Cold and flu season or not, knowing how to support your immune system after an illness is critical for getting back to doing the things you love. And for runners — that's running. While a number of factors can help your immune system, good nutrition is at the top of the list. 'Marathoners have a competitive mindset and are used to pushing through a little pain,' said Steve Hertzler, PhD, RD, a senior clinical research scientist at Abbott. 'But when you're sick, you need to take that seriously and focus on rebuilding your immune system with protein, carbs, vitamins, minerals and fluids.' Check out these nutrition tips that will help you recover from illness and get you back to doing those long runs you've been missing. Drink up those fluids fortified with Vitamin D The body is 'stressed' most when dehydrated due to illness. 'The risk of dehydration isn't just from fever and sweating, but also diarrhea and vomiting,' said Hertzler. 'Vitamin D is not naturally found in many foods, but it's important to the immune system; helping your white blood cells move around.' Hertzler said milk and dairy products are fortified with vitamin D, but it's also important for people to get plenty of sun exposure which helps the body naturally produce the vital nutrient. Say 'Yes' to mineral-rich foods Beef, yellowfin tuna, chicken, and hard-boiled eggs are rich in selenium, a mineral that works as an antioxidant to help protect immune cells. Brazil nuts and sunflower seeds are also good sources of selenium. 'Minerals like selenium and zinc are important in hundreds of chemical reactions in the body,' said Hertzler. 'They're known to help the body when it's under stress.' Bring on the dietary fiber Fiber helps feed the healthy bacteria and cells lining the inside of the large intestine, according to Hertzler. 'This is important because about 70% of immune tissue is in the gut and having a healthy gut is important for supporting immune function,' he said. 'The more you understand how the body works the more you're setting yourself up for success,' said Hertzler. Abbott is the title sponsor of the Abbott World Marathon Majors, a series of six of the largest and most renowned marathons in the world: Tokyo Marathon, Boston Marathon, TCS London Marathon, BMW BERLIN-MARATHON, Bank of America Chicago Marathon and TCS New York City Marathon. Click here to learn more. This story originally published on July 13, 2022, and was updated on Mar. 1, 2023.