Ah-choo! The cold winter months are here. To help keep your immune system working at its optimal level, it's key to keep up good eating habits and a healthy lifestyle. And part of good eating is incorporating probiotics--also known as "good" bacteria--into your diet. Probiotics are defined as "living microorganisms that confer a health benefit to the host when administered in adequate amounts," according to the World Health Organization. These benefits include improving bodily functions such as immune function, regularity, digestion and detoxification. "A lot of press is given to the 'bad' bacteria, so many people don't realize that some bacteria are good for you and should be consumed on a daily basis," explained Densie Webb, Ph.D., R.D., registered dietitian, columnist and co-author of the book "The Dish on Eating Healthy and Being Fabulous!" Our bodies have their own natural defense mechanisms, which protect us from invading "bad" bacteria and viruses. One major component of the body's defense system is immune function. About 70 percent of the body's immune system is located in the digestive tract, where specialized cells play an important role as a first line of defense against invading bacteria. "Research suggests that probiotics may have a beneficial impact on the function of the intestinal lining and the regulation of critical components of the immune system," said Miguel Freitas, Ph.D., Medical Marketing Manager, The Dannon Company Inc. The ecosystem of bacteria-also known as microflora-that occupies the lining of the intestinal tract also acts as a physical barrier. "Regular consumption of probiotics, therefore, helps regulate the level of 'friendly' bacteria, reinforcing this barrier and maintaining intestinal health," he added. We caught up with Dr. Webb to learn more. Q. How can I incorporate probiotics into my diet? A. There are several delicious fermented products, such as smoothies, yogurts and cultured dairy drinks like DanActive, that contain probiotic bacteria and can easily be incorporated into your daily diet. Not only are they a source of probiotics, they make great calcium-rich snacks, providing about 10 percent to 25 percent of the Daily Value for calcium per serving. Q. Should I only take probiotics when I'm feeling under the weather? A. It's best to help keep your immune system strong all year round. Certain probiotics may help strengthen the body's natural defenses while providing a regular source of "friendly" bacteria. Though benefits vary depending on the type and amount of probiotic bacteria you consume, experts agree that daily consumption of probiotics is the most beneficial. Q. What tips do you have for keeping my immune system strong? A. First, eat a healthful diet that includes lots of fruits and vegetables, which contain plant compounds called phytonutrients that may play a role in boosting immunity. Eat foods like fish that are rich in omega-3 fats, vitamin E-rich foods like nuts, avocados and vegetable oils, and foods rich in zinc (seafood and lean red meat) and vitamin C (oranges, grapefruit, kiwifruit, bell peppers). A daily source of certain probiotics in the form of a cultured dairy product may also help strengthen your body's natural defenses. In addition, exercise regularly, maintain a healthy weight and get plenty of sleep.