Physiological Effects of Food Carbohydrates

2 Metabolic Effects of Dietary Carbohydrates—A Review SHELDON REISER

Downloaded by UNIV OF BATH on June 20, 2016 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0015.ch002

U.S. Department of Agriculture, ARS, Nutrition Institute, Carbohydrate Nutrition Laboratory, Beltsville, Md. 20705

Many environmental changes have been characteristic of societies described as "Western", "urbanized" or "affluent." Among these changes are a decrease in physical activity, an increase in mental stress and changes in dietary patterns. The changes in dietary patterns of carbohydrate intake that have been developing in the United States are shown in Figure 1 (1). The share of total carbohydrate in the U.S. diet provided by sugars as compared to starch has risen from about 32% around the turn of the century until today sugars, predominantly sucrose, contribute more than 50% of the total carbohydrate. While the average per capita consumption of flours and cereals has dropped from 300 lbs/year in 1909 to 141 lbs/year in 1970, the consumption of refined sugar and other sweeteners has in creased from 87 to 126 lbs/year (1,2). These are average figures. Experts estimate that the sugar consumption by the young, that is between 6-20 years of age, probably ranges from 140 to 150 lbs/year (2). The metabolic implications of high sucrose intake in the young will be discussed later. These a f f l u e n t s o c i e t i e s are a l s o c h a r a c t e r i z e d by an i n crease i n the i n c i d e n c e o f heart disease and d i a b e t e s . Diabetes and heart disease represent two o f the most c r i t i c a l h e a l t h problems i n the U.S. today. Diabetes now a f f e c t s about 5 m i l l i o n Americans and r e s u l t s i n over 35,000 deaths a n n u a l l y . By 1980, i t i s estimated t h a t more than 10% o f a l l Americans w i l l have diabetes o r the i n h e r i t e d t r a i t o f diabetes ( 3 ) . One out o f every f o u r a d u l t s i n the U.S. between 18-79 years o f age has been diagnosed as having o r suspected o f having heart disease ( 4 ) . A c l o s e r e l a t i o n s h i p between heart disease and diabetes i s i n d i cated by the f i n d i n g s t h a t d i a b e t i c s have a much higher r i s k o f developing heart disease than the general p o p u l a t i o n (5,6) and t h a t 25% o r more o f p a t i e n t s w i t h v a s c u l a r disease are d i a b e t i c CDOne o f the most i n t r i g u i n g aspects o f t h i s changing p a t t e r n o f carbohydrate consumption i n urbanized c u l t u r e s i s the r e l a t i o n s h i p between the i n c r e a s e d i n t a k e o f r e f i n e d carbohydrates 20 Jeanes and Hodge; Physiological Effects of Food Carbohydrates ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

2.

21

Metabolic Effects

REISER

683


1909-13

ι * 4ftf

1972

47.2 52.8

10 STARCH SUGAR

20

30

40

50

60

70

PERCENT

Figure I. Carbohydrate from starch and sugar. Carbohydrate consumption in the United States during the indicated years is based on food disappearing into con sumption channels. Carbohydrate in foods such as milk, fruit, and sweeteners was assumed to be present mainly as sugar, and carbohydrate in foods such as grain products and vegetables was assumed to be present mainly as starch. Adapted from Réf. 1.

Jeanes and Hodge; Physiological Effects of Food Carbohydrates ACS Symposium Series; American Chemical Society: Washington, DC, 1975.


22

PHYSIOLOGICAL

EFFECTS

OF

FOOD

CARBOHYDRATES

such as sucrose and the e t i o l o g y of v a r i o u s d i s e a s e s . In recent years s e v e r a l c o n t r o v e r s i a l hypotheses have i m p l i c a t e d * t h e i n creased i n g e s t i o n of sucrose, as compared to the more complex carbohydrates, as an important f a c t o r i n the e t i o l o g y o f coronary heart disease Ç8-10) and diabetes (10,11). I t i s recognized t h a t many environmental f a c t o r s , i n c l u d i n g d i e t a r y f a c t o r s , as w e l l as genetic f a c t o r s i n f l u e n c e these diseases and thus the unequivocal r o l e of one of these f a c t o r s independent of the others i s d i f f i c u l t to evaluate. However, i n view o f the controversy surroundi n g d i e t a r y carbohydrate, i t i s the purpose o f t h i s review to d e s c r i b e some of the metabolic e f f e c t s observed a f t e r f e e d i n g sucrose to experimental animals and man and to evaluate the r e l a t i o n s h i p between these metabolic changes and the disease s t a t e s . An area of c o n s i d e r a b l e controversy i s the i n t e r p r e t a t i o n of r e t r o s p e c t i v e or e p i d e m i o l o g i c a l s t u d i e s t h a t attempt t o prove the i n c r e a s e d i n c i d e n c e of a disea$e by c o r r e l a t i o n w i t h the increased i n t a k e of a d i e t a r y c o n s t i t u e n t . Although r e t r o s p e c t i v e s t u d i e s do not permit d e f i n i t i v e conclusions t o be drawn as t o the causal s i g n i f i c a n c e o f the c o r r e l a t i o n s detected, they are u s e f u l i n i d e n t i f y i n g trends and i n suggesting s p e c i f i c problem areas worthy o f f u r t h e r study. Many r e t r o s p e c t i v e s t u d i e s have i n d i c a t e d a c o r r e l a t i o n between sucrose i n t a k e and heart disease (8,10,12-15), but Γ would l i k e t o concentrate p r i m a r i l y on the data gathered by an i n t e r n a t i o n a l cooperative study on the r e l a t i o n s h i p between d i e t a r y f a c t o r s and deaths from heart disease i n 37 c o u n t r i e s , p u b l i s h e d by M a s i r o n i i n 1970 (16). Table 1 summarizes these r e s u l t s . M o r t a l i t y data from heart disease ( a r t e r i o s c l e r o t i c and degenerative) were taken from "World Health S t a t i s t i c s Annuals" and v a r i o u s age and sex groups were d e f i n e d . D i e t a r y data were taken from the "Food balance sheets" p u b l i s h e d by the Food and A g r i c u l t u r e O r g a n i z a t i o n . From these c o r r e l a t i o n c o e f f i c i e n t s i t can be seen t h a t w h i l e sucrose i s somewhat l e s s s t r o n g l y c o r r e l a t e d w i t h death r a t e s than i s f a t , there i s nonetheless a s t r o n g p o s i t i v e c o r r e l a t i o n . Since the i n t a k e o f d i e t a r y c a l o r i e s , f a t and sucrose are s i m i l a r l y c o r r e l a t e d , these r e s u l t s are s t i l l open to v a r i o u s i n t e r p r e t a t i o n s . Although on the average d i e t a r y sucrose comprises w e l l over 50% of the simple sugars of the d i e t , i t appears to be much more s t r o n g l y c o r r e l a t e d w i t h heart disease deaths than the t o t a l of a l l the simple d i e t a r y sugars which a l s o i n c l u d e l a c t o s e , f r u c t o s e and glucose. This suggests t h a t sucrose has a s p e c i f i c a c t i o n on heart disease not shared by these other sugars. I t i s a l s o apparent t h a t a s t r o n g i n v e r s e r e l a t i o n s h i p e x i s t s between the amount of complex carbohydrate i n the d i e t and deaths from heart disease. This r e l a t i o n s h i p supports the contention of B u r k i t t (17) and Trowel1 (18) t h a t d i e t a r y f i b e r may exert an important p r e v e n t a t i v e a c t i o n against the i n c i d e n c e of heart disease. The question then a r i s e s as t o what metabolic p r o p e r t i e s o f d i e t a r y sucrose or i t s component monosaccharides can mediate


Jeanes and Hodge; Physiological Effects of Food Carbohydrates ACS Symposium Series; American Chemical Society: Washington, DC, 1975. ?

-0.72 -0.63

0.32 0.24 0.52

0.64 0.56 0.75

0.70 0.84 0.70

Males, 45-54 years

Both sexes, a l l ages

Both sexes, a l l ages (1940 s-1950 s)

Death r a t e s per were taken from and the v a r i o u s balance sheets"

(16)

100,000 p o p u l a t i o n f o r a r t e r i o s c l e r o t i c and degenerative heart disease "World H e a l t h S t a t i s t i c s Annuals" (World H e a l t h O r g a n i z a t i o n , 1958, 1968) groups d e f i n e d by age and sex. D i e t a r y data were taken i n from "Food p u b l i s h e d by the Food and A g r i c u l t u r e O r g a n i z a t i o n (1949, 1966).

Adapted from

-0.71

0.33

0.64

0.55

Females, 55-64 years

,

-0.59

0.31

0.66

0.74

Males, 55-64 years

f

-0.74

Simple sugars

Sucrose

Age-sex

Total fat

Complex carbohydrates

C o r r e l a t i o n c o e f f i c i e n t s between death r a t e s from heart d i s e a s e and d i e t a r y f a c t o r s f o r 37 c o u n t r i e s d u r i n g the 1960 s

Table 1



24

PHYSIOLOGICAL

EFFECTS

OF

FOOD

CARBOHYDRATES

an i n c r e a s e d i n c i d e n c e o f v a s c u l a r c o m p l i c a t i o n s , heart d i s e a s e and d i a b e t e s . Since a fundamental d i f f e r e n c e between dietarys t a r c h and sucrose r e s i d e s i n the nature o f the monosaccharide u n i t s comprising t h e r e s p e c t i v e molecules, much o f the i n t e r e s t i n d i e t a r y sucrose has focused on t h e metabolic e f f e c t s o f f r u c t o s e . S t u d i e s w i t h humans and experimental animals have e s t a b l i s h e d t h a t d i e t s c o n t a i n i n g sucrose o r f r u c t o s e produce l a r g e r i n c r e a s e s i n blood l i p i d s (19-23), e s p e c i a l l y the t r i g l y c e r i d e f r a c t i o n (24-28), and i n h e p a t i c l i p o g e n i c enzymes (29-35) than d i e t s c o n t a i n i n g an e q u i v a l e n t amount o f glucose or glucose polymers. The magnitude and d u r a t i o n o f the hyperl i p e m i a i s c o n t r o l l e d by f a c t o r s such as amount o f sugar f e d , age and sex o f t h e s u b j e c t , t h e nature o f the other d i e t a r y i n g r e d i e n t s and g e n e t i c p r e d i s p o s i t i o n . Younger s u b j e c t s and premenopausal females show less i n c r e a s e than o l d e r s u b j e c t s and males (25,26). An important f a c t o r i n t h i s sucrose e f f e c t appears t o be the amount and nature o f the d i e t a r y f a t . On low fat d i e t s , i . e . , l e s s than 5%, the i n c r e a s e i n t r i g l y c e r i d e s y n t h e s i s from carbohydrate i s a necessary and expected p h y s i o l o g i c a l process. Table 2, adapted from the work o f Macdonald (36), shows t h a t when young men were f e d a d i e t c o n t a i n i n g 60% carbohydrate, 30% f a t and 9% p r o t e i n f o r 5 days, the magnitude of the t r i g l y c e r i d e m i a was dependent on the nature o f both the carbohydrate and the f a t . Sucrose s i g n i f i c a n t l y i n c r e a s e d blood t r i g l y c e r i d e s o n l y when the d i e t a r y f a t was cream and not when i t was sunflower o i l . In c o n t r a s t , glucose d i d not i n c r e a s e the t r i g l y c e r i d e s w i t h e i t h e r f a t . The e f f e c t o f sunflower o i l may be due t o a c c e l e r a t i o n i n the removal o f endogenous t r i g l y c e r i d e s s i n c e N e s t e l and B a r t e r (37) have shown t h a t s u b j e c t s consuming d i e t s r i c h i n polyunsaturated fat have f a s t e r clearance r a t e s than s u b j e c t s f e d s a t u r a t e d fat. These r e s u l t s a l s o might e x p l a i n apparent c o n t r a d i c t i o n s found i n the l i t e r a t u r e as t o the e f f e c t o f d i e t a r y sucrose on serum l i p i d s i n t h a t unsaturated f a t t y a c i d s may mask t h i s e f f e c t . Work from Yudkin's l a b o r a t o r y (Table 3, (38)) shows t h a t sucrose produces a l a r g e r i n c r e a s e i n serum t r i g l y c e r i d e s and c h o l e s t e r o l than does s t a r c h i n r a t s f e d an atherogenic d i e t c o n t a i n i n g 16% hydrogenated coconut o i l and 1% c h o l e s t e r o l for 100 days. The carbohydrate comprised 47% o f the d i e t . By 180 days, t h e l e v e l s o f the blood l i p i d s had f a l l e n , but there was s t i l l the same r e l a t i v e i n c r e a s e i n c h o l e s t e r o l and t r i g l y c e r i d e l e v e l s produced by the sucrose as compared t o s t a r c h . These r e s u l t s again i n d i c a t e t h a t sucrose together w i t h other d i e t a r y f a c t o r s can produce a combination t h a t i s p o t e n t i a l l y more d e t r i m e n t a l t o the h e a l t h o f t h e consumer than e i t h e r o f the f a c t o r s alone. The major e f f e c t o f d i e t a r y sucrose on l i p i d metabolism i n v o l v e s the t r i g l y c e r i d e s . The r i s k f a c t o r i n v o l v e d i n e l e vated l e v e l s o f blood t r i g l y c e r i d e has r e c e n t l y been confirmed by a j o i n t statement on D i e t and Coronary Disease from the



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Physiological Effects of Food Carbohydrates

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