Vitamin D content and variability in fluid milks from a US Department of Agriculture nationwide sampling to update values in the National Nutrient Database for Standard Reference.

This study determined the vitamin D(3) content and variability of retail milk in the United States having a declared fortification level of 400 IU (10 µg) per quart (qt; 1 qt=946.4 mL), which is 25% daily value per 8 fluid ounce (236.6 mL) serving. In 2007, vitamin D(3) fortified milk (skim, 1%, 2%, whole, and 1% fat chocolate milk) was collected from 24 statistically selected supermarkets in the United States. Additionally, 2% milk samples from an earlier 2001 USDA nationwide collection were reanalyzed. Vitamin D(3) was determined using a specifically validated method involving HPLC with UV spectroscopic detection and vitamin D(2) as an internal standard. Quality control materials were analyzed with the samples. Of the 120 milk samples procured in 2007, 49% had vitamin D(3) within 100 to 125% of 400 IU (10 µg)/qt (label value), 28% had 501 to 600 IU (12.5-15 µg)/qt, 16% had a level below the label amount, and 7% had greater than 600 IU (15 µg)/qt (>150% of label). Even though the mean vitamin D(3) content did not differ statistically between milk types, a wide range in values was found among individual samples, from nondetectable [<20 IU (0.5 µg)/qt] for one sample to almost 800 IU (20 µg)/qt, with a trend toward more samples of whole milk having greater than 150% of the labeled content. On average, vitamin D(3) in 2% milk was higher in 2007 compared with in 2001 [473 vs. 426 IU (11.8 vs. 10.6 µg)/qt].

Nutrient composition and retention in whole turkeys with and without added solution.

Whole turkeys sold in retail outlets are typically processed with added solutions to improve their taste and tenderness. The purpose of this study was to evaluate the nutrient composition of whole turkeys with and without added solution, and to update the nutrient profile of turkey for the USDA National Nutrient Database for Standard Reference. Eleven pairs of turkeys with added solution were obtained from statistically representative retail outlets using a nationwide sampling plan developed for USDA's National Food and Nutrient Analysis Program; 4 pairs of turkeys without added solution were purchased from local food outlets. Turkeys were roasted to an internal temperature of 165°F (74°C). Values of selected nutrients in light and dark meat, including skin, were determined by USDA approved laboratories using quality assurance protocols. Both raw and cooked turkeys, with and without added solution, were compared by one-way and 2-way factorial ANOVA. The results showed a significant interaction for fat (P < 0.0001) and zinc (P = 0.0070) between turkeys that were raw and cooked and those prepared with or without added solution. Fat was higher in raw turkeys with added solution compared to without added solution. Similarly, sodium, phosphorus, and calcium values were significantly higher in turkeys with added solution (P < 0.05) than in turkeys without added solution. Data from this study will be useful for developing strategies to address sodium-related health issues, nutrition monitoring, consumption surveys, and policy development.

Effect of exercise (running) on serum glucose, insulin, glucagon, and chromium excretion.

Chromium is involved in normal glucose metabolism. To test whether chromium is also associated with the exercise-induced increases in glucose utilization, urinary chromium excretion, serum glucose, insulin, and glucagon of nine male runners (23-46 yr) were evaluated. Blood samples were taken prior to, immediately following, and 2 h after a strenuous 6-mile run. Urine samples were also taken at these times, and total daily urine collections were made the day of the run and the following day. Mean serum glucose for all runners immediately after running was 185 +/- 19 mg/dl compared with 90 +/- 1 mg/dl (mean +/- SE) prior to running. Mean serum glucagon immediately after running was significantly elevated compared with that observed prior to or 2 h after running; serum insulin levels were not altered significantly. Mean urinary chromium concentration was increased nearly five-fold 2 h after running; similar results were obtained when chromium concentration was expressed per mg of creatinine. Total daily urinary Cr excretion was approximately two times higher the day of running compared with the following nonrun day. Daily urinary excretion of sodium, potassium, and calcium were measured to determine if exercise had a general nonspecific effect on renal function; daily urinary excretion of these was not changed by exercise. These data demonstrate that accompanying the exercise-induced changes associated with increased glucose utilization, there is a significant increase in chromium excretion.

Nutrient database improvement project: Separable components and proximate composition of raw and cooked retail cuts from the beef loin and round.

Beef nutrition research has become increasingly important domestically and internationally for the beef industry and its consumers. The objective of this study was to analyze the nutrient composition of ten beef loin and round cuts to update the nutrient data in the USDA National Nutrient Database for Standard Reference. Seventy-two carcasses representing a national composite of Yield Grade, Quality Grade, sex classification, and genetic type were identified from six regions across the U.S. Beef short loins, strip loins, tenderloins, inside rounds, and eye of rounds (NAMP # 173, 175, 190A, 169A, and 171C) were collected from the selected carcasses and shipped to three university meat laboratories for storage, retail fabrication, and raw/cooked analysis of nutrients. Sample homogenates from each animal were analyzed for proximate composition. These data provide updated information regarding the nutrient status of beef, in addition, to determining the influence of Quality Grade, Yield Grade, and sex classification on nutrient composition.

Selenium utilization in humans--a long-term, self-labeling experiment with stable isotopes.

A stable (nonradioactive) isotope of selenium in a chemical form common in foods (selenomethionine) or inorganic selenite was taken orally (200 micrograms/d) for 3 wk to label deep body pools. By deep body pools we mean selenium compartments that are large and/or have a slow turnover (exchange) rate. Blood plasma was removed, stored for 11 mo, and later reinfused as a labeled tracer dose with the selenium label in all of the biologically significant chemical forms. Accessible tissues such as red blood cells were highly labeled (20-25%) in the subjects receiving selenomethionine. Selenium from deep body pools is excreted primarily via the urine (80%). Reexcretion of previously absorbed selenium back into the gastrointestinal tract can be measured, avoiding a major source of error in conventional balance studies used to estimate nutrient absorption.

Iron intake and status of men and women consuming self-selected diets.

Iron intakes and iron status (serum ferritin and iron balance) were determined in 16 women and 13 men consuming self-selected diets over a 1-yr period. Iron balance was determined during four 7-day balance periods corresponding to the four seasons of the year. The seasonal variation in iron intake and serum ferritin and the correlation among iron intake, iron balance, and serum ferritin was examined. No seasonal variation was found in iron intake or serum ferritin. No direct correlation could be found between iron status (ferritin levels and iron balance) and iron intake. However, the men who met or exceeded their recommended dietary allowance for iron intake had ferritin levels in a range indicative of adequate iron status. None of the women met their recommended dietary allowance and their ferritin levels indicated marginal iron stores.

Selenium utilization during human lactation by use of stable-isotope tracers.

We examined utilization of selenomethionine (SeMet) and selenite in six lactating (L) and six nonlactating (NL) women, 2-3 mo postpartum, and seven never-pregnant (NP) women by use of stable-isotope tracers. All groups had similar selenium status at the start of the study. Significantly more selenium from SeMet than from selenite was absorbed and appeared in plasma in all groups. Milk contained more selenium from apparently absorbed SeMet than from selenite. More selenium from apparently absorbed selenite than from SeMet appeared in urine of NP and NL subjects whereas L subjects had approximately the same amount of selenium from apparently absorbed selenite and SeMet in their urine. All groups retained significantly more selenium from SeMet than from selenite; L women retained more selenium from selenite than did the other two groups. Absorption and retention of selenium from SeMet in L women did not appear to be significantly different from that in other women, suggesting that selenium requirements during lactation are increased mainly because of milk losses.

Biochemical indices of selected trace minerals in men: effect of stress.

Plasma zinc, iron, copper, and selenium and selected blood proteins were measured in 66 men before (BHW) and after (AHW) a 5-d period of sustained physical and psychological stress called Hell Week. Recovery blood samples were obtained from 26 men 7 d after Hell Week. Dietary intakes were determined BHW and during Hell Week; zinc, iron, copper, and selenium intakes during Hell Week averaged 23.6 +/- 3.4 mg/d, 35.4 +/- 3.9 mg/d, 3.0 +/- 0.5 mg/d, and 92.5 +/- 26.7 micrograms/d, respectively. C-reactive protein was detected in only five subjects BHW and in all subjects AHW. Zinc, iron, selenium, and albumin decreased by 33%, 44%, 12%, and 9%, respectively, whereas ferritin, ceruloplasmin, and creatine kinase concentrations increased AHW by 59%, 8%, and 266%, respectively. Haptoglobin concentrations increased 57% in 30 subjects but decreased 32% in 23 subjects AHW. The biochemical changes were transitory because protein (except ferritin) and mineral concentrations were similar to BHW values 7 d after Hell Week. Hell Week induced changes characteristic of an acute-phase response in physically active men.

Sodium and potassium intake and balance in adults consuming self-selected diets.

Twenty eight adults, 12 men and 16 women, participated in a 1-yr study designed to assess daily nutrient intake accurately. All subjects lived at home, consumed self-chosen diets, and maintained a detailed daily dietary record throughout the year. During four 7-day balance studies, one in each season of the year, meals, beverages, urine, and feces were analyzed for sodium and potassium content by atomic absorption spectrometry. Total intakes averaged 3.4 g/day for sodium and 2.8 g/day for potassium. The Na:K ratio for all diets analyzed averaged 1.3. Nutrient densities of sodium and potassium were 1.8 and 1.5 g/1000 kcal, respectively. Apparent absorptions of sodium and potassium were 98 and 85%, respectively, and did not change significantly over the wide range of intakes. Average urinary excretions of sodium and potassium were 86 and 77% of total intake, respectively. Mean metabolic balances were positive for sodium, +0.47 g/day, and potassium, +0.28 g/day. The data of this study provide useful information concerning the dietary intakes, excretions, and balances of sodium and potassium for adults based on analytic determination.

Zinc, copper, and manganese intake and balance for adults consuming self-selected diets.

Twenty-eight adult men and women participated in a year-long study designed to determine accurately the nutrient intake of adults who lived at home and consumed self-selected diets. During four metabolic balance periods, 7 days each, corresponding to the seasons (spring, summer, fall, winter), duplicates of the diet, and all urine and feces were collected. Daily mean intakes for zinc and copper were 9.9 and 1.2 mg, respectively. These levels were less than the recommended daily intakes of 15 mg for zinc and 2 to 3 mg for copper. In contrast, the mean dietary intake of manganese was 3.0 mg/day which is within the suggested safe and adequate range of 2.5 to 5.0 mg. Metabolic balances were negative for all three elements possibly due to a reduction in food intake during the collection periods compared to the noncollection intervals. The collection of the duplicate diets apparently influenced the food intake during the collection weeks.

Urinary chromium excretion of human subjects: effects of chromium supplementation and glucose loading.

The utilization of inorganic chromium by free-living human subjects was studied in 76 volunteers (male, 48; female, 28) who were supplemented with 200 micrograms of inorganic chromium as chromic chloride or a placebo tablet for 3 months in a double-blind, cross-over experiment. For all subjects, initial mean +/- SEM urinary chromium (Cr) level was 0.20 +/- 0.01 (range, 0.05 to 0.58) ng/ml and did not differ by sex. Initial chromium/creatinine ratio (Cr/Ct) was 0.15 +/- 0.01 (range 0.03 to 0.36) ng Cr/mg creatinine for females and was significantly lower, 0.10 +/- 0.01 (range 0.03 to 0.36) for males. Mean urinary Cr level increased to 1.0 +/- 0.12 after 2 and to 1.13 +/- 0.08 ng/ml after 3 months' supplementation. The Cr/Ct ratio increased to 0.69 +/- 0.10 for females and to 0.50 +/- 0.04 for males after 2 months' supplementation; values were similar after 3 months. An increase in urinary Cr excretion in response to a glucose load was demonstrated for nonsupplemented normal free-living subjects but not for subjects supplemented daily with trivalent chromium. Urinary Cr excretion after a glucose challenge was not predictable and did not depend on Cr status.

Breast milk chromium and its association with chromium intake, chromium excretion, and serum chromium.

Chromium metabolism of lactating women was evaluated by measuring diet, breast milk, urine, and serum chromium in 17 subjects 60 d postpartum. Breast milk chromium concentration was similar for the 3 d of collection with a mean +/- SE concentration of 3.54 +/- 0.40 nmol/L (0.18 ng/mL). Dietary intake and urinary chromium values were also similar for each of the 3 collection days. Total chromium intake of lactating mothers (0.79 +/- 0.08 mumol/d) was greater than that of reference female subjects (0.48 +/- 0.02). There was a significant correlation (r = 0.84) between serum chromium and urinary chromium excretion. If a breast milk volume of 715 mL is assumed, chromium intake of exclusively breast-fed infants is < 2% of the estimated safe and adequate daily intake of 10 micrograms. In summary, breast milk chromium content is independent of dietary chromium intake and serum or urinary chromium values. Chromium intake also did not correlate with serum or urine chromium but there was a significant relationship between serum and urinary chromium concentrations.

Selenium in diet, blood, and toenails in relation to human health in a seleniferous area.

To determine whether high dietary selenium intake was associated with adverse effects, selenium in diet, blood, and toenails was studied in relation to human health in adults residing in western South Dakota and eastern Wyoming. Over a 2-y period 142 subjects were recruited from households selected at random and from ranches where unusually high selenium intakes were suspected. Subjects completed health questionnaires, underwent physical examinations, provided blood samples for clinical assessment, and provided blood, urine, toenails, and duplicate-plate food collections for selenium analysis. About half of the 142 free-living subjects had selenium intakes greater than 2.54 mumol/d (200 micrograms/d) (range 0.86-9.20 mumol/d, or 68-724 micrograms/d). Physical findings characteristic of selenium toxicity were not present nor were clinically significant changes in laboratory tests or frequency of symptoms related to selenium in the blood, toenails, or diet. We found no evidence of toxicity from selenium in subjects whose intake was as high as 9.20 mumol/d (724 micrograms/d).

Stable isotopes of minerals as metabolic tracers in human nutrition research.

Enriched stable isotopes used as tracers have proven to be valuable in studies of the absorption and metabolism of minerals. Unlike radioisotopes, they can be used in high-risk population groups such as infants, children, and pregnant or lactating women. Estimates of mineral absorption can be made from the oral administration of a single tracer or from two tracers, one given orally and the other intravenously (IV). It is possible to determine the metabolism of the mineral with modeling based on the amount of the tracer or tracers in different biological samples. One of the key decisions in studies of this type is determining which enriched isotope and what amount to use. An example is given of calculations to estimate and compare the amounts of tracers needed for an absorption study. Methods for calculating the amounts of tracer in oral and IV doses are presented, and limits of detection and quantitation are discussed in terms of percent of enrichment and related to isotope ratio measurement precision. A general review of the use of mass spectrometric instruments for quantifying various stable isotopes is given.

Red cell volume determination using a stable isotope of chromium.

OBJECTIVE: To validate and improve a method of red cell volume determination by use of a stable isotope of chromium. METHODS: Twelve subjects were sequentially injected with red blood cells labeled with a stable isotope of chromium (53Cr) and red blood cells labeled with radioisotopic chromium (51Cr). Measurement of 53Cr dilution was by gas chromatography/mass spectrometry. Measurement of 51Cr dilution was by gamma counter. RESULTS: Comparison of the two methods led to results that differed on average by 34.5 +/- 45.0 mL (1.8 +/- 2.2%), 0.3 to 3.2%, 95% confidence interval. CONCLUSION: Measurement of red cell volume by use of a stable isotope of chromium is accurate, with potential applications including measurement in pregnant women and children or other groups in whom exposure to radioisotopes is undesirable.

Bone-related mineral content of water samples collected on the Navajo reservation.

Although dairy food intake is low among the Navajo people, hip fracture rates are lower than in Caucasians. Genetic differences in bone density have been cited as the reasons for low fracture rates among Native Americans and other segments of the population. However, more detailed examination of mineral intakes suggests that environmental factors may provide part of the explanation for the lower fracture rates. Cultural practices such as the addition of ash to traditional foods and the high mineral content of water may provide much higher intakes of bone-related minerals than food intake surveys have previously reported. As part of a larger study to assess overall intake of minerals related to bone health and other conditions, water samples were collected from the Navajo reservation. Duplicates were collected at least one week apart from 53 sites including wells, springs, taps, and storage barrels and analyzed by atomic absorption and inductively coupled plasma spectrometry for a number of minerals. For average intakes of 2 l/day, water could provide up to 212 mg of calcium, 150 mg of magnesium and 8 mg of zinc. The combined contribution of mineral intakes provided by the addition of juniper ash to traditional foods, not genetic differences, may partially explain the lower fracture rates of the Navajo people. Further research in this area is required to confirm this hypothesis.

Mild peripheral neuropathy but biochemical chromium sufficiency during 16 months of "chromium-free" total parenteral nutrition.

A 6-yr, 4-month-old boy was started on total parenteral nutrition (TPN) because of chronic diarrhea. The TPN regimen (3 liter/day) initially included supplemented Cr (3 micrograms/day) in addition to standard components (including FreAmine III). At age 8 yr, 8 months, the serum Cr level was elevated: 3.7 ng/ml (normal 0.03-0.85). A repeat level at the same time by another commercial laboratory was also high (7.0). Cr supplementation was stopped. At age 10 yr, he was noted to have mild peripheral neuropathy although glucose tolerance was excellent (alpha-linolenic acid was undetectable in the plasma). Cr status was reevaluated in a research lab. The serum level was 1.4 ng/ml (normal 0.05-0.4). The urine chromium excretion was 1.27 micrograms/day (normal 0.22). The TPN regimen (unsupplemented with Cr) provided 4 micrograms/day. Normal Cr intake is about 60 micrograms/day with 0.4% absorption (net 0.24 microgram/day). We conclude that Cr contamination of standard PN fluid may prevent biochemical evidence of low Cr status. In addition, alpha-linolenic acid-free parenteral nutrition for 46 months was not associated with clinically significant neurological dysfunction.

EDTA chelation effects on urinary losses of cadmium, calcium, chromium, cobalt, copper, lead, magnesium, and zinc.

The efficacy of a chelating agent in binding a given metal in a biological system depends on the binding constants of the chelator for the particular metals in the system, the concentration of the metals, and the presence and concentrations of other ligands competing for the metals in question. In this study, we make a comparison of the in vitro binding constants for the chelator, ethylenediaminetetraacetic acid, with the quantitative urinary excretion of the metals measured before and after EDTA infusion in 16 patients. There were significant increases in lead, zinc, cadmium, and calcium, and these increases roughly corresponded to the expected relative increases predicted by the EDTA-metal-binding constants as measured in vitro. There were no significant increases in urinary cobalt, chromium, or copper as a result of EDTA infusion. The actual increase in cobalt could be entirely attributed to the cobalt content of the cyanocobalamin that was added to the infusion. Although copper did increase in the post-EDTA specimens, the increase was not statistically significant. In the case of magnesium, there was a net retention of approximately 85% following chelation. These data demonstrate that EDTA chelation therapy results in significantly increased urinary losses of lead, zinc, cadmium, and calcium following EDTA chelation therapy. There were no significant changes in cobalt, chromium, or copper and a retention of magnesium. These effects are likely to have significant effects on nutrient concentrations and interactions and partially explain the clinical improvements seen in patients undergoing EDTA chelation therapy.

Nutrient database improvement project: the influence of U.S.D.A. Quality and Yield Grade on the separable components and proximate composition of raw and cooked retail cuts from the beef rib and plate.

Beef nutrition is important to the worldwide beef industry. The objective of this study was to analyze proximate composition of eight beef rib and plate cuts to update the USDA National Nutrient Database for Standard Reference (SR). Furthermore, this study aimed to determine the influence of USDA Quality Grade on the separable components and proximate composition of the examined retail cuts. Carcasses (n=72) representing a composite of Yield Grade, Quality Grade, gender and genetic type were identified from six regions across the U.S. Beef plates and ribs (IMPS #109 and 121C and D) were collected from the selected carcasses and shipped to three university meat laboratories for storage, retail fabrication, cooking, and dissection and analysis of proximate composition. These data provide updated information regarding the nutrient content of beef and emphasize the influence of common classification systems (Yield Grade and Quality Grade) on the separable components, cooking yield, and proximate composition of retail beef cuts.

Trace elements in a commercial freeze-dried human urine reference material.

A large batch of freeze-dried human urine reference material, Seronorm Trace Elements Urine, Lot 101021, was prepared commercially (Nycomed Pharma AS, Oslo, Norway) for quality control purposes in trace element analysis. Analytes are being determined by a voluntary, international co-operative effort so that the material will be available to the scientific community at modest cost. The material is in stoppered glass vials and is to be reconstituted with 5.00 ml of water prior to use. We have evaluated the trace element content for several elements, including chromium and zinc, elements for which we have two independent methods available for the determinations, namely isotope dilution mass spectrometry (IDMS) and atomic absorption spectrometry (AAS). We also report on other trace elements measured by IDMS alone, such as Se, for which we have enriched stable isotopes available. Results for chromium indicate a mean +/- standard deviation (n = 10) of 1.2 +/- 0.3 (by IDMS) and 1.4 +/- 0.3 (by AAS) ng Cr per ml of reconstituted urine, indicating possible inhomogeneity and/or contamination (21-25% relative standard deviation, RSD). Approximately half of the observed chromium originates from the sample container. The values observed for zinc were 590 +/- 90 ng ml-1 (15% RSD) for freshly reconstituted material, 760 +/- 60 ng ml-1 (8% RSD) for material reconstituted 4 d earlier, and 940 +/- 60 ng ml-1 (6% RSD) 2 months after reconstitution. Selenium values by IDMS were very reproducible, with a mean concentration of 16 +/- 0.15 ng g-1 (0.9% RSD), suggesting little or no contamination and a high degree of sample homogeneity for this element. The source of potential contaminants has been evaluated by multielement determinations of leachates of the vials and stoppers. Elements noted in significant amounts include B, Ba, Sr, Mo, Cu and Zn, with most of the zinc coming from the rubber stopper.