Protein and Carbohydrate Supplementation to Support Immune Function in Athletes

As we all know, exercise provides many health benefits, including
positive effects on practically every system in the body, such as the
cardiovascular and muscular systems. These benefits also extend to the immune system, which is
strengthened through regular physical exercise, as discussed in a
previous post. In general, athletes can therefore be said to have stronger defenses against
infectious processes. 1 Several studies, for example, have shown that
athletes' immune cells—specifically natural killer cells, among
the main components of the immune system—are more active in athletes than in
sedentary or untrained people. 2,3 Similarly, in non-athletes,
beginning a progressive training program has been observed to increase both the
number and activity of these immune cells, 4 resulting in “stronger defenses”.

Beware of Infections During High-Load Periods

Despite these benefits, acute periods of very high training load can
temporarily weaken the immune system. We all know an athlete
who developed a cold lasting several weeks after a demanding event such as a marathon or Ironman;
or worse, whose infection at peak
training load prevented participation in competition. This may partly occur
because exhaustive exercise causes an acute decrease, 1 – 2 hours afterward, in
several circulating immune-cell types, such as lymphocytes.
Many have called this the post-exercise “open window”:
a process of immunosuppression that would increase infection risk immediately
after physical exercise. Some studies have indeed found a higher
prevalence of infections, especially respiratory conditions such as bronchitis, among
endurance athletes than in the general population. 5 This could potentially result from
an immune system weakened by high training loads and stress.

Protein and Carbohydrate Supplementation to Support Immune Function

Energy availability and,
especially, carbohydrate availability affect immune function. Low carbohydrate availability has been shown to impair immune function in athletes. 6 Until
now, however, it was unknown whether combining protein supplementation with carbohydrates could improve
immune function in athletes. A recent study led by
Dr. Fernando Naclerio of the University of Greenwich addressed this question. 7 The
researchers studied 30 athletes who trained for 10 weeks—6 – 10 hours per week,
across 4 to 6 weekly sessions. Half consumed a
carbohydrate supplement—24 g diluted in orange juice—after training, while the other half consumed the same
amount of a protein-and-carbohydrate supplement, specifically 24 g of Crown Sport Nutrition's
Beef & Whey ST diluted in orange juice. At the end of the 10
training weeks, the results showed differences in several immune-function markers despite
both groups completing the same training. Protein-and-carbohydrate
supplementation attenuated the increase in the neutrophil-to-
lymphocyte and platelet-to-lymphocyte ratios—both markers of greater inflammation—seen
in the carbohydrate-only group, and also reduced the systemic
inflammation index (Figure 1). Protein-and-carbohydrate supplementation
could therefore reduce the pro-inflammatory state associated with intense exercise that is observed when
only carbohydrates are consumed.

Figure 1. Effects of carbohydrate supplementation (CHO) or a carbohydrate-and-protein mixture (PROT) on the neutrophil-to-lymphocyte ratio (Panel A), platelet-to-lymphocyte ratio (Panel B), and systemic inflammation index (Panel C). The asterisk (*) indicates significant differences between groups.⁷

Conclusions

Maintaining optimal immune defenses should be a primary goal for every athlete, especially during high-load periods. Athletes should ensure not only adequate energy intake, but also that they meet their requirements for each macronutrient. Post-exercise carbohydrate intake can effectively attenuate the pro-inflammatory state and generally improve post-exercise defenses, but these effects appear to be maximized when protein is consumed alongside carbohydrates —for example, 20 – 25 g of protein with a carbohydrate-rich drink, or a prepared drink such as 3:1 PRO Recovery ST or 3:1 Recovery+.

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References:

1. Walsh NP, Gleeson M, Shephard RJ, et al. Position statement. Part one: Immune function and exercise. Exerc Immunol Rev. 2011;17:6-63.
2. Nieman DC, Buckley KS, Henson DA, et al. Immune function in marathon runners versus sedentary controls. Med Sci Sports Exerc. 1995;27(7):986-992. doi:10.1249/00005768-199507000-00006
3. Nieman DC, Nehlsen-Cannarella SL, Fagoaga OR, et al. Immune function in female elite rowers and non-athletes. Br J Sports Med. 2000;34(3):181-187. doi:10.1136/bjsm.34.3.181
4. Llavero F, Alejo L, FIuza-Luces C, et al. Exercise training effects on natural killer cells: a preliminary proteomics and systems biology approach. Exerc Immunol Rev. 2020;In press.
5. Harris MD. Infectious disease in athletes. Curr Sports Med Rep. 2011;10(2):84-89. doi:10.1249/JSR.0b013e3182142381
6. McKay AKA, Peeling P, Pyne DB, et al. Six Days of Low Carbohydrate, Not Energy Availability, Alters the Iron and Immune Response to Exercise in Elite Athletes. Med Sci Sports Exerc. 2022;54(3):377-387. doi:10.1249/MSS.0000000000002819
7. Moreno-Pérez D, López-Samanes Á, Larrosa M, et al. Effects of protein–carbohydrate vs. carbohydrate alone supplementation on immune inflammation markers in endurance athletes: a randomized controlled trial. Eur J Appl Physiol. 2023;(0123456789). doi:10.1007/s00421-023-05168-6