Colostrum is the milk produced by the mammary glands of all mammals, including humans, during the first 72 h after birth. It is fed to their newborns to provide essential nutrients and bioactive components including growth factors, immunoglobulins, vitamins, minerals and amino acids (7). Currently bovine colostrum is being marketed as a nutritional ergogenic aid, although there is limited research investigating the effects of colostrum supplementation on exercise performance.
A recent study reported that 60 g/d bovine colostrum supplementation for 8 wk improved the ability to perform a second bout of maximal exercise following a relatively short period of recovery from a prior bout of maximal exercise (1). Subjects were required to complete two treadmill V̇O2max running tests separated by 20 min. The amount of work completed in the second V̇O2max test compared with the first was significantly improved after the study period in the group supplemented with colostrum. The same protocol with a cycle ergometer and a second smaller dose (20 g) of colostrum is used in this study.
METHODS
Subjects
All testing occurred in the temperature and humidity controlled Human Performance Laboratory at the University of Tasmania and at the Tasmanian Institute of Sport. Written informed consent was obtained from 42 competitive male cyclists. Fourteen of the subjects were withdrawn from the study due to noncompliance with either the supplementation or training; their data are not presented. The physical characteristics (mean ± SD) of the remaining 28 subjects were: age, 30 ± 10 yr; body mass, 74 ± 21 kg; sum of seven skinfolds, 67 ± 48 mm; V̇O2max, 61 ± 9 mL·kg−1·min−1. Screening information was obtained to ensure that subjects met the following criteria: 1) no history of lactose or cow’s milk protein intolerance, 2) not taking nutritional supplements, 3) no history of vascular, metabolic or respiratory disease, and 4) no chronic health problems. Subjects attended a briefing session before any experimentation to ensure an understanding of the testing procedures and the benefits/risks of the study. Emphasis was placed on subject preparation for the laboratory tests. Specific instructions were given to the subjects concerning their diet and training before the testing sessions. Subjects were required to abstain from exercise for 2 d preceding the sessions. For the first session, subjects were required to document their nutritional and fluid intake in the 24 h before the test. For all remaining lab sessions, subjects were required to approximate this 24-h diet before reporting to the laboratory. At the start of each test session subjects documented their ability to adhere to these instructions. The protocol was approved by the University of Tasmania’s Ethics Committee.
Design
A randomized, double-blind, placebo (Alacen™, Fonterra Co-operative Group Ltd., New Zealand) controlled design was used to evaluate the dose effects of colostrum supplementation on physical work capacity in cyclists. Subjects were randomly allocated to one of three groups: 1. placebo control group supplemented with 60 g/d oral whey-protein powder (placebo, N = 10), 2. high dose colostrum group supplemented with 60 g/d oral bovine colostrum (60 g, intact*), (N = 9) or 3. low dose colostrum group supplemented with 20 g/d oral bovine colostrum (intact) and 40 g/d whey-protein powder (20 g), (N = 9). Each subject completed two performance tests before and after an eight week supplementation period.
Performance testing
Performance Measure One.
On the first visit, subjects reported to the laboratory in a rested condition, having eaten a substantial meal and abstained from caffeine, drugs, alcohol, and cigarettes 4 h before testing. Measurements of weight and skinfolds from 7 sites (bicep, tricep, subscapular, suprailiac, abdominal, quadriceps, and medial calf) were obtained before the commencement of performance Measure One. Following a 10 min warm up and stretching exercises, subjects completed two identical-protocol V̇O2max tests separated by 20 min. The protocol required subjects to maintain a self-selected cadence of between 70 and 100 rpm on a Lode cycling ergometer with an initial load of 100 W for 3 min, increased to 200 W for 3 min, and then 50 W every 3 min thereafter until exhaustion. Expired air was analyzed throughout the test using a Quinton Metabolic Cart (Quinton, QMC, Bothwell, WA). Subjects were required to breathe room air through a Hans Rudolph 2700 valve (Hans Rudolph, inc., Kansas City, MO) with expired air traveling via 3.5 cm tubing to the mixing chamber of the QMC. Both oxygen and carbon dioxide analyzers were calibrated before and verified after each test with alpha standard gases (BOC Gases, Australia) of two known concentrations (a = 14.2% O2 and 3.4% CO2 and b = 18.4% O2 and 5.1% CO2). The pneumotach was calibrated before and verified after each test session using a 3 L calibration syringe (Hans Rudolph). For the 20 min recovery period between the two V̇O2max tests, the mouthpiece and headgear were removed while subjects were given a 3 min cool down on the ergometer followed by stretching and were instructed to remain active by walking around the laboratory. Heart rate was recorded throughout the V̇O2max tests using a Sportstester PE3000 system (Polar Electro, Kempele, Finland).
Performance Measure Two.
Two days after the first performance test, subjects returned to the laboratory in a similar state of physical preparation and at the same time of the day for Performance Measure Two. The test consisted of a 2 h performance ride on the lode cycle ergometer at 65% of their maximal heart rate, determined as the highest heart rate obtained during Performance Measure One. During the post-supplementation test their maximal heart rate was determined from their post-supplementation Performance Measure One V̇O2max tests. Subjects were instructed to prepare for the ride as they would prepare for a 100 km road race by bringing food and drink, which they would usually consume during the race, to the laboratory. Subjects were permitted and encouraged to consume food and fluids ad libitum with additional supplies available on request. Nutrient and fluid intake was recorded during the ride. Heart rate was measured throughout the 2 h ride and time trial using a Sportstester system. At 5 min intervals during the 2 h ride, the intensity was adjusted to maintain the desired heart rate. The 2 h ride was immediately followed by a workload based time trial where each subject was required to complete 2.8 kJ/kg of work as fast as possible. The time for this trial was used as the second performance measure.
At the completion of the second visit subjects received a box of their respective supplement containing 20 g sachets labeled days 1 through 56. Each sachet contained a morning and evening packet. Subjects were required to consume a morning dose of 20 g with 85 mL warm water and 40 mL skim milk, and an evening dose of 40 g with 170 mL warm water and 80 mL skim milk. Subjects were also given a diet and training diary with instructions on how to complete it.
After 8 wk of supplementation, subjects reported back to the laboratory for re-testing (Performance Measure One and two days later for Performance Measure Two).
Training/Diet Diaries
Subjects were required to keep a daily training and diet diary for the 8 wk supplementation period. Dietary information was analyzed using Foodworks (Xyris Software, Queensland, Australia). The diet diary provided daily averages for energy, macro-, and micronutrient intake. Training volume was calculated as an average of minutes trained per day.
Blood Analysis
Plasma insulin-like growth factor I.
In response to the finding that bovine colostrum supplementation increased serum insulin-like growth factor I (IGF-1) concentrations during training (4), we measured plasma IGF-1 concentrations over the supplementation period. Blood was collected from each subject before Performance Measure Two pre- and post-supplementation. Plasma IGF-1 was measured by radioimmunoassay after separation from binding proteins by high performance size exclusion liquid chromotography at pH 2.5 according to the method of Scott and Baxter (9) as modified by Owens (6). Recombinant h IGF-1 (GroPep Pty Ltd, Adelaide, Australia) was used, and the radioligand was prepared to a specific activity of Ci/g with chloranane-T and Nal125 (Amersham Biosciences, Uppsala, Sweden). Antiserum to human IGF-1 was raised in rabbit (10). Samples were stripped of IGF-binding proteins in four chromatography sessions. The fraction containing IGF-I routinely eluted from the size exclusion HPLC column between 8.25 and 10.5 min after injection of the acidified plasma samples. The recovery from the column estimated from injections of [125I]-iodo-IGF-I was 85 ± 1% (mean ± SD, N = 5). Samples were measured in triplicate in a total of two assays, with each of the triplicates being included in the same chromatography session and measured in the same assay. The average minimal detectable concentration was 16 ng·mL−1 (range 9 to 21 ng·mL−1) and the average half-maximal response in the assay was produced by a sample containing 232 ng·mL−1 (range 225 to 234 ng·mL−1). For replicates of a quality control plasma specimen, whose average IGF-I concentration was determined to be 50 ng·mL−1 after being measured four times in each of the assays, the average within assay coefficient of variation was 4%, and the between assay coefficient of variation was 11%.
Means and standard deviations are used to represent the average and typical spread of values. The precision of the estimates for outcome statistics are shown as 95% confidence limits (the likely range of the true value). All data were analyzed using analysis of variance (ANOVA) with a Fisher post hoc test. Pre vs post repeated measures factor was adjusted with Greenhouse-Geisser epsilon. P < 0.05 was regarded as statistically significant.
RESULTS
There were no significant differences in changes in body mass, body composition, aerobic capacity (peak value obtained from both trials), or plasma IGF-1 between the three groups pre- and post-supplementation (Tab. 1). Table 2 shows the daily averages for nutrient intake and training volume for each group. There were no significant differences between groups for any of the variables.
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TABLE 1: Comparison of body mass, body composition, aerobic capacity (peak value obtained from both trials), and plasma IGF-1 between the three groups pre- and post-supplementation.
TABLE 2: Comparison of the nutrient intake and training volume of the three groups throughout the supplementation period.
Results for Performance Measure One are shown in Table 3 and Figure 1. There were no significant differences between groups or within groups (pre- vs post-supplementation) for any of the absolute values for work completed during each ride or the average of both rides. When the work from the second V̇O2max test is expressed as a percentage of the work completed in the first V̇O2max test, and pre-supplementation values are compared with post-supplementation, subjects improved by 3.4%, 4.0%, and 3.9% in the placebo, 20 g, and 60 g groups, respectively (Fig. 1). In each case the difference between the changes was not statistically significant (95% CI for differences, ±1.8%).
TABLE 3: Data from performance measure one
FIGURE 1: Performance measure one. Subjects were required to complete two V̇O2max tests separated by 20 min. The amount of work completed in the second ride as a percentage of the first is shown for the three groups pre- and post-supplementation. Means (±SD).
Nutritional and fluid intake was recorded during the Second Performance Measure. There were no significant differences (data not shown) between groups or within groups (pre- vs post-supplementation) in nutrient or fluid intake during the ride. In the Second Performance Measure (Tab. 4 and Fig. 2), there were increases of 37 s, 134 s, and 158 s in the placebo, 20 g, and 60 g groups, respectively (95% CI for differences, ±47 s). The performance improvements in the 20 g and 60 g groups were both significantly greater (P < 0.05) than that in the placebo group.
TABLE 4: Data from performance measure two.
FIGURE 2: Performance measure two. Subjects were required to cycle for 2 h at 65% V̇O2max then complete a work-based time trial. The time trial times for the three groups pre- and post-supplementation are shown. Means (±SD). * significantly less than placebo (P < 0.05).
DISCUSSION
To evaluate the dose effects of colostrum supplementation on cycling work capacity, two performance measures were chosen. The major finding of this study was that in one performance measure there was a significant improvement in cycling work capacity in those subjects consuming either 20 g or 60 g/d of bovine colostrum. Although we cannot discount the possibility that this was a chance finding, importantly the 95% confidence intervals for the differences in improvements in performance times did not overlap (placebo = 37 s, 20 g = 158 s, 60 g = 134 s; 95% CI for differences, 47 s)
The present finding that 8 wk of oral bovine colostrum supplementation improved the amount of work completed after a 2 h cycle at 65% V̇O2max is consistent with Buckley et al. (1) who used treadmill running. In this study, an 8 wk supplementation protocol of 60 g/d of colostrum was used. The present study indicates that similar performance benefits may be obtained with a smaller (20 g) dose.
Performance was not improved in Performance Measure One, which required subjects to complete two V̇O2max tests separated by 20 min with the amount of work completed in the second test used as the performance determinant. This design is similar to that used by Buckley who reported a greater amount of work completed in the second treadmill test after 8 wk of colostrum supplementation. A possible explanation for the different findings in the present study and that of Buckley is the mode of the exercise test. Cyclists are accustomed to events of longer duration compared with runners. The incremental short term design (∼ 20 min) of the V̇O2max protocols used in Performance Measure One may not have been specific to the demands of a typical cycling event, and this test may be more suitable for assessing running performance. The second performance measure was designed to approximate the demands of a 100 km time trial and may be viewed as a more appropriate exercise test for cycling. Again, it was this second performance measure that showed a significant improvement in cycling performance in subjects consuming both 20 g and 60 g/d of colostrum.
A number of mechanisms may explain the action of bovine colostrum that caused the performance enhancement. Mero et al. (4) reported that colostrum supplementation increases circulating IGF-1. As bovine IGF-1 shares 100% homology with human IGF-1, it was postulated that an increased circulating IGF-1 would improve anabolic processes post-recovery by causing a greater overall adaptation to training and resultant observed performance enhancement. Consistent with the findings of Buckley, the present study showed no difference in plasma IGF-1 levels between the three groups. A likely explanation for the contradictory findings to Mero is the type of assay used. Mero used a radioimmunoassay that measures both the IGF-1 and its associated binding protein. A more appropriate and accepted procedure for plasma IGF-1 was used in the present study to first remove the binding protein before measuring IGF-1 (6).
A second mechanistic hypothesis is that colostrum supplementation enhances nutrient absorption from the small intestine. IGF-I and epidermal growth factor (EGF) in the small intestine have been shown to stimulate gastrointestinal mucosal growth and brush border enzyme activity when given to suckling animals (2,5). Furthermore, it is well established that in adult animals administration of IGF-1 increases intestinal mucosal weight, protein and DNA content, villus height, and epithelial proliferation and function (3,8). We postulate that bovine colostrum supplementation improves small intestine function and nutrient absorption leading to enhanced nutrient availability to the recovering muscle cells. The enhanced nutrient availability may promote recovery after training by accelerating the repair of injured muscles, leading to a greater overall adaptation to training. Testing these postulates would provide an interesting area for future research.
A small but nonsignificant decrease was observed in V̇O2max in each of the three groups over the course of the trial. This was due to the periodization of the cyclists training. All subjects tested were competitive cyclists who completed their pre-supplementation V̇O2max test at the end of the road season when training volume was the highest. After these tests, the cyclists began preparing for the summer track season when training volume decreased due to a focus on power and strength work. They completed their post-supplementation V̇O2max tests leading into the track season.
The significant improvements in time trial performance in the colostrum groups, added to the small decrease in V̇O2max over the supplementation period, meant that subjects were working at a higher relative intensity during the post-supplementation time trial. We suspect that this was because of the aforementioned change in training to high intensity work. Training diaries support this postulate with subjects documenting more hill and track training leading up to the post-supplementation testing. This training may have increased anaerobic threshold enabling subjects to work at a higher relative intensity post-supplementation.
One of the major strengths of this study was the research design. To ensure supplement and training compliance over the 8 wk supplementation period, subjects were monitored for nutritional intake and training volume, and a number of subjects were excluded from the study owing to their inability to maintain training volume or product adherence. Analysis of diet and training diaries showed that there were no differences between groups in the total energy intake, the composition of macronutrients, or the training volume.
In summary, the purpose of the study was to determine the dose effects of oral bovine colostrum supplementation on physical work capacity in cyclists using two performance tests. Colostrum supplementation failed to improve the ability to perform a second maximal work bout after a relatively short rest period, following a prior maximal work bout. In the second test, after a 2 h ride at 65% V̇O2max two different colostrum supplement doses (20 g or 60 g/d) were associated with small but worthwhile enhanced performance in a work based time trial.
The authors thank Phillip Owens for analyzing plasma IGF-I, Tammy Ebert at the Tasmanian Institute of Sport for assistance with data collection, and the subjects for their patience and cooperation throughout the study.
* intact™ is a registered trademark by Numico Research Australia for its concentrated colostrum protein (Australian Patents 644468, 668033, New Zealand Patents 239466, 260568).
Address for correspondence: Jeff Coombes, PhD, School of Human Movement Studies, Rm 520 Connell Bldg., University of Queensland, St Lucia, QLD, 4072, Australia; E-mail: [email protected]
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