Bovine colostrum supplementation during endurance running training improves recovery, but not performance

Bovine Colostrum Supplementation during Endurance Running Training Improves Recovery, but not Performance JD Buckley I, MJ Abbott 1, GD Brinkworth I & PBD Whyte 2 1Centre for Research in Education and Sports Science, School of Physical Education Exercise and Sport Studies, University of South Australia, Adelaide, South Australia. 2Numico Research (Australia) Pry Ltd, Adelaide, South Australia. Buckley, J.D., Abbott, M.J., B~lkworth, G.D., & Whyte, P.B.D. (2002). Bovine colostrum supplementation during endurance running training improves recovery, but not performance. Journal of Science and Medicine in Sport 5 (2): 65-79. This study examined the effect of supplementation with concentrated bovine colostrum protein powder (intactTM) on plasma insulin-like growth factor I (IGF-I) concentrations, endurance miming performance and recovery. Thirty physically active males completed 8 weeks of running training whilst consuming 60 g , d a y 1 of intactTM powder (n=17) or a concentrated whey protein powder placebo (n=13) in a randomised, double-blind, parallel design. Plasma IGF-I concentrations were measured prior to subjects performing two (-30 min) incremental treadmill running tests to exhaustion (RUN1 and RUN2) separated by 20 min of passive recovery at Weeks 0, 4 and 8. Plasma IGF-I concentrations showed little change in either group (p=0.83). Effective peak running speed (PRSE; i,e. equivalent of peak power) during RUN1 was not different between groups at Week 0 (p>0.99), and had increased by a similar amount in both groups by Week 4 (mean_+SD, intactTM 2.2+4.0%, placebo 3.2_+3.3%; 95% confidence interval [95% CI] 15.7 to -13.7%; p=0.89) and Week 8 (intactTM 3.6_+5.6%, placebo 3.4-+4.4 %; 95% CI -100.0 to 100.0 %; p>0.99). PRSE was less in both groups during RUN2 (p<0.05), but was not significantly different between groups at Week 0 (p>0.99). PRSE during RUN2 tended to have increased more in the placebo group by Week 4 (intactTM 1.8_+4.8%, placebo 4.2-+3.9%; 95% CI 0.2 to -5 0%; p=0.OT), but the intactTM group had increased PRS E significantly more by Week 8 (intactTM 4.6_+6.1%, placebo 2.0_+4.5%; 95% CI 0.0 to 5.2%; p=0.05), resulting in a significantly faster PRSE (p=0.003). We conclude that supplementation with intactTM powder did not increase plasma IGF-I concentrations or improve performance during an initial bout of incremental running to exhaustion in our sample. However, performance during a second bout of exercise may be improved by as much as 5.2% in the average subject after 8 weeks of supplementation, possibly due to an enhancement of recovery.

Introduction B o v i n e c o l o s t r u m is t h e first m i l k s e c r e t e d b y cows a f t e r p a r t u r i t i o n a n d c o n t a i n s a n u m b e r of b i o a c t i v e p r o t e i n s , i n c l u d i n g g r o w t h f a c t o r s ( D o n o v a n & Odle, 1994; F r a n c i s et al., 1988; S c h a m s , 1994), of w h i c h i n s u l i n - l i k e g r o w t h f a c t o r I (IGF-I) is one of t h e m o s t a b u n d a n t a n d w e l l - c h a r a c t e r i s e d ( F r a n c i s et al., 1988). D i e t a r y c o l o s t r u m h a s b e e n s h o w n to i n c r e a s e c i r c u l a t i n g I G F - I c o n c e n t r a t i o n s ( B u r r i n et al., 1995; R o n g e & B l u m , 1988) a n d s k e l e t a l m u s c l e p r o t e i n s y n t h e s i s ( B u r r i n et al., 1992; B u r r i n et al., 1995) in n e w b o r n a n i m a l s . M o r e r e c e n t l y , s u p p l e m e n t a t i o n w i t h b o v i n e c o l o s t r u m h a s a l s o b e e n s h o w n to

65

Bovine Colostrum Supplementation during Endurance...

increase serum IGF-I concentrations in adult humans (Mero et al., 1997). IGFI stimulates lipoprotein lipase activity in adipocytes (Kern et al., 1985; Kern et al., 1989), and the administration of IGF-I in humans has been shown to increase lipolysis (Hussain et al., 1994) and lipid oxidation (Froesch et al., 1996). Circulatiri.g levels of IGF-I have also been shown to correlate with peak oxygen uptake (VO2peak) (Kelly et al., 1990; Poehlman & Copeland, 1990). Endurance exercise training typically increases maximal or peak oxygen uptake (VO2peak) (Holloszy, 1973) and reduces blood lactate concentrations during submaximal exercise (Bergman et al., 1999; Hurley et al., 1984). Perhaps the most important adaptation in terms of attenuating the blood lactate response to exercise is an increase in the ability of trained muscle to oxidize fat (Hurley et al., 1986; Kiens, 1997; Kiens et al.,. 1993). Given the relationship between circulating IGF-I concentrations and VO2peak, as well as the ability of IGF-I to increase fat oxidation (Froesch et al., 1996), it was of interest to determine whether bovine colostrum supplementation could improve endurance exercise performance by enhancing the effects of training on VO2peak, increasing fat metabolism, and reducing blood lactate concentrations during exercise. In addition to potential enhancements of endurance exercise performance, it has been proposed that colostrum supplementation might improve recovery from exercise (Anderson, 1994; Mero et al., 1997). The only study to date which has addressed the effect of colostrum supplementation on recovery found that a short period of supplementation (~5 days) had no effect on recovery from strength-speed training (Mero et al., 1997). However, the 5 day supplementation period may not have been long enough for any potential changes in recovery to be manifested. No studies have investigated the effects of bovine colostrum supplementation on recovery from endurance exercise. The purpose of the present study was to determine whether a relatively long period of oral supplementation with bovine colostrum could increase plasma IGF-I concentrations, enhance endurance running performance and improve recovery.

MethOdS and procedures Subjects Subjects were 18 to 35 year old males (mean+SD, intact TM 25.2+4.2 yr [n=17], placebo 26.6_+4.4 yr [n=13]; p=0.38) who had been participating in regular physical activity for at least three months prior to study commencement. All subjects were medically screened using a modified pre-exercise screening questionnaire prior to undertaking exercise testing (Olds & Norton, 1999). The protocol and the potential risks and benefits were fully explained to each subject before they provided written informed consent. All experimental procedures were apl~roved by the Human Research Ethics Committee of the University of South Australia.

Experimental protocol The study was carried out using a randomised, double-blind, placebo controlled, parallel design. All subjects were initially familiarised (2 wk) with the training, nutritional and testing procedures which would be carried out during the study. During the 8 week study period each subject attended the laboratory on

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Bovine Colostrum Supplementationduring Endurance... /

three separate occasions at four weekly intervals for testing (Weeks 0, 4 and 8) after a m i n i m u m four h o u r fast. Tests were conducted at the same time of day to avoid circadian effects. At each testing session body mass and stature were m e a s u r e d prior to a venous blood sample being drawn from a forearm vein for determination of the plasma IGF-I concentration. Each subject t h e n performed two incremental treadmill running tests (RUN1 and RUN2) to volitional exhaustion whilst expired air was collected for determination of gas exchange parameters, and fingertip blood samples were t a k e n for determination of blood lactate concentrations. RUN 1 and RUN2 were separated by a 20 mill period of passive recovery during which subjects remained seated. After being tested at Week 0, subjects were randomly allocated to consumption of 60 g.day -1 of either intact TM concentrated bovine colostrum protein powder containing 2 mg.kg -1 of IGF-I (Numico Research (Australia) Pty Ltd, Adelaide, Australia), or 60 g.day -1 of a concentrated whey protein powder placebo (Alacen, New Zealand Milk Products, Sydney, Australia). The concentration of IGF-I in the intact TM powder was determined using the same method, described below, as was used for determining the IGF-I concentration in the plasma samples. All supplements were provided in pre-packed 20g sachets and subjects consumed the contents of one sachet with their morning meal, and two sachets with their evening meal. The contents of each sachet were mixed with 85ml of w a r m water and 40ml of milk, shaken vigorously, and then chilled before drinking. The taste and color of the intact TM powder and the placebo were indistinguishable. On the day following the initial testing session subjects began taking the appropriate s u p p l e m e n t and commenced a 3 day per week r u n n i n g training program. Subjects did not use any additional nutritional supplements during the s t u d y period, and food intakes were recorded daily for s u b s e q u e n t dietary analysis. BOdy mass and stature Body mass was measured using electronic digital scales (AND Mercury, FV150, Tokyo, Japan). Stature was m e a s u r e d using a stadiometer (SECA, Hamburg, Germany) with subjects in the free-standing position (Norton & Olds, 1996). Treadmill running tests Baseline physiological data were collected whilst subjects stood quietly on the treadmill (Quinton Instruments, Model 1860, Washington, USA) for 3 mill prior to commencing each running test. Subjects t h e n commenced running at a speed of 1 0 k m . h r 1 and 0% grade. The treadmill speed remained constant t h r o u g h o u t the test and the work load was incremented every 3 minutes by increasing the slope of the treadmill by 1% grade until the subject reached volitional exhaustion. Preliminary experiments indicated that subjects reach exhaustion after - 3 0 rain using this protocol. The treadmill % grade a t exhaustion was used to predict the effective peak horizontal running speed (PRSE) at exhaustion by combining two formulae from Brooks et al. (1996) to give: PRSE = S + 0.05"i*S Where:

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Bovine Colostrum Supplementation during Endurance...

PRS E = effective p e a k horizontal r u n n i n g speed ( k m . h r -1) S = treadmill speed (i.e. 10 k m ° h r -1) i = treadmill % grade at e x h a u s t i o n The technical error of m e a s u r e m e n t (TEM) for the PRSE was 1%. This TEM was determined from two tests, s e p a r a t e d by one week, carried out on five subjects who did not participate in the experiment. The first test w a s conducted 2 weeks after a familiarisation trial.

Cardiorespiratory variables M e a s u r e m e n t s of oxygen u p t a k e (VO2) and c a r b o n dioxide production (VCO2) were recorded as 30 second averages t h r o u g h o u t e a c h treadmill r u n a n d the values averaged over the final 30 sec of each work load were recorded as the m e a s u r e d values. Subjects b r e a t h e d t h r o u g h a low resistance respiltatory valve (Hans Rudolph 2700 series, K a n s a s City, USA) with a pre-calibrated large flow turbine t r a n s d u c e r (P.K. Morgan M a r k 2, Seaford, Australia) a t t a c h e d to the inspiratory port to m e a s u r e ventilatory volumes. Expired air w a s directed to a 2.6 L mixing c h a m b e r (Sportech, Canberra, Australia) from which dried gas w a s s a m p l e d continuously (~ 500 ml°min -1) a n d p a s s e d to a n oxygen a n a l y s e r (Ametek S-3A/I, Pittsburgh, USA) a n d a carbon dioxide analyser (Ametek CD3A, Pittsburgh, USA), b o t h of which h a d been calibrated prior to each exercise test with c o m m e r c i a l l y - p r o d u c e d gas m i x t u r e s of k n o w n 02 a n d CO2 percentages (BOC Gases, Adelaide, Australia). The electrical o u t p u t s from the ventilation m e t e r a n d gas a n a l y s e r s were integrated using a personal c o m p u t e r which calculated the n e c e s s a r y ventilatory variables. Heart rate (HR) w a s recorded as 5 second averages during the 3 min rest period prior to e a c h treadmill r u n a n d during each r u n u s i n g a Sport Tester h e a r t rate m i c r o c o m p u t e r and chest t r a n s m i t t e r (Polar Accurex Plus, Polar Electro, Oulu, Finland). The 5 second averages at the end of the 3 rain rest period prior to each treadmill run, at the end of each 3 rain work load, and at the end of exercise were t a k e n to be the m e a s u r e d values for HR. Blood collection and analysis For determination of the p l a s m a IGF-I concentration, blood s a m p l e s (4 ml) were drawn from a n antecubital vein prior to performing a n y exercise at each testing session. The blood s a m p l e s were placed into t u b e s containing 9 m g of d i - p o t a s s i u m EDTA a n d centrifuged for 10 rain at 2000g a n d 4°C u s i n g a refrigerated centrifuge (Beckman GS-6R, Palo Alto, USA). The p l a s m a w a s t h e n drawn off a n d stored in a polypropylene tube below -20°C for determination of p l a s m a IGF-I concentrations at the end of the s t u d y (i.e. less t h a n 3 m o n t h s after sample collection). The p l a s m a concentration of IGF-I w a s m e a s u r e d in each s a m p l e three times b y radioimmunoass~ly after s e p a r a t i o n of IGF binding proteins b y high p e r f o r m a n c e size exclusion liquid c h r o m a t o g r a p h y at pH 2.5 according to the method of Scott a n d Baxter (Scott & Baxter, 1986) as modified b y Owens et. al. (Owens et al., 1994; Owens et al., 1990). R e c o m b i n a n t h u m a n IGF-I (hlGF-I) w a s obtained from GroPep Pry. Ltd. Adelaide, Australia. Radioligand was p r e p a r e d to a specific activity of ~90 Ci*g-1 with chloramine-T a n d Na1125 (Amersham P h a r m a c i a Biotech Inc, S a n Francisco, USA). A n t i s e r u m to hlGFI was raised in rabbit. S a m p l e s were stripped of IGF-binding proteins in

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Bovine Colostrum Supplementation during Endurance... /

fourteen c h r o m a t o g r a p h y sessions. The fraction containing IGF-I routinely eluted from the size exclusion HPLC c o l u m n between 8.75 a n d 11.0 m i n u t e s after injection of the acidified p l a s m a samples. The recovery from the c o l u m n estimated from injections of [125I]-iodo-IGF-I w a s 94_+5% (mean_+SD, n= 13). All s a m p l e s from each individual subject were included in the s a m e c h r o m a t o g r a p h y session and m e a s u r e d in the s a m e assay. The average minimal detectable concentration was 14 ng*m1-1 (range 12 to 19 ng*m1-1) and the average half-maximal r e s p o n s e in the a s s a y w a s produced b y a s a m p l e containing 271 ngom1-1 (range 235 to 315 ng°ml-1). For replicates of a quality control p l a s m a specimen whose average IGF-I concentration w a s determined to be 70 ng*m1-1 after being m e a s u r e d three t o five times in each assay, the average within a n d between a s s a y TEMs were 10% a n d 16% respectively. Blood lactate concentrations were determined from fingertip blood s a m p l e s (50 ~tl) t a k e n at the end of the 3 min r e s t period prior to each treadmill run, at the end of e a c h 3 m i n u t e work load during the runs, and immediately u p o n the cessation of exercise. 25~tl of each s a m p l e was immediately p a s s e d t h r o u g h a n a u t o m a t e d lactate analyser (Yellow Springs International, Model 1500 Sport, Yellow Springs, USA). The r e m a i n d e r of e a c h sample w a s discarded.

Lactate threshold A log-log t r a n s f o r m a t i o n (Beaver et al., 1985) of the VO2 and the blood lactate concentrations during RUN1 at each testing session were u s e d to determine the VO 2 corresponding to the lactate threshold. Linear regression analysis of the HR vs VO 2 response during exercise w a s t h e n u s e d to determine the HR corresponding to the VO2 at the lactate threshold. This HR was u s e d as the training HR (HR~ for the r u n n i n g training program. Training program Subjects were provided with a HR monitor (Polar Beat, Polar Electro, Finland) a n d r a n for 45 min, 3 times per week at HR t. During the first 4 weeks of the s t u d y they r a n at the HR t determined at week 0. During the second 4 weeks of the s t u d y they ran at the HR t determined at week 4. Nutrition Subjects were provided with a copy of, a n d were instructed to eat according to, the 12345+ Food and Nutrition Plan (Jackson, 1991). Subjects were required to keep a daily food diary for the duration of the s t u d y a n d a n analysis of dietary intakes was carried out using the SERVE Dietary Analysis Software p r o g r a m (M & H Williams Pty Ltd, Adelaide, Australia). Total energy intakes a n d p e r c e n t a g e s of energy intake contributed by carbohydrate, fat a n d protein were averaged over the first a n d second 4 weeks of the s t u d y to give m e a n daily intakes for e a c h 4 week period. Statistics The s t u d e n t t-test was u s e d to c o m p a r e the ages of the groups. Univariate two-way analysis of variance (ANOVA) with repeated m e a s u r e s was u s e d to determine the effect of the treatment, time of m e a s u r e m e n t , a n d their interactions on height and body m a s s . Relationships between variables were d e t e r m i n e d u s i n g linear regression analysis. To determine the effects of the treatment, time of m e a s u r e m e n t , a n d their interactions on the PRSE, the log 69

Bovine Colostrum Supplementation during Endurance...

of the PRSE was t a k e n to avoid n o n - u n i f o r m residuals, a n d these d a t a were t h e n analysed using univariate three-way ANOVA with repeated m e a s u r e s . One factor was the t r e a t m e n t group (i.e. intact TM powder or placebo) and the other factors (with repeated m e a s u r e s ) were the treadmill r u n (i.e. RUN1 or RUN2) and the week of testing (i.e. Week 0, 4 or 8). Univariate two-way ANOVA (treatment x week) with repeated m e a s u r e s was u s e d to determine the effect of the t r e a t m e n t a n d time of m e a s u r e m e n t on p l a s m a IGF-I concentrations. Univariate four-way ANOVA (treatment x r u n x week x time during run) with repeated m e a s u r e s was u s e d to determine effects on other d e p e n d e n t variables (i.e. VO 2, HR, blood lactate, RER) during exercise. ANOVA models incorporated a G r e e n h o u s e - G e i s s e r correction for m u l t i s a m p l e asphericity. Where ANOVA showed a statistically significant m a i n effect, pair-wise c o m p a r i s o n s were performed using Tukey's test for Honestly Significant Differences. 95% confidence intervals (95% CI) are s h o w n for the between-group differences in the within-group increases in PRS E. A level of p~_0.05 was t a k e n as indicating statistical significance. Unless otherwise stated, all values cited in the text and shown in figures r e p r e s e n t means+SD.

Results Height and body mass There was little difference in height (intact TM 180.7+5.0 cm, placebo 177.1+5.5 cm; p=0.09), or body m a s s (intact TM 77.2_+7.8kg, placebo 76.5-+12. lkg; p=0.90) between the groups at Week 0, a n d neither height (p=0.14), nor body m a s s (p=0.23) h a d changed s i g n i f c a n t l y in either group by Week 8. Treadmill runs There w a s no significant difference in PRSE achieved during RUN l between the two groups at Week 0 (p>0.99, Fig. 1). PRS E during RUN1 increased in b o t h groups during the s t u d y period, b u t there was still no difference between groups at Week 4 (p>0.99) or Week 8 (p>0.99). Expressed as percentage improvements, these increases in PRS E were not different between g r o u p s at Week 4 (intact TM) 2.2-+4.0%, placebo 3.2-+3.3%, 95% CI 15.7 to -13.7%; p=0.89), or at Week 8 (3.6-+5.6%, placebo 3.4_+4.4%, 95% CI -100 to 100%; p>0.99). The PRSE for RUN2 w a s less t h a n t h a t achieved during RUN1 in b o t h groups at all 3 testing sessions (p<0.05). There was no difference in PRS E during RUN2 between the two g r o u p s at Week 0 (p>0.99, Fig. 1) or week 4 (p=0.49), b u t by week 8, PRS E w a s significantly faster in the intact TM group c o m p a r e d with the placebo g r o u p (p=0.003). E x p r e s s e d as p e r c e n t a g e improvements, the increase in PRS E was not different between groups at Week 4 (intact TM 1.8-+4.8%, placebo 4.2-+3.9%, 95% CI 0.2 to -5.0%; p=0.07), b u t was significantly greater in the intact TM) group by Week 8 (intact TM 4.6-+6.1%, placebo 2.0+4.5%, 95% CI 0.0 to 5.2%; p=0.05). There were no significant differences in the VO2 r e s p o n s e to s u b m a x i m a l exercise between the two g r o u p s during either of the r u n s at Weeks 0, 4, or 8 (P>0.80). The VO2peak achieved at Week 0 (RUN 1) w a s not significantly different between the two groups (intact TM 53.2+5.4 m l . k g - l . m i n -1, placebo 53.9-+7.1 ml.kg-l.min-1; p=0.91) a n d ~rq2peak changed little in either group during the s t u d y period (p=0.58). The VO 2 (intact TM 37.6-+8.3 mlokg-l.min -1, placebo 40.2-+5.4 ml°kg-]*min-1; p=0.68}, a n d %VO2pea k (intact TM 70.7+13.7%, placebo 75.0-+7.8%; p=0.58} at the lactate threshold w a s not significantly different

70

Bovine Colostrum Supplementation during Endurance...

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Figure 1: Effective peak running speed (i.e. equivalent of peak power) during two incremental treadmill runs to exhaustion (RUN1 - pane) A, RUN2- panel B) separated by 20 rain of recovery, prior to, and after 4 weeks and 8 weeks of endurance training and oral supplementation with intactTM concentrated bovine colostrum protein powder or concentrated whey protein powder (placebo). *p<0.01 compared with week O. ?p=0.003 compared with placebo.

between the two groups at week 0, and neither the V02 (p>0.99}, nor the °/0~rO2peak (/9=0.86) at the lactate threshold changed significantly in either group during the s t u d y period. There was little difference in peak HR (HRpeak) between groups at Week 0 (intact TM 194+_10 beats*rain -1, placebo 192+_8 beats*min-1; p=0.26). HRpeak decreased in both groups during the study period (P<0.001), with no significant difference in the magnitude of the decrease between groups (p=0.47), s u c h that by Week 8 HRpeak was 190+_8 b e a t s , m i n -1 in the intact TM group and 187+_8 beats°rain q in the placebo group. HR at the lactate threshold (i.e. training heart rate; HR t) was not significantly different between groups at Week 0 (intact TM 163+18 beats°min -1, placebo 165_+12 beats°rain-i; p=0.60).

71

Bovine Colostrum Supplementation during Endurance... 14

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HR t decreased in b o t h groups during the s t u d y period (p=0.04), reaching 157_+14 beats*min -] in the intact T M group and 156_+10 b e a t s * m i n d in the placebo group by Week 8, b u t the extent of the decrease was not significantly different between the groups (p=0.50). T h r o u g h o u t the s t u d y period there was no significant difference between groups in the blood lactate r e s p o n s e to s u b m a x i m a l exercise during either of the two r u n s (p=0.23, Fig. 2). There was a n a t t e n u a t i o n of the s u b m a x i m a l exercise blood lactate r e s p o n s e during b o t h r u n s as the s t u d y p r o g r e s s e d (p=0.005), b u t the m a g n i t u d e of the a t t e n u a t i o n was similar in b o t h g r o u p s (p=0.23). The blood lactate concentration decreased during the 20 rain recovery period between treadmill r u n s in b o t h groups at all three testing sessions (p<0.0001), b u t h a d not r e t u r n e d to pre-exercise concentrations in either group by the end of recovery at a n y of the three testing sessions (p<0.0001). The p e a k blood lactate concentrations reached b y the end of RUN2 at each testing session were significantly lower t h a n those reached at the end of RUN1 (p<0.001), b u t there w a s no significant difference between the two groups (p=0.28). 72

Bovine Colostrum Supplementation during Endurance...

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Bovine Colostrum Supplementation during Endurance...

T h r o u g h o u t the study period there was no significant difference between groups in the RER response to submaximal exercise during either of the two r u n s (p=0.71, Fig. 3), and the RER response to submaximal exercise did not change significantly during the s t u d y period (p=0.20). The RER decreased in both groups at all three testing sessions during the 20 rain recovery period between treadmill runs, reaching values lower t h a n the RER prior to RUN 1 (p<0.0001). The RER reached by the end of RUN2 at each testing session was significantly lower t h a n the RER reached at the end of RUN1 (p<0.001), b u t there was no significant difference between the two groups (p=0.60) and these values changed little in either group during the study period (p=0.75). Plasma insulin-like growth factor 1 Plasma IGF-1 concentrations were not significantly different between the two groups at week 0 (p=0.51, Fig. 4) and the plasma IGF-1 concentration changed little in either group over the 8 week study period (p=0.83). Dietary Intake There was no significant difference in mean daily energy intake between the two groups during the first 4 weeks of the study (intactTM 9192_+2501 kJ.day d, placebo 9204_+1648 kJ*dayq; p=0.49) and m e a n daily energy intake did not change significantly in either group during the final 4 weeks of the study period (p=0.42). Similarly, there were no significant differences in the percentages of m e a n daily dietary energy intake accounted for by carbohydrate (intact TM 46.5_+5.2%, placebo 46.6_+5.7%; p=0.80), protein (intact TM 24.2_+2.9%, placebo 24.6+2.5%; p=0.98), or fat (intact TM 26.9_+4.5%, placebo 26.0+5.7%; p=0.94) between the two groups during the first 4 weeks of the study, and these values did not change significantly in either group during the final 4 weeks of the s t u d y period (P>0.42).

Discussion This study examined the effect of oral supplementation with bovine colostrum on e n d u r a n c e exercise performance and recovery. The principal finding was that supplementation with intact TM concentrated bovine colostrum protein powder during 8 weeks of training had little effect on performance during a n initial bout of incremental r u n n i n g exercise to exhaustion, b u t did improve performance in a second b o u t of exercise after a 20 min recovery period. It was h y p o t h e s i s e d t h a t a n y i m p r o v e m e n t in e n d u r a n c e exercise performance resulting from bovine colostrum supplementation would be mediated by an increase in the circulating IGF-I concentration. However, despite Mero et. al. (1997) previously demonstrating that bovine colostrum supplementation could increase the serum IGF-I concentration, supplementation with intact TM powder had little effect on the plasma IGF-I concentration in the present stud,y. The increase in serum IGF-I reported by Mero et. al. (1997) occurred after only 8 days of supplementation, and it is possible therefore that the increase was only transient and was not detected in the present study because of the relatively long interval (i.e. 4 weeks) between the commencement of supplementation and the first a s s e s s m e n t of changes in IGF-I. Alternatively, differences in the bioavailability of IGF-I between the supplements used in the two studies may have contributed to the different findings, b u t this would imply that the increase in serum IGF-I reported by 74

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Mero et. al. (1997) was due to absorption of IGF-I from the colostrum supplement, a n d these a u t h o r s were unable to determine w h e t h e r the additional IGFI w a s a b s o r b e d from the s u p p l e m e n t , or resulted from a n increase in e n d o g e n o u s IGF-I production. There is evidence from studies in neonatal a n i m a l s t h a t IGF-I in milk retains bioactivity within the gastrointestinal t r a c t ( B a u m r u c k e r et al., 1992; Philipps et al., 1995) a n d that orally administered 125I-IGF-I c a n be t r a n s p o r t e d into the circulation ( B a u m r u c k e r et al., 1992; Donovan et al., 1997; Xu & Wang, 1996), b u t gut closure occurs during the first two d a y s after birth (Westrom et al., 1984), and m a c r o m o l e c u l a r t r a n s p o r t ceases a s h o r t time after (Weaver & Walker, 1989). It is therefore difficult to see how a molecule s u c h as IGF-I, with a molecular weight of 7.5 k D a (Rechler & Nissley, 1991), would be a b s o r b e d in significant quantities in the adult gastrointestinal tract. Further investigation is required to better characterise the time-course of a n y c h a n g e s in circulating IGF-I, and to identify the source of a n y additional IGF-I, resulting from bovine c o l o s t r u m supplementation. An incremental r u n n i n g test to exhaustion, as u s e d in the p r e s e n t study, is generically a n incremental test to p e a k power (Hopkins et al., 1999). Perhaps the b e s t o u t c o m e m e a s u r e from s u c h a test is p e a k power or its equivalent, b e c a u s e there is a direct linear relationship between p e a k power achieved in a n incremental test and the m e a n power o u t p u t in competitive e n d u r a n c e events (Hawley & Noakes, 1992). Distance covered or time to e x h a u s t i o n in incremental exercise tests do not have this relationship b e c a u s e the tests do not s t a r t at zero power. With a treadmill test at fixed grade a n d increasing speed, the equivalent of p e a k power is p e a k speed. In the p r e s e n t s t u d y the speed was fixed a n d the grade was increased, which necessitated the grade at e x h a u s t i o n to be converted to an equivalent horizontal speed (i.e. effective p e a k r u n n i n g speed, PRSE) to provide a n estimate of p e a k power (Brooks et al., 1996). The first treadmill r u n (i.e. RUN1) at e a c h testing session provided a m e a s u r e of e n d u r a n c e r u n n i n g p e r f o r m a n c e and, although the training p r o g r a m provided a sufficient s t i m u l u s to induce i m p r o v e m e n t s in PRSE in b o t h groups, the intact TM s u p p l e m e n t did not provide a n y significant additional benefit. However, despite this a p p a r e n t zero effect, the 95% CI's for the differences in i m p r o v e m e n t between the two groups were quite wide, indicating t h a t the precision of the estimate of the effect of the s u p p l e m e n t in this s a m p l e w a s quite poor. From this we c a n conclude t h a t the intact TM s u p p l e m e n t did not a p p e a r to have a n y effect on p e r f o r m a n c e during RUN 1 in the p r e s e n t subject sample, b u t the possibility of the s u p p l e m e n t having a positive or negative effect on p e r f o r m a n c e should not be excluded until a m o r e precise estimate can be obtained t h r o u g h the testing of more subjects. The potential for bovine c o l o s t r u m s u p p l e m e n t a t i o n to e n h a n c e e n d u r a n c e r u n n i n g p e r f o r m a n c e h a d b e e n predicated on the ability of the s u p p l e m e n t to increase the circulating IGF-I concentration, and thereby promote increases in ~'O2peak a n d fat m e t a b o l i s m (assessed b y m e a s u r e m e n t s of RER). However, the s u p p l e m e n t h a d no significant effect on p l a s m a IGF-I concentrations in the p r e s e n t sample, so it is p e r h a p s not too surprising t h a t the s u p p l e m e n t did not improve r u n n i n g performance. Despite the intact TM s u p p l e m e n t failing to improve p e r f o r m a n c e during RUN1, there w a s good evidence t h a t 8 weeks of s u p p l e m e n t a t i o n provided a greater i m p r o v e m e n t in PRS E during RUN2. Given t h a t p e r f o r m a n c e s during

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Bovine Colostrum Supplementation during Endurance...

RUN1 were not significantly different between the two groups, it could be inferred t h a t a n y differences in p e r f o r m a n c e during RUN2 would reflect differences in the extent to which subjects were able to recover during the 20 min period between treadmill runs. Any s u c h difference could not be attributed to differences in diet or training since, a p a r t from the different s u p p l e m e n t s c o n s u m e d , neither the dietary intakes, nor the training loads differed significantly between the two groups. There a p p e a r e d to be little difference in recovery between the two groups prior to supplementation, b e c a u s e b o t h groups achieved similar PRS E during RUN2 at Week 0. Similarly, there w a s no significant difference in PRS E between g r o u p s b y Week 4. However, the 95% CI for the change in PRS E by Week 4 overlapped zero, indicating that, although the intact TM s u p p l e m e n t did not have a significant effect on PRSE in our sample, until more subjects are tested we c a n n o t exclude the possibility t h a t 4 weeks of s u p p l e m e n t a t i o n m a y have a small positive effect (0.2%) or a relatively large negative effect (-5%) on PRS E during a second b o u t of incremental exercise. An i m p r o v e m e n t in PRSE of only 0.2% over a 4 week period is unlikely to be of a n y great consequence, b u t athletes should take into a c c o u n t the possibility of a decrement of u p to 5% during the first 4 weeks of s u p p l e m e n t a t i o n w h e n considering taking the intact TM s u p p l e m e n t , at least until further studies are carried out. Irrespective of a n y potential negative effect during the first 4 weeks of supplementation, s u c h a n effect would a p p e a r to be only t r a n s i e n t since, after 8 weeks of supplementation, the intact TM powder h a d provided a 2.6% greater i m p r o v e m e n t in PRS E in our sample. F u r t h e r m o r e , unlike the values at Week 4, the 95% CI for the i m p r o v e m e n t in PRSE b y Week 8 did not overlap zero (0 to 5.2%), indicating t h a t the likely range of the true effect of the intact TM s u p p l e m e n t on PRS E during a second b o u t of incremental exercise lies somewhere between no effect (i.e. 0%) a n d a 5.2% increase in PRS E for the average subject. Although a positive effect of up to 5.2% would r e p r e s e n t a s u b s t a n t i a l i m p r o v e m e n t for a training a n d s u p p l e m e n t a t i o n period which was only 8 weeks in duration, it m u s t not be forgotten t h a t the subject cohort u s e d in the p r e s e n t s t u d y consisted of active males, a n d it c a n n o t necessarily be a s s u m e d t h a t similar results would be obtained in well-trained or elite athletes, since s u c h athletes a l m o s t certainly have a different training history a n d a physiological development t h a t is closer to their genetic limits (Hopkins et al., 1999). Although the a p p a r e n t i m p r o v e m e n t in PRSE during RUN2 tends to suggest t h a t the intact TM s u p p l e m e n t e n h a n c e d the ability to recover during the 20 min period between runs, the m e c h a n i s m by which it exerted this effect could not be determined from the p r e s e n t data. The systemic physiological and metabolic p a r a m e t e r s a s s e s s e d (oxygen uptake, RER, blood lactate, h e a r t rate) provided no evidence of a difference between the two groups during exercise, or by the end of the 20 min recovery period between runs. Perturbations within the tissues themselve*s, particularly the active skeletal muscles, m a y have recovered to a greater extent in the intact TM group without affecting a n y of these systemic p a r a m e t e r s but, given t h a t there are no published studies on the effects of colostrum s u p p l e m e n t a t i o n on changes in m u s c l e biochemistry during training, it is difficult to speculate a b o u t a potential m e c h a n i s m . However, now t h a t a n effect h a s b e e n demonstrated, further w o r k should a d d r e s s the m e c h a n i s m of action of this supplement. Despite s u p p l e m e n t a t i o n with intact TM powder not providing a direct benefit

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Bovine Colostrum Supplementation during Endurance... /

for e n d u r a n c e e x e r c i s e p e r f o r m a n c e p e r se, a n i m p r o v e m e n t in r e c o v e r y c o u l d i n d i r e c t l y f a c i l i t a t e p e r f o r m a n c e i m p r o v e m e n t s b y allowing g r e a t e r t r a i n i n g i m p u l s e s ( f r e q u e n c y x d u r a t i o n x i n t e n s i t y ) to b e u n d e r t a k e n . It w a s n o t p o s s i b l e to t e s t t h i s h y p o t h e s i s u s i n g t h e c u r r e n t d a t a b e c a u s e t h e t r a i n i n g i m p u l s e s e m p l o y e d in t h e p r e s e n t s t u d y w e r e c o n t r o l l e d , s u c h t h a t b o t h g r o u p s p e r f o r m e d t h e s a m e t r a i n i n g w h e t h e r t h e y h a d t h e c a p a c i t y to do m o r e o r not. It is a l s o n o t c l e a r w h e t h e r t h e a p p a r e n t i m p r o v e m e n t in r e c o v e r y is l i m i t e d to s h o r t - t e r m r e c o v e r y p e r i o d s (i.e a p p r o x 20 m i n in d u r a t i o n ) , o r w h e t h e r t h e r e is s o m e l o n g e r t e r m b e n e f i t w h i c h e x t e n d s over a p e r i o d of h o u r s or d a y s . F u r t h e r r e s e a r c h is r e q u i r e d to p r o v i d e a n a n s w e r to t h i s q u e s t i o n . In c o n c l u s i o n , t h e p r e s e n t s t u d y d e m o n s t r a t e d t h a t 8 w e e k s of s u p p l e m e n t a t i o n w i t h 60 g , d a y -1 of i n t a c t TM p o w d e r h a d little effect o n p e r f o r m a n c e d u r i n g a n i n i t i a l b o u t of i n c r e m e n t a l r u n n i n g e x e r c i s e to e x h a u s t i o n , b u t d i d i m p r o v e p e r f o r m a n c e in a s u b s e q u e n t e x e r c i s e b o u t a f t e r a 2 0 r a i n r e c o v e r y p e r i o d . T h e i m p r o v e d p e r f o r m a n c e i n t h e s e c o n d e x e r c i s e b o u t w o u l d s e e m to reflect a n e n h a n c e d a b i l i t y to r e c o v e r f r o m p r i o r exercise, a t l e a s t w h e n t h e r e c o v e r y p e r i o d is 20 r a i n in d u r a t i o n , b u t t h e m e c h a n i s m u n d e r l y i n g t h i s b e n e f i t c o u l d n o t b e identified. F u r t h e r s t u d i e s s h o u l d u s e l a r g e r s u b j e c t s a m p l e s i n o r d e r to g a i n a m o r e p r e c i s e e s t i m a t e o f t h e m a g n i t u d e of t h e effect of t h e s u p p l e m e n t , a n d s h o u l d also i n v e s t i g a t e t h e s u p p l e m e n t ' s m e c h a n i s m ( s ) of a c t i o n .

Acknowledgements T h i s w o r k w a s s u p p o r t e d j o i n t l y b y f u n d i n g f r o m N u m i c o R e s e a r c h (Australia) Pty Ltd, A d e l a i d e , A u s t r a l i a a n d t h e A u s t r a l i a n I n d u s t r y R e s e a r c h a n d Development Board. T h e a u t h o r s g r a t e f u l l y a c k n o w l e d g e A n d r e w M o d r a a n d S i m o n G u l m for t h e i r a s s i s t a n c e w i t h s o m e of t h e d a t a c o l l e c t i o n for t h i s s t u d y , a n d D r Phillip O w e n s f r o m t h e U n i v e r s i t y of A d e l a i d e , for p e r f o r m i n g t h e IGF-I a s s a y s .

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