The best defense is a good offense, and staying healthy during the holiday season starts with preparing your body to fight back. Colds and flu are more common in winter as people gather indoors and viruses spread more easily. Experts say optimizing your immune system with the right foods and supplements can help reduce your risk of illness.

“Fall and winter are the most common seasons for contagious diseases like the cold and flu,” says David Friedman, an award-winning clinical nutritionist. “Viruses thrive in cooler, drier air, and people spend more time indoors in close contact with others. That gives germs a much shorter journey from person to person.”

Certain foods and supplements can help strengthen your immune defenses during the holidays.

Citrus fruits such as oranges, grapefruits, lemons, and limes are rich in vitamin C, a nutrient known to support immune function. Vitamin C helps stimulate the production of white blood cells that fight infection and acts as an antioxidant that protects cells from damage, according to Verywell Health. Including citrus fruits in your daily diet may help reduce the severity and duration of colds.

Vitamin D also plays a key role in immune health. Friedman notes that many people get less sunlight during winter months, limiting the body’s ability to produce vitamin D naturally. Low levels of vitamin D have been linked to an increased risk of acute respiratory illnesses. Good food sources include fatty fish such as salmon, sardines, herring, and mackerel, as well as red meat, liver, and egg yolks. During winter, supplementation of 1,000 to 4,000 IU per day can help maintain healthy blood levels.

Garlic is another immune-boosting staple with antiviral, antibacterial, and antifungal properties. Research shows that taking a daily garlic supplement can significantly reduce both the number of colds and the length of symptoms compared with a placebo, Friedman says. “Garlic is part of my daily regimen, and I credit it for why I never get a cold or the flu,” he tells Newsmax. Recommended amounts include one 300-milligram tablet of dried garlic powder taken twice daily or 7.2 grams of aged garlic extract per day.

Vegetables are essential for immune health, particularly leafy greens, carrots, onions, cauliflower, beets, squash, and seaweed. Sprouts, which are young vegetable plants, may offer even greater benefits. They are packed with immune-supporting compounds such as sulforaphane and isothiocyanates.

Zinc is another important nutrient for fighting infections. Friedman points to multiple randomized, placebo-controlled trials showing that taking zinc soon after cold symptoms begin can reduce both their duration and severity. Zinc also helps the immune system combat invading bacteria and viruses, and some studies suggest it may interfere with viral replication. Friedman recommends zinc picolinate, which research shows is better absorbed by the body. The recommended daily intake is eight milligrams for women and 11 milligrams for men.