As temperatures drop and the flu season still lingers, ensure you stay healthy by maintaining a nutritious diet. Learn valuable tips from a nutrition expert to help boost immunity and fend off cold and flu this winter.

According to Bonnie Taub-Dix, a registered dietitian and nutritionist from New York City, healthy eating should be the focus all through the year. Still, specific care should be given in winter, when cold, flu and other viruses are more prevalent.

If you are wondering about the foods to incorporate into your daily routine, Taub-Dix recommends including immunity-boosting food, those rich in vitamin C, omega-3 fatty acids and lean protein.

"Foods that help support a healthy immune system are those that have antibacterial properties like garlic and ginger, those that are rich in vitamins and minerals like a bounty of colorful fruits and veggies with an emphasis on those high vitamin C like citrus fruit. Seafood provides omega-3 fatty acids, important for immune health, and an important source of lean protein. Protein is key in keeping your immune system strong," Taub-Dix told Medical Daily.

"To support your immune system it's particularly important to focus on foods that provide vitamin C (citrus fruits and juices, broccoli, baked potato, bell peppers, tomatoes, strawberries), vitamin A (sweet potato, carrots, leafy greens), vitamin E (almonds), omega-3 fatty acids (fatty fish) and garlic, ginger, turmeric. I'd also add some yogurt to help support gut health," she explained.

Consider adding warm soup brimming with antioxidant-rich vegetables and lean protein to your diet. Additionally, incorporate herbal teas with immune-supporting properties like elderberry, echinacea, turmeric, peppermint and chamomile.

But don't wait until you are sick to include healthy foods or supplements into the diet, Taub-Dix said. Having a habit of taking these items regularly can help you build strength and immunity throughout the year.

While certain foods can help in combating infections by boosting the body's immunity, some others, such as alcohol and those high in sugar have the potential to weaken the immune system.

"Although there are no foods that could cause you to catch a cold or flu — certain foods are not going to help you stay strong and support your health. If I had to pick any foods it would be those high sugar and lacking in valuable nutrients. Alcohol could also depress your immune system especially if it takes the place of healthier foods and beverages. Perhaps just as important is thinking about having healthier habits in general, like getting enough sleep and washing your hands regularly," Taub-Dix said.

When a person gets sick, getting plenty of rest and sleep is equally essential as vitamins and supplements that support immunity.

"At the first sign of a sore throat or cough, many people run to take supplements. Although cold care takes more than pills including consuming warm liquids, getting plenty of rest, and getting a good night's sleep, there are some supplements that might help reduce the severity or duration of a cold like vitamin C and zinc. Some people rely on echinacea but studies have shown mixed results as to whether it can be relied upon. Moreover, echinacea might interfere with certain health conditions such as autoimmune disorders," she added.