Chapter 13
Manganese Availability for Humans Effect of Selected Dietary Factors
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Constance Kies, K. D. Aldrich, Jan M. Johnson, C. Creps, C. Kowalski, and R. H. Wang Department of Human Nutrition and Food Service Management, University of Nebraska, Lincoln, NE 68583
The objective of the project was to determine the effect of several dietary constituents on manganese bioavailability of young adult humans. In a series of studies, human subjects were fed constant, laboratory-controlled diets in order to create a background against which several different dietary variations could be tested during treatment periods ranging from seven to 28 days. Manganese contents of food, feces, urine and whole blood were analyzed using a carbon rod attachment on an atomic absorption spectrophotometer. At low manganese intake levels, manganese bioavailability was apparently enhanced by ascorbic acid and by meat-containing diets but was possibly inhibited by iron, ascorbic acid (at high manganese intake levels) and by some dietary fiber sources. Recommended and/or projected changes i n the American diet i n d i r e c t l y may change intakes of s p e c i f i c nutrients or of a v a i l a b i l i t y of s p e c i f i c nutrients i n unpredicted or unpredictable ways. Dietary f i b e r , ascorbic acid and dietary f a t have a l l been shown to affect the a v a i l a b i l i t y of some nutrient minerals. Hence, i t i s not unreasonable to assume that a l t e r a t i o n s i n intake of these dietary constituents might have a direct effect on the b i o a v a i l a b i l i t y of manganese or might i n d i r e c t l y affect manganese b i o a v a i l a b i l i t y by, for example, a f f e c t i n g the a v a i l a b i l i t y of other minerals with which manganese competes for absorption s i t e s . Stress on reduced c a l o r i c intake to avoid obesity has received a p a r t i c u l a r l y attentive audience among American women. Ideally, dietary reduction i n c a l o r ies i s achieved v i a decreased consumption of empty-calorie foods which leaves consumption of vitamins and minerals unchanged. In "real world" s i t u a t i o n s , a decrease i n c a l o r i c consumption almost invariably leads to a decreased intake of a l l nutrients. Impact of dietary factors on manganese b i o a v a i l a b i l i t y and on manganese n u t r i t i o n a l status have not been extensively investigated. The objective of the current project was to determine e f f e c t s of
0097-6156/87/0354-0136506.00/0 © 1987 American Chemical Society
In Nutritional Bioavailability of Manganese; Kies, Constance; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.
13.
KIES ET AL.
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Availability
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a l t e r a t i o n s i n i r o n , a s c o r b i c a c i d , f i b e r and meat i n t a k e on manganese u t i l i z a t i o n by young human a d u l t s .
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Procedures
(General)
I n a s e r i e s o f s t u d i e s r a n g i n g from 14 t o 56 days e a c h , a d u l t human s u b j e c t s were f e d c o n s t a n t , measured, l a b o r a t o r y c o n t r o l l e d d i e t s . D i e t s were based on o r d i n a r y foods and i n c l u d e d t h e f o l l o w i n g i t e m s : m i l k , u n e n r i c h e d 70% f l o u r bread ( p l u s wheat bran i n some s t u d i e s ) , r e a d y - t o - e a t o a t o r c o r n based b r e a k f a s t c e r e a l s , green beans, tomato and orange j u i c e ( o r a p p l e j u i c e i n some s t u d i e s ) , peanut b u t t e r , ground beef and tuna ( o r soy i s o l a t e p r o d u c t s ) , peaches, p e a r s , p o t a t o e s and r i c e . Water was a l l o w e d ad l i b i t u m . Jelly, b u t t e r and s o f t d r i n k s were used t o a d j u s t c a l o r i c i n t a k e f o r each s u b j e c t t o t h a t needed f o r weight maintenance. Thus, some d i f f e r ences i n t h e b a s a l d i e t s o c c u r r e d among s u b j e c t s b u t d i e t s were m a i n t a i n e d c o n s t a n t f o r any one s u b j e c t . E x p e r i m e n t a l v a r i a b l e s were superimposed on these b a s a l d i e t s as demanded by t h e o b j e c t i v e o f each study as d e s c r i b e d i n g r e a t e r d e t a i l w i t h t h e r e s u l t s . A l l food was p r e p a r e d and eaten under s u p e r v i s i o n o f p e r s o n n e l i n t h e human n u t r i t i o n m e t a b o l i c u n i t s p e c i a l d i e t k i t c h e n , Department o f Human N u t r i t i o n and Food S e r v i c e Management, U n i v e r s i t y o f Nebraska. Each s t u d y was d i v i d e d i n t o e x p e r i m e n t a l p e r i o d s o f 7 t o 28 days each. W i t h i n each s t u d y , a l l s u b j e c t s r e c e i v e d a l l e x p e r i m e n t a l v a r i a b l e s a c c o r d i n g t o a randomized, c r o s s - o v e r d e s i g n . S u b j e c t s were a l l s t u d e n t s o r employees o f t h e U n i v e r s i t y o f Nebraska who m a i n t a i n e d t h e i r u s u a l work, study and s o c i a l a c t i v i t i e s except f o r t h e e a t i n g o f t h e e x p e r i m e n t a l d i e t s and n o t h i n g e l s e , making c o l l e c t i o n s o f e x c r e t a , g i v i n g b l o o d samples, and f i l l i n g o u t v a r i o u s q u e s t i o n n a i r e s . A l l were assumed t o be i n good h e a l t h as e v a l u a t e d from h e a l t h h i s t o r i e s by m e d i c a l p e r s o n n e l o f the U n i v e r s i t y o f Nebraska H e a l t h C e n t e r . S i g n i n g o f s u b j e c t consent forms was r e q u i r e d o f a l l p a r t i c i p a n t s p r i o r t o p a r t i c i p a t i o n . This p r o j e c t was approved f o r human s u b j e c t p a r t i c i p a t i o n by t h e U n i v e r s i t y o f Nebraska I n s t i t u t i o n a l Review Board f o r t h e P r o t e c t i o n o f Human Research S u b j e c t s . S u b j e c t s made complete c o l l e c t i o n s o f u r i n e and s t o o l s t h r o u g h out each s t u d y . Feces f o r each s u b j e c t were d i v i d e d i n t o p e r i o d l o t s r e p r e s e n t i n g food eaten d u r i n g each p e r i o d by use o f f e c a l dyes ( b r i l l i a n t b l u e and carmine r e d ) and c o l o r e d g l a s s beads, composited, mixed and sampled f o r l a t e r a n a l y s e s . U r i n e f o r each s u b j e c t f o r each day was composited on t h e b a s i s o f t i m e , d i l u t e d t o a c o n s t a n t volume w i t h d i s t i l l e d w a t e r , mixed, sampled and f r o z e n f o r l a t e r a n a l y s e s . F a s t i n g b l o o d samples were drawn a t t h e b e g i n n i n g o f each study and a t t h e end o f each e x p e r i m e n t a l p e r i o d . Food, u r i n e , f e c e s and whole b l o o d were a n a l y z e d f o r manganese c o n t e n t s u s i n g a V a r i a n Model 1150 o r 1275 Atomic A b s o r p t i o n Spectrophotometer w i t h carbon r o d attachment a c c o r d i n g t o manual d i r e c t i o n s . A l t h o u g h manganese c o n t e n t s o f u r i n e were measured, r e s u l t s a r e n o t r e p o r t e d i n t h i s paper because o f t h e m i n u t e , unchangeable amounts w h i c h were found. Whole b l o o d manganese v a l u e s a l s o w i l l n o t be r e p o r t e d s i n c e t h i s a n a l y s i s was n o t performed on samples from a l l s u b j e c t s f o r a l l s t u d i e s . Those r e s u l t s which were o b t a i n e d i n d i c a t e d t h a t whole b l o o d manganese l e v e l s were r e s i s t a n t t o change i n the s h o r t term s t u d i e s w h i c h comprised t h i s p r o j e c t .
In Nutritional Bioavailability of Manganese; Kies, Constance; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.
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138
NUTRITIONAL BIOAVAILABILITY OF MANGANESE
I n e v a l u a t i o n o f d a t a o b t a i n e d , i t was assumed t h a t an i n c r e a s e i n f e c a l manganese l o s s a t s i m i l a r l e v e l s o f manganese i n t a k e denoted a d e c r e a s e i n manganese a b s o r p t i o n and u t i l i z a t i o n . Manganese i n t h e f e c e s may r e p r e s e n t exogenous, unabsorbed food manganese o r may be endogenous manganese w h i c h has been s e c r e t e d i n t o t h e g a s t r o i n t e s tinal tract. S i n c e t h i s endogenous manganese can be r e c y c l e d , an i n c r e a s e i n f e c a l manganese l o s s due t o an i n c r e a s e i n endogenous f e c a l manganese l o s s may even-so be due t o d i e t a r y c o n s t i t u e n t s . Apparent manganese r e t e n t i o n was c a l c u l a t e d by s u b t r a c t i n g t h e f e c a l manganese l o s s from t h e d i e t a r y i n t a k e . The p e r c e n t manganese r e t e n t i o n was c a l c u l a t e d by d i v i d i n g t h e manganese r e t e n t i o n by t h e manganese i n t a k e and m u l t i p l y i n g t h e r e s u l t i n g f i g u r e by 100. An i n c r e a s e i n apparent manganese r e t e n t i o n o r p e r c e n t manganese r e t e n t i o n was assumed t o i n d i c a t e an i n c r e a s e i n manganese b i o a v a i l ability. T h i s would be c o n s i d e r e d good i n s i t u a t i o n s i n v o l v i n g low manganese i n t a k e s but t h e r e v e r s e would be t r u e i f manganese t o x i c i t i e s are the issue. Data f o r each study were s u b j e c t e d t o s t a t i s t i c a l a n a l y s e s . These t e s t s i n c l u d e d a n a l y s i s o f v a r i a n c e and, i f t h e d e s i g n o f t h e s t u d y w a r r a n t e d , Duncan s M u l t i p l e Range Test and/or o r t h o g o n a l contrast. 1
Manganese U t i l i z a t i o n from Omnivore and V e g e t a r i a n
Diets
Americans a r e b e i n g encouraged t o i n c r e a s e t h e i r i n t a k e o f p l a n t based foods w h i l e d e c r e a s i n g t h e i r i n t a k e s o f a n i m a l o r i g i n products. S i n c e meat, m i l k , p o u l t r y and f i s h a r e known t o c o n t a i n o n l y s m a l l amounts o f manganese, t h i s recommendation would be e x p e c t e d t o have l i t t l e e f f e c t on t h e manganese i n t a k e l e v e l s o f humans. P l a n t p r o d u c t s such as soy w h i c h a r e o f t e n used i n p l a c e o f meat i n v e g e t a r i a n d i e t s may c o n t a i n h i g h e r amounts o f manganese t h a n does meat but c o n c u r r e n t l y t h e s e foods c o n t a i n g r e a t e r amounts o f p h y t a t e s w h i c h may i n h i b i t manganese u t i l i z a t i o n . The e f f e c t o f s u b s t i t u t i n g 100 g / s u b j e c t / d a y o f soy i s o l a t e based p r o d u c t s f o r t h e 50 g o f ground beef and 50 g o f t u n a / s u b j e c t / day i n t h e u s u a l b a s a l d i e t on manganese u t i l i z a t i o n was i n v e s t i gated i n one 56-day study a t t h e U n i v e r s i t y o f Nebraska. The p r o j e c t i n v o l v e d two 28-day p e r i o d s a r r a n g e d a c c o r d i n g t o a randomized c r o s s o v e r d e s i g n f o r each s u b j e c t . The s u b j e c t s were 10 a d u l t women who l i v e d and a t e a l l meals i n t h e d e p a r t m e n t a l m e t a b o l i c u n i t . D u r i n g one p e r i o d t h e s u b j e c t s r e c e i v e d t h e meat d i e t w h i l e , d u r i n g t h e o t h e r p e r i o d , t h e m e a t - f r e e ( s o y - c o n t a i n i n g ) d i e t was g i v e n . As shown i n T a b l e I , s u b s t i t u t i o n o f 50 g o f ground beef and 50 g o f t u n a f i s h / s u b j e c t / d a y w i t h 100 g / s u b j e c t / d a y o f soy i s o l a t e based p r o d u c t s r e s u l t e d i n a s i g n i f i c a n t decrease i n apparent manganese r e t e n t i o n o f t h e s u b j e c t s (p
