NUTRITION RESEARCH, Vol. 3, pp. 279-284, ]983 027|-53|7/83 $3.00 + .00 Printed in the USA. Copyright (c) 1983 Pergamon Press Ltd. All r ights reserved.

CHANGES IN PLASMA ZINC FOLLOWING THE INGESTION OF A ZINC MULTIVITAMIN-MINERAL SUPPLEMENT WITH AND WITHOUT BREAKFAST

Phylis B. Moser and Cathy J. Gunderson

Department of Food, Nutrition and Institution Administration, University of Maryland, College Park, Maryland 20742

ABSTRACT

The change in concentration of plasma zinc after the oral administration of zinc was used as an index of zinc absorption. The source of zinc was a multivitamin mineral supplement, which contained 25 mg of elemental zinc as zinc oxide. Taking the supplement without breakfast caused a significant increase (P < .01) in plasma zinc over the baseline concentration. Eating breakfast prior to taking the supplement prevented a rise in plasma zinc for at least three hours after taking the supplement. This suggests that a meal either inhibits the absorption of zinc from the supplement or reduces the rate of absorption, or increases turnover and/or excretion.

KEY WORDS: ZINC OXIDE, ABSORPTION

INTRODUCTION

Many multiple vitamin and mineral supplements currently available contain zinc in the form of zinc oxide. Only limited information can be found in the literature on the availability of this form of zinc (I, 2). Also, this zinc compound is often found in combination with iron compounds in multivitamin and mineral supplements. Solomons and Jacob (3) have suggested that the iron content in multivitamin-mineral supplements might inhibit the absorption of zinc. Thus it becomes important to investigate to what extent zinc in the form of zinc oxide in multiple vitamin-mineral supplements containing iron is absorbed. Since supplements containing iron are often recommended to be taken after a meal, it is important to determine how a meal affects the absorption of zinc from such a supplement. The following study was undertaken to determine if zinc, contained in a multiple vitamin- mineral supplement as zinc oxide, will increase plasma zinc concentration and to determine the effect of a meal on this increase.

METHODS

Ten women graduate students, none of whom took or were taking oral contra- ceptives, participated in a total of forty zinc absorption index tests. Each woman participated in four tests over a four week period. The protocol was approved by the Cormmittee on Human Subjects of the University of Maryland, College Park. The purpose of the study was explained to each of the subjects, as well as what would be expected of them. Each subject then gave written informed consent.

279

Z80 P.B. Moser and C.J. Gunderson

The study was a factorial design with two factors represented at two levels each: the supplement being one factor and breakfast the other. Each woman served as her own control and received all four possible treat- ments: zinc-containing supplement with breakfast, zinc-containing supplement without breakfast, zinc-free supplement with breakfast, and zinc-free supplement without breakfast. The treatments were applied to the subjects so that each treatment was represented at least twice on each of the four study days.

The composition of the zinc-containing and zinc-free vitamin and mineral supplements is given in Table i.

TABLE 1

Vitamin and Mineral Supplements

Each of the supplements contained:

Nutrient Amount

Vitamin A acetate Vitamin D 2 Vitamin E (as dl ~ -tocopherol acetate) Vitamin C Folic Acid Vitamin BI (as thiamine mononitrate) Vitamin B 2 Niacinamide Vitamin B 6 (as pyridoxine HCI) Vitamin BI2 Calcium (as calcium carbonate) lodine (as potassium iodide) Iron (as ferrous fumatate) Magnesium (as magnesium oxide) Copper (as cupric oxide) Zinc (as zinc oxide)

8000 IU 400 IU 30 IU

120 mg 1.2 mg 2.6 mg 2.8 mg

18.9 mg 4.0 mg 4.6 ug

350 mg 0.3 mg

60 mg I00 mg

2 mg 0 mg or 25 mg

The supplements with zinc contained 25 mg of elemental zinc as zinc oxide; the zinc-free supplements had the same composition except that they contained no zinc.

The breakfast used for this study consisted of the following items: 6 oz. orange juice, I oz. oat cereal (Cheerios) with 4 oz. whole milk, I large egg scrambled with Itsp. of butter, I slice whole wheat toast with i tbsp. strawberry preserves and 8 oz. spiced tea. Chemical analysis of the breakfast from each of the four study days showed it to contain 2 9!0.i mg (mean + SEM) of zinc.

A venous blood sample was drawn from each of the subjects after an eight hour fast from midnight. Additional samples were drawn at 1/2, I, 2 and 3 hours after the vitamin-mineral supplements were ingested. All supplements were taken with 8 oz. of deionized water and immediately after breakfast, if it was to be eaten. Nothing else was consumed until after the last blood sample was obtained.

P]asma Zinc Changes with Supplement and a Meal 281

Blood samples were collected in zinc-free 5 cc plastic syringes (Sarstedt Co., Princeton, N.J.) to which i mg of zinc free heparin had been added. The blood was centrifuged at 4~ for 12 minutes at 740 x g. The plasma was removed and frozen in polypropylene tubes until analysis. Plasma was analyzed by the method of Smith and Butrimovitz (4) using a Perkin Elmer Series 4000 atomic absorption spectrophotometer.

Data were analyzed by a two way analysis of variance for repeated measures and Duncan's multiple range test (5).

RESULTS

Figure 1 shows the changes in plasma zinc concentration from the baseline concentration that occurred after the ingestion of a vitamin-mineral supplement containing either 25 mg or 0 mg of elemental zinc as zinc oxide. This figure also shows the effect of eating breakfast on the changes in plasma zinc when either supplement was taken. There was a significant (P <.05) supplement-breakfast interaction on plasma zinc concentration. The women taking the zinc-containing supplement without breakfast had a significant increase in plasma zinc (P < .01) compared to the women taking the zinc-free supplement or to the women who ate breakfast and then took the zinc supplement. This significant increase was seen at 1/2, i, 2 and 3 hours after the supplement was taken. Women taking the zinc-free supplement without breakfast did not show a significant change from the baseline in plasma zinc concentration over the three hour period. Women who ate breakfast had plasma zinc levels which fell below the baseline for the three hours after breakfast regardless of the presence of zinc in their supplement.

DISCUSSION

Experiments with chicks have shown zinc oxide to be an available source of zinc to the young growing chick (I, 2). Also, when Hambidge et al. (6) fed a breakfast cereal fortified with zinc oxide over a period of several months to children they observed an increase in plasma zinc. These data along with our observations of an increase in plasma zinc after taking the supplement containing zinc oxide, suggest that zinc oxide is an available source of zinc for humans.

The ratio of iron to zinc in our supplement was 2.4:1, This is in the range which Solomons and Jacob (3) have found to substantially inhibit zinc uptake. In our study even with the iron contained in the supplement there was an increase in plasma zinc of 40 ug/dl over the baseline concentration; an increase of 41%. This increase of 40 ug/dl over baseline is slightly greater than that found by Solomons and Jacob when subjects received 50 mg of ferrous sulfate and 25 mg of zinc sulfate. However, the percent chance of plasma zinc from the baseline concentration was similar for the two studies. Perhaps, the increase in plasma zinc would have been substantially greater, if there had been no iron in the supplement. Of interest is the fact that plasma zinc increased by 41% while the iron to zinc ratio in the supplement was 2.4:1. Other constituents in the supplement, such as calcium, may have had an influence on the increase in plasma zinc also.

282 P.B. Moser and C.J. Gunderson

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Figure I. Plasma zinc response (change in plasma zinc concentration from baseline value) to a multivitamin andmineral supplement with and without zinc taken with and without breakfast.

Plasma Zinc Changes with Supplement and a Meal 283

Consumption of the supplement after breakfast reduced plasma zinc below the baseline concentration. Other investigators have observed~a similar pattern of plasma zinc response after a meal. For the same intakes of zinc, the change in plasma zinc concentration variedwith the composition of the meal (7-11). Other researchers report that the response of plasma zinc to a load dose is influenced not only by the amount of zinc (12) but also by the types of foods consumed with the load dose (8-12).

Breakfast foods that have been reported to decrease zinc intake are eggs (12), whole wheat bread and~milk (9). Further investigation is needed to determine which food items or combinations in the study breakfasts were responsible for the decrease in plasma zinc.

In summary, zinc oxide contained in a multivitamin and mineral supplement with an iron to zinc ratio of 2,4:1 is an available source of zinc for humans. Consumption of the supplement with a breakfast which~contained eggs, whole wheat bread, milk and oat cereal inhibited the rise in plasma zinc associated with zinc supplementation. If changes in plasma zinc concentration are reflective of absorption, then the breakfast either reduced the rate of or inhibited absorption of zinc and/or increased the turnover and excretion of zinc.

ACKNOWLEDGEMENTS

The authors wish to express their appreciation to Stuart Pharmaceuticals for supplying us with the vitamin-mineral supplements. The authors also wish to acknowledge the expert technical assistance of Pat Howard and to thank the subjects who participated in this study.

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REFERENCES

EDWARDS, H. The availability to chicks of zinc in various compounds and ores. J. of Nutr. 69: 306-308, 1959.

ROBERSON, R. and SCHARBLE, P. The availability to chicks of zinc as the sulfate, oxide or carbonate. Poul. Sci. 39: 835-836, 1960.

SOLOMONS, N.W. and JACOB, R. Studies on the bioavailability of zinc in humans: Effects of heme and nonheme iron on the absorption of zinc. Am. J. Clin. Nutr. 34: 475-482, 1981.

SMITH, J.C. and BUTRIMOVITZ, G.P. Direct measurement of zinc in plasma by atomic absorption spectroscopy. Clin. Chem. 25: 1487-1491, 1978.

SOKAL, R.R. and ROHLF, J.F. Biometry. of statistics in biological research. 1969.

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HAMBIDGE, M.K., CHAVEZ, M.N., BROWN, R.M., and WALRAVENS, P. Zinc nutritional status of young middle-income children and effects of consuming zinc-fortified breakfast cereals. Am. J. Clin. Nutr. 32: 2532-2539, 1979.

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CASEY, C., WALRAVEN, P. and HAMBIDGE, K.M. Zinc absorption and plasma response. Am. J. Clin. Nutr. 34: 1443-1444, 1981.

PECOUD, A., CONZEL, P. and SCHELLING, J.L. Effect of food stuffs on the absorption of zinc sulfate. Clin Pharmacol. Ther. 17: 469- 474, 1975.

SOLOMONS, N.W., JACOB, R.A., PINEDA, O. and VITERI, F.E. Studies in the bioavailability of zinc in man. Effects of the Guatemalan rural diet and the iron-fortifying agent, NaFeEDTA. J. Nutr. 109: 1519-28, !979.

SOLOMONS, N.W., JACOB, R.A., PINEDA, O. and VITERI, F.E. Studies on the bioavailability of zinc in man. II. Absorption of zinc from organic and inorganic sources. J. Lab. Clin Med. 94: 335-43, 1979.

OELSHLEGEL, F.J. and BREWER, G.J. Absorption of pharmacologic doses of zinc. In: Zinc Metabolism: Current aspects in health and disease. G.J. Brewer and A.S. Prasad (eds.). Alan R. Liss, Inc., New York, 1977, pp. 299-311.