Chemistry and Function of Pectins - American Chemical Society

19

Effects o f Pectin o n H u m a n M e t a b o l i s m Kay Behall and Sheldon Reiser

Downloaded by MICHIGAN STATE UNIV on August 15, 2013 | http://pubs.acs.org Publication Date: June 5, 1986 | doi: 10.1021/bk-1986-0310.ch019

Carbohydrate Nutrition Laboratory, Agricultural Research Service, Beltsville Human Nutrition Research Center, U.S. Department of Agriculture, Beltsville, MD 20705 Recommendations have been made to include more fiber in the average U.S. diet. Pectin has been shown to lower blood cholesterol levels and the low density lipoprotein cholesterol fraction without changing levels of high density lipoprotein cholesterol or t r i glycerides. Pectin appears to be effective in reducing the postprandial rise in glucose in normal, obese and diabetic individuals when it is consumed with a meal or glucose tolerance test. The potentially detrimental effect of decreased mineral absorption in the presence of some high fiber diets has not been reported to occur with pectin consumption. It would appear that consumption of pectin in foods or as a supplement by hypercholesterolemic, diabetic or obese individuals should be of metabolic benefit without adverse mineral loss in the stool. During the past few years there has been a great increase in interest in the type and amount of fiber in foods and the role of the various fibers that are consumed on human health. Part of the increased interest is due to the reported association of low fiber diets with diverticular disease of the colon, cancer of the colon and other diseases of the gastrointestinal tract (1,2), ischemic heart disease (3) and diabetes (4). Two major approaches have been used to study the effects of fiber on humans: 1) to replace low-fiber foods with higher fiber foods and 2) to add refined fibers to self-selected or controlled diets. High pectin foods or refined pectin have been fed to man and animals alone or in combination with other fiber sources to investigate the effect of pectin on metabolic parameters. Table I shows the pectin content of some foods, primarily fruits, and vegetables, as determined analytically (5). Pectin content of a single food source varies depending on several factors including analytical methodology, variety, maturity, harvest season, and cooking method. Citrus fruits, relatively high in pectin and low in calories, are commonly used as food sources of pectin. This chapter not subject to U.S. copyright. Published 1986, American Chemical Society

In Chemistry and Function of Pectins; Fishman, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

19.

BEHALL AND REISER

Effects of Pectin on Human Metabolism

Table I . P e c t i n and Unavailable Carbohydrate Content of F r u i t s , Nuts, and Vegetables


Dry matter

Pectin Unavailable Ca Pectate Carbazol carbohydrate Fresh weight of edible portion (%)

Fruit Apple 0.78 0.45 15.9 Apricot 13.4 0.70 1.00 Banana 29.3 0.94 Blackberry 18.0 0.30 0.94 Blueberry 16.8 0.30 Cherry 18.5 0.36 0.39 15.4 1.11 Fig Grape 19.3 0.20 0.19 Grapefruit 9.3 3.90 Lemon 14.8 2.90 Loganberry 15.0 0.59 Orange 13.9 2.36 Peach 13.8 0.39 0.64 Pear 17.0 0.46 0.49 Pineapple 15.7 0.09 Plum 15.9 0.44 0.59 Raspberry 16.8 0.97 0.34 Rhubarb 5.8 0.44 0.34 Strawberry 11.1 0.50 0.75 Watermelon 7.4 0.18 its Peanut 5.98 95.5 Walnut 76.5 5.80 ige table 0.22 Asparagus 7.6 2.86 Avocado 7.8 0.70 0.55 Bean 8.4 0.91 0.42 Beet 12.9 0.49 Broccoli 9.2 0.78 Brussels Sprou t 9.2 0.53 Cabbage, red 10.3 0.96 2.00 Carrot 10.2 0.38 Cauliflower 10.9 0.16 0.17 Cucumber 3.6 0.47 Eggplant 6.6 1.11 Garlic 38.7 0.38 Kohlrabi 9.7 0.34 Lettuce 4.8 1.53 Okra 11.1 0.35 0.44 Onion 7.2 0.34 Pea 21.5 0.57 Pea, with pod 0.09 Pepper, green 16.6 0.83 0.34 Potato 24.2 0.20 1.24 Pumpkin 5.3 Radish 0.45 6.7 0.80 Rutabaga 13.0 3.45 Soybean 90.0 0.33 Spinach 14.9 0.78 Sweet potato 28.0 0.20 0.30 Tomato 6.6 0.29 Turnip 6.7 0.62 Yam 26.5 Source: Reproduced with permission from reference 5. Raven Press.

1.7 2.1 3.4 7.3 1.7 2.5 0.4 0.6 5.2 6.2 2.0 1.4 2.5 1.2 2.1 7.4 2.6 2.2

8.1 5.2 1.5 3.0 3.1 4.2 4.8 3.4 2.9 1.5 0.4 2.5

1.4 1.3 5.2

2.1 0.5 1.0

6.3 2.1 1.5 2.8 Copyright 1979


249

CHEMISTRY AND FUNCTION OF PECTINS

250


A p p l e s , plums and peaches c o n t a i n a h i g h l y m e t h y l a t e d (95, 93 and 89% o f t o t a l p e c t i n , r e s p e c t i v e l y ) form o f p e c t i n (f>). D u r i n g the more than two decades t h a t p e c t i n r e s e a r c h has been c a r r i e d o u t , two a r e a s o f i n v e s t i g a t i o n w i t h p o t e n t i a l b e n e f i t t o human h e a l t h have been i n l i p i d m e t a b o l i s m ( T a b l e I I ) and c a r b o h y d r a t e m e t a b o l i s m ( T a b l e I I I ) . P e c t i n has been shown t o decrease serum c h o l e s t e r o l i n humans (6-11) as w e l l as o t h e r a n i m a l s p e c i e s (10). H i g h l e v e l s o f serum c h o l e s t e r o l a r e g e n e r a l l y c o n s i d e r e d t o be a r i s k f a c t o r a s s o c i a t e d w i t h i s c h e m i c h e a r t d i s e a s e (11-13). Consumption o f p e c t i n t o reduce c h o l e s t e r o l l e v e l s i n t h e b l o o d might be expected t o reduce the i n c i d e n c e o f h e a r t d i s e a s e espec i a l l y when serum c h o l e s t e r o l i s e l e v a t e d . Lipid

Effects

The e f f e c t o f p e c t i n as p a r t o f a c o n t r o l l e d d i e t has been r e p o r t e d . Keys e t a l (6) were a b l e t o show i n serum c h o l e s t e r o l l e v e l s o f normal men a 5% decrease by f e e d i n g 15 g o f p e c t i n p e r day f o r 3 weeks. The p e c t i n was i n c o r p o r a t e d i n t o a b i s c u i t as p a r t o f the d i e t . Kay and T r u s w e l l (_7) observed d e c r e a s e s i n serum c h o l e s t e r o l , r a n g i n g from 5 t o 26% ( a v e r a g i n g 13%), i n f o u r male and f i v e female s u b j e c t s f e d a c o n t r o l l e d d i e t c o n t a i n i n g 15 g o f p e c t i n i n c o r p o r a t e d i n t o a f r u i t g e l f o r 3 weeks. J e n k i n s and coworkers (8) a l s o observed a 13% average decrease i n serum c h o l e s t e r o l i n f i v e men f e d 30 g o f p e c t i n as p a r t o f a c o n t r o l l e d d i e t f o r 3 weeks. T r i g l y c e r i d e s and h i g h d e n s i t y l i p o p r o t e i n (HDL) c h o l e s t e r o l d i d not change s i g n i f i c a n t l y i n t h i s s t u d y . I n c l u s i o n o f 21 g o f a p p l e o r 20 g o f c a r r o t s as the f i b e r source i n a d i e t a l s o d e c r e a s e d c h o l e s t e r o l a l t h o u g h the change was n o t c o n s i d e r e d significant. S t a s s e - W o l t h u i s e t a l (9) f e d 62 s u b j e c t s , 40 men and 22 women, a c o n t r o l l e d low f i b e r d i e t f o r 2h weeks f o l l o w e d by e i t h e r a h i g h f r u i t and v e g e t a b l e d i e t , 37 g o f b r a n , o r 28 g o f c i t r u s p e c t i n f o r 5 weeks. P e c t i n was i n c o r p o r a t e d i n t o a d e s s e r t made from f r u i t j u i c e s and b u t t e r m i l k . Serum c h o l e s t e r o l d e c r e a s e d s i g n i f i c a n t l y i n the 15 s u b j e c t s who consumed the p e c t i n d i e t , d e c r e a s e d s l i g h t l y i n t h e f r u i t and v e g e t a b l e group and i n c r e a s e d i n t h e h i g h b r a n group. High d e n s i t y l i p o p r o t e i n c h o l e s t e r o l d i d n o t change s i g n i f i c a n t l y i n any o f the groups. C h a l l e n e t a l (14) fed s i x males a c o n t r o l l e d d i e t c o n t a i n i n g 36 g o f p e c t i n per day f o r 3 weeks. C h o l e s t e r o l d e c r e a s e d an average o f 10% i n t h e i r s u b j e c t s w h i l e o t h e r b l o o d parameters s t u d i e d i n c l u d i n g p l a t e l e t a g g r e g a t i o n and h a e m o s t a s i s d i d not change. C h a l l e n c o n c l u d e d t h a t the e f f e c t o f p e c t i n on h e a r t d i s e a s e was p r o b a b l y n o t a c h i e v e d through changes i n p l a t e l e t a g g r e g a t i o n o r h a e m o s t a s i s b u t through some o t h e r mechanism. Raymond e t a l Q5) f e d a c o n t r o l l e d f o r m u l a d i e t c o n t a i n i n g 2 g p e c t i n , 14 g c e l l u l o s e , 39 g h e m i c e l l u l o s e and 5 g l i g n i n t o s i x s u b j e c t s f o r 4 weeks. No s i g n i f i c a n t change i n serum c h o l e s t e r o l was observed w i t h the f o r m u l a d i e t w i t h o r w i t h o u t c h o l e s t e r o l p r e s e n t i n the d i e t . The e f f e c t o f a d d i n g p e c t i n t o s e l f - s e l e c t e d d i e t has a l s o been s t u d i e d . As w i t h the c o n t r o l l e d d i e t s t u d i e s , v a r i o u s amounts o f p e c t i n have been added t o t h e s e l f - s e l e c t e d d i e t s . Palmer and D i x o n (16) f e d a c a p s u l e c o n t a i n i n g 2 t o 10 g o f p e c t i n per day f o r 4 weeks t o 16 males w i t h normal t o h i g h serum



19.

BEHALL AND REISER


251

c h o l e s t e r o l l e v e l s . When 6 g more o f p e c t i n per day was f e d , a s i g n i f i c a n t decrease i n c h o l e s t e r o l a v e r a g i n g 6% was o b s e r v e d . J e n k i n s e t a l (_17) fed 36 g o f p e c t i n per day i n water t o 12 men consuming s e l f - s e l e c t e d d i e t f o r 4 weeks. C h o l e s t e r o l d e c r e a s e d 12% a f t e r p e c t i n i n c o n t r a s t t o 16% w i t h guar gum and no s i g n i f i c a n t change w i t h wheat b r a n . D u r r i n g t o n and coworkers (18) fed 12 g p e c t i n per day i n j u i c e t o 12 men f o r 3 weeks. Serum c h o l e s t e r o l and apo-& c h o l e s t e r o l s i g n i f i c a n t l y d e c r e a s e d , a v e r a g i n g 8% f o r the group, w h i l e t r i g l y c e r i d e s and v e r y low d e n s i t y l i p o p r o t e i n s (VLDL) d i d not change s i g n i f i c a n t l y . Judd and T r u s w e l l (19) added 15 g o f low m e t h o x y l p e c t i n or h i g h methoxyl p e c t i n i n j e l l y t o the s e l f - s e l e c t e d d i e t o f f i v e h e a l t h y men and f i v e h e a l t h y women. S u b j e c t s were g i v e n a copy of the f i r s t 3 weeks of r e c o r d e d d i e t and asked t o consume as c l o s e as p o s s i b l e the same d i e t f o r the second 3 weeks. C h o l e s t e r o l d e c r e a s e d 16% i n response t o low m e t h o x y l p e c t i n and 18% a f t e r h i g h m e t h o x y l p e c t i n . Serum c h o l e s t e r o l r e d u c t i o n s produced by a d d i n g p e c t i n to s e l f - s e l e c t e d d i e t s were a l s o r e p o r t e d by Lopez e t a l (29) and L a g l e y and Thye ( 2 1 ) , w n i i e Fahrenbach e t a l (22) observed no change i n serum c h o l e s t e r o l . Sable-Amples e t a l (23) added 2 t o 3 a p p l e s per day (containing 2 t o 3 g p e c t i n ) f o r 4 weeks to s e l f - s e l e c t e d d i e t s and r e p o r t e d a s i g n i f i c a n t d e c r e a s e i n c h o l e s t e r o l , s i g n i f i c a n t decrease i n low d e n s i t y l i p o p r o t e i n s (LDL) and an i n c r e a s e i n HDL c h o l e s t e r o l and HDL r a t i o . Mahalko e t a l (24) added a p p l e powder which c o n t a i n e d a p p r o x i m a t e l y 2.5 t o 6 g p e c t i n per day t o d i e t s o f n o n - i n s u l i n dependent d i a b e t i c s and r e p o r t e d e i t h e r no change or some i n c r e a s e i n serum c h o l e s t e r o l . Sable-Amples suggested t h a t the d e c r e a s e s they observed may be r e l a t e d t o the presence o f v i t a m i n C o r some o t h e r component i n the a p p l e s a c t i n g s y n e r g i s t i c l y and making the p e c t i n more e f f e c t i v e than powdered a p p l e p e c t i n a l o n e . The e f f e c t o f p e c t i n has a l s o been s t u d i e d i n some h y p e r c h o l e s terolemic subjects. G i n t e r e t a l (25) f e d 15 g p e c t i n w i t h 450 mg v i t a m i n C f o r 6 weeks t o 10 men and 11 women. Serum c h o l e s t e r o l d e c r e a s e d 9% i n m i l d l y h y p e r c h o l e s t e r o l e m i c and 19% i n s e v e r e l y hypercholesterolemic subjects. HDL c h o l e s t e r o l remained unchanged w h i l e changes i n t r i g l y c e r i d e l e v e l s v a r i e d . Nakamura e t a l (26) observed d e c r e a s e s i n t o t a l c h o l e s t e r o l i n 12 m i l d l y h y p e r c h o l e s t e r o l e m i c s u b j e c t s fed 9 g p e c t i n per day f o r 2 weeks s i m i l a r to those r e p o r t e d by G i n t e r . I n c o n t r a s t D e l b a r r e e t a l (27) observed no change i n serum c h o l e s t e r o l l e v e l s i n 10 h y p e r l i p i d e m i c subjects fed a h y p o l i p e m i c d i e t w t i h or w i t h o u t 6 g o f p e c t i n . Schwardt e t a l (28) compared r e s u l t s a f t e r a s e l f - s e l e c t e d d i e t a l o n e , w i t h c h o l e s t y r a m i n e added and w i t h c h o l e s t y r a m i n e and 12 g a p p l e p e c t i n added f o r 12 weeks. Compared t o the s u b j e c t s s e l f - s e l e c t e d d i e t a l o n e , the a d d i t i o n of p e c t i n p l u s c h o l e s t y r a m i n e d e c r e a s e d c h o l e s t e r o l 31% and LDL l e v e l s 35%, w h i l e the a d d i t i o n o f o n l y c h o l e s t y r a m i n e d e c r e a s e d c h o l e s t e r o l 19% and LDL l e v e l s 22%. N e i t h e r the HDL r a t i o nor t r i g l y c e r i d e s changed s i g n i f i c a n t l y from the p r e s t u d y l e v e l s . I n c r e a s e d e x c r e t i o n of c h o l e s t e r o l i s thought t o be the mechanism f o r r e d u c i n g serum c h o l e s t e r o l . S e v e r a l i n v e s t i g a t o r s have r e p o r t e d i n c r e a s e d f e c a l f a t ( 7 , 1 9 ) , s t e r o l s (7,9,19,26) o r b i l e a c i d s (7,9, 29,30). Kay and T r u s w e l l (7) r e p o r t e d s i g n i f i c a n t i n c r e a s e s i n f e c a l f a t e x c r e t i o n , a v e r a g i n g 44%; f e c a l c h o l e s t e r o l ,



23 s u b j e c t s 16 males

12 males

3 subjects 12 males

9

Fahren Bach e t a l , 1965 Palmer and D i x o n , 1966

J e n k i n s e t a l , 1975

Hopson, Lopez e t a l , 1975 D u r r i n g t o n e t a l , 1976

Kay and T r u s w e l l ,

Stasse-Wolthuis et a l , 1980

G i n t e r e t a l , 1979

L a n g l e y and Thye, 1977 J e n k i n s e t a l , 1979

21 m i l d h y p e r cholesterolemic subjects 11 h y p e r c h o l e s terolemic subjects 62 s u b j e c t s

10 h y p e r l i p i d e m i c subjects 11 males 5 males 6 males

e t a l , 1977

Delbarre

subjects

6

controlled controlled controlled self-selected

self-selected

controlled

4 wk 3 wk 3 wk 6 wk

6 wk

5 wk

4 wk 6 wk

controlled

controlled self-selected

self-selected

self-selected

controlled

Diet

controlledformula hypolipemic

3 wk

5 wk 3 wk

4 wk

7--9 wk 4 wk

3 wk

Time

-19%

-10%

15 g i n d e s s e r t made w i t h j u i c e s and buttermilk

- 9%

S i g n i f i c a n t Decrease -13% - 7%

0

0

-13%

-13% - 8%

0 - 6% on 6 g or more/d -12%

Change i n C h o l e s t e r o l (% changes) - 5%

15 g/d w i t h 450 mg V i t C

10 g/d 30 g/d 21 g a p p l e powder 15 g/d w i t h 450 mg V i t C

15 g/d in biscuits 6-12 g/d 2-10 g/d i n capsule 36 g/d i n water 20-23 g/d 12 g/d i n w a t e r or j u i c e 15 g/d in fruit gell 2 g/d w i t h other f i b e r s 6 g/d

Amount P e c t i n

P e c t i n and Serum C h o l e s t e r o l i n Man

Raymond e t a l , 1977

subjects

24 males

Keys e t a l , 1961

1977

Subjects

Reference

Table I I .


H

z o •n -o tn o

O

H

a -n c z o

Z

< >

H

So

m

In Chemistry and Function of Pectins; Fishman, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986. 4 wk 3 wk 4 wk 4 wk

30 s u b j e c t s 6 males

10 s u b j e c t s 8 subjects

Judd and T r u s w e l l , 1982

Sable-Amples e t a l , 1983 C h a l l e n e t a l , 1983

Mahalho e t a l , 1984

Schwandt e t a l , 1982

12 m i l d h y p e r 2 wk cholesterolemic subjects 6 severely hy8 wk percholesterolemic males 10 s u b j e c t s 3 wk

Nakamura e t a l , 1982

12 g p e c t i n / d 16 g c h o l e s t y r a m i n e

s e l f - 15 g Low m e t h o x y l / d in j e l l y selected 15 g H i g h m e t h o x y l / d in j e l l y s e l f - s e l e c t e d 2-3 a p p l e s / d controlled 36 g/d i n b r e a d diet s e l f - s e l e c t e d 26 g a p p l e powder s e l f - s e l e c t e d 52 g a p p l e powder

recorded

self-selected

9 g


0 + 6%

-14% -10%

-18%

-16%

-31%

-10%


gastric surgery patients with dumping syndrome 6 non i n s u l i n dependent diabetics

Leeds e t a l , 1977

J e n k i n s e t a l , 1978

J e n k i n s e t a l , 1977

8 non i n s u l i n dependent diabetics and 3 insulin dependent 13 normal subjects

Subjects

J e n k i n s e t a l , 1976

Reference

10 g i n j e l l y w i t h o u t and w i t h 16 g guar b r e a d

10.5 g h i g h methoxyol i n water

meal

75 g glucose

50 g 14.5 g p e c t i n i n water glucose 25 g xylose 15 g lactose 40 g lemon juice

10 g i n j e l l y w i t h 16 g guar gum i n b r e a d

meal

Amount P e c t i n Added

Non-Significant d e c r e a s e from c o n t r o l l o a d dose

S i g n i f i c a n t Decrease a t 30 t h r o u g h 120 min. S i g n i f i c a n t Decrease a t 15 min. NonS i g n i f i c a n t Decrease 30 t h r o u g h 90 min. samples. Guar gum f u r t h e r lowered response curve. S i g n i f i c a n t Decrease a t 30 min. samples Improved r e t e n t i o n o f l o a d i n stomach

S i g n i f i c a n t Decrease a t 30 t h r o u g h 90 m i n . samples

Non-Significant decrease

S i g n i f i c a n t Decrease a t 15 t h r o u g h 45 min. samples

S i g n i f i c a n t Decrease a t 30 t h r o u g h 120 min. samples

Response c u r v e change from c o n t r o l Serum g l u c o s e Serum i n s u l i n

P e c t i n and Serum G l u c o s e and I n s u l i n i n Man

Control Load Dose

Table I I I .


H

H

z o •n -o m o

O

H

c z o

D

< >

So


gastric 50 g g l u c o s e surgery patients 3 hypoglycemic patients 8 insulin meal dependent diabetics meal 7 insulin dependent diabetics

6 normal subjects

Gold e t a l , 1980

W i l l i a m s e t a l , 1980 13 non i n s u l i n dependent diabetics

Poynard e t a l , 1980

V a a l e r e t a l , 1980

meal

100 g glucose meal

23

L a b a y l e e t a l , 1980

H o l t e t a l , 1979

45 g g l u c o s e / sq meter body surface 50 g g l u c o s e

6 non i n s u l i n dependent diabetics 6 normal subjects

Monnier e t a l , 1978

10 g as powder added t o food

10 g i n orange j u i c e 10 g

7 g

15 g p e c t i n i n jam

5 g with each meal

10-20 g

9 g pectin/ sq meter body surface 14.5 g

No S i g n i f i c a n t change from c o n t r o l S i g n i f i c a t Decrease a t 60 and 90 min. samples S i g n i f i c a n t Decrease a t 60 m i n . sample Non S i g n i f i c a n t Decrease f o r r e m a i n d e r of curve

S i g n i f i c a n t Decrease a t 15 t h r o u g h 90 m i n . samples S i g n i f i c a n t Decrease a t 60 t h r o u g h 90 m i n . samples

S i g n i f i c a n t Decrease a t 30 t h r o u g h 60 min. samples S i g n i f i c a n t Decrease a t 30 t h r o u g h 45 m i n . samples S i g n i f i c a n t Decrease a t 30 m i n . sample Hypoglycemia o v e r t e d


Continued on next page

No S i g n i f i c a n t change from c o n t r o l

Mean i n s u l i n delivery Significant Decrease 35% o v e r 180 min. No S i g n i f i c a n t change from c o n t r o l No S i g n i f i c a n t change from c o n t r o l

No S i g n i f i c a n t change from c o n t r o l

70

O

I

2 §

§

70

m m


7 normal

10 non 4 wk s e l f i n s u l i n selected diet dependent diabetics 8 non insulin dependent diabetics

Schwartz e t a l , 1983

Mahalko e t a l , 1984

50 g monosaccharides i n 610 g orange j u i c e (depectinated) 2 wk c o n t r o l l e d diet

10 normal males

B o l t o n e t a l , 1981

meal

Control Load Dose

5 normal, 6 obese 5 latent diabetics

Subjects

(Continued)

K a n t e r e t a l , 1980

Reference

Table I I I .

26 g a p p l e pectin/d 52 g a p p l e pectin/d

20 g/d

10 g w i t h 16 g guar gum t e s t meal preceeded by 3 days o f added fiber/day 626 g orange (containing approximately 14 g p e c t i n )

Amount P e c t i n Added S i g n i f i c a n t Decrease in a l l subjects. G r e a t e s t change i n obese and d i a b e t i c subjects No S i g n i f i c a n t difference before 105 min. samples. Orange8 were l e s s hypoglycemic No S i g n i f i c a n t change from c o n t r o l . G a s t r i c emptying time increased 1 s u b j e c t had S i g n i f i c a n t l y lower l e v e l s on b o t h p e c t i n supplements

S i g n i f i c a n t Decrease in a l l subjects. G r e a t e s t change i n obese and d i a b e t i c subjects S i g n i f i c a n t Decrease a t 40 t h r o u g h 150 min. samples a f t e r oranges

Response c u r v e change from c o n t r o l Serum g l u c o s e Serum i n s u l i n



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17%; and f e c a l b i l e a c i d s , 33%, compared t o c o n t r o l l e v e l s . StasseW o l t h u i s et a l (9) r e p o r t e d s i g n i f i c a n t i n c r e a s e s i n n e u t r a l s t e r o i d s and b i l e a c i d s i n male but not i n female s u b j e c t s a f t e r p e c t i n consumption. Cummings et a l (29) r e p o r t e d s i g n i f i c a n t l y g r e a t e r e x c r e t i o n o f f a t t y a c i d s (80%) and b i l e a c i d s (35%) when f i v e h e a l thy men consumed f o r 6 weeks 36 g of p e c t i n per day i n c o r p o r a t e d i n t o a c o n t r o l l e d d i e t compared t o e x c r e t i o n d u r i n g the c o n t r o l p e r i o d . Ross and Leklem (30) f e d e i g h t men a c o n t r o l l e d d i e t w i t h or w i t h o u t 15 g c i t r u s p e c t i n f o r t h r e e 21 day p e r i o d s i n a double crossover design. Mean 7 a - d e h y d r o z y l a s e a c t i v i t y was increased 35%, mean n e u t r a l s t e r o i d c o n c e n t r a t i o n 8%, and t o t a l e x c r e t i o n o f a c i d s t e r o i d s 11%, when the p e c t i n - c o n t a i n i n g d i e t was f e d . Judd and T r u s w e l l (19) observed no d i f f e r e n c e i n l i p i d response between the h i g h and low m e t h o x y l p e c t i n and suggested t h a t the a b i l i t y o f p e c t i n t o lower c h o l e s t e r o l l i e s i n i t s g e l l i n g p r o p e r t i e s . B i n d i n g o f b i l e a c i d s or c h o l e s t e r o l to p e c t i n has been r e p o r t e d i n a n i m a l s t u d i e s (10) and may reduce a v a i l a b l e c h o l e s t e r o l and l i p i d s f o r a b s o r p t i o n . I n v i t r o s t u d i e s have suggested some c h e m i c a l i n t e r a c t i o n s i n c l u d i n g e l e c t r o s t a t i c and hydrogen bonding between i n t e s t i n a l l i p i d s and p e c t i n . B a i g and Cerda (31) i n v e s t i g a t e d human serum l i p o p r o t e i n and g r a p e f r u i t p e c t i n i n t e r a c t i o n s r e p o r t i n g a s p e c i f i c i n t e r a c t i o n between p e c t i n and low d e n s i t y l i p o p r o t e i n s . T h e i r r e s u l t s i n d i c a t e d t h a t the i n t e r a c t i o n was o f an e l e c t r o s t a t i c n a t u r e . F a l k and Nagyvary (32) i n an i n v i t r o e q u i l i b r i u m d i a l y s i s s t u d y observed b i n d i n g o f p e c t i n and l i p i d m i c r o e m u l s i o n s and m i c e l l e s o f low charge d e n s i t y . T h e i r r e s u l t s suggested a hydrogen bonding between the p e c t i n c a r b o x y l i c m o i e t i e s and l i p i d s which under optimum c o n d i t i o n s would r e s u l t i n b i n d i n g f o u r times i t s w e i g h t i n l i p i d s . The mechanism i n v o l v e d i n the a c t i o n o f p e c t i n r e d u c i n g serum c h o l e s t e r o l o r c h o l e s t e r o l a b s o r p t i o n i s not c l e a r a t t h i s t i m e . Chemical b i n d i n g as w e l l as entrapment due t o the v i s c o u s n a t u r e o f p e c t i n may b o t h p l a y a r o l e i n r e d u c i n g l i p i d , c h o l e s t e r o l , or b i l e a c i d a v a i l a b i l i t y f o r absorption thereby d e c r e a s i n g serum c h o l e s t e r o l l e v e l s . Glycemic E f f e c t s U n l i k e the experiments r e p o r t i n g the e f f e c t o f p e c t i n on serum l i p i d s , most s t u d i e s i n v e s t i g a t i n g the e f f e c t o f p e c t i n on g l u c o s e m e t a b o l i s m have been c a r r i e d out i n response t o a meal or o r a l g l u c o s e t o l e r a n c e t e s t w i t h and w i t h o u t p e c t i n ( 3 3 - 4 4 ) , r a t h e r than a f t e r a d a p t a t i o n t o a p e c t i n - f r e e o r p e c t i n - c o n t a i n i n g d i e t . S t u d i e s r e p o r t i n g the e f f e c t s o f c o n t r o l l e d d i e t a r y i n t a k e o f p e c t i n on g l u c o s e o r i n s u l i n are l i m i t e d (24,44,45). Most o f the s t u d i e s i n v e s t i g a t i n g the e f f e c t o f p e c t i n on g l u c o s e and i n s u l i n have been c a r r i e d out w i t h d i a b e t i c s u b j e c t s , e i t h e r i n s u l i n dependent (ID) o r n o n - i n s u l i n dependent (NID) d i a b e t i c s (38-43,45). Diabetics may b e n e f i t i f e i t h e r l o n g - t e r m consumption o f p e c t i n d e c r e a s e s b l o o d g l u c o s e , o r a f f e c t s the amount o f i n s u l i n r e q u i r e d t o c o n t r o l b l o o d g l u c o s e l e v e l s by d i e t a r y means. J e n k i n s e t a l (33) fed a meal i n c l u d i n g 10 g o f p e c t i n t o 13 normal g l y c e m i c s u b j e c t s . Compared t o the c o n t r o l meal w i t h o u t the p e c t i n p r e s e n t the g l u c o s e response c u r v e was s i g n i f i c a n t l y lower a t 15 minutes a f t e r the l o a d and l o w e r , a l t h o u g h not



258


s i g n i f i c a n t l y , a t t h e 30 through 90 minute p o r t i o n o f the response c u r v e . When guar gum was added t o t h e meal i n a d d i t i o n t o the p e c t i n the response curve was s i g n i f i c a n t l y reduced a t 15 and 30 minutes w i t h the r e s t o f the c u r v e d e c r e a s e d b u t n o t s i g n i f i c a n t l y compared t o the c o n t r o l . I n s u l i n was s i m i l a r l y d e c r e a s e d i n comp a r i s o n t o the c o n t r o l meal a t 15 through 45 minutes w i t h p e c t i n and a t 15 through 90 minutes w i t h p e c t i n and t h e guar. L e v i t t e t a l (34) f e d a mixed meal w i t h and w i t h o u t 5 g o f p e c t i n and 5 g o f guar gum t o 12 normal s u b j e c t s and r e p o r t e d s i g n i f i c a n t d e c r e a s e s i n g l u c o s e a t 15 and 30 minutes and g l u c a g o n response a t 180 t o 240 minutes i n comparison t o t h e c o n t r o l . Glucose and g l u c a g o n a l s o tended t o d e c r e a s e i n comparison t o c o n t r o l l e v e l s over t h e remainder o f t h e response c u r v e w h i l e no changes i n i n s u l i n o r g a s t r i c i n h i b i t o r y p o l y p e p t i d e response were observed. H o l t e t a l (35) and Gold e t a l (36) b o t h gave o r a l g l u c o s e t o l e r a n c e t e s t s t o normal g l y c e m i c s u b j e c t s . H o l t and coworkers r e p o r t e d s i g n i f i c a n t d e c r e a s e s i n serum g l u c o s e from c o n t r o l r e sponse l e v e l s a t 30 and 45 minutes when 14.5 g o f p e c t i n was added, w h i l e Gold and coworkers observed no s i g n i f i c a n t d i f f e r e n c e s w i t h 10 g o f p e c t i n added. Gold e t a l (36) d i d observe s i g n i f i c a n t d e c r e a s e s i n g l u c o s e a t 60 and 90 minutes when the 10 g o f p e c t i n was consumed w i t h a meal. N e i t h e r H o l t n o r Gold r e p o r t e d a s i g n i f i c a n t change i n i n s u l i n l e v e l s between t h e p e c t i n - c o n t a i n i n g and control diet. B o l t o n e t a l (37) compared g l u c o s e and i n s u l i n responses t o oranges compared t o d e p e c t i n a t e d orange j u i c e , each c o n t a i n i n g e q u i v a l e n t amounts o f monosaccharides. Glucose response a f t e r oranges was n o t s i g n i f i c a n t l y d i f f e r e n t from t h a t a f t e r orange j u i c e u n t i l 105 minutes a f t e r the l o a d dose. S u b j e c t s had l e s s h y p o g l y c e m i a and i n s u l i n l e v e l s were s i g n i f i c a n t l y lower i n r e sponse t o oranges than t o orange j u i c e . L a b a y l e e t a l (38) r e p o r t e d t h a t when t h r e e hypoglycemic p a t i e n t s consumed 5 g o f p e c t i n w i t h each meal, hypoglycemia was a v e r t e d . Schwartz e t a l (46) c a r r i e d out one o f the few f e e d i n g s t u d i e s i n c l u d i n g p e c t i n as the f i b e r s o u r c e . The c o n t r o l l e d d i e t was fed f o r 2 weeks w i t h and w i t h o u t 20 g o f p e c t i n p e r day t o seven normal g l y c e m i c s u b j e c t s . No s i g n i f i c a n t change i n g l u c o s e response was observed compared t o t h e d i e t w i t h o u t p e c t i n b u t g a s t r i c emptyi n g time was s i g n i f i c a n t l y i n c r e a s e d w i t h p e c t i n . G a s t r i c s u r g e r y p a t i e n t s a l s o showed a s i g n i f i c a n t i n c r e a s e i n g a s t r i c emptying time when g i v e n 10 t o 20 g o f p e c t i n w i t h a g l u c o s e l o a d dose (38,39). D i a b e t i c s when t e s t e d w i t h 7 t o 10 g o f p e c t i n p r e s e n t i n a meal o r o r a l g l u c o s e t o l e r a n c e t e s t g e n e r a l l y responded w i t h lower serum g l u c o s e l e v e l s than when they were g i v e n the c o n t r o l meal o r t o l e r a n c e t e s t w i t h o u t p e c t i n . J e n k i n s e t a l (40) f e d 10 g o f p e c t i n w i t h 16 g o f guar gum i n a meal t o e i g h t NID d i a b e t i c s and t h r e e ID d i a b e t i c s . Both groups had s i g n i f i c a n t l y lower serum g l u c o s e response w i t h p e c t i n p r e s e n t , a t 30 through 90 minutes i n the NID and a t 30 through 120 minutes i n the ID d i a b e t i c s . I n s u l i n response i n t h e NID d i a b e t i c s was a l s o s i g n i f i c a n t l y dec r e a s e d from c o n t r o l response l e v e l s a t 30 through 120 m i n u t e s . When J e n k i n s e t a l (41^) f e d 14.5 g p e c t i n w i t h s i m p l e sugars i n an o r a l t o l e r a n c e t e s t t o e i g h t NID d i a b e t i c s , no s i g n i f i c a n t d i f f e r e n c e s from c o n t r o l l e v e l s i n e i t h e r t h e g l u c o s e o r i n s u l i n response c u r v e s were observed.



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259

Monnier e t a l (42) and W i l l i a m s e t a l (43) r e p o r t e d s i g n i f i c a n t d e c r e a s e s i n the serum g l u c o s e response curves o f t h e i r NID d i a b e t i c s from t h e c o n t r o l l e v e l s when p e c t i n was p r e s e n t a t 30 and 60 minutes and 60 m i n u t e s , r e s p e c t i v e l y , w i t h some n o n - s i g n i f i c a n t decrease d u r i n g the r e s t o f t h e c u r v e . I n s u l i n was n o t s i g n i f i c a n t l y d e c r e a s e d i n e i t h e r experiment a l t h o u g h W i l l i a m s d i d r e p o r t some d e l a y i n mean r e s p o n s e . L e v i t t e t a l (34) r e p o r t e d t h e i n g e s t i o n o f the mixed meal w i t h and w i t h o u t p e c t i n and guar gum by NID d i a b e t i c s s i g n i f i c a n t l y improved g l u c o s e t o l e r a n c e w i t h o u t s i g n i f i c a n t changes i n i n s u l i n , g l u c a g o n o r g a s t r i c i n h i b i t o r y p o l y p e p t i d e when autonomic neuropathy was n o t p r e s e n t . However, when autonomic neuropathy was p r e s e n t i n the d i a b e t i c s g l u c o s e t o l e r a n c e was n o t improved; i n s u l i n and g a s t r i c i n h i b i t o r y p o l y p e p t i d e r e s p o n s e s remained unchanged b u t g l u c a g o n l e v e l s were decreased. V a a l e r e t a l (44) and Poynard e t a l (45) f e d 15 and 7 g o f p e c t i n , r e s p e c t i v e l y , t o ID d i a b e t i c s i n a meal. B o t h r e s e a r c h e r s r e p o r t e d s i g n i f i c a n t d e c r e a s e s i n serum g l u c o s e w i t h p e c t i n p r e s e n t compared t o t h e meal w i t h o u t p e c t i n . V a a l e r observed the s i g n i f i cant decrease 15 through 90 minutes a f t e r the meal w h i l e Poynard r e p o r t e d d e c r e a s e s a t 60 through 90 m i n u t e s . Poynard e t a l (45) a l s o measured i n s u l i n , and r e p o r t e d mean i n s u l i n d e l i v e r y was s i g n i f i c a n t l y d e c r e a s e d , a v e r a g i n g 35% d e c r e a s e over 180 m i n u t e s , when p e c t i n was i n c l u d e d compared t o the c o n t r o l . Kanter e t a l (47) f e d a meal w i t h and w i t h o u t p e c t i n t o s e v e r a l groups o f s u b j e c t s a f t e r they had been f e d a c o n t r o l l e d d i e t w i t h and w i t h o u t 10 g o f p e c t i n and 16 g o f guar gum f o r 3 days p r e c e d i n g the t e s t meal. The f i v e n o r m a l , s i x obese ( 1 3 0 % i d e a l mean w e i g h t ) , f i v e l a t e n t d i a b e t i c s and s i x o v e r t d i a b e t i c s a l l showed some dec r e a s e i n peak g l u c o s e response a f t e r t h e i n c l u s i o n o f the gums i n the d i e t and meal. Normal s u b j e c t s responded l e a s t t o t h e p r e sence o f t h e gums, a l l d e c r e a s e s b e i n g n o n - s i g n i f i c a n t , w h i l e t h e o v e r t d i a b e t i c s had the g r e a t e s t response t o the meal. Obese and d i a b e t i c s u b j e c t s had s i g n i f i c a n t d e c r e a s e s i n serum g l u c o s e , the obese a t 30 and 60 minutes a f t e r t h e meal and the d i a b e t i c s a t 0 through 90 minutes a f t e r t h e meal w i t h t h e gums. I n s u l i n response to the i n c l u s i o n o f p e c t i n w i t h guar gum i n the d i e t and meal f o l lowed t h e same p a t t e r n as t h e serum g l u c o s e w i t h t h e g r e a t e s t d e c r e a s e i n t h e d i a b e t i c s u b j e c t s and the l e a s t change i n the normal s u b j e c t s . Normal s u b j e c t s had s i g n i f i c a n t l o w e r i n g o f i n s u l i n response a t 45 t o 90 minutes a f t e r the meal c o n t a i n i n g p e c t i n , obese s u b j e c t s a t 15 t o 120 m i n u t e s ; l a t e n t d i a b e t i c s , 15 t o 60 m i n u t e s ; and o v e r t d i a b e t i c s 45 t o 120 minutes compared t o the response when p e c t i n was n o t i n c l u d e d i n t h e meal. Mahalko e t a l (24) r e p o r t e d no s i g n i f i c a n t change i n serum g l u c o s e response t o a low f i b e r formula f o l l o w i n g d i e t s c o n t a i n i n g a low f i b e r w h i t e b r e a d ( c o n t r o l ) , 26 g o r 52 g o f the apple powder o f d e h y d r a t e d powdered a p p l e s as the p e c t i n s o u r c e . One s u b j e c t , who consumed b o t h l e v e l s o f powdered a p p l e , d i d respond w i t h s i g n i f i c a n t dec r e a s e s i n serum g l u c o s e . Mahalko suggested t h a t t h i s s u b j e c t might be p a r t o f a s u b p o p u l a t i o n o f persons w i t h NID d i a b e t e s t h a t responds t o t h i s f i b e r s o u r c e . Gardner e t a l (48) were u n a b l e to f i n d s i g n i f i c a n t changes i n hemoglobin A ^ o r g l y c o s y l a t e d serum p r o t e i n i n 17 ID d i a b e t i c s f e d 5 g o f p e c t i n w i t h each meal and


260

CHEMISTRY AND

FUNCTION OF PECTINS

a t bedtime w i t h t h e i r s e l f - s e l e c t e d d i e t f o r 3 months. The a u t h o r s f e l t these two parameters should have d e c r e a s e d s i n c e most s t u d i e s r e p o r t a decreased g l u c o s e response t o a t o l e r a n c e t e s t when p e c t i n was p r e s e n t .


Mineral

Bioavailability

The e f f e c t o f p e c t i n consumption on m i n e r a l b a l a n c e has not been e x t e n s i v e l y s t u d i e d . Cummings e t a l (29) fed f i v e normal men a c o n t r o l l e d d i e t f o r 3 weeks f o l l o w e d by the c o n t r o l l e d d i e t s u p p l e mented w i t h 36 g o f p e c t i n . C a l c i u m e x c r e t i o n was not s i g n i f i c a n t l y d i f f e r e n t between the two d i e t p e r i o d s and a l l s u b j e c t s were i n c a l c i u m b a l a n c e d u r i n g the c o n t r o l and p e c t i n supplemented p e r i o d . S t a s s e - W o l t h u i s e t a l (9) a f t e r 5 weeks o f f e e d i n g 15 g o f p e c t i n t o t h e i r s u b j e c t s d i d not observe any s i g n i f i c a n t change i n c a l c i u m , magnesium, sodium, o r p o t a s s i u m e x c r e t i o n compared t o l e v e l s a f t e r the c o n t r o l d i e t . Sandberg e t a l (50) fed s i x i l e o s t o m i c p a t i e n t s 15 g o f p e c t i n a day i n a double c r o s s o v e r ; 4 days o f c o n t r o l , 3 days o f p e c t i n s u p p l e m e n t a t i o n and 3 days o f c o n t r o l d i e t . A f t e r the p e c t i n was consumed t h e r e was i n c r e a s e d e x c r e t i o n o f sodium, p o t a s s i u m , and i r o n w h i l e c a l c i u m , magnesium and z i n c were not s i g n i f i c a n t l y changed from c o n t r o l l e v e l s . Apparent i r o n b a l a n c e was s i g n i f i c a n t l y d e c r e a s e d . Monnier e t a l (51) r e p o r t e d i r o n a b s o r p t i o n s i g n i f i c a n t l y decreased i n e i g h t p a t i e n t s w i t h i d i o p a t h i c hemochromatosis a f t e r a l o a d dose o f i r o n w i t h 9 g o f p e c t i n per meter squared o f body s u r f a c e compared t o r e t e n t i o n o f the l o a d without p e c t i n present. I n v i t r o (51) p e c t i n was found t o have a h i g h b i n d i n g a c t i v i t y f o r i r o n a v e r a g i n g 83 t o 92% a t v a r y i n g pH's. L e i e t a l (52) fed n i n e normal s u b j e c t s , seven women and two men, a c o n t r o l l e d d i e t f o r 3 weeks w i t h and w i t h o u t 15 g o f p e c t i n per day. The l a s t 6 days o f each p e r i o d were used f o r sample c o l l e c t i o n . No s i g n i f i c a n t d i f f e r e n c e s were observed i n e x c r e t i o n o r apparent i r o n , z i n c , or copper b a l a n c e between the c o n t r o l o r p e c t i n supplemented d i e t s . B a i g e t a l (52) fed r a t s f o r 40 days one o f f o u r d i e t s , low or^adequate i r o n d i e t s w i t h o r w i t h o u t 2% p e c t i n . A l o a d dose o f Fe w i t h o r w i t h o u t p e c t i n was g i v e n t o the r a t s by gavage. The r a t s fed the low i r o n d i e t s absorbed more i r o n than those on the adequate d i e t s r e q a r d l e s s o f the presence o r absence o f p e c t i n i n the d i e t o r l o a d dose. Drews e t a l (53) f e d a d o l e s c e n t boys a c o n t r o l l e d d i e t w i t h and w i t h o u t i s o l a t e d f i b e r s f o r 4 days each. Consumption o f 14.2 g o f p e c t i n had no e f f e c t on the e x c r e t i o n o r apparent b a l a n c e o f z i n c , copper o r magnesium. A d d i t i o n a l r e s e a r c h needs t o be c a r r i e d out on m i n e r a l r e t e n t i o n when p e c t i n i s p r e s e n t i n the d i e t . I r o n showed b o t h d e c r e a s e d a b s o r p t i o n and no s i g n i f i c a n t d i f f e r e n c e s from the c o n t r o l . I n g e n e r a l the l o n g e r s t u d i e s showed l e s s d i f f e r e n c e s i n i r o n r e t e n t i o n from c o n t r o l l e v e l s than d i d the l o a d dose o r v e r y s h o r t s t u d i e s . Other m i n e r a l s s t u d i e d d i d not s i g n i f i c a n t l y change when p e c t i n was p r e s e n t i n the s t u d i e s r e p o r t e d . Vitamin

Bioavailability

Scant d a t a are a v a i l a b l e on i n t e r a c t i o n s between p e c t i n and v i t a m i n utilization. G i n t e r e t a l (25) added 450 mg o f v i t a m i n C per day



19.

BEHALL AND REISER


261

t o t h e 15 g o f p e c t i n f e d t o h y p e r c h o l e s t e r o l e m i c s u b j e c t s . They r e p o r t e d a s i g n i f i c a n t r e d u c t i o n i n serum c h o l e s t e r o l , a g r e a t e r r e d u c t i o n than a n t i c i p a t e d on t h e b a s i s o f the amount o f p e c t i n added. The g r e a t e r r e d u c t i o n i n c h o l e s t e r o l l e v e l s was a t t r i b u t e d to s y n e r g i s t i c a c t i o n between the v i t a m i n C and t h e p e c t i n . They hypothesized that v i t a m i n C acted to stimulate the production o f 7 - a - h y d r o x y c h o l e s t e r o l which subsequently i n c r e a s e d b i l e a c i d p r o d u c t i o n . P e c t i n i n t u r n i n c r e a s e d c h o l e s t e r o l and b i l e a c i d e x c r e t i o n by b i n d i n g o r entrapment. K e l t z e t a l (54) i n v e s t i g a t e d v i t a m i n C u r i n a r y e x c r e t i o n i n r e l a t i o n t o f e e d i n g 14.2 g o f p e c t i n p e r day w i t h and w i t h o u t z i n c supplementation. V i t a m i n C e x c r e t i o n decreased w i t h p e c t i n p r e s e n t i n t h e d i e t w i t h o r w i t h o u t the z i n c supplement. I n c r e a s e d u t i l i z a t i o n o f v i t a m i n C o r decreased a b s o r p t i o n o r a c o m b i n a t i o n o f these f a c t o r s was suggested as r e s p o n s i b l e f o r changing the vitamin C available for excretion. Rat s t u d i e s by C u l l e n and Oace (56) r e p o r t e d i n c r e a s e d e x c r e t i o n o f methylmalonic a c i d r e s u l t i n g i n B^ d e p l e t i o n i n r a t s fed p e c t i n . The a u t h o r s suggested t h a t p e c t i n i n t e r f e r e d w i t h r e c y c l i n g p o s s i b l y by s t i m u l a t i n g m i c r o b i a l a c t i v i t y i n c r e a s i n g the B^2 requirement when p e c t i n was b e i n g degraded and thereby d e c r e a s i n g t h e B ^ a v a i l a b i l i t y f o r r e a b s o r p t i o n . However, t h e a d d i t i o n o f p e c t i n t o t h e d i e t s o f r a t s o r c h i c k s h a s n o t been found t o have d e l e t e r i o u s e f f e c t s on the b i o a v a i l a b i l i t y o f p y r i d o x i n e (52), f o l i c a c i d (58) o r V i t a m i n A o r 8-carotene ( 5 9 ) . A d d i t i o n a l r e s e a r c h w i t h animals and u l t i m a t e l y w i t h man on the e f f e c t s o f p e c t i n consumption on v i t a m i n u t i l i z a t i o n and a v a i l a b i l i t y i s needed. Too l i t t l e r e s e a r c h has been c a r r i e d o u t t o p r o v i d e a d e f i n i t i v e answer o f the e f f e c t s o f p e c t i n consumption over a long p e r i o d o f t i m e . 2

E f f e c t and F a t e o f P e c t i n i n the G a s t r o i n t e s t i n a l T r a c t P e c t i n appears t o be b e t t e r t o l e r a t e d when i t i s i n c l u d e d i n t h e d i e t as a food source o r c o m p l e t e l y h y d r a t e d i n a food product (7) than when g i v e n as a powder mixed w i t h w a t e r , j u i c e o r t h e s u b j e c t s own food (IS). S u b j e c t s complained o f t h e t a s t e , gummy f e e l , and t h e s t i c k i n e s s i n mouth and on t e e t h when powered p e c t i n was g i v e n w h i l e food s o u r c e s , even those f o r m u l a t e d by the r e s e a r c h e r s , were w e l l a c c e p t e d . Some s i d e a f f e c t s noted by some s u b j e c t s i n human s t u d i e s i n c l u d e d r e c t a l f l a t u l e n c e , f l a t u l e n c e , abdominal d i s t e n t i o n and abdominal cramps. I n c o n t r a s t w i t h some o t h e r f i b e r sources such as wheat b r a n no s i g n i f i c a n t d e c r e a s e i n mean t r a n s i t times has been r e p o r t e d by most r e s e a r c h e r s (7,9,18,29,30) i n v e s t i g a t i n g the e f f e c t o f p e c t i n on bowel f u n c t i o n o r m i n e r a l b i o a v a i l a b i l i t y . Only one study (15) r e p o r t e d a s i g n i f i c a n t d e c r e a s e i n t r a n s i t time from a s t a r t i n g time a v e r a g i n g 63 h o u r s . No s i g n i f i c a n t d i f f e r e n c e i n t r a n s i t time between h i g h and low m e t h o x y l p e c t i n s was observed by Judd and T r u s w e l l ( 1 9 ) . Both i n c r e a s e d frequency o f d e f e c a t i o n ( 7 ) and change i n s t o o l number (9,29) have been r e p o r t e d when p e c t i n was added t o the d i e t o f human s u b j e c t s . S i g n i f i c a n t i n c r e a s e s i n f e c a l wet o r d r y weight have been r e p o r t e d by some i n v e s t i g a t o r s (7,15,18,29) and no s i g n i f i c a n t changes i n f e c a l w e i g h t by o t h e r s (9,30,59,60). 1




262

Most o f t h e p e c t i n consumed appears t o be d i g e s t e d by normal human s u b j e c t s (29,61,62). P e c t i n r e c o v e r e d i n t h e f e c e s has ranged from 0 t o 25% (61,62). Most o f t h e d i g e s t i o n (up t o 80%) o c c u r s i n the l a r g e i n t e s t i n e w i t h up t o 4 0 % o c c u r r i n g i n the s m a l l i n t e s t i n e (61,63). I t has been suggested t h a t p e c t i n added t o the d i e t i s d i g e s t e d by i n c r e a s e d b a c t e r i a l a c t i o n (29,61). I n c r e a s e d methane hydrogen, carbon d i o x i d e and f l a t u s volume have been r e p o r t e d w i t h p e c t i n consumption compared t o a f i b e r free d i e t (64). Increases i n f e c a l content of f a t t y acids (80%), n i t r o g e n ( 4 7 % ) , b i l e a c i d s (35%) and t o t a l s o l i d s (28%) compared t o c o n t r o l l e v e l s (29) were thought t o be due t o i n c r e a s e d b a c t e r i a l and i n t e s t i n a l c e l l mass. The degree o f p e c t i n d i g e s t i o n and c e l l u l a r e x c r e t i o n would a f f e c t s t o o l b u l k and d r y f e c a l w e i g h t r e s u l t i n g i n t h e wide range r e p o r t e d i n s t o o l w e i g h t changes. Conclusion D i e t s c o n t a i n i n g p e c t i n i n c o r p o r a t e d i n t o a food source appeared t o be b e t t e r t o l e r a t e d and g r e a t e r amounts c o u l d be consumed than when powder o r c a p s u l e s were consumed. The consumption o f p e c t i n by normal and h y p e r c h o l e s t e r o l e m i c i n d i v i d u a l s has been r e p o r t e d i n most s t u d i e s t o lower b l o o d c h o l e s t e r o l l e v e l s w i t h o u t changing t r i g l y c e r i d e o r HDL l e v e l s . The g r e a t e s t d e c r e a s e s i n b l o o d c h o l e s t e r o l were r e p o r t e d i n h y p e r c h o l e s t e r o l e m i c s u b j e c t s . Low-fat d i e t s and d i e t s supplemented w i t h l e s s than 6 g o f p e c t i n p e r day g e n e r a l l y produced t h e l e a s t change i n b l o o d c h o l e s t e r o l l e v e l s . E x c r e t i o n o f f e c a l f a t , s t e r o i d s , and b i l e a c i d s were i n c r e a s e d . L i p i d s a r e thought t o be bound t o o r entrapped i n t h e p e c t i n g e l so t h a t they cannot be absorbed i n the s m a l l i n t e s t i n e . The consumption o f p e c t i n by normal and d i a b e t i c i n d i v i d u a l s has been r e p o r t e d t o lower the g l u c o s e response c u r v e a f t e r a l o a d dose o r meal. I n s u l i n response c u r v e s were s i m i l a r l y decreased i n responses t o p e c t i n i n a p p r o x i m a t e l y t w o - t h i r d s o f the s t u d i e s i n which i n s u l i n was measured. Hypoglycemia and g a s t r i c dumping syndrome appear t o be l e s s e n e d o r a v e r t e d when p e c t i n was consumed w i t h t h e meal. Very few l o n g - t e r m s t u d i e s have been c a r r i e d out i n v e s t i g a t i n g p e c t i n feeding i n r e l a t i o n to glucose, i n s u l i n or o t h e r g l u c o g e n i c parameters. More r e s e a r c h i s needed b e f o r e p e c t i n can be s a f e l y recommended t o d i a b e t i c s as a d i e t a r y means t o reduce t h e i r blood glucose. The e f f e c t o f p e c t i n consumption on m i n e r a l b a l a n c e has n o t been s t u d i e d e x t e n s i v e l y a l t h o u g h the e x c r e t i o n and apparent b a l a n c e o f most m i n e r a l s appears t o be u n a f f e c t e d by d i e t a r y p e c t i n . I r o n u t i l i z a t i o n o r a b s o r p t i o n may be a f f e c t e d by p e c t i n consumption but t h e l o n g e r f e e d i n g s t u d i e s d i d n o t r e p o r t any s i g n i f i c a n t changes i n apparent b a l a n c e from c o n t r o l l e v e l s . F u r t h e r l o n g term s t u d i e s a r e needed. I n t e r a c t i o n o f p e c t i n w i t h v i t a m i n s has been s t u d i e d l i t t l e i n man o r a n i m a l s . V i t a m i n C consumption w i t h p e c t i n may be b e n e f i c i a l t o h y p e r c h o l e s t e r o l e m i c p e r s o n s . Vitamin B j ^ a b s o r p t i o n appears t o be reduced w i t h p e c t i n w h i l e o t h e r v i t a m i n s s t u d i e d showed no r e d u c t i o n i n b i o a v a i l a b i l i t y . More r e s e a r c h i s needed t o determine i f p e c t i n i s b e n e f i c i a l , d e t r i m e n t a l o r b e n i g n when consumed as p a r t o f t h e d i e t .




263

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