Fauci previously said that for those who have vitamin D deficiency, taking supplements can reduce susceptibility to infection (and Fauci himself takes vitamin D) and that vitamin C is good antioxidant. But Fauci has stressed that supplements are not a silver bullet or a replacement for things like social distancing or wearing a mask.

“If you really want to keep your immune system working optimally, there are things that you do that are normal things,” Fauci told Business Insider Thursday. These science-backed strategies are “much more healthy living than giving yourself supplements of anything.”

Here’s are the simple habits that Fauci recommends:

Sleep

“Get a reasonable amount of sleep,” Fauci told Business Insider.

Studies have shown that people who sleep six hours a night or less are four times more likely to catch a cold than those who sleep seven hours a night. The reason? When you sleep, your body produces proteins that are responsible for fighting infection and reducing inflammation, according to the Mayo Clinic. But if you skimp on sleep, your body has a harder time fending off infection.

Other research suggests that sleep deprivation can impact how well your body responds to a vaccine.

Eat well

“Get a good diet,” Fauci told BI.

There’s evidence that eating a balanced diet that includes a range of vitamins and minerals can help your immune cells function properly. On the flip side, eating a diet of highly-processed foods (think: sugary drinks, cookies, chips and lunch meats) can negatively affect a healthy immune system.

While one specific food can’t boost your immune system, research has shown that nutrients such as vitamin C, vitamin D, zinc, selenium, iron and protein can help immune cells function.

Reduce stress

These are undoubtedly tough times. A survey from July found that 55% of American adults said they were more stressed than in January before the pandemic. But “try to avoid or alleviate severe stress, which we know can sometimes impact the immune system,” Fauci said.

Stress hormones lower your body’s ability to fight infection, making your more susceptible to getting sick. Long-term stress (stress that lasts for a few days to a few years) has been shown to “ravage the immune system,” according to the American Psychological Association.

There are a few doable ways to reduce stress right now. For starters, it’s important to stick to a routine during the pandemic, because it can be grounding during times of uncertainty. Exercise is also a great way to relax when you’re cooped up at home. And mindfulness meditation, an exercise that focuses on observing thoughts and emotions without judgement, is shown to decrease stress and improve focus.