Now that the colder months are upon us, it’s time to be proactive with our nutrition for the best immune system defence.
For active people, immune function plays a role not only in fighting off infections but also in promoting tissue repair to recover from exercise and injury (1). To function properly, the immune system requires lots of nutrients – both macro and micronutrients. For an athlete under heavy training load, requirements are even higher putting you at risk of a suppressed immune system if you’re not meeting your needs.
To help you stay well over the colder months, we’ve put together a few key points to keep you firing on all cylinders this winter!
Regardless of the type or intensity, exercise places stress on the body – meaning your immune system has to work harder to build and repair damaged tissue (1). Moderate training loads can be protective against illness. Whereas heavy training loads, particularly with high-intensity sessions, compromise the immune system. Our immune system is down for up to 72 hours following high-intensity training, making this a key time for susceptibility, especially if you train outside where you’re more likely to pick up bacteria from the road (3).
This is where rest and recovery are key to prevent unwanted illness and the decreased performance and sick days that follow! Although these effects are transient in the majority of people, if you’re doing continual intense exercise with minimal rest, your immune system can be compromised long term. Sometimes it’s hard to stop, but don’t ever underestimate the importance of rest days!
Energy Availability refers to the amount of energy left available to support regular body functions, (like your immune response), once energy has been expended on exercise (1). When we don’t have enough energy available to meet our daily demands, we’re fighting an uphill battle already. Even before injury or infection occurs. If you then pick up a bug, the body is not adequately equipped to fight it off and chances are you’ll get sick.
Endurance athletes, in particular, need to ensure their energy intake matches their energy expenditure – a true skill where training volumes fluctuate across the week, months and year. You shouldn’t eat the same thing each day unless you’re training is exactly the same each day (read more about Periodisation HERE). Support your immune function by scaling up on heavier training days and having some strategies in place to eat appropriately for a rest day. A Sports Dietitian is your best point of call for how to do this for your program.
Carbohydrate contributes to meeting our daily energy needs but is often the first thing to be thrown out the window when trying to lose weight. However, training in a carbohydrate-depleted state, or not refuelling properly can be a contributing factor to impaired immunity.
After sustained exercise, there’s an automatic release of stress hormones. These hormones in excess (think cortisol) suppress the body’s immune response immediately following a training session, leaving us susceptible to infectious agents (2). When training in a glycogen depleted state (low carbohydrate stores), this stress hormone release is markedly increased (2). But by ensuring we have enough carbohydrate in our diet to support the demands of training, we can blunt the release of stress hormones and reduce the stress placed on the immune system (2). If you’re constantly getting sick, consider adding carbohydrate during some of your aerobic exercise sessions as this can help to reduce inflammation, support the immune system and decrease recovery time (2).
If you are unsure of your individual carbohydrate requirements, meet with a sports dietitian to calculate the correct amount and timing for your training schedule.
Fruit and vegetables contain a wide range of different micronutrients with varying roles within the body. Many of which are involved in immune function such as zinc, iron, vitamin A, C, D and E (1, 2). Athletes with even mild deficiencies in any of these micronutrients can have an altered immune response (1).
The easiest way to ensure you’re getting enough micronutrients is to consume a wide variety of different fruit and vegetables. Eat the rainbow! If you find yourself always reaching for the same two or three varieties, it may be time to change it up! If you’re in need of some serious inspiration, check out our Foundations of Healthy Eating Module to nail this one!
Unfortunately, it’s not only food you need to watch out for as being dehydrated can also contribute to a compromised immune system. During the colder months, it’s easy to forget to drink but it’s just as important. One of the front line defences of the immune system is immune proteins in our saliva. When we’re dehydrated, the levels of these proteins decreases, meaning our initial defence to bacteria entering through the mouth is also decreased (1, 2). So don’t wait to feel thirsty before you drink up, carry a water bottle with you (everywhere!) and keep sipping throughout the day.
Like everything else, there’s no magic pill to 'boost' your immunity. Be cautious of anyone peddling magic pills and potions that claim to do this! Plan rest days and some lighter training weeks, eat a variety of fruit and vegetables and ensure you’re meeting your energy and carbohydrate requirements. Sleep well, wash your hands regularly, especially before eating and stay well this winter.
If you're looking for more information to help support your immune system - check out our Stay Healthy During Isolation online course!
It covers everything you need to know to maximise your health and stay well in a time where having a robust immune system is key!
(1) Burke, L., & Deakin, V. (2015). Clinical Sports Nutrition (5th ed.). North Ryde, NSW: McGraw-Hill.
(2) Gleeson, M., Nieman, D., & Pedersen, B. (2004). Exercise, nutrition and immune function. Journal of Sports Sciences, 22(1), 115–125. doi:10.1080/0264041031000140590
(3) Seher Çağdaş Şenişik. (2015). Exercise and the immune system. Turkish Journal of Sports Medicine, 50(1), 11–20.
(4) Nutrition and the Immune System. (2018). Nutrition Health Review. 118(1), p13.
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