One of the reasons why large-scale studies are inconclusive is that while most people do not experience any benefits, there are outliers. “If you’re eating a healthy diet, adding vitamin C is not going to do a whole lot,” says Karen Duus, PhD, professor of microbiology and immunology at Touro University Nevada. However, for people with specific documented nutrient deficiencies, supplementing can help pick up the slack. “There are certain supplements that have proven effects when there’s a deficiency,” says Ernst von Schwarz MD, PhD, clinical professor of medicine at UCLA.
Ultimately, it’s kind of like saying supplementing with insulin can boost your health—if you’re diabetic. Most people are not diabetic, and a vitamin C deficiency is even less common. “We almost never see vitamin C deficiency in the average American,” says Purdy.
If you focus on one thing, make it a healthy diet
Research has consistently failed to show that nutritional supplements can be used as a replacement for the nutrients we get from eating whole foods. Of course, science has a hard time competing with marketing fueled by an approximately $430 billion global supplement industry. Nonetheless, as the saying goes, you can’t supplement your way out of a bad diet. Not only that, but maintaining a healthy, balanced diet is also critical for supporting gut health, which may well be the most important factor in immunity.
“Immune health and the gut microbiome are deeply intertwined; around 80% of your immune system resides in the gut,” says Dr. Gioffre. “When your gut is out of balance, your immune system becomes less effective at fighting off invaders, leaving you more vulnerable to infections and illness. Supporting your gut health is one of the most important things you can do to strengthen your immune system.”
“Just like a mucus membrane in your nose, your gut is a line of defense,” explains Dr. Purdy. “It’s an entry point into your body.” Truth be told, immunity is just one of the mission-critical systems your gut plays a role in regulating, alongside things like brain function, metabolism, and mental well-being. Just another reason to prioritize a wholesome diet with plenty of fruit and vegetables.
That said, nailing the other major pillars of well-being like movement and sleep will also help you not get sick.
Vaccinations are not designed to prevent you from getting sick (but you should still get them)
Another one of the biggest misconceptions that people have during cold and flu season is that the flu shot is intended to shield you from getting the flu. Inevitably, every year a bunch of people get sick and decry the shots as being ineffective. We saw the same thing happen when the first Covid vaccines began rolling out. “People think that vaccines are to keep you from getting sick at all, but they’re actually not,” says Dr. Duus.
“What they are doing is keeping the immune system updated so that if you do get exposed to something that’s going around, like Covid or the flu, the vaccines will make sure that if you do catch it, it doesn’t kill you. That’s what vaccines are really good at. Making sure whatever it is doesn’t kill you,” she says. “In many cases they do help keep you from actually having symptomatic disease, and that’s great, but that’s really not what they are ultimately designed to do.”
“What you’re doing is you’re providing your body the opportunity to make antibodies before you come into contact with the virus,” says Dr. Purdy. “So, again, instead of ‘boosting’ immunity, it’s more about just readying your defenses and making sure you’re prepared.”
