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Iron stores were assessed in 27 postmenopausal healthy women who donated five units of blood (approximately 485 mL/unit) over approximately 1 y. The mean (+/- SD) age was 67.7 +/- 4.0 y and the average time between successive blood donations was approximately 10 wk (range 8-30 wk). Steady-state iron stores at entrance were 10.59 +/- 3.88 mg/kg body wt (mean +/- SD) and declined to 1.03 +/- 3.20 mg/kg by the fifth donation. Determination of iron stores was based on biochemical measures of iron status at each donation. Iron intakes were 23.3 +/- 10.1 mg/d. From these data we developed equations that can be used to predict the frequency at which healthy postmenopausal women can donate blood without becoming iron deficient. The ability of elderly women to become successful blood donors depends primarily on initial iron stores, iron intake, and frequency of donation. Women with low steady-state iron stores may be able to donate only two times per year without becoming iron deficient.

The pharmacokinetics of vitamin C after a 500-mg oral tablet dose were compared in 15 healthy young men aged 25.20 +/- 2.54 (means +/- SD) and in 15 healthy elderly men aged 69.31 +/- 2.52 y. The doses were characterized with the subjects in two states of vitamin C nutriture: a depleted state, which was achieved by 4-5 wk of compliance with a vitamin C-restricted diet of less than 10 mg/d and a supplemented state, in which the subjects were given 500 mg vitamin C/d for 3 wk. Plasma and urine samples were collected for 72 h after the dose of vitamin C from depleted subjects and for 24 h from supplemented subjects and analyzed for vitamin C. Several of the pharmacokinetic indices measured were different in depleted vs supplemented subjects but none exhibited any age-related differences. This indicates that vitamin C nutriture affects vitamin C pharmacokinetics but age does not.

Background The serum total homocysteine concentration (tHcy), an indicator of folate status and a possible risk factor for vascular disease, is elevated with impaired renal function and poor vitamin B-12 status, which are common in the elderly. Objective Our objective was to determine the association between tHcy, folate intake, alcohol consumption, and other lifestyle factors in elderly persons. Design This cross-sectional study used linear regression to model changes in tHcy. Subjects were 278 men and women aged 66-94 y studied in 1993. Results Total folate intake was negatively associated with tHcy in models adjusted for age, sex, serum creatinine, and serum albumin. We found an interaction between food folate intake and supplement use. Food folate intake had an inverse dose-response relation with tHcy that was limited to nonusers of supplements. Predicted tHcy was 1.5 micromol/L lower in users of supplements containing folate and vitamin B-12 than in nonusers and was independent of food folate intake. We found a positive dose-response relation of coffee and tea intake with tHcy, a positive association for alcohol intake of > or = 60 drinks/mo compared with low intake, and an interaction of alcohol use with folate intake and supplement use. Compared with alcohol users, nonusers had higher predicted tHcy and a lower inverse dose-response relation of food folate intake with tHcy. Conclusions The inverse association between folate intake and tHcy was strongest among nonusers of supplements and among alcohol drinkers. Identifying modifiable factors related to tHcy, a possible risk factor for vascular disease, is especially important in elderly persons.

Dietary intakes and blood lipid concentrations were assessed in elderly men (n 65) and women (n 92) from 1980 through 1989.Mean age in 1980 was 70 y (range60-84 y). Health and socioeconomic status was above that found in the general US elderly population. Cross-sectional and longi- tudinal changes in variables were determined by using least- squares linear regression. No significant cross-sectional differ- ences in energy (Id/kg), protein (g/kg), total fat, and carbohydrate intake with age was noted. Significant longitudinal decreases in total fat, saturated and polyunsaturated fatty acids, and choles- terol intakes were noted in both men and women. Significant decreases in total, HDL, and LDL plasma cholesterol concen- trations were noted over time in both men and women. Ratios ofboth total and LDL cholesterol to HDL cholesterol increased over time. The decrease in total fat and cholesterol intakes were significantly correlated with the decrease in total plasma cho- lesterol. Am J Cliii Nutr l992;55:682-8.

An automated AutoAnalyzer method using 5:S'dithiobis-2-nitrobenzoic acid is described for determining whole blood gluthathione reductase (BGR) activity and for measuring in vitro activation of BGR with flavin adenine dinucleotide (FAD). BGR activity is expressed as Mmoles glutathione regenerated from oxidized glutathione per ml of whole blood (WB) or per g of hemoglobin. The stimulatory effect of FAD on BGR activity divided by the activity without FAD determined the activity coefficient (AC). We found that NADPH and oxidized glutathione assay concentrations of 0.100 mmole/liter and 0.250 mmole/liter, respectively, in 0.1 mole/liter phosphate buffer, pH 7.4, gave consistent results when WB, before assay, was diluted 20-fold. WB samples to be stored are initially diluted 10-fold with distilled water and frozen. Prior to assay, two aliquots of the sample are diluted 2-fold, one aliquot with distilled water and another with 46 Mmole/liter FAD. With sample and manifold dilutions the assay FAD concentration is 1.0 Mmole/liter: assay concentrations greater than 5.0 Mmole FAD/liter were shown to be inhibijory. We examined blood samples from 617 children in the age range 6 to 60 months and determined the normal AC range to be between 1.00 and 1.35. Six weaned rats (23 days of age), maintained on a riboflavin-deficient diet, showed a mean AC of 1.23, 1.54, 2.02, and 2.41 at 23, 26, 30, and 36 days of age, respectively. Six control rats maintained an AC of 1.23 ± 0.05 (SD) during the same period. Am. J. Clin. Nutr. 29: 663 674, 1966.

In 1979, 304 healthy elderly individuals in New Mexico were recruited for a longitudinal study of nutrition and aging. Repeat measurements on a yearly basis of commonly requested clinical chemistry analytes allowed the calculation of reference intervals, between and within-subject variance components, and percentiles for change in concentration between two yearly measurements. The latter was further divided into analytical and biological variance components. The upper 95th percentile for the difference between two yearly measurements, expressed as a percent of the population mean, ranged from 4% for Na+ to approximately 20% for total cholesterol and to greater than 90% for ferritin. Year-to-year differences attributable to the biological component ranged from a low of 2% of the population mean for Na+ to 70% for gamma-glutamyltransferase.

We studied the milk iron content and iron status of lactating rats and their pups to investigatethe relationshipsbetween the iron concentrations of maternal diet and the iron content of milk, and that between the milk iron content and neonatal iron status. Three days after parturition lactating rats were divided into three groups and fed a control (250 ppm iron), a high iron (2500 ppm iron), and an iron-deficient (no iron) diet. During lactation pups and dams from each group were killed periodically and iron status determined by measurements of hemoglobin, plasma iron, total iron binding capacity, and ferritin. Milk iron concentration decreased in all diet groups during lactation. The rate of decrease was diet dependent. A definite relationship was seen between the milk iron content of dams and the iron status of their pups. The iron concentration of rat diet was also found to influence the maternal iron status during lactation. Am. J. Clin. Nutr. 34: 1505-15 12, 1981.