What's Cool In Road Cycling

Flu Fighters Part II: Seeing Vitamin C

Last month, we reinforced mom’s various lectures by focusing on the basic practices associated with maintaining good health. This month, we’ll take a look at what we can stuff into our Christmas turkey in terms of supplements that may help to strengthen our immune systems and ward off infections and illnesses.

Growing like Germs
Hopefully, every Toolbox reader has become a fanatical hand-washer and nobody has succumbed to the ravages of flu season since our last article on immune function. As we saw, elite athletes are often-times at a slightly greater risk of depressed immunity compared to recreationally fit individuals, and sometimes even compared to sedentary couch potatoes. That’s because immune factors can often be impaired by heavy exercise, leading to a greater potential risk for infections and illnesses.

The exact mechanism for this immune depression remains unclear and open to scientific debate. Indeed, analogous to germs sprouting like mad within our body, the entire field of exercise and immune function is one of the fastest growing fields within exercise physiology itself. This has become especially true with technological advances permitting more detailed and elaborate analyses of blood markers and cellular response to exercise.

Ultra-Elite and the Rest of Us
One of the underlying problems in the field of immune function and exercise is that much of the research has focused on the “extreme” ultra-elite athletes and events. For example, Nieman et al. found that 24% of ultramarathoners completing a 160 km running event experienced a significant episode of Upper Respiratory Tract Infection (URTI) in the following week (2). Even with the typical Toolbox reader’s juggling of multiple demands in addition to training, such stress is still far beyond what we would consider “typical.” Therefore, while it makes for clear research design by ensuring a definite exercise stress, focus on such extreme events can make it difficult to extrapolate findings to a more general population of athletes.

With that in mind, now that it’s clear that extreme exercise may be negative, recent research has begun focusing on more moderate or typical exercise for the general population.

Gimme a Pill!
The other concurrent theme, given our pill-crazed society, is whether any particular nutrients or supplements may help to strengthen our immune system. Besides getting onto Oprah, there is obviously a major imperative for such research amongst exercise physiologists, most of whom are also active recreational or competitive athletes. We will focus on two such articles in this and a future article, with the first one from my own laboratory studying the effects of Vitamin C supplementation and exercise in the heat on immune factors.

Ya Scurvy Dog!
The first study was by my M.Sc. student Andres Carrillo, one of the last projects I performed at Dalhousie University, and appearing soon in the January 2009 issue of the International Journal of Sports Physiology and Performance (1). In this study, our supplement of interest was Vitamin C, that most famous of vitamins. First gaining prominence as the cause behind the scourge of scurvy in seafarers, Vitamin C has become a common additive in many foods, along with being one of the most popular supplements taken by the general public.

Vitamin C has multiple roles within the body, including being a critical component of collagen and connective tissue (which explains the major scurvy symptoms of bleeding gums and pain within the joints and muscles). From an immunological standpoint, Vitamin C is important as a potential antioxidant, helping to protect the body from damage by free radicals produced during metabolism.

So the aim was to look at the effects of both acute and chronic Vitamin C (VC). To do this, we had a VC group ingest 1500 mg daily for 12 days. The Control group received a placebo for the same period. Both groups consisted of men and women and were typical competitive athletes, including cyclists, triathletes, and varsity soccer players. None would be considered super-elite athletes of national level.

Feeling Hot Hot Hot
The first tweak that we added was to lower the volume and intensity of exercise to a level more representative of typical recreational and competitive athletes. So rather than ultra-marathon efforts, we exercised subjects on the bike at 55% VO2max, and effort roughly representative of a steady tempo effort. The overall “feel” we aimed for was a steady effort of about 2.5h.

The other major context of our study was to investigate the effects of exercise in the heat, rather than the typical research conducted in thermoneutral environments. Temperature serves as an additional stress on the exercising body, and higher body temperatures has been associated with increased immunological impairment. Hey, I have to have a temperature context to keep things interesting for me! So exercise was conducted in a 35oC and 13% relative humidity chamber.

Overall, we had subjects perform the above heat stress test first as a baseline. Then at least a week later, the two groups began taking the VC or placebo, then performed the heat stress test after the first day of supplementation, and again at the end of 8 days. Why test at 8 days when we had 12 days of supplementation? We wanted to look at the changes in immune function not just directly following exercise, but over the 72 hours or so “open window” typical of impaired immune function.

Besides the standard temperature and physiological data, the three immune parameters we studied were:
• Salivary cortisol. This is commonly analyzed as a marker of physiological/immunological stress post-exercise. In this case, generally the lower the cortisol level, the better.

• Salivary immunoglobin-A (IgA). This is one of the main markers of immune function. In this case, the higher the IgA levels post-exercise, the better.

• Incidences of Upper Respiratory Tract Infections (URTI). Daily, subjects filled out a detailed standardized questionnaire of their health status, including both symptoms of fatigue and also distinct illness.

Results
At the end of the day, our results were a slightly mixed bag. On the one hand, the VC group had distinctly lower salivary cortisol post-exercise throughout the entire supplementation period. This would seem to suggest that VC can indeed be beneficial in lowering the overall physiological and immunological stress imposed through moderately hard exercise.

Mitigating the cortisol results, however, we observed no differences in IgA levels with either VC or placebo. So while the “stress” on the body appeared to be less with VC, it didn’t appear to actually elicit a direct “positive” response in the immune system. Furthermore, both the VC and placebo group subjects experienced about the same number of URTI episodes throughout the experiment, again suggesting no benefit in real-life practical terms.

Caveats and Summary
What would I ultimately recommend about the importance of Vitamin C supplementation for recreational and competitive athletes that are not at the ultra-endurance level? In addition to ensuring an adequate intake of natural VC within food, moderate levels of supplementation does have some potential to be beneficial in improving immunological response to moderate training. Being a water-soluble substance, the body is generally efficient at excreting excess, such that it is difficult to overdose. So as nutritional insurance goes, this is a fairly benign and inexpensive option.

As always, a number of considerations exist in the interpretation and ultimate application of this study:

• The study primarily took place in October through January, in the height of the wintertime flu season, and it is possible that this increased sensitivity to infections dampened or masked the potential benefits of any supplements.

• Our IgA and URTI data contrasted with other research demonstrating immunological benefits from VC supplementation in ultra-endurance athletes. However, we saw the same pattern of decreased cortisol. So it may be the case that supplementation provides truly significant benefits only with very heavy training stress.

This is the final original Toolbox article of 2008, as our crew of writers takes a couple of weeks off to be naughty and undo all the training we’ve put in ourselves over the year! Keep posted the next couple of weeks for our favourite Toolbox articles from the past year.

Best wishes to all for a wonderful holiday season, and see you in 2009!

Reference
1. Carrillo AE, Murphy RJL, and Cheung SS. Vitamin C supplementation and salivary immune function following exercise-heat stress. Int J Sports Physiol Perf. 3:1-16, 2009.
2. Nieman, DC et al. Relationship between salivary IgA secretion and upper respiratory tract infection following a 160-km race. J Sports Med Phys Fitness. 46:158-162, 2006.


About Stephen:
Stephen Cheung is a Canada Research Chair at Brock University, with a research specialization in the effects of thermal stress on human physiology and performance. He can be reached for comments at [email protected] .

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