Postprandial increases in serum antioxidant capacity in older women

Eight women were recruited for studying the effects of a meal on overall antioxidant status. Subjects resided in a metabolic research unit for two 36-h periods. During period A, subjects fasted overnight (12 h) and were then given a breakfast, a lunch, a snack, and a dinner. During period B, subjects fasted for 23 h and were then given a dinner. These meals were designed to contain negligible antioxidants. Blood samples were collected for analyzing total antioxidant capacity (TAC) and individual antioxidants. The results showed that serum TAC significantly increased by up to 23% after the consumption of the lunch and dinner during period A. Serum TAC did not increase until after the consumption of the dinner during period B. Among the antioxidants (vitamin C, α-tocopherol, bilirubin, and uric acid) examined, serum uric acid was the only one that showed a significant postprandial increase, which was also parallel to the postprandial response in serum TAC. These results indicate that food intake, even if low in antioxidants, can increase the serum total antioxidant activity.

Bioavailability of Calcium from Common Vegetables Assessed in Teenagers

Calcium is an essential human nutrient that is important in bone growth and metabolism. While dairy products in reasonable quantity can supply minimum daily requirements of calcium, the current decline in the consumption of dairy products, especially among teenagers, implies that dietary requirements must be met from other sources. Green beans, spinach and broccoli contain high concentrations of calcium, but the bioavailability of calcium from these food sources has not been determined in children. To provide accurate dietary recommendations for these foods, we have developed a recirculating hydroponic system for the growth and intrinsic labeling of plants with stable isotopes. Plants were maintained on a non-labeled nutrient solution until an appropriate developmental age and were then presented with nutrient solution containing 42-Ca. Labeled green bean pods and spinach were harvested at the proper commercial age, and were cooked, pureed and frozen until use. Thirteen teenage subjects seven girls, six boys) were recruited for a 2-week stay in the Metabolic Research Unit, and were fed 42-Ca-labeled vegetables along with 48-Ca-enriched milk; an intravenous dose of 46-Ca was also administered. Blood, urine and fecal samples were collected during the 2-week study. Calcium bioavailability and kinetics were determined using a multi-compartment model. The bioavailability of calcium averaged 28% from green beans, which was comparable to that of milk calcium. Calcium bioavailability from spinach averaged only 3%, due probably to the high oxalate content of spinach. Our results suggest that low-oxalate containing vegetables such as green beans can serve as good dietary sources of calcium. This research was funded in part by USDA-ARS Coop. Agr. No. 58-6250-1-003 and USDA-CRS Grant No. 94-347200-0605.

Establishment of creatinine clearance reference values for older women

Age-adjusted reference ranges for creatinine clearance were determined in 279 women, ages 40-95 years, who were housed in a metabolic research unit and consumed a meat-free diet. Creatinine clearance, but not serum creatinine, declined with age by 0.63 mL/min per 1.73 m2 per year. Serum and urine creatinine concentrations, used to calculate clearances, were analyzed by a kinetic Jaffé procedure. In a subset of 100 subjects, fasting serum creatinine values averaged 8.3 +/- 5.2 (SD) mumol/L higher when measured by the kinetic Jaffé procedure than by an enzymatic method (creatinine PAP). The Cockcroft-Gault formula for estimating creatinine clearance from serum creatinine in women was validated, and the modification factor for the male equation was determined to be 0.84 (95% confidence interval 0.83-0.86) confirming the suggested 15% correction. A prediction formula derived from this population was similar in accuracy to the Cockcroft-Gault formula.