It’s true that vitamin C can play an important role in immune function. A study published in Nutrients in 2017 noted that vitamin C helps with everything from killing off microbes to clearing away spent immune cells. However, giving yourself high doses of vitamin C doesn’t have any apparent advantage when it comes to staving off colds, according to Harvard Health.

“Emergen-C isn’t your best bet for boosting your immune system,” Christina Belitsky M.S. RPA-C, advanced practitioner lead for Northwell Health-GoHealth Urgent Care, tells Bustle. “Instead, eat real, whole foods, especially leafy greens.” Maintaining a reasonable level of vitamin C in your diet will sustain your immune system much better over time than lots of it in big bursts.

Multivitamins, which contain a range of vitamins, are rarely a bad idea — but Harvard Health points out they’re not likely to make any difference to your immune system unless you’re seriously malnourished. “A good multivitamin is great for your daily routine, but nothing compares to proper sleep hygiene, a balanced diet, and regular exercise,” Belitsky says. A multivitamin will ensure you have enough vitamins to support your health, but it's not likely to make any difference to your immune function.

You’ve probably heard some variation on the idea that drinking tea helps your immune system, or at least makes you feel better when you're sick. One study published in 2011 in Immunology Letters found that a polyphenol found in green tea could help T-cells in mice, but it’s not clear if this happens in humans. “No need to buy pricey beverages labeled as 'immune boosting'," Belitsky says. “Instead, choose water.” Hydration, she says, is a part of good immune functioning, because the immune system relies on the bloodstream to transport its cells around the body, and that becomes hard if you''re dehydrated. Keep a bottle of water around even when you're not thirsty to make staying hydrated a habit.

The idea of boosting immune function makes it seem like the sky’s the limit, but when the immune system is too strong, it can start causing health problems, according to Cedars-Sinai Hospital. This is the root of conditions like autoimmune diseases, where the immune system starts attacking healthy tissue instead of viruses or illnesses. It's also what lies behind the "cytokine storms" that can cause serious symptoms for people with COVID-19; their immune systems over-react to the virus, causing a blast of immune activity that damages tissue and organs. You want an immune system that’s balanced, not one that’s super-powered.

While there’s no way to take a pill or eat a certain food and immediately gain 10 immune system points, there *are* definite ways to influence your immune function over time. “The best way to develop and maintain healthy immunity is to get adequate sleep, eat a balanced diet that emphasizes vegetables and fruits, exercise regularly but not to excess, and stay current on all vaccinations including yearly flu vaccines,” Dr. Mordkin says. All of these can support immune system function by giving it enough fuel and rest, and, in the case of vaccines, building it up to fight specific threats.

Making lifestyle changes over time can help your immune system in the long run, so that it operates smoothly and defeats all those pesky pathogens trying to ruin your day.