While many people are still waiting for swine-flu vaccine to become available in their area, there is a lot they can do in their own kitchens to help fight off disease and build a strong immune system.
Scientists in the growing field of nutritional immunology are unveiling new evidence of the complex role that nutrition plays in fighting off infectious diseases like influenza. A diet rich in nutrients such as vitamin A, found in colorful fruits and vegetables, and zinc, found in seafood, nuts and whole grains, can provide the critical fuel the body needs to fight off disease, heal injuries, and survive illness when it does strike, experts say.
Scientists are still studying all the complex ways in which nutrients interact with the immune system. There is still much that they don't know about minerals such as zinc, for instance, including how they are absorbed and all the roles they play in the body. But scientists do know that certain vitamins and minerals can improve the body's ability to fight off infection: Studies in healthy elderly adults, for example, have shown an improved immune response to vaccination and fewer infections after receiving extra doses of vitamin E.
哈佛大学公共健康学院(Harvard School of Public Health)研究人员Anuraj Shankar说，为了制造抵抗感染的免疫细胞，人体必须从血液循环系统迅速获取营养成分。如果不摄入足够的维他命和矿物质，就无法制造所需数量的免疫细胞，而制造出来的免疫细胞也可能有问题。这样一来就不可能对感染做出有效的应对。
To create immune cells to fight off a specific infection, the body has to rapidly draw nutrients from the bloodstream, says Anuraj Shankar, a researcher at the Harvard School of Public Health. 'If you don't have an adequate intake of vitamins and minerals, you won't be able to produce the number of immune cells you need, and the immune cells you do produce may be compromised,' Dr. Shankar says. That makes it impossible to mount an effective response to infection, he says.
研究人员警告说，营养不良者可能产生更危险的传染病。北卡罗来纳大学(University of North Carolina)的动物研究表明，在营养状况不良的宿主内，面对虚弱免疫反应的病毒会发生变异，变得更为强大。而一旦出现变异，就算是营养状况良好的宿主也会受到新的恶性病毒影响。北卡罗来纳大学研究人员贝克(Melinda A. Beck)说，许多人或许认为地球另一边的人营养不良不关他们的事，但正是营养不良促使了在全球肆虐的新型传染疾病的出现。
Researchers warn that malnourished people may be a breeding ground for more dangerous infectious diseases. Animal studies at the University of North Carolina show that in a host with poor nutrition, viruses mutate in the face of a weak immune response to become more powerful. And once those mutations occur, even well-nourished hosts are susceptible to the newly virulent virus. 'A lot of people may think malnutrition on the other side of the world isn't their problem,' says Melinda A. Beck, a researcher at the University of North Carolina, Chapel Hill. But malnutrition 'is a driving force in emerging infectious diseases that are spreading around the world,' she says.
The human body doesn't have to be starving to suffer from malnutrition. Studies show that obesity, in addition to its other health risks, may also make people more susceptible to infections like the flu. A diet heavy on processed and fast foods may be low in the vitamins and minerals important for health. And diets that are high in saturated fat appear to actually depress the body's immune response, increasing the risk of infections.
Dr. Beck says studies of mice show that only 4% of lean animals infected with the flu virus die. That compares with a death rate of between 40% and 60% in obese mice infected with the virus. And after a small study showed that obese people vaccinated for the flu didn't mount a strong immune response, the University of North Carolina is expanding its trials to compare vaccination response rates in lean and obese people.
梅约医院(Mayo Clinic)预防和内科专家韩斯鲁德(Donald Hensrud)说，肥胖者一旦生病，其免疫机能可能不足以积聚有效的反应。韩斯鲁德是《梅约医院减肥节食法》（The Mayo Clinic Diet）一书的主编，这本新书提倡通过健康饮食减肥，不限制水果蔬菜的量。
When obese people fall ill, 'their immune function may not be strong enough to mount an effective response,' says Donald Hensrud, a Mayo Clinic specialist in preventive and internal medicine and editor-in-chief of 'The Mayo Clinic Diet,' a new book promoting weight loss through a healthy diet that allows unlimited quantities of fruits and vegetables.
Dr. Hensrud and other experts caution against loading up on supplements to add vitamins and minerals to the diet. While a multivitamin is a good addition to any balanced diet, individual supplements and vitamin pills may not be as well absorbed by the body as nutrients in foods. Some supplements also can have toxic effects in too-high quantities. An excess of zinc, for example, can interfere with absorption of other nutrients, including iron and copper. And too much of the mineral selenium can cause nerve damage and has been linked recently to an increased risk of diabetes.
Scientists have long known that some vitamins, minerals and other nutrients can play a key role in the immune system by acting as antioxidants. These protect and repair cells from oxidative stress, the damage caused by molecules known as free radicals.
Nutritional experts generally agree that the best way to get the right balance of nutrients is a balanced diet that includes plenty of fresh fruits and vegetables, lean proteins and dietary fiber.
Nutrition experts say to boost immunity it is also important to avoid processed foods, and to minimize trans fats and unhealthy saturated fats from animal products and vegetable oils like palm and coconut. Instead, they say, people should eat foods rich in unsaturated fats such as olive oil.