Nobody wants to be poorly prepared for a game, race or competition or even have to cancel due to illness, do they? The colder season has arrived and with it, the risk of colds and influenza (common flu). Runny nose, coughing and a sore throat – it’s starting again. Good health and immunity, i.e. protection against infections by pathogens, is one of the hottest topics of 2020, especially due to the current COVID-19/coronavirus pandemic. Find out here what you can do to support a healthy immune system and how you can reduce the risk of acute respiratory tract infections.
Risk factors for reduced immune function and acute infections
Acute infections of the upper respiratory tract (e.g. sinusitis, otitis media and tonsillitis) are among the most common illnesses. Factors such as mental stress, anxiety, depression, sleep disorders or malnutrition have a negative influence on our immune function and thus our protection against pathogens. Exercise and sports also have an influence on our immune system. The relationship between exercise and risk of upper respiratory tract infection is illustrated in the well-known J-shaped model (1):
This demonstrates, as numerous studies have also shown, the undisputed preventive effect of moderate physical activity compared to physical inactivity. On the other hand, very high exercise workloads, such as marathon type events or heavy training regimens, are for many athletes associated with an increased risk of upper respiratory tract infection. Only in elite athletes on the highest level may this seem to not be the case (2). However, overtraining can result in increased susceptibility to infections, regardless of the athlete’s performance level.
Not only physical exertion but also behaviour during the recovery phase has an influence on the risk of infection. Sebastian Kienle, top triathlete and multiple winner of full and middle distances, says: “Anyone who uses crowded public transportation after swimming certainly has increased exposure to catching potential pathogens. There’s also an inherently high risk at a training camp – the body is already under a high amount of strain and on top of that comes contact with many people at a buffet. Air travel and travel stress are also typical scenarios where you can easily catch a cold.”
Proper nutrition supports a robust function of the immune system
What we eat and drink affects our health and immune system. Many nutrients, especially essential micronutrients (vitamins and minerals) and protein, are extremely important to maintain our body’s natural defenses. A well-functioning and balanced immune system calls for a balanced diet in order to avoid nutrient deficiencies. Tempting advertising promises suggest that an additional intake of vitamin supplements or wondrous foods acts as an immune booster. This sounds great, because who of us would not like to “tune up” our immune system? However, so far there’s no sound evidence that taking additional amounts of vitamins or minerals further strengthens the immune system or fully protects us from infections. However, for those who suffer from micronutrient inadequacies or deficiency, an appropriate dietary supplement can be useful for optimal immune health.
Here are some of the most effective nutritional measures to support immune health and minimise the risk of respiratory tract infections in athletes:
1. A balanced, varied and needs-based diet provides the body with the best possible supply of valuable nutrients such as protein and micronutrients. Whole foods, that have been processed as little as possible, are preferred and food preparation should be done gently (e.g. vegetables should still be slightly firm instead of overcooked). Consume at least 3 portions of vegetables (raw and/or cooked) and 2 portions of fruit daily in the bright colors of a rainbow. A colorful mix provides the body with essential vitamins and minerals and a palette of different phytochemicals. Phytochemicals impart plants for example with color and aroma. They are also attributed with various health-promoting effects for our body (e.g. anti-inflammatory, antioxidant, antibacterial effects). Incidentally, nuts, seeds, legumes and whole grain products are also rich in phytochemicals. For a healthy diet, regular consumption of fermented foods such as yogurt, kefir, sauerkraut and kimchi is also recommended. Likewise, the intake of omega 3 fatty acids EPA and DHA. These are involved in the regulation of inflammatory processes in the body and are mainly found in fish and seafood and alternatively in microalgae products.
2. Vitamin D deficiency is associated with an increased risk of respiratory tract infections (3). Sufficient vitamin D intake through food alone is rarely possible. However, the skin can synthesize vitamin D through adequate exposure to UVB sunlight. Those who don’t get enough sunlight exposure (e.g. during the darker seasons or for other reasons) should consider taking a supplement in consultation with a doctor.
3. Crash diets should be avoided. If you want to lose weight, you should ideally take it slowly. Moderately reduce overall caloric intake and pay particular attention to adequate protein and micronutrient intake.
4. Excessive alcohol consumption should be avoided, especially after strenuous training sessions and competitions.
5. Ensure adequate fluid intake during exercise. This not only prevents dehydration (which is associated with an increased release of stress hormones), but also maintains saliva production in the mouth (4,5). Saliva contains antimicrobial components.
6. Ensure sufficient carbohydrate intake (30-60 g/ h) during prolonged intense endurance exercise longer than 90 minutes. This counteracts a drop in blood sugar level, lowers the level of circulating stress hormones (e.g. cortisol) and attenuates inflammation (6). Thereby the exercise-induced changes in immune function can be positively influenced. A medium-sized banana, gel or 500 ml isotonic sports drink contain, for example, approximately 25-30 g carbohydrates.
7. A probiotic supplement with adequate amounts of bifido bacteria and/or lacto bacteria (beneficial bacteria for the gut flora) may possibly be beneficial during times of increased risk of respiratory tract infections. There is limited evidence that this can reduce the incidence and duration of upper respiratory tract infections (3).
8. Do not share drinking bottles, cups or cutlery with others. Likewise, you should not take a bite of a colleague’s delicious sandwich. These measures help prevent transmission of germs and reduce the risk of infection.
Pro triathlete Sebastian Kienle shares three practical personal tips
- Restful sleep: I always try to sleep from 22.00 to 07.30 o’clock, so a total of more than 9 hours per night. In addition to that I usually take a 30-minute mid-day nap.
- Especially during intense sessions, I make sure to have a sufficient supply of carbohydrates and I drink a Recovery Max with carbohydrates, protein and zinc immediately after training.
- I avoid crowds after an intense training session and I also pay attention to appropriate hand hygiene (washing and disinfecting hands regularly) – this is especially relevant at award ceremonies.
Author: Corinne Mäder Reinhard, International Sports Nutrition Lead at Active Nutrition International. She has a postgraduate diploma in Sports Nutrition from the International Olympic Committee and is a certified Sports Nutritionist from the International Society of Sports Nutrition.
The implementation of the nutrition information and recommendations described in this article is at your own risk and cannot replace personal and individual advice. In particular, for persons under 18 years of age, health restrictions (especially internal medical conditions/illnesses or food intolerances or allergies), during pregnancy or while breastfeeding, a doctor should always be consulted in advance. If complaints arise during the implementation of nutritional measures, a doctor should always be consulted immediately. Active Nutrition International GmbH assumes no liability whatsoever.
(1) Nieman, D.C. (1994). Exercise, infection, and immunity. Int J Sports Med, 15 Suppl 3:S131-41.
(2) Schwellnuss, M. et al. (2016). How much is too much? (Part 2) International Olympic Committee consensus statement on load in sport and risk of illness. Br J Sports Med, 50(17):1043-52.
(3) Walsh, N.P. (2019). Nutrition and Athlete Immune Health: New Perspectives on an Old Paradigm. Sports Med, 49(Suppl 2):153-168.
(4) Gleeson, M. (2020). Eat, Move, Sleep, Repeat. Meyer&Meyer Sport, UK.
(5) Fortes, M.B. et al. (2012). Dehydration decreases saliva antimicrobial proteins important for mucosal immunity. Appl Physiol Nutr Metab, (6) Nieman, D.C. & Wentz, L.M. (2019). The compelling link between physical activity and the body’s defense system. J Sport Health Sci, 8(3):201-217.