Reducing The Burden Of Infection In Athletes
Article by Maya Tu BSc ANutr
Different types of infection, including both upper respiratory and gastrointestinal, pose a big threat to athletes as it can often mean reduced training time and affect upcoming competitions and events. Ecological immunologists, who study the causes and consequences of certain diseases, have introduced a new theoretical perspective that suggests that two concepts are important for athletes. These concepts include immune resistance and immune tolerance.
Immune resistance vs immune tolerance
Immune resistance focuses on how the body destroys and eliminates the microbes that cause an infection. Immune tolerance, on the other hand, focuses on managing and controlling the infection, reducing the number of defence mechanisms required. Athletes’ bodies are often under stress and so they should have an immune system that can withstand an increased risk and therefore incidence of infection. Immune tolerance may therefore be more beneficial for athletes and evidence suggests that taking certain supplements could help increase an individual’s tolerance and therefore reduce this burden of infection. So, what if there were ways of shortening the duration of a common cold or reducing the occurrence of illness?
Mediterranean Diet
By following the Mediterranean diet, a balanced healthy diet, the risk of infection and development of other conditions may decrease. The Mediterranean diet is characterised by consuming large amounts of olive oil, fruit and vegetables, legumes and wholegrain cereals with a lower consumption of alcohol, meat and dairy products. This diet is linked with antioxidant effects and anti-inflammatory properties, ultimately benefiting the immune system, due to the high concentrations of polyunsaturated fatty acids, polyphenols, antioxidants and phytochemicals (6). Studies even highlight that individuals consuming a Mediterranean diet have a lower risk of developing COVID-19 (6). Therefore, it is key to follow a healthy diet in order to reduce the risk of developing illness.
Hydration
Although it may seem self-explanatory, proper hydration is key to maintain a healthy lifestyle and to also reduce infection. Keeping hydrated can prevent foreign microbes from entering the body as it can aid the cells in the skin to act as a barrier. Additionally, evidence shows that dehydration can increase the risk of urinary tract infections which further shows the importance of hydration (7). It needs to be highlighted, however, that further studies are required to assess the relationship between hydration and disease and infection.
Probiotics
Probiotics have received a lot of attention online and in the media for their ability to promote and support gut health, but they may also help to increase immune tolerances which could be advantageous for athletes. Probiotics are live microorganisms that can show health benefits to the individual consuming them, when given at appropriate doses, by influencing their immunity. That being said, the mechanisms involved in how probiotics prevent infection have not been clearly identified.
Current evidence, however, shows that probiotics may display anti-inflammatory properties in the gut to prevent inflammatory responses to harmful, foreign substances that could cause illness (1). Several studies have shown that supplementation may be most beneficial during periods when susceptibility of infection is higher, such as in the weeks before and during travel in foreign countries. Supplementation for athletes may increase the concentration of a molecule called IFN-gamma which is crucial for immunity and may decrease the severity and duration of infection (2). But what we should remember is that many studies are not completely conclusive or reliable; some do not recruit enough people; some only recruit one gender and some are only observational. Similarly, would the effects be the same in athletes that compete in different sports or when consuming different strains of probiotics? These are questions that still need answering.
Vitamin C
Secondly, vitamin C may also be beneficial to athletes. Vitamin C is a water-soluble antioxidant that can act to reduce an excessive build-up of harmful species called reactive oxygen species. Vitamin C levels drop when levels of oxidative stress increase, for example during an infection such as a common cold. As a result, vitamin C supplementation may prevent and reduce the effects and even incidence of upper respiratory infections by reducing tissue damage caused by reactive oxygen species (3). If you follow a healthy & balanced diet which contains lots of fruit and veg, such as peppers, kiwis, and citrus fruits, you should be able to get enough vitamin C each day, without the need to supplement.
It should be noted, however, that high doses of vitamin C could be detrimental to those taking part in endurance training as it may stop the production of mitochondria which are responsible for producing the chemical energy otherwise known as ATP (4). These observations, however, have also been contradicted and so further research must be completed.
Polyphenols
Polyphenols, specifically plant flavonoids, have been studied for their anti-inflammatory and antioxidant properties which could be involved in immune tolerance in athletes. They can display advantageous properties for the immune system by promoting immunity against substances that may be foreign. Studies show that garlic extract, for example, can reduce the duration and incidence of infection 33% in those completing exercise (5). The mechanisms involved, however, seem unclear as there were no significant changes in specific anti-inflammatory markers which would otherwise be expected.
In summary, try where possible to incorporate more vegetables such as broccoli, onions, spinach, garlic, to increase your polyphenol levels and fruits such as berries to increase both your polyphenol and vitamin C levels. Making sure you consume a well-balanced, nutritious diet, along with maintaining hydration levels, adequate rest, and good hygiene practices such as regular hand washing, with an extra focus on periods when your body may be under more stress or more susceptible to infection.
Overall, immune tolerance could be the way forward for athletes to maintain training levels and to prevent their training sessions from being affected. It is clear that taking certain supplements are beneficial for overall health, however, optimal dosage needs to be determined and further research is required to understand the underlying mechanisms. Remember that we are all unique and so what may be beneficial to some, may not be suitable for others. It is also encouraged to speak with your GP or a registered healthcare professional before taking any kind of supplement to make sure the type and dosage is correct for your body’s individual requirements.
This blog was written by Maya Tu. Maya graduated with a First-Class Honours in BSc Nutrition and has just completed her Master's in Clinical and Public Health Nutrition, graduating with Distinction. She is a part of Jamie Oliver’s nutrition team and has a passion for childhood and sports nutrition.
References:
(1) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7434852/
(2) https://pubmed.ncbi.nlm.nih.gov/18272539/
(3) https://pubmed.ncbi.nlm.nih.gov/31691927/
(4) https://pubmed.ncbi.nlm.nih.gov/24492839/
(5) https://academic.oup.com/advances/article/7/3/488/4558085