The immune system is our body’s defence system against external elements such as viruses, bacteria, and fungi. It has been proven that physical activity, following adequate training, activates it, thus strengthening our barriers. Nevertheless, the high demands of competitive sport, with two and up to three matches per week, can cause the immune system to be suppressed. This is what is called immunosuppression.

For this reason, the key is to find the balance as the demands of elite competition imply maximum-intensity efforts. We need to also take in mind the emotional stress and alterations in the intestinal barrier due to both intense exercise and sleeping patterns, with numerous trips taking place to play the matches scheduled.

All these elements from elite sports can reverse the protective effect of exercise on the immune system, lowering the defences. This immunosuppression can occur after exercising or it can be due to a lack of sleep, causing the athlete to have alterations in the intestinal microbiota or making him have a greater predisposition to suffer infections such as colds or flu.

It should be considered that these opportunistic infections are the most common in football players and that they are especially frequent in the winter months as they have to stay in closed spaces for longer periods.

An aspect that must not be forgotten is that competition is very stressful, in addition, it can cause inflammation for not having enough time to recover. These processes generate cortisol, the stress hormone. If cortisol is permanently high, it can even become chronic and be detrimental to the immune system. Especially for the Natural Killers, a type of cell of this system, which keep viruses, bacteria and other possible external agents under control.

Rest is key

Good sleep and rest are essential. There is scientific evidence in this field that has shown that the majority of people who sleep less than seven hours suffer physiological repercussions, such as the immune system. Again, the lack of sleep often activates cortisol and lowers the defences, also making people feel more tired, irritable, and irascible.

Food can play a favourable role in strengthening the immune system. Different diets can compromise the immune function, such as those high in protein, carbohydrates and fats, those very low in energy, fasting, and big doses of vitamins and minerals.

In sports, there is the so-called ‘metabolic window’ that, at the same time, is the ideal time to recover and in which there is a greater risk of suffering infections, with lowered defences, due to higher sweating and temperature changes in the body. This window takes place in the first two hours after exercise and it is when cortisol is at its highest, so it can be modulated with nutrition and metabolically recovered with a dietary plan.

The importance of immunonutrition

During the rest of the day, there are eating habits that can activate the immune system. This is called ‘immunonutrition’, a nutrition plan based on a high content of protective plant based foods, that allows for strengthening and activating the intestinal barrier thanks to products such as probiotics.

Vitamin D is also an immune nutrient and is found in foods such as milk, cereals, egg yolks, and fish such as salmon or tuna. Many athletes avoid dairy products to minimise their intake of saturated fat, but in doing so they are excluding this vitamin, as well as vitamins B and calcium, which play a key role in this area. For this reason, an option is fat-free or low-fat dairy products.

In addition, foods with omega-3 acids can help raise the defences. Among others, olive oil, flax and chia seeds, fish such as anchovies, sardines, tuna and salmon, as well as nuts and avocado.

Foods high in sugar and ultra-processed should be avoided, because, apart from being very poor from a nutritional standpoint, they do not have the ability to activate the immune system.

Among the minerals with modulating effects on the immune system, we find zinc, iron, selenium, and copper. Chicken and turkey, cheese, oat flakes, red meat, some shellfish, and nuts such as hazelnuts and almonds contain zinc.

Foods rich in iron are red meats –veal and beef–, nuts such as walnuts and cashews, sesame, vegetables such as spinach, watercress and chard, and shellfish such as oysters, clams, mussels, and cockles.

Selenium is also found in red meat, fish, vegetables, nuts such as Brazil nuts and pine nuts, shellfish, eggs, chicken, tuna, and grains.

Legumes (lentils, chickpeas, beans), whole foods and cereals, shellfish, plums, and raisins are rich in copper.

Finally, supplements such as beta-glucans, bovine colostrum, carbohydrates, echinacea, glutamine, kaloba, N-3 polyunsaturated fatty acids, probiotics, quercetin, vitamin C, vitamin D3 and vitamin E, and the aforementioned zinc may be useful.

In summary, professional sports compromise the immune system, which must be cared for with rest, stress management and a proper nutrition plan. The two hours after exercise, the so-called ‘metabolic window’, represent a key time frame upon to take action.

Javier Granda