As the numbers of H1N1 flu infections and fatalities increase, the government is working to stem the spread of the virus with efforts such as public campaigns encouraging people to practice careful personal hygiene and wash their hands frequently. But following these guidelines is sometimes not enough to prevent an infection. Once the virus invades the body, strengthening the immune system is the best way to fight back. People with strong immune systems are less likely to develop serious symptoms when they are infected. Here are some foods which can help bolster the body's immune system. * Kiwi Fruit a Rich Source of Vitamin C Kiwi fruit has high levels of vitamin C which helps to shore up the immune system. Vitamin C encourages the generation of interferon, which limits the growth of viruses and cancer cells. One kiwi fruit contains over 100 mg of vitamin C, 1.4 times the amount found in a lemon, twice that of an orange, and six times that of an apple. In fact one kiwi fruit a day is enough to fulfill the daily recommended intake of vitamin C (60~70 mg). * Ginger and its Active Constituent Gingerol Ginger is effective in killing bacteria that could lead to flu viruses, pneumonia, and bronchitis. According to Yeo Esther, director of the Esther Clinic, ginger's active constituent gingerol is known to inhibit COX-2, an enzyme that causes inflammation. However, excessive intake of ginger can stimulate the secretion of gastric acid, damaging the gastric mucous membrane. Since boiling does not affect its potency, people with weak stomachs should boil ginger before eating it. * Oysters, Beef Good Ways to Consume Zinc Zinc in oysters and beef helps strengthen leukocytes. A U.S. study showed that intake of zinc within 24 hours after developing flu symptoms can help alleviate them. But Dr. Lee Ji-young of GH Clinic warned that consuming too much zinc can actually weaken the immune system, so it is better to avoid zinc supplements and instead have beef, oysters, beans, and squid which are rich in zinc. * Chitosan Abundant in Red Snow Crab Chitosan is recognized by the Korea Food and Drug Administration as a healthy substance which strengthens the immune system. Large amounts of chitosan are found in red snow crabs. According to a study on 800 people by a cancer center in Saitama Prefecture, Japan, chitosan activates NKcells which directly kill viruses and cancer cells. * Mackerel Excellent Source of Omega-3 Fatty Acid Omega-3 fatty acid in mackerel inhibits inflammation and helps activate leukocytes. It stimulates body metabolism and has better effects when it is consumed through fish rather than in plants such as walnuts. To promote body metabolism, it is good to consume two to four grams of omega-3 fatty acid a day. A piece of fresh mackerel contains 0.5 to one gram of the substance. http://english.chosun.com/site/data/html_dir/2009/09/19/2009091900209.html