6 Downloaded via YORK UNIV on December 4, 2018 at 19:05:18 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
Riboflavin Requirements and Exercise Daphne A. Roe and Amy Z. Belko Division of Nutritional Sciences, Savage Hall, Cornell University, Ithaca, NY 14853
Current questions frequently posed to nutritionists are whether people who are exercising have special vitamin needs and whether, if they have special needs, these can be met by a normal diet or whether they require nutrient supplements. A response to such questions can now be made with respect to a particular Β vitamin, riboflavin. Riboflavin deficiency and the dietary means to prevent such deficiency have been known since the late 1930's when early accounts of the clinical signs of riboflavin deficiency were published (1). Clinical signs of riboflavin deficiency include fissures at the corners of the lips (angular stomatitis), dermatitis of skin creases, folds and areas of trauma (seborrhoeic dermatitis of the nasolabial folds, the periorbital creases and the inguinal areas, the vulva, and the scrotum), as well as peeling and/or fissuring of the lips (chei losis) and sore tongue (glossitis). Other signs which are sometimes present include vascularization of the cornea, keratitis, blepharitis and anemia. Subsequently, the functions of the vitamin were better estab lished and requirements for the vitamin were set. R i b o f l a v i n i s an 1
i n t e g r a l p a r t o f two coenzymes, f l a v i n - 5 - p h o s p h a t e (FMN) and f l a v i n adenine d i n u c l e o t i d e (FAD), w h i c h f u n c t i o n i n o x i d a t i o n / r e d u c t i o n reactions. Indeed, r i b o f l a v i n i s an enzyme c o f a c t o r w h i c h i s n e c e s s a r y i n m e t a b o l i c p r o c e s s e s i n which o x i d a t i o n o f g l u c o s e o r f a t t y a c i d i s used f o r p r o d u c t i o n o f adenosine t r i p h o s p h a t e (ATP) as w e l l as i n r e a c t i o n s i n which o x i d a t i o n o f amino a c i d s i s a c c o m p l i s h e d . The minimum r e q u i r e m e n t f o r r i b o f l a v i n has been e s t a b l i s h e d a s t h a t amount which a c t u a l l y p r e v e n t s t h e s i g n s o f d e f i c i e n c y . A range o f i n t a k e s v a r y i n g from 0.55 t o 0.75 mg/day o f r i b o f l a v i n h a s been e s t a b l i s h e d a s t h e minimum amount w h i c h i s r e q u i r e d t o p r e v e n t appearance o f d e f i c i e n c y s i g n s . Today, b i o c h e m i c a l d e f i c i e n c y o f r i b o f l a v i n i s accepted i n the absence o f c l i n i c a l s i g n s o f d e f i c i e n c y . Biochemical signs o f d e f i c i e n c y i n c l u d e change i n t h e amount o f t h e v i t a m i n which i s e x c r e t e d i n t h e u r i n e , o r change i n t h e l e v e l o f a c t i v i t y o f a r e d b l o o d c e l l ( e r y t h r o c y t e ) enzyme, w h i c h i s known a s t h e e r y t h r o c y t e g l u t a t h i o n e reductase. Requirements f o r t h e v i t a m i n a r e d e f i n e d as t h a t amount w h i c h w i l l p r e v e n t b o t h c l i n i c a l and b i o c h e m i c a l s i g n s o f d e f i c i e n c y . 0097-6156/ 86/ 0294-0080$06.00/ 0 © 1986 American Chemical Society
Layman; Nutrition and Aerobic Exercise ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
6.
How
ROE AND
BELKO
Riboflavin
Have Optimum I n t a k e s
Requirements
and
Exercise
81
f o r R i b o f l a v i n Been Determined?
Whereas r i b o f l a v i n f u n c t i o n s as a coenzyme o f f l a v o p r o t e i n s , w h i c h a r e concerned w i t h b i o l o g i c a l o x i d a t i o n s o r energy u t i l i z a t i o n , i t has been proposed t h a t w i t h i n c r e a s e d energy e x p e n d i t u r e , the body's need f o r r i b o f l a v i n may be i n c r e a s e d . In the p a s t , the assessment o f r i b o f l a v i n n u t r i t u r e was p r i m a r i l y dependent on measurement o f the u r i n a r y e x c r e t i o n o f the v i t a m i n . If riboflavin intake i s low, e x c r e t i o n o f the v i t a m i n i s d i m i n i s h e d . As r i b o f l a v i n intake i s i n c r e a s e d t o meet need, r i b o f l a v i n e x c r e t i o n i n the u r i n e i n c r e a s e s . Indeed, u r i n a r y e x c r e t i o n o f r i b o f l a v i n b o t h by a d u l t s and c h i l d r e n on d i e t s c o n t a i n i n g up t o a p p r o x i m a t e l y 0.5 mg r i b o f l a v i n / 1 0 0 0 Kcal is low and the e x c r e t i o n r i s e s s h a r p l y as the d i e t a r y i n t a k e i s increased t o 0.75 mg/1000 K c a l or above ( 2 ) . S i n c e 1972 red cell enzyme a s s a y o f r i b o f l a v i n s t a t u s has been w i d e l y used. Indeed, i n epidemiological and c l i n i c a l s t u d i e s o f r i b o f l a v i n s t a t u s , the e r y throcyte ( r e d c e l l ) g l u t a t h i o n e r e d u c t a s e a s s a y (EGR) i s the test which i s u s u a l l y undertaken. In 1972 T i l l o t s o n and Baker (_3) showed t h a t t h i s enzyme a s s a y was s e n s i t i v e t o r i b o f l a v i n d e p l e t i o n . I t has f u r t h e r been shown t h a t change i n t h i s r e d c e l l enzyme a c t i v i t y i s one o f the f i r s t changes t o be found w i t h r e d u c t i o n i n i n t a k e o f the v i t a m i n below need ( 4 , 5 ) . Arguments have been p u b l i s h e d i n f a v o r o f r e l a t i n g s t a n d a r d s f o r r i b o f l a v i n r e q u i r e m e n t s t o food-energy intake (6,7). However, s i n c e i n the p a s t no s a t i s f a c t o r y e v i d e n c e was obtained from s t u d i e s o f the u r i n a r y e x c r e t i o n o f r i b o f l a v i n that riboflavin r e q u i r e m e n t s were i n c r e a s e d when energy u t i l i z a t i o n was i n c r e a s e d , a l l o w a n c e s f o r t h i s v i t a m i n i n the U n i t e d S t a t e s have been s e t f o r people engaging i n " n o r m a l " a c t i v i t y ( i . e . , n e i t h e r s e d e n t a r y nor engaged i n heavy p h y s i c a l work) ( 8 ) , and no m o d i f i c a t i o n of i n t a k e has been recommended, based on change i n food-energy r e q u i r e ments. The c u r r e n t Recommended D i e t a r y A l l o w a n c e (RDA) f o r riboflavin f o r young a d u l t males and f o r nonpregnant, n o n l a c t a t i n g young a d u l t women i s s e t i n the U.S. a t the l e v e l of 0.6 mg/1000 K c a l ( 9 ) . I n t e r n a t i o n a l l y , recommendations f o r d a i l y i n t a k e s o f r i b o f l a v i n vary. Thus, i n the P h i l i p p i n e s w h i c h have the l o w e s t recommended d i e t a r y i n t a k e f o r r i b o f l a v i n , the l e v e l i s s e t a t 0.5 mg/1000 K c a l , w h i l e i n the USSR i t i s s e t a t 0.79 mg/1000 K c a l . In s e v e r a l c o u n t r i e s i n c l u d i n g B u l g a r i a , C h i l i , The P e o p l e ' s R e p u b l i c o f C h i n a , C z e c h o s l o v a k i a , Hungary, I n d i a , The N e t h e r l a n d s , P o l a n d , Taiwan and the USSR, the recommended d i e t a r y i n t a k e s f o r r i b o f l a v i n v a r y w i t h o c c u p a t i o n a l or energy e x p e n d i t u r e c a t e g o r i e s ( 1 0 ) . I s There E x p e r i m e n t a l E v i d e n c e That R i b o f l a v i n Requirements Are I n f l u e n c e d by the L e v e l of P h y s i c a l A c t i v i t y ? Tucker e t a l . showed t h a t b o t h sudden s e v e r e p h y s i c a l e x e r c i s e and longer s u s t a i n e d work on a t r e a d m i l l d u r i n g t r a i n i n g d e c r e a s e s urin a r y r i b o f l a v i n e x c r e t i o n d u r i n g the e x p e r i m e n t a l p e r i o d s (11). The a c u t e r e d u c t i o n i n r i b o f l a v i n e x c r e t i o n observed by t h e s e i n v e s t i g a t o r s was a t t r i b u t e d t o a r e d u c t i o n i n r e n a l plasma f l o w . In o r d e r t o e x p l a i n the l o n g - t e r m reduced e x c r e t i o n o f the v i t a m i n , t h e y proposed t h a t r i b o f l a v i n was r e t a i n e d f o r i n c o r p o r a t i o n i n t o "new muscle tissue". The s i g n i f i c a n c e o f t h i s s t u d y i s t h a t i f the hypotheses
Layman; Nutrition and Aerobic Exercise ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
82
NUTRT IO IN AND AEROBC I EXERCS IE
put f o r w a r d were p r o v e n , i t would mean t h a t r i b o f l a v i n requirements are increased with e x e r c i s e , b u t i n r e l a t i o n t o change i n l e a n body mass r a t h e r than due t o change i n energy e x p e n d i t u r e . In a 1979 s t u d y we showed t h a t female v o l u n t e e r s who were f e d diets f o r 10 weeks w i t h e i t h e r a s c e n d i n g o r d e s c e n d i n g riboflavin content required i n t a k e s e q u a l t o o r g r e a t e r than 0.7 m g / r i b o f l a v i n / 1 0 0 0 K c a l i n o r d e r t o n o r m a l i z e t h e i r EGR v a l u e s . In a second study c a r r i e d o u t by us which was d e s i g n e d t o examine t h e e f f e c t s o f oral c o n t r a c e p t i v e s on r i b o f l a v i n r e q u i r e m e n t s , 18 female subjects were f e d a s c e n d i n g l e v e l s o f d i e t a r y r i b o f l a v i n u n t i l EGR v a l u e s were normalized. No s i g n i f i c a n t group d i f f e r e n c e s were found between p i l l users and n o n - p i l l u s e r s i n t h e amounts o f r i b o f l a v i n required t o n o r m a l i z e t h e EGR. However, i t was found t h a t t h o s e s u b j e c t s with the h i g h e s t f o o d - e n e r g y r e q u i r e m e n t s a l s o had h i g h r e q u i r e m e n t s f o r riboflavin. The s u b j e c t s w i t h t h e h i g h e s t r i b o f l a v i n requirements were a l s o t h o s e who performed t h e g r e a t e s t amount o f p h y s i c a l a c t i v i t y (12-14). We then carried o u t a f u r t h e r s t u d y i n which t h e e f f e c t s o f exercise on r i b o f l a v i n r e q u i r e m e n t s o f young women o f n o r m a l body weight were a s s e s s e d ( L 5 ) . D u r i n g a 12 week s t u d y , s u b j e c t s f o l l o w e d a six-week, s e d e n t a r y p e r i o d b y a six-week e x e r c i s e p e r i o d i n w h i c h they jogged around a t r a c k f o r 20 o r 50 m i n u t e s p e r day. The s t u d y participants were aged 19-27 y e a r s . They were f e d a b a s i c diet containing 0.6 mg r i b o f l a v i n / 1 0 0 0 K c a l o f food i n t a k e . Their riboflavin i n t a k e i n a d i e t o f d e f i n e d c a l o r i e c o n t e n t was i n c r e a s e d b y 0.2 mg/1000 K c a l i n c r e m e n t s by p r o v i s i o n o f r i b o f l a v i n i n a glucose polymer m i x t u r e . L i n e a r r e g r e s s i o n a n a l y s i s was used t o e s t i m a t e t h e riboflavin i n t a k e r e q u i r e d f o r an EGR a c t i v i t y c o e f f i c i e n t of 1.25 d u r i n g b o t h t h e no e x e r c i s e and e x e r c i s e p e r i o d . Individual riboflavin r e q u i r e m e n t s ranged from 0.62 t o 1.21 mg/1000 K c a l b e f o r e exercise. The r i b o f l a v i n r e q u i r e m e n t f o r an EGR a c t i v i t y c o e f f i c i e n t o f
