Eating for Immunity

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 injury1. 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 supressed 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!

1. Rest and Recovery is Key

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 tissue1. Moderate training loads can be protective against illness by boosting the immune system. 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 road3.

This is where rest and recovery is 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!

2. Avoid Low Energy Availability

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 exercise1. 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. Boost 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.

3. Carbohydrate is Protective

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 agents2. When training in a glycogen depleted state (low carbohydrate stores), this stress hormone release is markedly increased2. 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 system2. 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 time2.

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.

4. Eat the Rainbow

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 iron, vitamin C and D, and zinc1,2. Athletes with even mild deficiencies in any of these micronutrients can have an altered immune response1.

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 earlier blog on how to make veggies tasty!

5. Prevent dehydration

Unfortunately it’s not only food you need to watch out for, 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 decreased1,2. So don’t wait to feel thirsty before you drink up, carry a water bottle with you (everywhere!) and keep sipping throughout the day.

Take Home

Like everything else, there’s no magic pill to boost your immunity. 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 before eating and stay well this winter.

Happy training!

 

References

(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.