified cow's milk formula (61.6 +/? 12.9 micrograms/dl) were significantly lower than those of the infants using cow's milk formula not fortified with iron (77.5 +/? 13.4 micrograms/dl). The plasma copper levels of the infants using the different formulas were not significantly different from each other. Fortification of infant formulas with high levels of iron may reduce the zinc absorption from such formulas.     

Oral diet does not alter pulmonary pentane or ethane excretion in healthy subjects.

Ethane and pentane are alkanes that are excreted through the lungs to a small degree in healthy subjects. These gasses are produced from the peroxidation of unsaturated fats which are found both in body tissues and in foods. These gasses are excreted in larger amounts by patients with increased production of reactive oxygen metabolites, including those with inflammation or ischemia. Thus, detection of these gasses in excessive quantities is considered evidence for lipid peroxidation. However, the effects of dietary factors on these measurements have not been defined. To define the effects of eating on the pulmonary excretion of these alkanes, 29 healthy subjects were fed a standardized liquid diet (1060 kcal, 12.9 g linoleic acid and 385 mg linolenic acid) after an overnight fast. Breath alkanes were measured at 0, 1, 3, and 6 hours. All subjects had normal vitamin E (1.11 + 0.26 mg/dl), retinol (64 +/? 14 micrograms/dl), beta carotene (27 +/? 21 micrograms/dl), lycopene (23 +/? 12 micrograms/dl) and zinc (81.9 +/? 13.5 micrograms/dl) levels. No statistically significant changes in either alkane were noted relative to the fasting level. We conclude that oral diet does not alter pulmonary ethane or pentane excretion in healthy subjects.     

肝硬化病人维生素A、E及某些矿物质营养状况探讨

本文观察了24例肝硬化病人维生素A、E及铁、锌、铜、锰、钙和镁的营养状况。结果显示,肝硬化(代偿期)病人除维生素E外,上述各种营养素的摄入量均显著低于健康对照组;肝腹水病人的摄入量更低。肝硬化(代偿期)病人血清维生素A、E、铁、锌、铜和锰的含量显著低于健康对照组;肝腹水病人血清铜、镁的含量未见明显变化,但血清钙的含量显著下降,其他各项指标的值更低。上述结果提示,肝硬化病人有维生素A、E、铁、锌、锰和钙的不足或缺乏。     

The effect of sodium intake on zinc excretion in patients with sickle cell anemia.

Urinary zinc excretion is known to be elevated in subjects with sickle cell anemia. Sodium intake has been suggested to influence zinc excretion in normal subjects. In order to assess the effect of sodium on zinc excretion in subjects with sickle cell anemia, urinary zinc excretion was measured in thirteen children and adolescents with sickle cell anemia on both a high (140 mEq/day) and low (20 mEq/day) sodium intake. Urinary zinc excretion was elevated on both diets. The mean urinary zinc excretion on the high sodium diet (775 +/? 238 micrograms/24 h) was significantly lower (P less than .005) than that on the low sodium diet (947 +/? 344 micrograms/24 h). The zinc excretion did not correlate with calcium or magnesium excretion or aldosterone secretion rates or plasma renin activity. Although elevated, the urinary zinc excretion in patients with sickle cell anemia is still significantly lowered by increasing sodium intake.     

Program

Seven healthy older volunteers participated in a 33-day study consisting of three sample collection periods, a 10-day control, and two 10-day experimental periods. Subjects consumed their usual self-selected diets throughout and a daily wheat bran supplement (30 g) during the two experimental periods. Food intake was recorded daily by subjects and accuracy and completeness checked daily by personal interview. Apparent calcium absorption decreased significantly from 22.1 +/? 5.6% (mean +/? SD) during the control to 8.6 +/? 5.2% during the second bran period. The wheat bran supplement significantly increased wet and dry stool weights but had no effect on stool moisture or defecation frequency. Gastrointestinal transit time of a dose of chromium decreased significantly, from 75 +/? 33 to 54 +/? 19 hr; of a dose of polyethylene glycol insignificantly, from 98 +/? 59 to 69 +/? 46 hr. Mean recovery of 21 doses of chromium of 98.7 +/? 5.0% verified that stool collection was complete. The results suggest that the ability of wheat bran to regulate bowel function in the apparently healthy older adult may be accompanied by increased fecal calcium losses similar to what has been reported for younger adults.     

Effects of acute starvation on vitamin A status in rats

Maintenance of vitamin A stores in the body is dependent on a number of basic metabolic processes. These processes, such as protein and carbohydrate metabolism, are disrupted in acute starvation, and, as a result, alterations in vitamin A status may result. We investigated this possibility in 8-week-old Sprague-Dawley male rats. The rats were starved for 24, 48, and 72 hr but had free access to water. At 24 hours of starvation, the plasma retinol concentration was depressed, but not significantly so. After 48 and 72 hours of starvation, however, the plasma retinol concentration decreased to less than half of the control values (61 +/- 4 vs 124 +/- 12 nmol/dl at 72 hours, mean +/- SEM, (p less than 0.005). The hepatic retinoid (retinyl esters + retinol) concentration (nmol/g liver) was increased at 24 and 48 hours of starvation compared to controls (p less than 0.05), and by 72 hours the concentration was 56% greater in starved rats than in fed controls (p less than 0.001). The total hepatic retinoid content (mumol/total liver) was decreased moderately at all periods of starvation compared to controls (p less than 0.05). In both starved and fed animals, the total hepatic content per 100 g body weight, a measure of total vitamin A reserves, was statistically the same. These results demonstrate that acute starvation in rats alters the vitamin A equilibrium between the plasma and hepatic stores without affecting the overall vitamin A reserves.(ABSTRACT TRUNCATED AT 250 WORDS)     

妊娠期补充微量元素及维生素对妊娠高血压疾病的预防作用

目的探讨孕妇妊娠期补充微量元素(铁和锌)及维生素(叶酸和维生素D)对妊娠高血压疾病的预防作用。方法以2014年1月到2016年3月期间在海南省三亚市妇幼保健医院妇产科就诊经医学检查确认怀孕的768例育龄期女性为研究对象,随机平均分为A、B、C三组,其中A组补充适量的维生素(包括叶酸和维生素D)和微量元素(包括铁和锌);B组补充适量铁和锌两种微量元素,而不补充维生素;C组既不补充维生素也不补充微量元素。考察在经过补充微量元素和维生素后,三组血中铁、锌含量,叶酸及维生素含量,24小时动态血压指标和妊娠高血压发病率上的差异。结果 A、B组血液中的铁、锌含量较C组有明显提高;通过口服补充维生素,A组血液中的叶酸和维生素D含量较B、C两组有明显提高。经24小时动态血压检测比较发现,A、B、C三组在收缩压和舒张压存在显著差异,三组在妊娠高血压总发病率、1级高血压发病率和2级高血压发病率比较上也存在显著差异,C组B组A组,差异均有统计学意义。结论孕妇妊娠期补充微量元素(铁和锌)和维生素(叶酸和维生素D)相比不补充的孕妇,妊娠高血压综合征的发生率明显下降,妊娠期补充微量元素(铁和锌)和维生素(叶酸和维生素D)对预防妊娠高血压疾病具有一定的作用。     

Comparative bioavailability to humans of ascorbic acid alone or in a citrus extract

This study was performed to determine whether synthetic ascorbic acid (AA) alone or in a natural citrus extract containing bioflavonoids, proteins, and carbohydrates was more bioavailable to human subjects. The effect of a single 500-mg ascorbate dose of the two forms and a placebo citrus extract on plasma ascorbate was examined in eight fasting subjects. A comparison of the areas under the plasma concentration-time curves showed that the citrus extract was 35% more absorbed than AA (p less than 0.001) and was more slowly absorbed than AA (p less than 0.001). In six ascorbate-saturated male subjects the ascorbate in the citrus extract produced a greater ascorbate excretion than AA alone in 24-h post-dose urine (p less than 0.05). Citrus extract ascorbate was less excreted than AA (p less than 0.05) in 12 nonsaturated subjects. Ascorbate in the citrus extract was found to be more bioavailable than AA alone in human subjects.     

Feasibility of outpatient electrolyte balance studies.

Clinical studies requiring controlled electrolyte balance have traditionally been conducted in an inpatient (IP), metabolic ward setting. The purpose of this study was to test the feasibility of performing such studies in an outpatient (OP) clinical research setting. Focusing on sodium (Na) and potassium (K) balance, we retrospectively compared 28 subjects studied as OP vs 25 studied as IP on our metabolic ward. We assessed their adherence to our metabolic diets and their compliance with serial 24-hr urine collections. Dietary compliance was assessed by checksheet and urinary Na excretion; urine collection accuracy was determined by serial 24-hr creatinine excretion. The diets for both studies contained a low Na phase (10 mEq) and a high Na phase (200 mEq for IP and 250 mEq for OP), each lasting 1 week. When in balance on the low Na diet, 24-hr Na excretion was 4.6 +/? 0.7 mEq for OP and 13.4 +/? 2.2 mEq for IP, indicating excellent compliance with the low salt diet. Na excretion on the high Na diet was 184.5 +/? 7.4 mEq for OP and 195.3 +/? 9.6 mEq for IP. These values were not significantly different from each other; however, the OP were significantly less than their diet of 250 mEq Na (p less than 0.05). This difference may have been due to dermal Na losses. K excretion was also similar in the two groups. There was no significant difference in the reproducibility of individual multiple urinary creatinine measurements in OP vs IP.(ABSTRACT TRUNCATED AT 250 WORDS)     

Stable isotope-labelled vitamin C as a probe for vitamin C absorption by human subjects

Factors affecting absorption of physiological doses of vitamin C in man have not been widely studied, partly because few suitable tools exist to distinguish recently absorbed vitamin C from endogenous vitamin. Stable isotope-labelled vitamin C provides such a tool. Fifteen healthy non-smoking subjects aged 26-59 years were studied. Each received 30 mg l-[1-(13)C]ascorbic acid orally on two occasions, 3-4 weeks apart. The ascorbate was given alone or with Fe (100 mg as ferrous fumarate) or with red grape juice, which is rich in polyphenols. Blood was collected at frequent intervals for 1 h, and then each hour for a further 3 h. Total concentration of vitamin C was measured fluorometrically and its (13)C-isotope enrichment was measured by GC-MS after conversion to volatile trimethylsilyl esters. Peak plasma enrichment occurred within 25-50 min. No kinetic variables were significantly altered by the iron fumarate supplement. Grape juice attenuated vitamin C absorption, reaching significance at the 20 min time point. There were weak correlations between isotope enrichment and body weight or endogenous ascorbate concentration. The increment in total plasma ascorbate was smaller if calculated from isotope enrichment than from vitamin C concentration increase. The dilution pool was much larger than the plasma ascorbate pool. Further studies are needed to resolve these paradoxes. Stable isotope-labelled ascorbate is potentially useful for measurement of vitamin C absorption by human subjects.     

Plasma changes in micronutrients following a multivitamin and mineral supplement in healthy adults

OBJECTIVE: To estimate the micronutrient (riboflavin, folate, vitamin C, vitamin B(12), iron, zinc and copper) bioavailability in healthy adults from a multi-micronutrient dietary supplement to assess the possible influence on it by the tablet disintegration properties and by the relative intestinal permeability of subject. METHODS: The bioavailability of seven micronutrients from a single brand of multi-micronutrient dietary supplement was measured on two separate occasions in the presence of a standardized test meal in 15 healthy adult subjects. Each subject visited the Metabolic Research Unit on four separate randomized occasions for an absorption test. One test measured the intestinal permeability. The other three tests measured the postprandial changes in plasma or serum concentrations after consuming a test meal alone (control:placebo effect), or the test meal with either whole or crushed and powdered dietary supplements. 15 healthy Caucasian adult volunteers, aged 42 +/- 14 years. RESULTS: The 12 hour-post-dose AUC for riboflavin, folate and vitamin C (whole and crushed tablet), and that for vitamin B(12) (only for the crushed tablet treatment) and iron (only for the whole tablet treatment) were all significantly (p < 0.001) higher than after a test meal alone. In contrast there was no significant increase in the AUC after supplement intake for zinc and copper. Neither the form of the supplement for all micronutrients tested nor intestinal permeability of the subject for riboflavin, folate, vitamin C, iron, zinc and copper influenced the postdose nutrient AUC. In contrast, for vitamin B(12) the intestinal permeability of the subject influenced significantly the nutrient AUC (p = 0.003). CONCLUSION: Tablet disintegration characteristics of this dietary supplement did not limit absorption of these seven micronutrients. The intestinal permeability of subject was only positively correlated with the B(12) bioavailability. Results are suggestive of using multi-micronutrients dietary supplements as a vehicle to decrease the prevalence of multiple micronutrient deficiencies overall for vitamins in healthy adults.     

Serum concentrations of retinol and retinyl esters in adults in response to mixed vitamin A and carotenoid containing meals.

Previous studies using spectrophotometric methods for vitamin A analysis concluded that fasting prior to blood collection is not necessary for determining vitamin A status of children or young adult subjects. We measured the effect of mixed vitamin A and carotenoid containing meals with less than 3, 50, and 100% of the recommended dietary allowance (RDA) for vitamin A on serum concentrations of retinyl esters, retinol, and carotenoids in elderly and young adults after an overnight fast. Retinyl ester concentrations rose significantly in both age groups with a numerically higher rise over baseline in the elderly subjects: 6.0 +/? 0.9 micrograms/dl for elderly (p less than 0.001), 5.0 +/? 0.5 micrograms/dl for young (p less than 0.001) at 50% RDA; 9.0 +/? 1.3 micrograms/dl for elderly (p less than 0.001) and 6.8 +/? 1.6 micrograms/dl for young (p less than 0.05) at 100% RDA. We conclude that in both young and elderly adults, but especially in the elderly, fasting conditions are necessary for the accurate assessment of vitamin A status if spectrophotometric methods are used for measuring vitamin A.     

Postprandial thermogenesis at rest and during exercise in elderly men ingesting two levels of protein.

Seven elderly male subjects (69 +/? 3 yr, 67.8 +/? 9.2 kg, 24.5 +/? 3.6% body fat) lived for 12 consecutive weeks in a metabolic unit and maintained their weight with two different diets fed for 6 weeks each: Diet A, consisted of their habitual protein intake as determined on the outside by a dietary record (mean +/? SD, 1.12 +/? 0.22 g/kg d). Diet B was an isocaloric diet with reduced protein intake (70 mgN/kg d, i.e., 0.44 g protein/kg d) at the level of physiological protein requirement [7]. After 3 weeks on each diet, the thermogenic response to single meals A and B containing 38% of weight maintenance energy for each subject (731-994 kcal) was studied by indirect calorimetry under two situations: (1) at rest over a 4 hr period and (2) during graded exercise on a bicycle ergometer at four stepwise workloads (0,80, 200, and 300 kg/min). A postabsorptive control exercise was also performed in order to assess the net effect of the meal during exercise. Eating alone increased the energy expenditure by +0.18 +/? 0.07 kcal/min with meal A and +0.13 +/? 0.06 kcal/min with meal B. There was a positive correlation (r = 0.84, p less than 0.01) between the % energy derived from protein and the thermogenic response expressed as % of the energy content of test meal. Exercise failed to influence the thermogenic response to meals since the overall net increase in energy expenditure induced by the meals while exercising was not different from that obtained at rest: +0.22 +/? 0.17 kcal/min and +0.15 +/? 0.13 kcal/min with meal A and meal B, respectively. This study failed to show any interaction between exercise and postprandial thermogenesis in elderly individuals.     

Iron and zinc supplementation improves indicators of vitamin A status of Mexican preschoolers

BACKGROUND: The coexistence of multiple micronutrient deficiencies is a widespread public health problem in many regions of the world. Interactions between zinc deficiency and vitamin A metabolism have been reported but no longitudinal studies have evaluated the effect of iron deficiency on vitamin A. OBJECTIVE: The objective of this study was to investigate the effect of supplementation with iron, zinc, or both on vitamin A and its metabolically related proteins retinol binding protein (RBP) and transthyretin. DESIGN: The study was a longitudinal, double-blind, placebo-controlled trial in which 219 rural Mexican children aged 18-36 mo were randomly assigned to receive 20 mg Zn/d, 20 mg Fe/d, 20 mg Zn/d plus 20 mg Fe/d, or placebo. RESULTS: Six months after supplementation, plasma retinol increased in all supplemented groups. Compared with placebo, zinc supplementation was associated with significantly higher plasma retinol and transthyretin but the increase in RBP was not significant. Iron supplementation significantly increased plasma retinol, RBP, and transthyretin. Supplementation with zinc plus iron significantly increased plasma retinol but not RBP or transthyretin. Children deficient in zinc, iron, or vitamin A (as indicated by nutrient plasma concentration) at the beginning of the study had a significantly greater increase in retinol than did children with adequate nutrient status. CONCLUSIONS: Supplementation with zinc, iron, or both improved indicators of vitamin A status. The results of this study agree with previous observations of a metabolic interaction between zinc and vitamin A and suggest an interaction between iron and vitamin A metabolism.     

Comparison of dietary histories and seven-day food records in a nutritional assessment of older adults

Dietary histories and seven-day food records were obtained for 54 apparently healthy older adults. The two dietary methods correlated for most nutrients, but mean differences were significant for several nutrients. Intakes below recommended levels occurred most frequently for energy, calcium, and zinc. Biochemical evidence of thiamin and riboflavin deficiency was unexpectedly frequent. Using food records, dietary iron correlated with serum ferritin. Using dietary histories, dietary protein correlated with serum albumin, and dietary zinc correlated with plasma zinc. Using either dietary method, plasma ascorbate was associated positively with both dietary ascorbate and ascorbate supplements, and negatively with cigarette smoking. Use of thiamin- or folate-containing supplements was associated with improved biochemical status for the respective vitamin. Though neither dietary histories nor food records give precise intake data for individuals, either method may be useful for epidemiologic studies with appropriate sample sizes.     

Spatiotemporal biodistribution of α-tocopherol is impacted by the source of 13C-labeled α-tocopherol in mice following a single oral dose

Natural (RRR-) α-tocopherol (αT) is more bioactive than synthetic (all racemic, all rac-) αT, but not enough is known about the tissue kinetics of the 2 αT sources. We examined the time-course bioaccumulation of natural versus synthetic αT in tissues of young, marginally vitamin E-deficient mice using ¹³C-RRR-αT or ¹³C-all rac-αT tracers. In experiment 1, 3-week old male wild-type mice were fed a vitamin E-deficient diet for 0, 1, 2, or 3 weeks (n = 5/time point). Tissue αT levels were analyzed by HPLC-PDA. Feeding a vitamin E-deficient diet for up to 3 weeks decreased total αT concentrations in all analyzed tissues except the brain, which maintained its αT level. In experiment 2, a 2-week αT-depletion period was followed by administration of a single oral dose of 0.5 mg of ¹³C-RRR-αT or ¹³C-all rac-αT. At 12 hr, 1, 2, and 4 days post-dose, serum and multiple tissues were collected (n = 3/time point). αT was quantified by HPLC-PDA, and ¹³C-αT enrichment was determined by LC-MS. Both sources of ¹³C-αT reached maximum serum levels at 12 hr post-dose. ¹³C-RRR-αT levels were significantly higher than ¹³C-all rac-αT in serum at 1 d post-dose, and in heart, lungs, and kidney at 2d post-dose. In brain, ¹³C-RRR-αT concentrations were significantly higher than ¹³C-all rac-αT at 2 and 4 d post-dose. At 4 d post-dose, ¹³C-αT levels were similar between the 2 sources in examined tissues except for brain and adipose tissue where ¹³C-RRR-αT was higher. In conclusion, αT bioaccumulation over time varied substantially depending on αT source and tissue type.