Zinc status of elderly black Americans from urban low-income households

The relationship between the zinc nutritive status and biochemical markers of bone turnover in older European adults: the ZENITH study

OBJECTIVE

To investigate the relationship between indices of zinc nutritive status and biochemical markers of bone turnover in older adult European subjects.

DESIGN

Use of baseline data from a multicentre prospective zinc intervention (ZENITH) study.

SETTING

Centres in France, Italy and Northern Ireland.

PARTICIPANTS

A total of 387 healthy adults, aged 55-87 y.

METHODS

Zinc intake was assessed by 4-day recall records. Circulating and urinary biochemical zinc status measures were assessed by atomic absorption spectrophometry. Serum bone-specific alkaline phosphatase and osteocalcin were assessed by ELISA and urinary pyridinoline (Pyr) and deoxypyridinoline (Dpyr) by HPLC.

RESULTS

Zinc intake was negatively correlated with urinary Pyr and Dpyr (r = -0.298 and -0.304, respectively; P < 0.0001), but was not correlated with bone formation markers. There was a tendency for serum zinc to be negatively correlated with urinary Dpyr (r = -0.211; P = 0.080). Erythrocyte zinc was negatively correlated with serum osteocalcin (r = -0.090; P < 0.0001). None of the other correlations were significant. After adjustment for confounder (age, gender and research centre) the only significant association that remained was between serum osteocalcin and erythrocyte zinc (beta = -0.124; P = 0.011).

CONCLUSIONS

There was some, albeit inconsistent, evidence of a relationship between zinc nutritive status and bone turnover in the older adult participants of the ZENITH study.

The effect of income on selenium intake and status in Utah County, Utah

Foodstuffs produced and/or purchased locally were analyzed for Se. The effect of income and gender on Se intake and status of Utah County residents was evaluated by measurement of the following indicators: erythrocyte (RBC) and plasma Se concentration, and activity of Se-glutathione peroxidase (Se-GSH-Px) (EC 1.11.1.9) in RBCs, platelets, and plasma. A Random Digit Dialing procedure was employed to stratify subjects according to gender and annual family income (less than +10,000, +10,000-20,000, greater than +20,000) in a 2 x 3 factorial design, seven subjects per cell. The weekly consumption of 44 foods shown to contribute over 90% of the Se intake of U.S. subjects was recorded for each study participant. The estimated minimum daily intake for this sample was 76.0 +/- 4.5 micrograms Se/day (mean +/- SEM). Available grain products are not produced locally, and their Se content is lower than average values reported by the U.S.D.A. Locally produced meat and dairy products had higher than average Se contents. In spite of lower grain Se and higher meat Se concentrations, subjects in this study derived more Se from grain and dairy products, and less from meat products than did subjects in a nationwide sample. The Se status of Utah County residents is similar to several other populations in the United States. There were no significant differences in Se status or intake due to gender or income. The results suggest that consumption of other foods produced in a "high Se" area can maintain Se intake and status in spite of reduced consumption of meat products generally viewed as more reliable sources of dietary Se.

[Trace elements in artificial nutrition. Art and practice]

The trace elements known to be necessary for man are iron, zinc, copper, selenium, chromium, manganese, molybdenum, cobalt and iodine. This review article, which excludes iron, deals with the need for supplemental trace elements during artificial feeding, and the way they should be administered. The biological importance of these trace elements is argued on the basis of their biochemical involvement and the clinical pictures seen in accidental or experimental deficiency states. Assessing a patient's trace element status is rather difficult. The relative merits of different laboratory investigations is discussed: plasma, erythrocyte, capillary and urinary levels, specific enzyme activities, loading tests. The different situations when trace elements are required, assessing the amount needed and the possible toxic risks, are presented from a literature survey.

Trace elements in nutrition of the elderly. 1. Established RDAs for iron, zinc, and iodine

Trace elements play a poorly understood role in human metabolism and nutrition. In the elderly, the normal effects of aging further complicate an understanding of trace element nutriture. The RDA standards established to date for the elderly have important limitations in that "healthy" persons 51 years of age and older constitute a single, regrettably imprecise category. Although any minor elemental constituent of the body is considered to be a trace element, only 16 are currently believed to be of biologic importance to humans. A recommended dietary allowance (RDA) has been established for only three of these--iron, zinc, and iodine.

Is aging inevitable? The intracellular zinc deficiency hypothesis of aging

A review of the literature suggests that an intracellular zinc deficiency may be the primary cause of the aging process. Zinc-metalloenzymes play an important role in many aspects of cellular metabolism including DNA replication, repair and transcription. The main enzymes affected by zinc deficiency may be specific for each cell type. Depending on which zinc enzymes are "overvulnerable", zinc deficiency may result in accumulation of useless (or toxic) materials, malproduction of essential proteins, a neoplastic change or cell death, thus explaining the variability in aging patterns in different cell types. There is no simple and reliable index of zinc status in humans and a therapeutic trial may be needed to establish zinc deficiency. Finding a zinc-compound which can enter the cell and avoid the development of intracellular zinc deficiency may retard the aging process and postpone age-related diseases.

Nutritional evaluation and supplementation of elderly subjects participating in a "meals on wheels" program

A nutritional assessment of 33 elderly subjects participating in a "meals on wheels" program revealed a high prevalence of nutritional deficiencies. Twelve of these subjects, who were considered to be at high risk for protein calorie malnutrition, received 240 ml of a polymeric dietary supplement three times daily for 16 wk. This resulted in a significant (50%) increase in total caloric and protein intake which was maintained for the entire 16 wk of study. In seven of the 12 subjects a weight gain of greater than 2 kg was found. Modest but significant elevations in serum albumin and highly significant elevations of the total iron binding capacity, serum and red cell folate, leukocyte ascorbate, and serum vitamin B12 provided strong evidence for improved nutritional status. In contrast no improvement in the hemoglobin, total lymphocyte count, T cell number, T suppressor cells, T helper, or B cells was noted. In no anergic subjects was skin test conversion found. In addition no increase in serum trace metals or vitamin B6 levels were noted. Thus this study demonstrates that nutritional supplementation results in significant improvement in selected nutritional parameters. The fact that the hematopoietic and immunological status of these patients was unchanged suggest that the abnormalities may be age rather than nutritionally related or that a critical nutritional deficiency was not corrected.

Analysis and evaluation of zinc and copper in human plasma and serum

Recommendations for daily dietary intakes of copper and zinc have been made by the National Academy of Sciences during the last decade. As a result there is increasing interest in analytic techniques for accurate and precise assessment of these trace elements in human tissues, including blood. In addition, the importance of standardizing techniques for the collection, preparation, and analysis of biologic samples is now recognized. The necessity for preventing contamination or losses requires careful monitoring at each step, from collection to analysis. Likewise, precision and accuracy must be established for techniques and certified reference standards employed. The selection of an ideal anticoagulant for preparing plasma for copper and zinc analyses is receiving increased attention. The discrepancy observed regarding higher concentrations (10-15%) of zinc and copper in serum than citrated plasma remains to be resolved. Following analysis and summary of the data, interpretation of the results is of paramount importance. It must be remembered that abnormal plasma or serum zinc or copper concentrations do not necessarily reflect true aberrations in metabolism, since several conditions (disease and nondisease) can also influence these indices of trace element nutriture. Immediate attention must be given to advancing the concept that trace element analysis of biological materials requires special collection, storage, and analysis precautions.

Biological assay for zinc availability in wheat germ

Our objective was to develop a method to determine the bioavailability of zinc in wheat germ. Weanling rats were fed for 10 days a Zn-free diet supplemented with different levels of Zn, with or without 2% wheat germ. Zinc concentrations of either tibia or femurs were plotted directly against Zn added to the diet, giving two lines that were essentially parallel. A multiple regression model was used to obtain a common slope but different intercepts for the lines. The amount of available Zn was calculated by taking the ratio of the difference in intercepts to the common slope. The result showed that wheat germ contained 163.7 micrograms Zn/g, of which 86.7% was bioavailable to the rat.

Zinc concentrations in hair, plasma, and saliva and changes in taste acuity of adults supplemented with zinc

The effect of zinc supplementation as zinc acetate (15 mg Zn/day for 5 weeks) was determined on stimulated parotid salivary zinc levels and taste acuity. In addition, zinc and copper levels of hair and plasma in 10 healthy subjects (five male and five female) between the ages of 17 and 37 years were studied. Presupplementation and 5 weeks postsupplementation levels were evaluated as well. Taste acuity for sweet improved with zinc supplementation and returned to presupplementation levels after supplementation ceased. No changes in plasma copper or salivary zinc levels were found with zinc supplementation although stimulated parotid saliva flow rate increased. Plasma zinc levels increased significantly while hair copper increased slightly with supplementation. All indices returned to presupplementation levels by 5 weeks after cessation of supplementation.

Zinc and protein status in the elderly

Protein and zinc status were assessed in 24 community based and 66 institutionalised elderly Australians, aged 60 to 99 years. Serum albumin concentrations were significantly related to both protein intake (r = 0.36, P less than 0.001) and zinc intake (r = 0.33, P less than 0.001). Plasma zinc concentrations were not related to zinc intake (r = 0.12, P greater than 0.05) or to protein intake (r = 0.007, P greater than 0.05). Thus in aged persons with low serum albumin, it would appear useful to consider both protein and zinc intake.