Nutritional Bioavailability of Zinc - American Chemical Society

11 Dietary Phytate/Zinc Molar Ratio and Zinc Balance in Humans

Downloaded by PURDUE UNIV on May 27, 2016 | http://pubs.acs.org Publication Date: January 20, 1983 | doi: 10.1021/bk-1983-0210.ch011

EUGENE R. MORRIS and R E X ELLIS U.S. Department of Agriculture, Agricultural Research Service, Beltsville Human Nutrition Research Center, Beltsville Agricultural Research Center, Beltsville, MD 20705

The effect on zinc balance of a 10-fold difference in dietary molar ratio of phytate/zinc was tested i n a metabolic balance study with 10 adult men. The mean zinc balance was 2.74 mg per day when the dietary molar ratio of phytate/zinc was about 12 and 2.0 mg per day when the r a t i o was about 1. Menus consisted of foods commonly consumed i n the United States. The mean daily intake of zinc was 17 mg and of neutral detergent fiber 16 g. The molar ratios of phytate/zinc were attained by using 36 g per day of whole or dephytinized wheat bran. Analysis of hospital and self-chosen diets indicate that the majority of the United States population consume diets with molar ratios of phytate/zinc less than 10, but which provide less than the recommended dietary allowance of z i n c . The balance results are discussed i n relation to magnitude of the zinc intake, the type of food consumed and the role of adaptive responses i n maintaining adequate zinc nutriture. Zinc i s a required mineral nutrient i n the diet of animals and the signs and effects of a dietary deficiency have been described in several species (jL). Nutritional zinc deficiency has also been described i n humans (2). Signs of n u t r i t i o n a l zinc deficiency may be manifest even though the individual i s consuming an amount of dietary zinc that exceeds the usually designated requirement (3). Thus, b i o a v a i l a b i l i t y of dietary zinc i s a factor that must be evaluated i n considering adequacy of dietary intake (JO. Phytic acid and dietary fiber i n foods have been implicated as important determinants of dietary zinc b i o a v a i l a b i l i t y (5,.6,7). For rats, the molar ratio of phytic acid to zinc i s a good predictor of b i o a v a i l a b i l i t y of dietary zinc when semipurified type diets are fed i n which ZnS04 and either sodium phytate or This chapter not subject to U.S. copyright Published 1983 American Chemical Society Inglett; Nutritional Bioavailability of Zinc ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

N U T R I T I O N A L BIOAVAILABILITY OF


160

ZINC

soy p r o t e i n are the d i e t a r y source of z i n c and p h y t i c a c i d , r e s p e c t i v e l y (8,9,10). L i t t l e i n f o r m a t i o n i s a v a i l a b l e to a s c e r t a i n the i n f l u e n c e of the d i e t a r y molar r a t i o of phytate/ z i n c on z i n c n u t r i t i o n o f humans. D i e t a r y f i b e r from wheat bran i n the d i e t of r a t s does not seem to i n f l u e n c e b i o a v a i l a b i l i t y of z i n c but the phytate does (JL1,12,JL3). D i f f e r e n t i a t i o n between the e f f e c t o f phytate and f i b e r i s d i f f i c u l t i n b i o a v a i l a b i l i t y s t u d i e s w i t h wheat bran or other c e r e a l and legume products t h a t c o n t a i n both phytate and d i e t a r y f i b e r . By the a c t i o n of the endogenous phytase, wheat bran can be dephytinized without changing the d i e t a r y f i b e r c o n c e n t r a t i o n (1^)· Although there may be an as yet u n i d e n t i f i e d chemical change i n the d i e t a r y f i b e r , e n z y m a t i c a l l y dephytinized wheat bran provides a r e l a t i v e l y high f i b e r food product from c e r e a l g r a i n that i s low i n phytate. We conducted a human metabolic balance study to t e s t the concept o f d i e t a r y p h y t a t e / z i n c molar r a t i o as a p r e d i c t o r o f z i n c b i o a v a i l a b i l i t y to humans. Using unaltered or e n z y m a t i c a l l y d e p h y t i n i z e d wheat bran w i t h o r d i n a r y foods we a t t a i n e d phytate z i n c molar r a t i o s of about 1 and 12 w i t h r e l a t i v e l y high i n t a k e s o f d i e t a r y f i b e r i n the menus and found no d i f f e r e n c e i n z i n c balance. R e t r o s p e c t i v e l y , the r e s u l t may be q u a l i f i e d on the b a s i s o f the magnitude of the z i n c i n t a k e and p o s s i b l e adaptive or homestatic responses over the period of the study. A second study was then conducted and a wider range o f p h y t a t e / z i n c molar r a t i o was provided than i n the f i r s t study. We w i l l b r i e f l y o u t l i n e the f i r s t study, g i v e a progress report on the second study and, w i t h some i n f o r m a t i o n on phytate i n t a k e s obtained by our l a b o r a t o r y , d i s c u s s the n u t r i t i o n a l i m p l i c a t i o n . Balance Study I Study P r o t o c o l and M a t e r i a l s . Ten healthy men ranging i n age from 23 to 48 years volunteered as subjects f o r the study. Each gave informed consent and was given a p h y s i c a l examination p r i o r to the study. An o u t l i n e o f the study p r o t o c o l i s shown i n Figure 1. Each phytate/zinc molar r a t i o was consumed f o r 15 days, three repeats o f the 5-day menu c y c l e . S t o o l and u r i n e c o l l e c t i o n s were pooled f o r the periods as i n d i c a t e d i n Figure 1. A f a s t i n g blood sample f o r serum z i n c a n a l y s i s was taken on days 1, 16 and 31. The menus c o n s i s t e d of foods r o u t i n e l y consumed i n the United S t a t e s . An example o f one day's menu i s given i n Table I . D i f f e r e n t c a l o r i c i n t a k e s were provided, to maintain each subjects weight, by v a r y i n g the amount of the non-muffin items i n i n c r e ments of 10% using the 3200 k c a l meals as base. Each subject consumed two bran muffins w i t h each meal, 6 g o f bran per m u f f i n . A l l food was supplied and cooked by the Human Study F a c i l i t y o f the B e l t s v i l l e Human N u t r i t i o n Research Center. Monday through F r i d a y meals were consumed at the Human Study F a c i l i t y and take-home packs were s u p p l i e d f o r weekends and one h o l i d a y .

Inglett; Nutritional Bioavailability of Zinc ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

11.

AND

MORRIS

15

Phytate/Zinc Molar Ratio

ELLIS

DAYS

15

161

DAYS

GROUP A WHOLE BRAN

MUFFINS

DEPHYTINIZED

GROUP


DEPHYTINIZED

BRAN

I

WHOLE BRAN COLLECTION

II

STOOL

5,6

STOOL &

MUFFINS

PERIODS

III URINE

15

16

MUFFINS

Β

MUFFINS EXCRETA

1

BRAN

IV

STOOL

20,21

STOOL & URINE

31

Figure 1. Outline of experimental protocol. Menus repeated in 5-day cycles. T bran muffins consumed with each meal (6 g of bran/muffin). Five subjects e subgroup, A & B. Brilliant blue dye (50 mg) was given with breakfast on days 1, 6, 16, 21, and 31 (lower line) to aid in demarcation of stool.

DEIONIZED

WATER,

DRINKING,

B U T NO OTHER B E V E R A G E S WERE A L L O W E D .

THE TORY, OUR

INSTANT

WHEAT BRAN

WAS

LABORATORY AT B E L T S V I L L E ,

ONE-HALF OF

T H E BRAN

USED

DEIONIZED WITH

(WHOLE

PHYTASE WATER

CONSTANT

INCUBATION

(1

BRAN)

ACTIVITY G BRAN

SHAKING

THE ENTIRE

PRODUCTS,

STORED

AND

CONSUMED

6

CONSUMED

EACH

BUT 5

MUFFINS

(GROUP

CONSUMED ALTERNATE

DRIED BEFORE

G O F BRAN

OR 36

CONSUMED

COMPOSITES

SAMPLING

FOR

MUFFIN

A PORCELAIN CRUCIBLE

MUFFINS

AND

A

HOMOGENIZED AND

ML A L I Q U O T

DRY A S H E D .

ZINC

BRAN

WAS

WERE

SUBJECT

SUBJECT OF

THE

(GROUP 15

STUDY, B)

DAYS

AND T H E

DAYS.

FREEZE-DRIED 50

5

THE 3200 KCAL

SEPARATELY), WERE

EACH AND

37°

HYDROLYSIS

EACH

THE F I R S T 15

AT

T H E BRANS AND

BY IN

AFTER

AND

DAY.

T H E SECOND

WERE MADE O F

STOOLS

SUSPENDED

INCUBATED

USE.

IN

REFRIGER

OF DEPHYTINIZED

MUFFIN,

FOR

WAS

HOURS.

NUTRIENTS

EACH

MUFFINS

ANALYSIS.

AND 16

LABORA

WHEAT.

DEPHYTINIZED

WAS

OVER T H E COURSE

WHOLE BRAN

MUFFIN

COMPOSITED

FOR A N A L Y S I S .

PER

G O F BRAN

BRAN

T Y P E O F BRAN WERE

OR ABOUT

REFRIGERATED UNTIL 6

DEPHYTINIZED

DAILY (MUFFINS

ML WATER)

THE MINERAL

T Y P E O F BRAN A)

10

T H E BRAN

WATER S U S P E N S I O N

RETAINING

INTO MUFFINS,

TO

SPRING

O N E - H A L F WAS

(12).

OVERNIGHT

FREEZE-DRIED, BAKED

AND

FOR

T H E USDA WHEAT Q U A L I T Y RED

ENDOGENOUS

IN

M I L L E D BY

L O T O F HARD

UNTIL

ND

C O F F E E WERE S U P P L I E D

FROM A S I N G L E

ATED

FARGO,

T E A AND

MENU AND

ITEMS FREEZE-

THROUGHLY M I X E D

OF URINE

ANALYSIS

WAS

WAS


BY

DRIED FLAME

162

N U T R I T I O N A L BIOAVAILABILITY OF

Table I .

Example of One Day's Menu

ZINC

1

BREAKFAST Orange/Grapefruit Scrambled Egg Margarine Sausage L i n k s M i l k , 2% Muffins


2

Jelly Margarine Sugar

2

2

Juice

124 grams 50 5 42 246 120 66 40 10

LUNCH Turkey Roast Macaroni Mayonnaise Cranberry J u i c e Ice Cream Muffins

90 70 15 126 100 120

DINNER Steak B o i l e d Potato Stewed Tomato Pumpkin P i e M i l k , 2% Grape J u i c e Muffins

2

10 50 50 100 2H6 253 120

I32OO 2

k c a l , 132 g p r o t e i n , 40% c a l o r i e s from f a t , P/S G i v e n with breakfast and used throughout the day.

0.66.

atomic absorption spectroscopy o f 1 N HC1 s o l u t i o n o f dry ashed d i e t or s t o o l composite. Phytate a n a l y s i s was by the method of E l l i s et a l . (14). N e u t r a l detergent f i b e r was determined by the approved method o f the American A s s o c i a t i o n of C e r e a l Chemists (15). Results Results p e r t a i n i n g to z i n c w i l l be summarized here. Information concerning other mineral n u t r i e n t s have been published i n part i n a b s t r a c t s and a short communication (16,17,18).


11.

MORRIS

NUTRIENT ZINC

INTAKE.

AND P H Y T I C

THE D I F F E R E N T ZINC

Phytate/ Zinc Molar Ratio

A N D ELLIS

SUMMARIZES

T H E RANGE O F Z I N C

C A L O R I C L E V E L S CONSUMED.

CONSUMED WAS CONTAINED

PHYTIC

A C I D WAS D E R I V E D

THE DAILY INTAKE

FROM T H E M U F F I N S

AND, SINCE

WAS NO D I F F E R E N C E

DUE TO T H E C A L O R I C L E V E L

BY AND

TABLE

II.

I N PHYTIC

I N PHYTIC

DAILY

INTAKES

MUFFIN

THERE

ACID

ACID

INTAKES.

INTAKES

T H E MEAN C A L C U L A T E D MOLAR R A T I O O F

WAS ABOUT 12 WHEN WHOLE BRAN M U F F I N S

G R E A T E R THAN 1 WHEN D E P H Y T I N I Z E D

JUST

T H E SAME

REGARDLESS O F CALORIC L E V E L ,

A TEN-FOLD DIFFERENCE

T Y P E O F BRAN M U F F I N .

OF THE

ABOUT 9 5 Î O F T H E

WAS E A T E N

PHYTATE/ZINC

INTAKES OF

I S T H E RESULT O F

ABOUT ONE-THIRD

IN THE MUFFINS.

NUMBER O F M U F F I N S

T H E R E WAS, HOWEVER,


TABLE I I

ACID.

163

OF ZINC

AND P H Y T I C

ZINC

PHYTIC

WERE CONSUMED

BRAN M U F F I N S

WERE

ACID

P H Y / Z N MOLAR

ACID

RATIO

TYPE MG WHOLE BRAN

G

DEPHYTINIZED

-

18.9)

(10.5

1

-

13.6)

1

1.2

0.2

17.1

BRAN

11.8

2.0

16.8 (14.7

^-RANGE CONSUMED. SUPPLIED

A N EQUAL AMOUNT O F N E U T R A L D E T E R G E N T F I B E R WAS BY EACH

T Y P E O F BRAN M U F F I N .

G O F NEUTRAL DETERGENT F I B E R ZINC EACH

BALANCE.

15 DAY PERIOD

FIGURE

2.

T H E ZINC

AND I V , F I G U R E

WERE I N P O S I T I V E Z I N C

O F T H E T Y P E O F BRAN M U F F I N CONSUMED. SUBJECTS,

THE ZINC

WHOLE BRAN M U F F I N S .

INDIVIDUAL

ONE I N E A C H

B A L A N C E WHEN CONSUMING

O V E R A L L T H E MEAN B A L A N C E WAS 0 . 7

BRAN M U F F I N S .

10 DAYS O F A R E SHOWN I N

BALANCE REGARDLESS

O F T H E 10

ONLY TWO I N D I V I D U A L S ,

G R E A T E R WHEN E A T I N G WHOLE BRAN M U F F I N S IZED

1)

B A L A N C E FOR 8 WAS G R E A T E S T WHEN CONSUMING T H E

WERE I N MORE P O S I T I V E Z I N C BRAN M U F F I N S .

A MEAN O F 1 6

DAILY.

B A L A N C E S FOR T H E L A S T

(PERIODS I I

A L L SUBJECTS

BY ANALYSIS,

WAS CONSUMED

THIS

SUBGROUP,

DEPHYTINIZED

MG P E R DAY

THAN WHEN E A T I N G

DEPHYTIN-

D I F F E R E N C E WAS NOT S T A T I S T I C A L L Y

SIGNIFICANT. VALUES IN

FOR I N T A K E M I N U S F E C A L

TABLE I I I .

AND

III

AND T H E 10 DAYS

SEQUENCE FOR DAYS

EXCRETION OF ZINC

T H E V A L U E S AR E M G / D A Y FOR T H E 5 DAYS O F PERIODS

II

AND I V .

ARE P R E S E N T E D O F PERIODS

REGARDLESS

I N WHICH T H E TWO T Y P E S O F BRAN WERE CONSUMED,

VALUES

I N T A K E MINUS F E C A L E X R E T I O N WERE G R E A T E R FOR T H E L A S T EACH

TYPE O F MUFFIN

WAS CONSUMED

I

OF THE

THAN FOR T H E F I R S T 5


10 DAYS,


164

NUTRITIONAL

SUBJECTS I

SUJECTS 6-10

BIOAVAILABILITY

OF

ZINC

A L L SUBJECTS

Figure 2. Zinc balances for metabolic periods II and IV. Mean daily balance for individual subjects shown in the sequence of type of bran muffin consumed. Wit each subgroup, each individual is represented by a different shapedfigure.Mean are shown by horizontal lines for each subgroup and the arrows for all subjects. Key: solid symbols, whole bran; and open symbols, dephytinized bran.


11.

PERIODS

II

AND I V COMPARED TO I

AND I I I ,

MAGNITUDE O F T H E S . D . FOR P E R I O D S INDIVIDUALS

O F EACH

THAN WAS CONSUMED,

SUBGROUP

FECAL

E X C R E T I O N V A L U E S WERE ALWAYS

FIRST

5 DAYS

TABLE

MUFFINS

DEPHYTINIZED

BRAN

LESS

PERIOD

THE

I N MAGNITUDE

MINUS

THAN T H E

WERE CONSUMED,

GROUP A

III VS. I.

EXCRETION OF ZINC

I

II

PERIOD

2

III

MG/DAY

IV

1

(zl

(+)3 -1.4+1.8

I.

THE INTAKE

EXCRETA COLLECTION

SUBGROUP

THAT SOME

I N T H E STOOL

A DURING

CONSUMED

MUFFINS

I N T A K E MINUS F E C A L

SUBJECT


WERE

V S . I L L AND Β P E R I O D S

III.

RESPECTIVELY. THE

AND I I I V E R I F Y

E S P E C I A L L Y SUBGROUP

5 DAYS WHOLE BRAN

I

I

E X C R E T E D MORE Z I N C

FIRST

PERIODS

165

Phytate IZinc Molar Ratio

MORRIS A N D ELLIS

3.2+0.9

1.8+3.6

2.4+1.6

0.9+2.0

(-)

2.4+1.1 (+)

1.2+1.3

3.0+0.4

IMEAN + S . D . 2

SEE

FIGURE

3(+)

1.

WHOLE BRAN SERUM Z I N C

SERUM Z I N C DURING 1

RESPONSE.

DEPHYTINIZED

TABLE

THE STUDY.

THE INITIAL DURING

OF PHYTATE. PHYTATE

OBERLEAS DISCUSSES

THAT I N F L U E N C E RATS

GROWTH,

EQUIVALENT

TO WHEN Z N S 0 4

APPARENTLY

THEZINC

OF ZINC

ZINC

RATS

EXHIBIT

ZINC

(9,20).

ABSORPTION,

ZINC

ZINC OF ANY

R E S P O N S E WAS

SOURCE. COMPLEXES D I S S O C I

FROM E X T R A C T I N G T H E Z I N C .

I N THE DIET SIGNS

I N 12

TO 1 5 - F O L D

T H E M E T A B O L I C B A L A N C E DOES

OF B I O A V A I L A B L E NUTRIENT

HOWEVER,

WHEN

MOLAR E X C E S S

OVER

O F DECREASED B I O A V A I L A B I L I T Y NOT MEASURE

B U T A MEASURE C A N B E O B T A I N E D

BIOAVAILABILITY

SOME O F

T R A C T OR T H E COMPLEX I S NOT STRONG ENOUGH

TO P R E V E N T T H E I N T E S T I N E IS PRESENT

B U T NOT FEMUR Z I N C

WAS T H E D I E T A R Y

FOR 1 5

I N THE PRESENCE

O F WATER I N S O L U B L E

O F T H E S E WATER I N S O L U B L E

IN THE DIGESTIVE

PHYTATE

BRAN

DIFFERENT.

OR C A L C I U M - Z I N C P H Y T A T E C O M P L E X E S I N T H E A B S E N C E

ADDED P H Y T A T E ( . 1 0 , 1 9 ) .

ATES

T H E MEAN S E R U M Z I N C WAS

I N THESE PROCEEDINGS

THEZINC

TYPE OF

VALUES

Β WAS LOWER THAN

THE DEPHYTINIZED

THE SOLUBILITY

CAN U T I L I Z E

EACH

SERUM Z I N C

WERE S T A T I S T I C A L L Y

B U T T H E MEANS WERE NOT S I G N I F I C A N T L Y

FACTORS

CONSUMING

MEAN FOR SUBGROUP

T H E STUDY

A V E R A G I N G BOTH S U B G R O U P S ,

DISCUSSION. THE

MUFFINS.

I V I S A SUMMARY O F T H E I N I T I A L

iJg/100 ML G R E A T E R A F T E R CONSUMING

DAYS,

BRAN

T H E TENDENCY WAS TOWARD H I G H E R

AND T H E I N C R E A S E S

SIGNIFICANT. 10

(-)

V A L U E S AND A T T H E END O F 1 5 DAYS

BRAN M U F F I N S . A S

MUFFINS,

UNDER

A GIVEN

WOULD B E I N D I C A T E D

O F DIETARY TRUE

OVER T I M E O F T H E AMOUNT

DIETARY

REGIMEN.

DECREASED

BY A DECREASE I N APPARENT


166

NUTRITIONAL

BIOAVAILABILITY

OF

ZINC

Table IV. Serum Zinc Response to Bran Muffins

Sub jec t Subgroup

Day 16

Day 1

Day

31


Pg/100 ml A

92+23

Β

80+ll

a

(+)2ll7+l6

(-)111+12

(-)

(+)110+13°

136+8°

iMean + S.D., F a s t i n g blood sample morning o f day i n d i c a t e d . (+)Whole bran muffins preceding 15 days, (-) dephytinized bran muffins preceeding 15 days. a,b,c S i g n i f i c a n t l y d i f f e r e n t , Ρ < 0.05. 2

a b s o r p t i o n , that i s an i n c r e a s e i n f e c a l e x c r e t i o n r e l a t i v e to i n t a k e . Apparent absorption o f z i n c by subjects on our study was lower the f i r s t 5 days the whole bran muffins were consumed than when dephytinized bran muffins were consumed, mean -0.2 and 1.5 mg/day, r e s p e c t i v e l y . T h i s i n d i c a t e s that the 12 molar r a t i o o f phytate/zinc decreased b i o a v a i l a b i l i t y o f z i n c the i n i t i a l 5 days whole bran muffins were consumed and e v i d e n t l y prevented r e a b s o r p t i o n o f z i n c that had been secreted i n t o the i n t e s t i n e (some i n d i v i d u a l s excreted more i n the s t o o l than they consumed). However, the r e l a t i o n reversed over the remaining 10 days each regimen was eaten, 3.1 v s . 2.4 mg/day f o r whole bran and dephytin i z e d bran muffins, r e s p e c t i v e l y . Reversal o f the apparent absorption values suggest an adaptation to the d i e t , e i t h e r a change i n the a b i l i t y o f the i n t e s t i n e to absorb z i n c or a homeostatic response which decreases s e c r e t i o n o f endogenous z i n c i n t o the i n t e s t i n e . The i n t a k e o f z i n c i n our study was g r e a t e r than from some h o s p i t a l and s e l f chosen d i e t s (20,21,22) and exceeded s l i g h t l y the recommended d i e t a r y i n t a k e (3). We d i d not determine the usual i n t a k e by our v o l u n t e e r s p r i o r to the study and i t i s p o s s i b l e t h a t the magnitude o f the balances was i n f l u e n c e d by the high i n t a k e s . The f a s t i n g serum z i n c values during the study were markedly elevated compared to the i n i t i a l value, supporting the conjecture that they consumed more z i n c during than p r i o r t o the study. Prasad summarizes l i t e r a t u r e i n d i c a t i n g that balance may i n c r e a s e during a p e r i o d o f adequate z i n c i n t a k e when preceded by a period o f low i n t a k e (23). Women showed increased plasma response to a z i n c load f o l l o w i n g a v e g e t a r i a n d i e t compared to a f t e r a d i e t that contained meat (24). The dephytinized bran contained the same percentage o f n e u t r a l detergent f i b e r as the nonincubated whole bran. Thus, the i n t a k e s o f n e u t r a l detergent f i b e r d i d not d i f f e r between the two d i e t a r y



11.

MORRIS

A N D ELLIS

Phytate I Zinc Molar Ratio

167

regimens. Experiments on i r o n absorption by humans i n d i c a t e the d e p h y t i n i z a t i o n process may a l t e r b i n d i n g o f i r o n by d i e t a r y f i b e r i n wheat bran (25). Lower z i n c balances when dephytinized wheat bran was consumed might i n d i c a t e the a f f i n i t y f o r z i n c by the f i b e r i n dephytinized bran may be g r e a t e r than t h a t of the f i b e r i n the unincubated whole bran. That c o n c l u s i o n i s e q u i v o c a l , however, i f based only on our study. The molar r a t i o o f p h y t a t e / z i n c o f some mid-eastern d i e t s was estimated to be 20 (26), but only small amounts of meat were g e n e r a l l y a v a i l a b l e . Sandstrom et a l . obtained r e s u l t s t h a t i n d i c a t e absorption of z i n c from a meal may be a p p r e c i a b l y i n f l u e n c e d by the type o f p r o t e i n i n the meal (27,28). Our menus provided p r o t e i n from meat i n most of the meals which may have a f f e c t e d b i o u t i l i z a t i o n o f the d i e t a r y z i n c . I n one comparison Sandstrom et a l . found t h a t whole wheat bread decreased percentage a b s o r p t i o n , but the absolute amount o f z i n c absorbed was g r e a t e r because t o t a l z i n c i n the whole wheat bread meal was g r e a t e r . Although the balance r e s u l t s i n d i c a t e that i n human d i e t s a phytate/zinc molar r a t i o o f 12 i s not a d e t e r r e n t to adequate z i n c n u t r i t u r e i n a d u l t men, q u a l i f i c a t i o n s as discussed above r a i s e questions i n i n t e r p r e t i n g the p r a c t i c a l a p p l i c a t i o n . We have pursued two questions (1) What i s the molar r a t i o o f phytate/ z i n c i n our t y p i c a l d i e t s ? (2) What would be the e f f e c t o f lower z i n c i n t a k e s i n a metabolic balance study with phytate/zinc molar r a t i o as the v a r i a b l e ? Part o f question 1 has been completed, but only p r e l i m i n a r y i n f o r m a t i o n i s a v a i l a b l e on question 2. A n a l y s i s of H o s p i t a l and Self-Chosen

Diets

Sample t r a y s o f three d i f f e r e n t h o s p i t a l menus, r e g u l a r , ovo-lacto vegetarian and soy-meat s u b s t i t u t e , were c o l l e c t e d f o r seven c o n s e c t i v e days and analyzed f o r minerals, p h y t i c a c i d and f i b e r (29). Each meal was composited, homogenized and analyzed s e p a r a t e l y . The c a l c u l a t e d c a l o r i c l e v e l o f the meals was 2800 k c a l per day. The mean d a i l y amount o f z i n c , phytate, f i b e r and the molar r a t i o phytate/zinc provided by the three d i e t s i s summarized i n Table V. Only the soy-meat s u b s t i t u t e d i e t supplied the recommended d i e t a r y i n t a k e o f z i n c f o r a d u l t males. The values found f o r the r e g u l a r and ovo-lacto vegetarian menus are s i m i l a r to those reported by Brown et a l . (20). The p h y t i c a c i d i n the ovo-lacto vegetarian menu was s l i g h t l y g r e a t e r than i n the r e g u l a r menu, but both were c o n s i d e r a b l y l e s s than provided by the soy-meat s u b s t i t u t e menu. The phytate/zinc molar r a t i o o f soy-meat s u b s t i t u t e menu was about 2.3 and 1.7 times g r e a t e r than o f the r e g u l a r and ovo-lacto vegetarian menus. The r a t i o of 7.6 i s , however, considerably lower than 12 from our human study I . N e u t r a l detergent f i b e r content o f the r e g u l a r and ovo-lacto v e g e t a r i a n d i e t s was s i g n i f i c a n t l y l e s s than i n the soy-meat s u b s t i t u t e and the l a t t e r d i e t supplied an amount equal


168

NUTRITIONAL

TABLE

V.

ANALYSIS THREE

OF ZINC,

HOSPITAL

NUTRIENT

ACID

(26)

REGULAR

ZINC MG/DAY

PHYTIC

PHYTIC

DIETS

ACID

12.2

+

3.3

387

+

60

3.3

+

1.4

7.8

+

0.6

a

AND F I B E R

S U P P L I E D BY

1

OVO-LAETO

SOY-MEAT

V E G E TARIAN

S UB ST I TU T E

A

9.7

+ 1.4

440

+ 210

A

4.5

+ 0.8

A

9.4

+

A

BIOAVAILABILITY O F ZINC

15.0

+

1.8°

1144

+

I44

B

B

7.6

+

0.7

C

A

16.9

±

1.7

B

A


MG/DAY

PHY/ZN

2

FIBER3

3.3

G/DAY

^MEAN + S D FOR 7 DIFFERENT MULTIPLE 2

MOLAR

CONSECUTIVE

SUPERSCRIPT RANGE T E S T ,

RATIO

3NEUTRAL

Ρ

DETERGENT

THE OVO-LACTO VEGETARIAN

STUDY

DIET.

T H ESLIGHT OVER

CONTAINED

ZINC

BRIEF

BELOW,

AND BROUGHT ALL

FOOD

JUICES,

15

AND L I Q U I D AND L I Q U I D S IS

ADDITIONAL

ZINC,

ZINC

FROM 5 . 6 2.1

RANGED ZINC

TO 2 0 . 6 MG.

FROM 3 0 0

FROM 3 . 5

DIETS

WITH

OVERALL

FOOD,

WERE K E P T

ADDED

(SD O F + MG/DAY.

3.9)

DESCRIBED

FOR 1 W E E K ,

INCLUDING

DIET

ZINC

WILL

O F T H E FOOD

CONTRIBUTE

TO 2 5 0 0

CONTENT O F T H E FOOD

INDIVIDUAL MG/DAY ONLY

MEAN P H Y T A T E / Z I N C

ACID

MOLAR R A T I O

RANGED

FROM

OF PHYTATE/

INDIVIDUALS

G R E A T E R THAN WAS 7 . 2

AND S E L F - C H O S E N

RANGED

FOR I N D I V I D U A L S

AND T H E MOLAR R A T I O

TWO O F T H E 15

OF PHYTATE/ZINC

OF HOSPITAL

INTAKES

INTAKES

LITTLE

OF THE COMPOSITES

FOR I N D I V I D U A L S

DAILY

DIARIES

DUPLICATING

M I L K AND F R U I T

ANALYSIS

LIQUIDS

AND MEANS

T H E MEAN P H Y T I C

ZINC

FOR T H E M E A T , AND

T H E R E F O R E WE KNOW A C L O S E A P P R O X I M A T I O N

TO 1 6 . 4 .

OUR A N A L Y S I S

WERE

FOR T H E LOW

BALANCE STUDY,

SEPARATE.

T H E BULK

THAT

THAN T H E

LOW.

MAINTAINED

CONSUMED.

MEAN MOLAR R A T I O

INFORMATION

SUBSTITUTED

I N A SECOND

T H E MEAN D A I L Y

MG/DAY

TO 2 9 . 2

PRODUCTS

TO COMPENSATE

MENU WAS

VOLUNTEERS

COMPLETED.

INTAKES. 11.2

MENU

INDICATES

ITEMS

TO T H E LABORATORY 2ND P L A T E C O L L E C T I O N S

COMPOSITES

WAS

BY T H I S

TO P A R T I C I P A T I N G

I N P H Y T A T E AND F I B E R

MORE WHOLE G R A I N

I N D A I R Y PRODUCTS

SUPPLIED

PRIOR

INCREASE

T H E REGULAR D I E T

B U T , NOT ENOUGH WHOLE G R A I N

THE OVO-LACTO VEGETARIAN

CONCENTRATION

IN

I.

FORMER P R O B A B L Y

THE

WITH

BY D U N C A N ' S

FIBER.

OUR HUMAN

TO

IN A LINE

DIFFERENT

Nutritional Bioavailability of Zinc - American Chemical Society

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