Immunological Determinants in the Nutrition of Physically Active Individuals

Carbohydrates consumed during physical exertion can contribute to reducing metabolic stress and maintaining appropriate blood glucose levels. Adopting a carbohydrate-rich diet during long exercise sessions (30–60 g/h) can help lower stress hormone levels (such as adrenaline and cortisol), anti-inflammatory cytokines (e.g. Interleukin 10), and delay the onset of fatigue.

Continuous intake of fluids during exertion prevents dehydration of the body (an imbalanced fluid balance contributes to increased levels of stress hormones). Additionally, it affects the secretion of saliva, which contains antimicrobial proteins such as immunoglobulin A (IgA), lysozyme, lactoferrins, and defensins. Saliva production decreases during exercise. In combination with dehydration, this may lead to a reduced secretion of antimicrobial proteins. Continuous consumption of fluids in amounts of 100 to 250 ml every 20 minutes prevents this condition.

Probiotics, which are live cultures of bacteria, can have a positive impact on the health of individuals with inflammatory or chronic colds. This is due to changes in the gut microflora and improved integrity of the respiratory tract. Furthermore, these bacterial cultures affect the release of macrophages and lymphocytes and increase the expression of antimicrobial peptides. Probiotics can be used as dietary supplements for individuals with recurrent or chronic upper respiratory tract infections (URTI), which include colds, bronchitis, and laryngitis, as well as symptoms such as fever, cough, sore throat, and headache. Probiotics can be found in foods like Maślanka, Kefir, fermented vegetables - pickled cucumbers, sauerkraut - and in the form of tablets or water-soluble sachets. Most studies suggest that supplementation with probiotics in an amount of 10^10, i.e., about 10 billion, is effective. Some preparations available on the market in 2015 contained 25-50 billion bacteria per dose. Studies conducted by the Australian Institute of Sport showed that most athletes safely tolerated a dose of 35-50 billion bacteria of commercial products. Lower doses may be beneficial for some individuals. Probiotics for active individuals should contain bacteria of the genus Lactobacillus and/or Bifidobacterium.

The discovery of a receptor for vitamin D VDR in most human non-skin cells suggests its effect on other systems, including the immune system. Vitamin D is involved in numerous immunological processes, including the activation and proliferation of lymphocytes, the production of antibodies, and the regulation of the immune response. Vitamin D is available in some foodstuffs, such as eggs, milk, and cheese. It can also be ingested as a dietary supplement or produced in the skin. Due to Poland's geographical location, supplementation with vitamin D is recommended from September to the end of April for children (1-10 years) in the amount of: 600-1000 IU daily, for adolescents and adults (11-65 years): 800-2000 IU daily. The permissible maximum dose of vitamin D for an adult with normal body weight is 4000 IU daily.

Fatty acids play a significant role in regulating the immune system in various ways. Some of them participate in the synthesis of pro-inflammatory cytokines, such as fatty acids from the omega-6 family, which contribute to the development of inflammation. Omega-3 fatty acids exhibit anti-inflammatory action (decreasing the amount of cytokines). They deserve special attention. Physical exertion increases the formation of inflammatory mediators, which is why supplementation with fatty acids is recommended not only during periods of increased infections. The recommended dose is DHA + EPA omega-3 - 650 mg, including DHA 350 mg. Apart from supplementation with omega-3 fatty acids, it is very important to maintain the correct ratio of omega-6 to omega-3 fatty acids in the diet - it should be 3:1 (in the typical Polish diet, it is 20:1). To maintain the proper ratio, include sea fish and vegetable oils (rapeseed, linseed, olive oil) in the diet, and limit the consumption of processed products and sweets, grapeseed oil.

Glutamic acid is an amino acid that may be considered by athletes during an infectious period (autumn and spring). It is an energy substrate for lymphocytes, erythrocytes and bone marrow cells. In addition, it is worth noting that consumption after exercise can reduce experienced subjective discomfort (which is especially important for individuals who have difficulty eating immediately after exercise). However, despite its benefits, glutamic acid has not yet been proven to be 100% effective in supporting the immune system after physical exertion. Only a few researchers emphasize its positive effect on URTI. Recommended dosages are 0.1 g/kg of body weight or 5-10 g.