Dr. Sam Madeira, NMDThere are plenty of theories about how to “boost” your immune system, especially during cold and flu season, when it seems like everyone around you is sick. Let’s look at a few of the most common ones, true or false, and the habits that actually help year-round.
“Eating more fruits and vegetables keeps your immune system strong.” True.
It isn’t just an old wives’ tale. Fruits and vegetables provide vitamins, minerals, fiber and plant compounds (phytochemicals) that your immune system needs to work well. Aim to “eat a rainbow” every day: different colors bring different nutrients.
“Megadoses of vitamin C will keep you from catching a cold.” False.
For most people, vitamin C doesn’t lower the risk of catching a cold. People who take it regularly may have slightly shorter colds, but starting it after symptoms begin doesn’t appear to help. Your body can’t store vitamin C, and more than 2,000 mg a day can cause stomach upset and diarrhea, and rarely kidney stones.1
A daily multivitamin can fill gaps in an otherwise healthy diet, but it’s no substitute for good food. And more isn’t always better: vitamin A, for example, is stored in the body, and too much can be toxic.
One caution: zinc products sprayed or swabbed into the nose have been linked to a lasting loss of smell, so skip those.
“Getting enough sleep supports your immune system.” True.
Sleep and immunity are closely linked. When you’re short on sleep, you feel run down, and you may be more vulnerable to getting sick. The CDC recommends at least 7 hours a night for adults, with a consistent bedtime and wake time.3 Occasional bad nights are normal; if poor sleep becomes chronic, talk with your doctor. I’ve written more about sleep in Got sleep?
“Covering your cough keeps you from getting sick.” Mostly false.
Covering your cough protects the people around you, which matters. But it does little to protect you unless everyone around you does it too. Germs also live on doorknobs, phones and countertops. Handwashing with soap and clean water helps prevent respiratory and diarrheal infections:2 wash before eating and preparing food, after using the toilet, and after blowing your nose, coughing or sneezing. Try not to touch your eyes, nose and mouth.
“Probiotics can help.” Partly true.
In a review of 23 trials with nearly 7,000 people, those taking probiotics were less likely to catch colds and other upper respiratory infections, though the evidence is still low to moderate in quality.4 Read more in How probiotics can help your immune system.
“A positive outlook is good for your health.” Likely true.
Chronic stress takes a toll on the body, and many people notice they get sick more often during stressful stretches. Managing stress, staying connected with people you care about and finding reasons for optimism are good for your mental health, and likely your physical health too.
The bottom line
There’s no magic pill for immunity. The habits that help are the everyday ones: good food, enough sleep, regular movement, clean hands and less stress. If you seem to catch everything that goes around, or never quite recover, that’s worth a closer look with your doctor.
Want to go further?
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This article is general education, not medical advice, and does not create a doctor–patient relationship. Talk with your own doctor before changing your diet, supplements or medications.