Investigations in animals suggest that dietary nucleotides influence several indices of immune function. Patients who receive enteral or parenteral feeds as their sole source of nutrition could potentially be a group whose intake of nucleotides is minimal and in whom deficiency symptoms might manifest. It is not clear whether this has been observed but studies in critically ill, ICU patients show that whilst enteral feeds improve nutritional deficiencies they do not ameliorate the impaired immune response (1).

Several enteral feeds containing so-called immunomodulators (usually arginine, omega-3 fatty acids and nucleotides) are available for clinical use. Several have been subject to clinical review with encouraging results in terms of decreased infection rate (1), improvements in markers of immune function (2) and shorter hospital stay (1).

A number of aspects of the immune systems in athletes exhibit transient dysfunction after prolonged, heavy exertion, effectively leaving an open window of impaired immunity for pathogens to gain a foothold, increasing infection risk (3). Indeed prolonged training increases the rates of infection, particularly upper respiratory tract infections (URTI) like colds and coughs (4). Nutritional supplements (glutamine, omega-3 fatty acids and antioxidants) have been studied as countermeasures to exercise-induced immune changes with limited success (5). This may be due to the limitation of a single nutrient in abolishing immune suppression. But human studies have demonstrated an improvement in markers of immune function with nucleotides (2).

Endurance exercise has been shown to decrease salivary IgA (6). Salivary IgA is the first line of defence against pathogens causing URTI.

Two small studies by McNaughton et al., (2006 & 2007) examined trained males before and after a 60 day supplementation period with a commercially available nucleotide supplement, Nucell (Wyreside, Preston, UK) on salivary IgA following a 2 minute maximum exercise test (7) and a 90 minute cycle ride (8). No difference was observed in performance, lactate or other markers of physiological stress but salivary IgA was significantly increased following the period of supplementation after both exercise trials. These results are encouraging and warrant further investigation to show whether the incidence of URTI is affected.

1. Kulkarni AD, Rudolph FB and Van Buren CT. (1994). The role of dietary sources of nucleotides in immune function: A review. J. Nutr. 124:8, 1442S-1446S.
2. Bower RH, Cerra FB, Bershadsky B, Licari JJ, Hoyt DB, Jensen GL, Van Buren CT, Rothkopf MM, Daly JM, Adelsberg BR. Early enteral administration of a formula (Impact) supplemented with arginine, nucleotides, and fish oil in intensive care unit patients: results of a multicenter, prospective, randomized, clinical trial. Crit Care Med. 1995; 23(3):436-49.
3. Gleeson M, Nieman DC, Pedersen BK. (2004). Exercise, nutrition and immune function. J. Sports Sci. 22:1, 115 – 125.
4. Maughan R, and Gleeson M. (2004). The biochemical basis of sports performance. Oxford University Press.
5. Pedersen BK, Ostrowski K, Rohde T, and Bruunsgaard H. (1998). Nutrition, exercise and the immune system. Proceedings of the Nutrition Society 57:43-47.
6. Nieman, D. (2007). Marathon training and immune function. Sports Med. 37:4-6, 412-415.
7. Mc Naughton L, Bentley D, Koeppel P. The effects of a nucleotide supplement on the immune and metabolic response to short term, high intensity exercise performance in trained male subjects. J Sports Med Phys Fitness. 2007 Mar;47(1):112-8.
8. Mc Naughton L, Bentley DJ, Koeppel P. The effects of a nucleotide supplement on salivary IgA and cortisol after moderate endurance exercise. J Sports Med Phys Fitness. 2006 Mar; 46(1):84-9.