Cold and flu season is upon us, with added concerns this year due to the prevalence of the H1N1 virus. To stay healthy, it's a good idea to do everything you can to boost your body's natural ability to fight off infection.

A good place to start is a healthy diet with lots of fresh fruit and vegetables, and plenty of water. Vitamin C helps your body to produce interferon, an important part of your immune system, and stimulates the activity of bacteria-killing cells. Citrus fruits, strawberries and blueberries are well-known sources of Vitamin C, but broccoli, bell peppers, kale, cauliflower, mustard greens and Brussels sprouts are also rich in the nutrient. Beta carotene – found in sweet potatoes, carrots, winter squash and the leafy greens that are also high in Vitamin C – increases the number of infection-fighting cells.

You may also want to add some nutritional supplements on a daily basis. Taking 600-1000 mg of Vitamin C and 200 IU of Vitamin E daily has been shown to strengthen immunity. Zinc, selenium, and Omega-3 fatty acids (such as those that come from flax seed or fish oil) increase the number and activity of white blood cells. Other antioxidant options include oil of oregano, echinacea and olive leaf. Source Naturals Wellness Formula is a powerful combination of vitamins, minerals and herbs designed to boost immunity. Probiotic acidophilus is available in capsules and liquids in adult, children's and infant strengths. Many require refrigeration for maximum potency, but there are also shelf-stable forms that don't require refrigeration if you need an immune boost on the go.

If you're already suffering from flu symptoms, Boiron's Oscillococcinum, a homeopathic medication, can help reduce the severity and duration of flu symptoms, and elderberry extract can also bring you relief. Researchers from the Florida-based Herbal Science Group LLC, writing in the July 2009 issue of the journal Phytochemistry, reported that flavonoids from elderberry extract bind with H1N1 (swine flu) virus, blocking its ability to infect a host. They compared the elderberry flavonoids' antiviral action with those of Tamiflu and Amantadine. Our Healthy Living Department has a number of products containing elderberry extract, including New Chapter Immunity Take Care, Nature's Way Sambucus, Dr. Dunner Sambu Guard and Gaia Black Elderberry Syrup.