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Biomedical subjects

R P Abernathy

Publications and source records attributed to R P Abernathy.

At least 19 recordsLinked to original sources
PubMed1994

Is adipose tissue oversold as a health risk?

A high percentage of body fat is considered to be the primary cause of risks associated with high body weight. Yet body fat content per se may not cause the risks. The contribution of obesity to risks may be because overfilled adipose tissue cannot remove offending substances from circulation. The ability to remove excess glucose, lipids, and offending materials from circulation, not the amount of body fat, may be the important factor. People with large, partially filled adipose depots may have less risk than people with small, but filled adipose depots. This concept is supported by many studies. Energy restriction in genetically obese animals greatly increases longevity and slows signs of aging even while the animals remain obese. Weight reduction often corrects weight-associated medical problems in obese persons without returning body-fat levels to normal. Statistically generated desirable body-fat contents or desirable height-weight tables may have little meaning for individuals and may cause more harm than good. Because these standards are not appropriate for some people, they should be discarded as a guide for all. More emphasis should be placed on healthy lifestyles and less on body-fat percentages.

Adipose Tissue↗
PubMed1982

Chromium and insulin in young subjects with normal glucose tolerance.

In a group of 20 college subjects, the fasting serum chromium level was found to correlate with the fasting serum insulin level (r = 0.512, p less than 0.05), with the percentage of ideal body weight (r = 0.637, p less than 0.01), and with the triceps skinfold thickness (r = 0.525, p less than 0.02). The relative chromium response at insulin peak was inversely correlated with the total insulin (r = -0.451, p less than 0.05) as well as with the ratio of the total insulin to the total glucose (r = -0.554, p less than 0.02). In order to examine the close relationship between chromium and insulin, the 20 subjects were divided into age- and sex-matched lower insulin secretors and higher insulin secretors based on individuals' total insulin levels calculated as the sum of six measurements in microunits/ml during a 3-h oral glucose tolerance test. The 10 subjects in LI had total insulin levels less than 500, and the 10 subjects in HI had total insulin levels equal to or greater than 500. The means (+/- SEM) of total insulin for LI and HI were 354 +/- 39 and 740 +/- 46, respectively (p less than 0.001). The relative chromium response was significantly higher in LI than that in HI (198.0 +/- 31.0% and 76.2 +/- 18.0%, respectively; p less than 0.005); and the ratio of the total insulin to the total glucose was significantly lower in LI than that in HI (0.585 +/- 0.067 and 1.286 +/- 0.094, respectively; p less than 0.001).

Adolescent↗
PubMed1978

Position paper on RDA for protein for children.

The Recommended Dietary Allowances (RDA) by the National Academy of Sciences are revised approximately every five years. The RDA are compromise opinions of highly qualified nutritional scientists based on interpretations of available data. As with any interpretations of available data. As with any, interpretations and opinions not found on definitive information, they are subject to challenges. The RDA for protein for 7-to 9-uear-old children have been adjusted downward from 60 g in 1958 to 36 g in 1974, a 40% reduction. Data from our laboratories have shown positive apparent nitrogen balances on intakes as low as 18 g daily when no allowances were made for integumental and other nitrogen losses, however, based on accumulative data over several years we calculate the protein requirement to be 45 g daily from a typical American diet. If a safety factor of 30% is added the allowance would become 58.5 g. Currently the RDA for protein for the 7- to 10-year-old child supplies 6% of the RDA for Calories which contrasts to 8.30 and 9.20% for adult males and females, respectively. For comparison, energy from protein as a percentage of total energy for some common foods are: white bread, 12%; corn meal 10%; white rice 7%; and wheat flour 13%.

Adult↗
PubMed1978

Zinc and nitrogen balance in adolescent females fed varying levels of zinc and soy protein.

Zinc and nitrogen balances were determined in 14 girls, 12.5 to 14.5 years of age, during a 30-day period. Diets were composed of ordinary foods and supplied 100% of the Recommended Daily Allowance for protein. The lunch menus were typical of those served in School Lunch Programs except that milk was omitted and calcium supplements were added. The dietary variables were the levels of zinc and the amount of defatted soy which replaced the meat in noon meals. The diets were: S0Z13.4 (13.4 mg zinc and no soy); S30Z13.4 (13.5 mg zinc and 30% of meat replaced by soy); and S30Z7.4 (7.4 mg zinc and 30% of meat replaced by soy). Subjects fed 7.4 mg zinc daily lost significantly (P less than 0.01) less zinc in their feces than the subjects fed the higher level of zinc during the 18-day collection period. Partial substitution of soy for meat in lunch menus did not affect fecal or urinary zinc or nitrogen losses. Mean retentions of zinc by subjects Diets S0Z13.4 nad S30Z7.4 were +0.53, +0.42 and -0.32 mg/day, respectively. Nitrogen retention was not significantly affected by zinc intake. However, nitrogen and zinc retentions were significantly correlated (r = 0.416, P less than 0.015).

Adolescent↗
PubMed1978

Calcium, magnesium, phosphorus, copper, and manganese balance in adolescent females.

Calcium, magnesium, phosphorus, copper, and manganese balances were determined in 14 girls (12.5 to 14.5 years of age) during a 30-day period. Menus were composed of ordinary foods and were typical of subjects' usual dietary habits. The diets contained 1.07 g calcium, 193 mg magnesium, 0.85 g phosphorus, 2.8 mg copper, 3.0 mg manganese, and 7.4 or 13.4 mg zinc daily. Defatted soy was substituted for 0, 15, or 30% of the meat in lunch menus. Neither the alteration of dietary zinc levels or the partial substitution of soy for meat significantly affected retention of the five minerals. Retentions of calcium (r = 0.654), magnesium (r = 0.786), phosphorus (r = 0.560), copper (r - 0.805), and manganese (r = 0.855) by subjects were all significantly (P less than 0.001) correlated to retention of zinc. These correlations probably reflect the correlations between fecal losses of calcium (r = 0.438), magnesium (r = 0.434), phosphorus (r = 0.377), copper (r = 0.318), and manganese (r = 0.318) and the volume of feces. On these dietary regimes adolescents were in positive balances for calcium, phosphorus, and copper, but were in negative balances for magnesium and managenese.

Adolescent↗
PubMed1978

Nutritional status of adolescent girls in regard to zinc, copper, and iron.

Adolescent girls in the sixth through eight grades were surveyed for dietary intake and nutritional status in regard to zinc, copper, and iron in both the fall of 1975 and the spring of 1976. The adolescents (183 girls in the fall and 184 girls in the spring) consumed on the average 60 and 75% of the Recommended Dietary Allowances for iron and zinc, respectively. The mean concentration of zinc in hair samples was 216 +/- 64 microgram/g in the fall and 191 +/- 36 microgram/g in the spring. The mean concentration of copper in hair samples was 31 +/- 23 microgram/g. None of the girls had a concentration of zinc in their hair samples of less than 100 microgram/g. Hair concentrations of zinc anc copper were significantly correlated, but serum and hair concentrations of zinc were inversely correlated. However, in subsample of 102 girls, 3% has serum zinc levels below 70 microgram/100 ml and 4% had serum copper levels below 70 microgram/100 ml. Only 1% of the subjects had a hematocrit below 36%. No significant difference in any of these parameters was noted between girls who had experienced menarche and those who had not.

Adolescent↗
PubMed1978

Zinc, nitrogen, copper, iron, and manganese balance in adolescent females fed two levels of zinc.

The effect of feeding two different levels of zinc (Diet Z11.5 and Diet Z14.7) on zinc, nitrogen, copper, iron, and manganese balances was determined in 11 girls, 12.5 to 14.2 years, during a 30-day period. Diet Z11.5 provided 11.32 or 11.64 mg zinc daily, levels similar to that determined previously to be consumed by average adolescent females. Diet Z14.7 provided 14.52 or 14.84 mg zinc daily. These levels were just slightly less than the Recommended Dietary Allowance for zinc. When fed Diet Z14.7, subjects lost significantly more zinc in their feces than when fed Diet Z11.5. Regression analyses were applied to the zinc balance data from this study and a previous study with adolescent females. By extrapolation, a dietary intake of 11 mg zinc daily was estimated to compensate for fecal and urinary zinc losses of the average girl in these studies. The standard error of the estimate was 2.18 mg zinc daily. Nitrogen excretion and retention were unaffected by the variations in zinc intake. Copper excretion in the feces was significantly increased when subjects were fed Diet Z14.7 rather than Diet Z11.5. Manganese and iron fecal losses were also significantly correlated to zinc fecal losses.

Adolescent↗
PubMed1976

The effects of sweat nitrogen losses in evaluating protein utilization by preadolescent children.

A nitrogen balance study was conducted to determine the effects of three levels of nitrogen intake on the loss of nitrogen through sweat and to assess further the impact of sweat nitrogen on protein needs of preadolescent children. Values were determined through the collection of 24-hr, total body sweat samples from twelve healthy boys having a mean age of 8 years, 8 months. Mean height and weight of the subjects were 131.4 cm and 31.0 kg, respectively. Environmental conditions were relatively constant during the study. Mean sweat nitrogen losses were 208, 287, and 368 mg/day on daily protein intakes of 29, 54, and 84 g, respectively. Mean nitrogen balances per day were 0.39, 0.09, and 1.95 g when sweat nitrogen losses were included in the calculations. At the lower and moderate levels of protein intake, nine and six subjects were in negative nitrogen balance when sweat losses were considered. Sweat nitrogen losses in the boys were similar to a previous study with preadolescent girls. Based upon published basal metabolic rates and mean sweat nitrogen losses of 261 and 288 mg/day for girls and boys, the nitrogen lost through sweat was 0.25 mg/basal kcal for both sexes. An estimation of 0.5 mg/basal kcal for integumental nitrogen loss appears realistic for this age group.

Body Surface Area↗
PubMed1975

Sweat nitrogen losses by and nitrogen balance of preadolescent girls consuming three levels of dietary protein.

A nitrogen balance study was undertaken to determine the effects of three levels of nitrogen intake on the loss of nitrogen through sweat and to assess the impact of sweat nitrogen on the protein needs of preadolescent girls. Values were determined through the collection of 24-hour, total body sweat samples from 15 healthy girls with a mean age of 8 years, 7 months. Mean height and weight of the subjects were 132 cm and 28.9 kg, respectively. Mean sweat nitrogen losses, collected under uncontrolled environmental conditions, were 201 mg, 263 mg and 319 mg/day on 34 g, 57 g and 88 g of protein intake. The environmental conditions throughout the study remained fairly constant. Mean nitrogen balances per day were 0.04 g, 0.55 g and 1.42 g on the respective levels of nitrogen intake, with the inclusion of sweat nitrogen loss, however, a negative nitrogen balance per day was found in 8 and 2 subjects on 34 g and 57 g protein intake. After considering nitrogen retention of 0.3 g which has been recommended by NRC for the minimum nitrogen allowance for growth of preadolescent children, protein intakes higher than that recommended by the NRC-RDA for preadolescent girls may be required for support of normal growth.

Body Surface Area↗