A handful of habits genuinely reduce your chances of catching a cold, and they’re backed by large-scale research. Handwashing alone cuts the risk of respiratory infections by roughly 16 to 24 percent. Combine that with enough sleep, regular exercise, and a few targeted supplements, and you can meaningfully shrink the number of colds you get each year.
Handwashing and Hand Sanitizer
Washing your hands remains the single most reliable way to avoid catching a cold. A systematic review of eight studies found risk reductions ranging from 6 to 44 percent, with the overall pooled estimate landing around a 24 percent reduction in respiratory infections. The key is frequency: studies that showed the strongest results had participants washing at least four to five times a day, particularly after using the restroom, before eating, and after coughing or sneezing.
For rhinoviruses specifically, the most common cause of colds, alcohol-based hand sanitizer actually outperforms soap and water. In lab testing, soap and water removed detectable rhinovirus from only 31 percent of hands, while ethanol-based sanitizers eliminated it from the vast majority. This doesn’t mean you should skip the sink, but keeping a bottle of hand sanitizer in your bag or on your desk gives you a real advantage when soap isn’t available.
Sleep: The 7-Hour Threshold
Getting fewer than seven hours of sleep per night raises your odds of catching an upper respiratory infection by about 31 percent. A systematic review pooling multiple studies found that the 7 to 9 hour range is the sweet spot. Interestingly, sleeping longer than nine hours was also linked to more infections, though the connection to short sleep was much stronger and more consistent across studies. If you’re someone who routinely gets six hours and “feels fine,” your immune system may disagree.
Exercise at the Right Intensity
Moderate exercise is one of the most effective cold-prevention tools available, and the evidence is surprisingly strong. In one trial, sedentary women who started walking 45 minutes a day, five days a week, cut their sick days nearly in half compared to controls (5.1 days versus 10.8 days of illness symptoms over the study period). Another year-long trial found cold incidence dropped from 48 percent in the control group to 30 percent in exercisers. A large epidemiological study of over 1,000 adults found that people who exercised five or more days per week had 43 percent fewer sick days than those who were mostly sedentary.
The pattern follows what researchers call a J-curve: moderate activity protects you, but prolonged, intense exercise (think marathon training or military drills in extreme conditions) can temporarily suppress immune function and actually increase infection risk. For most people, 20 to 45 minutes of brisk walking or similar aerobic activity on most days hits the protective range without overdoing it.
Zinc Lozenges Shorten Colds Significantly
Zinc won’t prevent you from catching a cold, but starting lozenges at the first sign of symptoms can cut the duration by about a third. A meta-analysis of seven trials found that doses between 80 and 92 milligrams per day reduced cold duration by 33 percent. Higher doses (up to 207 milligrams per day) didn’t provide meaningfully greater benefit, topping out at a 35 percent reduction.
The catch is that dosage matters enormously. Trials using less than 75 milligrams per day of zinc uniformly found no effect at all. The lozenge formulation also matters: zinc acetate and zinc gluconate both work, but lozenges containing ingredients that bind to zinc (like citric acid) can neutralize the benefit. If you’re buying zinc lozenges for cold season, check the label for elemental zinc content and aim for roughly 80 milligrams spread across the day.
Vitamin C: Only for Extreme Exertion
Daily vitamin C supplementation does not reduce how often the average person catches a cold. A Cochrane review pooling data from over 10,700 participants in the general population found essentially zero effect on cold incidence. The risk ratio was 0.97, which is statistically and practically meaningless.
The exception is notable, though. Among marathon runners, skiers, and soldiers exercising in subarctic conditions, vitamin C cut cold incidence in half. If you’re training for an ultramarathon or doing heavy physical work in cold weather, supplementing may be worthwhile. For everyone else, the evidence simply isn’t there, despite decades of popular belief.
Vitamin D Offers a Modest Shield
Vitamin D supplementation provides a small but real reduction in respiratory infections. A large individual-patient-data meta-analysis published in The Lancet found that people taking vitamin D were less likely to develop at least one acute respiratory infection compared to placebo (61.3 percent versus 62.3 percent). That translates to needing to treat 33 people for a year to prevent one infection, which is a modest effect at the population level.
The benefit is most pronounced in people who are deficient to begin with. If you spend most of your time indoors, live at a northern latitude, or have darker skin, your vitamin D levels are more likely to be low, and supplementation is more likely to make a difference.
Probiotics and Green Tea Compounds
Certain probiotics reduce the frequency of respiratory infections, though the effect depends on the strain. A network meta-analysis published in a Lancet journal found that multi-strain probiotics (combinations of Lactobacillus, Bifidobacterium, and other species) reduced respiratory infection incidence by about 10 percent. A specific strain, Bifidobacterium animalis, performed better, cutting risk by 21 percent.
The same analysis found that catechins, the antioxidant compounds found in green tea, matched that 21 percent reduction across five trials. This was rated as high-certainty evidence, making it one of the more robust findings for any nutritional supplement. Whether you get catechins from supplements or from drinking several cups of green tea daily, the data suggests a protective effect worth considering.
Putting It All Together
No single habit makes you cold-proof, but stacking several evidence-based strategies adds up. Washing your hands frequently (and using hand sanitizer when you can’t), sleeping seven to nine hours, and exercising at moderate intensity most days form the foundation. Adding a probiotic with multiple strains or drinking green tea regularly provides an additional layer of protection. Keep zinc lozenges on hand for when symptoms first appear, and skip the vitamin C megadoses unless you’re pushing your body to extremes in cold weather.