LARS McNAUGHTON DISCUSSES DIETARY
Professor Lars McNaughton recently published a paper in the prestigious
Journal of Sports Medicine and Physical Fitness, where he looked at how
nucleotide supplementation can mitigate stress on the body from endurance
exercise. He sat down with nuBound recently to answer questions about the
implications of this study for athletes.
McNaughton, L., Bentley, David J., and Koeppel, P. (2006). The effects of a
nucleotide supplement on salivary IgA and cortisol after moderate
endurance exercise, J. Sports Medicine and Physical Fitness, 46:84-89.
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Q What was the purpose of your study?
A The goal of this study was to determine whether the consumption of a dietary
nucleotide supplement had any effect on endurance athletes.
The model we used was to look at stress, because that’s how athletic training works--
it’s a stressor to the system. In training, an athlete stresses their system and then in
recovery, the body adapts to that stress and increases its capacity. In this sense,
stress is positive.
However, there are additional repercussions of stress which have negative effects on
the body. For example, there is substantial evidence that over-training (or a large
increase in training load and/or a major effort, such as racing a marathon) depresses
the immune system. It is well documented that endurance athletes have a higher
incidence of colds and other upper respiratory infections as a result.
Similarly, during and after exercise, the body releases the hormone cortisol into the
bloodstream in response to stress. Cortisol is a catabolic hormone, which means that
its effect is to degrade tissue. While the release of cortisol is part of the body’s normal
response to stress, prolonged high levels of cortisol can possibly lead to muscle
wastage, which is the opposite from what an athlete wants.
In our study we measured the stress imposed on the body by a prolonged session of
endurance exercise, and looked at the question of how dietary nucleotide
supplementation affected the reaction to this stress.
Q You looked at two markers (salivary IgA and cortisol). What relevance
do these have to athletes?
A These two markers are the most common indicators used to measure stress in
the field of exercise physiology. They have multiple advantages, they are both easily
measured via a test of the athlete’s saliva and since they are widely measured, this
provides a broad basis for comparison with other studies.
Salivary immunoglobin (IgA) is the main form of immunoglobin found in saliva and the
mucosal membranes, thus it plays a front line role in defending the body against colds
and other respiratory infections. It is a readily measured marker for immune system
Cortisol is a hormone released when the body is under stress. While it is normal for an
athlete to have a higher level of cortisol after exercise, elevated levels indicate higher
stress. All things being equal, an athlete with a lower level of cortisol post-exercise will
have a faster recovery, since there is less catabolism [tissue degradation] during
Together, these markers for immune function and hormonal change provide a good
picture of how the body reacts to stress. Differential reactions to stress can be
attributed to the supplementation regime we studied.
Q What was the protocol for the study?
A We measured the two markers in all subjects at the start of the trial two times:
prior to exercise and after a 90 minute endurance cycling test at approximately 60% of
VO2max. The subjects were then provided the supplement or a placebo for 60 days,
on a double blind basis (ie, neither the researchers nor the subjects knew who had the
supplement and who had the placebo). At the end of the supplementation period the
subjects again underwent testing for the two markers, prior to and following the 90
minute endurance cycling test.
Q What were the results of the study?
A After 60 days of supplementation, we found significant differences in the two
markers between the control and the experimental groups. Those subjects who were
taking the nucleotide supplement had significantly higher levels of salivary IgA than the
control group. Analogously, cortisol levels were significantly lower in the experimental
group than the control.
This work suggests that a dietary nucleotide supplement may offset the hormonal
response associated with demanding endurance activity. Specifically, the body’s
reaction to the stress of training may be lessened.
The implications are that nucleotide supplementation strengthens the immune system,
leading to fewer colds and upper respiratory infections, and that it lowers the hormonal
reaction to stress, meaning lower levels of cortisol during and after exercise, and thus
to less tissue damage, which in turn permits faster recovery.
Q Aren’t dietary nucleotides metabolized completely in the stomach?
What benefit can oral supplementation provide?
A The current study does show measurable benefits from dietary nucleotides,
although it didn’t examine the mechanism of these benefits. The traditional view had
been that nucleotide supplementation was not needed as the body could synthesize all
the nucleotides needed on its own. Research over the past several years has shown
that under conditions of stress, the body does utilize dietary nucleotides.
Research into dietary nucleotides is an area of active interest. In fact, I have another
paper on this topic, currently undergoing the peer review process, which should be
published in the next year.
Q Are there any WADA or NCAA restrictions on oral nucleotide
A No, there are no restrictions. The ingredients in nuBound simply provide a
concentrated form of nucleotides, which are present in all food products to some
Q How do the ingredients in nuBound compare to the product used in
A They are identical. The nucleotide supplement used in our study came from the
same manufacturer. Both products provide a high level of specific, purified, yeast-
extracted dietary nucleotides in a complex with antioxidant vitamins C and E.
Q Would you recommend nuBound to athletes?
A Yes, I would. I take a nucleotide supplement every day, even though I consider
myself to have a pretty balanced diet. Its not expensive, it certainly does no harm and
based on our results there is a real benefit.
Lars McNaughton is Head of the Department of Sport, Health & Exercise
Science at the University of Hull in England. A native of England who grew up
in Australia, Professor McNaughton completed his PhD at the University of
Oregon (home of coach Bill Bowerman and runners Steve Prefontaine,
Alberto Salazar, etc). He has published over 100 publications in
peer-reviewed journals during a 21 year career including stints in Australia,
the US and Europe. He is a Fellow of the American College of Sports
Medicine (ACSM), the Australian Association for Exercise and Sports
Science (AESS) and the European College of Sports Science (ECSS).
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