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1 Department of Biology of
Physical Activity, ABSTRACT Mero, Antti, Heidi Miikkulainen, Jarmo Riski, Raimo
Pakkanen, Jouni Aalto, and Timo Takala. Effects of bovine
colostrum supplementation on serum IGF-I, IgG, hormone, and saliva IgA
during training. J. Appl. Physiol.
83(4): 1144-1151, 1997.
insulin-like growth factor I; immungolobulin G and immunoglobulin A
concentrations
INTRODUCTION BOVINE COLOSTRUM IS A MILK secreted during the first
few days after calving, and its importance for the health of calves has been known for a long time (23). Colostrum contains not
only nutrients like proteins, carbohydrates, fat, vitamins, and
minerals but also bioactive components like growth factors and
antimicrobial factors (12, 33).
The most abundant and well-characterized growth factors in bovine
colostrum are probably insulin-like growth factors I and II (IGF-I and
IGF-II, respectively) (13). They stimulate cell growth and are proposed
to act both as endocrine hormones via the blood and as paracrine and
autocrine growth factors locally (12, 19). IGF-I is a major form in
bovine colostrum and is biologically more potent than IGF-II (13). The
concentration of IGF-I in bovine colostrum is 200-2,000 µg/l
(36), whereas normal milk contains <10 µg/l (9). In normal adult
humans, IGF-I occurs at a concentration of ~200 µg/l in serum
(19). IGF-I has a strong anabolic effect on muscle tissue
(25, 37), and it is associated with regulatory feedback of growth
hormone (25, 34). IGF-I can mimic most, but probably not
all, effects of growth hormone (10). The effects of growth hormone on
skeletal muscle are thought to be mediated by IGF-I (21).
Consequently, this raises a very interesting question as to whether it
would be possible to increase IGF-I concentration in human blood and
muscle by drinking colostrum or colostrum supplements. If this occurs,
it may have positive effects on human tissues, for example, during
strenuous training. This hypothesis is supported by the finding that
dietary cow colostrum has been shown to increase blood IGF-I
concentration in calves (16, 35). In addition, orally administered
125I-labeled IGF-I has been
demonstrated to be transported into circulation in calves
(4). Dietary bovine colostrum may also exert local effects
in the gut of human subjects, because it has been shown to promote the
growth of small intestine of newborn piglets (38). The increased growth
and turnover of intestine may increase uptake of dietary components
like amino acids.
Another important group of bioactive components in bovine colostrum is
composed of antimicrobial factors, including immunoglobulins, lactoperoxidase, lysozyme, and lactoferrin. Bovine colostrum is an
extremely rich source of immunoglobulins. The concentration of
immunoglobulin G (IgG) 1 (52-87 g/l), IgG2 (1.6-2.1 g/l),
immunoglobulin M (3.7-6.1 g/l), and immunoglobulin A (IgA;
3.2-6.2 g/l) in bovine colostrum is ~100-fold higher than in
normal milk (30).
The primary purpose of the present study was to examine the effect of
bovine colostrum supplementation (Bioenervi, which is a colostrum whey
product sold in some European countries but is not approved for sale in
the United States. Bioenervi is not on the banned drug list of the
International Olympic Committee) on serum concentration of IGF-I in
athletes. A further purpose was to investigate whether
there are any other changes in physiological responses during a
short-term strength and speed training period when a bovine colostrum
supplement that contains not only proteins, carbohydrates, vitamins,
and minerals but also IGF-I and immunoglobulins is taken.
METHODS
The purpose of this study was to examine
the effects of bovine colostrum supplementation (Bioenervi) on serum
insulin-like growth factor I (IGF-I), immunoglobulin G, hormone, and
amino acid and saliva immunoglobulin A concentrations during a strength
and speed training period. Nine male sprinters and jumpers
underwent three randomized experimental training treatments of 8 days
separated by 13 days. The only difference in the treatments was the
drink of 125 ml consumed per day. Posttraining increases were noticed
for serum IGF-I in the 25-ml Bioenervi treatment (125 ml contained 25 ml Bioenervi) and especially in the 125-ml Bioenervi treatment (125 ml
contained 125 ml Bioenervi) compared with the placebo (normal milk
whey) treatment (P < 0.05). The change in IGF-I concentration during the 8-day periods correlated positively with the change in insulin concentration during the same
periods with 25-ml Bioenervi treatment
(r = 0.68;
P = 0.045) and with 125-ml Bioenervi
treatment (r = 0.69;
P = 0.038). Serum immunoglobulin G,
hormone, and amino acid and saliva immunoglobulin A responses were
similar during the three treatments. It appears that a bovine colostrum
supplement (Bioenervi) may increase serum IGF-I concentration in
athletes during strength and speed training.
Fig. 1.
Experimental study design during an 8-day period. IGF-I, insulin-like
growth factor I; IgA, immunoglobulin A; IgG, immunoglobulin G.
[View Larger Version of this Image (14K GIF file)]
Fig. 2.
Time line for test training session.
[View Larger Version of this Image (9K GIF file)]
20°C. The samples that
required storage were stored for no longer than 3 mo and thawed only
once for analysis.
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RESULTS
The IGF-I, IgA, and IgG results are presented in Figs.
3, 4, 5.
The only significant (P < 0.05)
difference was noticed in the IGF-I change (from the beginning of the
8-day period to the end of the 8-day period) when the three treatments
were compared (Fig. 6). The trend of time
with 125-ml Bioenervi showed that the IGF-I values increased in a
linear fashion [~0.54 ± 0.26 (SE) nmol/l;
P < 0.05].
The serum insulin concentration (Fig. 7) increased
(P < 0.001) after the
breakfast, decreased (P < 0.001)
after the test training session, and was low during the acute recovery
in all treatments. At the end of the 8-day period, the insulin
concentration was similar to that at the beginning of the period. The
change in IGF-I level between pretraining and posttraining (change
after 8 days) concentrations correlated positively with the change in insulin concentrations between the same time points with placebo (r = 0.60;
P = 0.088), 25-ml Bioenervi
(r = 0.68;
P = 0.045), and 125-ml Bioenervi
(r = 0.69;
P = 0.038).
The growth hormone concentrations (Fig. 8) increased
(P < 0.05) immediately after the
test training session and decreased (P < 0.05) thereafter. The testosterone concentrations
(Fig. 9) were similar in the fasting conditions
(measurements 1, 2, 8, and
9). Before the test training session
the testosterone concentration decreased
(P < 0.01-0.001), but it
increased (P < 0.01) after the
session. During the acute recovery (90-min) phase the testosterone concentration decreased (P < 0.05-0.001). The cortisol concentration (Fig. 10)
was similar in the fasting conditions but decreased
(P < 0.001) strongly from the
fasting value to the end of the acute (90-min) recovery during the test
training session. There were no significant differences in any hormone
concentration between the three treatments.
The average daily energy intakes (5-day periods) were similar during
each treatment (10.50 ± 1.08 MJ for placebo, 11.55 ± 2.80 MJ
for 25-ml Bioenervi, and 11.34 ± 1.54 MJ for 125-ml Bioenervi), and
there were no differences in carbohydrate, protein, and fat distribution. The serum amino acid concentrations are presented in Fig.
11. There were no differences between the three
treatments. The test training session achieved a significant
(P < 0.001) decrease in the sum of
the concentrations of all amino acids, in the essential amino acids,
and in the branched-chain amino acids during all treatments.
The test training session slightly increased (not significant) blood lactate concentrations, which were 3.4 ± 1.0, 3.4 ± 0.6, and 2.8 ± 0.6 mmol/l for placebo, 25-ml Bioenervi, and 125-ml Bioenervi, respectively.
The countermovement jump was performed immediately before the test training session (56.3 ± 7.9, 54.8 ± 8.0, and 54.6 ± 7.8 cm for placebo, 25-ml Bioenervi, and 125-ml Bioenervi, respectively), and the values decreased (P < 0.05) after the session in all treatments. The values immediately after the session were 51.2 ± 8.2, 51.5 ± 7.4, and 50.4 ± 7.5 cm for placebo, 25-ml Bioenervi, and 125-ml Bioenervi, respectively. There were no measurable training effects in jumping performance during the three treatments.
DISCUSSION
The most important finding of this study was that increases occurred in
the serum IGF-I concentration during the Bioenervi supplementation. The
IGF-I values increased in a linear fashion, which implies that the
IGF-I level increased with increasing usage time with 125-ml Bioenervi.
However, the sharpness of the increase was quite low (0.54 nmol · l
1 · day1),
especially compared with normally day-to-day variability. On the other
hand, during 20 days the IGF-I concentration would increase, for
example, to 10.8 nmol/l with 125-ml Bioenervi. Because
the amino acid sequences of human and bovine IGF-I are identical (13), the RIA method used in our study measured the total amount of IGF-I
(both bovine and human). Thus the possible increase in serum IGF-I can
be due to either direct absorption of the growth factor from Bioenervi
or enhanced stimulation of human IGF-I synthesis. It should be noted
that the initial mean level of IGF-I was somewhat greater in the
placebo group. This means the possibility that reasons other than
Bioenervi supplementation may have contributed to the difference in the
IGF-I concentrations between the groups.
Similar results have been obtained in animal studies. It has been shown that both dietary colostrum (16, 35) and purified recombinant IGF-I (3) increased blood IGF-I concentration in calves. In addition, orally administered 125I-IGF-I has been demonstrated to be transported into circulation (4). Dietary IGF-I has been shown to suppress erratic insulin secretion and stimulate prolactin secretion in calves (2, 3), indicating that even systemic effects may occur. However, the predominant natural target of growth factors in colostrum is probably the gastrointestinal tract (38). The increased growth and turnover of intestine can provide for a healthier gut by increasing uptake of dietary components, which may enhance growth generally. Whether the dietary colostrum would have any effects on the gastrointestinal tract in human subject requires further studies.
In our study the training session consisted of not only heavy-resistance exercises but also many speed strength (power) exercises (e.g., jumps). The recoveries were long (from 2 to 3 min), and intensity (effort) was maximal (as fast as possible). No acute increase in serum IGF-I was observed after the training session, which is not consistent with a previous study where an increase in serum IGF-I was detected after a heavy-resistance exercise (27, 28). On the other hand, our protocol resulted in IGF-I and growth hormone responses that were similar to those observed during 23 h of recovery after a moderate-intensity and low-volume heavy-resistance exercise protocol (24). It should also be mentioned that in contrast to our study, the subjects have been nonathletes in previous studies. The negligible change in IGF-I level in our study could be due to the training effect in our subject group. Growth hormone is a primary endocrine stimulus for IGF-I production, and it mediates IGF-I synthesis, synthesis of the components of the 150-kDa complex of IGF-I, and binding protein 3 (20). However, IGF-I concentrations may be independent of growth hormone stimulatory mechanisms after exercise (26). It has been shown earlier (25, 27, 28) that not all heavy-resistance exercise protocols produce the same magnitude of serum growth hormone elevations. It has also been speculated that there may be many unrelated acute and chronic effects of exercise on IGF-I not related to growth hormone production (1, 6).
The serum testosterone concentrations were similar in all three treatments, and there were increases in response to the training session as documented earlier (28). The concentrations were recovered at the end of the 8-day period, and there were no significant relationships between the changes in IGF-I and in testosterone during the 8-day period. The serum cortisol concentrations decreased strongly after the morning measurement and were very low during the test day. This could be explained mainly by the daily periodic changes (17), which show that the high concentrations occur in the morning hours and that they decline during daytime.
The serum insulin concentration was high after the standard breakfast, as expected. The test training session decreased the concentration that was recovered at the end of the 8-day period. This insulin curve is typical of physical exercise (15). The strong relationship between IGF-I and insulin observed with Bioenervi supplementation confirms the role of IGF-I and insulin in protein anabolism (14). IGF-I promotes muscle protein anabolism principally by stimulating protein synthesis, whereas insulin inhibits proteolysis in human muscle thereby, increasing protein anabolism. Thus it is possible that Bioenervi supplementation may strengthen the effects of IGF-I and insulin on protein anabolism in athletes.
The serum amino acid concentration decreased strongly during the test
sessions. Earlier it has been shown that the essential amino acids show acute decreases during the short intensive anaerobic running exercises but that the concentration of the total amino acids
did not change significantly (32). The duration of the training session
in the present study (90 min) was longer than those of the running
exercises (
30 min). The blood amino acids are transported into
muscles where they are mainly needed for the synthesis of tissue
proteins, hormones, enzymes, and neurotransmitters. They are also
involved in energy metabolism via gluconeogenesis and in the regulation
of numerous metabolic pathways. During the training session a small
part of the amino acids is used for energy requirements (11), but the
main need for amino acids is during the postexercise recovery when the
rate of protein synthesis increases. In the study by Chesley et al.
(8), it was shown that protein synthesis was significantly elevated 4 h
after exercise. The increased protein synthesis rate persisted at least
for 24 h. The results were obtained after a resistance session of 4 sets of 6-12 repetitions of various biceps-curl exercises with a
resistance equal to 80% of one repetition maximum. In the present
study the rate of protein synthesis might have been similar, lasting
many hours. This is partly supported by the finding that the amino acid
concentrations were slightly lowered at the end of the period. However,
there were no significant differences in the amino acid concentrations between placebo and the Bioenervi-supplemented groups, which means that
the increased IGF-I did not change the serum amino acid concentrations.
The treatments did not have any significant effects on the saliva IgA
and serum IgG concentrations. It should be noted that transforming
growth factor-
(TGF-) found in bovine colostrum increases both
IgG (7) and especially IgA production in vitro (7). In addition,
TGF- has been demonstrated to enhance expression of secretory
component in rat epithelial cells, which is responsible for the
transport of polymeric IgA into intestinal lumen (31). Because it is
well known that IgA plays a major role in immunological protection of
mucous membranes (5), it could also be possible (at least in theory)
that dietary bovine colostrum may activate immunological defense system
against microbes on mucous membranes.
ACKNOWLEDGEMENTS
The authors thank Ursula Salonen for help in blood collection and Hannu Tuuri for help in statistical analysis.
FOOTNOTES
Address for reprint requests: A. Mero, Univ. of Jyväskylä, Dept. of Biology of Physical Activity, P.O. Box 35, 40351 Jyväskylä, Finland.
Received 3 May 1996; accepted in final form 6 June 1997.
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ABSTRACT
