How to boost your immune systemWhat

How to boost your immune system
What can you do?
On the whole, your immune system does a remarkable job of defending you against disease-causing microorganisms. But sometimes it fails: A germ invades successfully and makes you sick. Is it possible to intervene in this process and make your immune system stronger? What if you improve your diet? Take certain vitamins or herbal preparations? Make other lifestyle changes in the hope of producing a near-perfect immune response?
The idea of boosting your immunity is enticing, but the ability to do so has proved elusive for several reasons. The immune system is precisely that — a system, not a single entity. To function well, it requires balance and harmony. There is still much that researchers don’t know about the intricacies and interconnectedness of the immune response. For now, there are no scientifically proven direct links between lifestyle and enhanced immune function.
But that doesn’t mean the effects of lifestyle on the immune system aren’t intriguing and shouldn’t be studied. Quite a number of researchers are exploring the effects of diet, exercise, age, psychological stress, herbal supplements, and other factors on the immune response, both in animals and in humans. Although interesting results are emerging, thus far they can only be considered preliminary. That’s because researchers are still trying to understand how the immune system works and how to interpret measurements of immune function. The following sections summarize some of the most active areas of research into these topics. In the meantime, general healthy-living strategies are a good way to start giving your immune system the upper hand.

Immunity in action. A healthy immune system can defeat invading pathogens as shown above, where two bacteria that cause gonorrhea are no match for the large phagocyte, called a neutrophil, that engulfs and kills them (see arrows).
Photos courtesy of Michael N. Starnbach, Ph.D., Harvard Medical School
Adopt healthy-living strategies
Your first line of defense is to choose a healthy lifestyle. Following general good-health guidelines is the single best step you can take toward keeping your immune system strong and healthy. Every part of your body, including your immune system, functions better when protected from environmental assaults and bolstered by healthy-living strategies such as these:
• Don’t smoke.
• Eat a diet high in fruits, vegetables, and whole grains, and low in saturated fat.
• Exercise regularly.
• Maintain a healthy weight.
• Control your blood pressure.
• If you drink alcohol, drink only in moderation.
• Get adequate sleep.
• Take steps to avoid infection, such as washing your hands frequently and cooking meats thoroughly.
• Get regular medical screening tests for people in your age group and risk category.
Be skeptical
Many products on store shelves claim to boost or support immunity. But the concept of boosting immunity actually makes little sense scientifically. In fact, boosting the number of cells in your body — immune cells or others — is not necessarily a good thing. For example, athletes who engage in “blood doping” — pumping blood into their systems to boost their number of blood cells and enhance their performance — run the risk of strokes.
Attempting to boost the cells of the immune system is especially complicated because there are so many different kinds of cells in the immune system that respond to so many different microbes in so many ways. Which cells should you boost, and to what number? So far, scientists do not know the answer. What is known is that the body is continually generating immune cells. Certainly it produces many more lymphocytes than it can possibly use. The extra cells remove themselves through a natural process of cell death called apoptosis — some before they see any action, some after the battle is won. No one knows how many cells or what kinds of cells the immune system needs to function at its optimum level.
Scientists do know more about the low end of the scale. When the number of T cells in anHIV/AIDS patient drops below a certain level, the patient gets sick because the immune system doesn’t have enough T cells to fight off infection. So there is a bottom number below which the immune system can’t do its job. But how many T cells is comfortably enough, and beyond that point, is more better? We don’t know.
Many researchers are trying to explore the effects of a variety of factors — from foods and herbal supplements to exercise and stress — on immunity. Some take measures of certain blood components like lymphocytes or cytokines. But thus far, no one really knows what these measurements mean in terms of your body’s ability to fight disease. They provide a way of detecting whether something is going on, but science isn’t yet sufficiently advanced to understand how this translates into success in warding off disease.
A different scientific approach looks at the effect of certain lifestyle modifications on the incidence of disease. If a study shows significantly less disease, researchers consider whether the immune system is being strengthened in some way. Based on these studies, there is now evidence that even though we may not be able to prove a direct link between a certain lifestyle and an improved immune response, we can at least show that some links are likely.
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Age and immunity
Earlier in this report (see “Cancer: Missed cues”), we noted that one active area of research is how the immune system functions as the body ages. Researchers believe that the aging process somehow leads to a reduction of immune response capability, which in turn contributes to more infections, more inflammatory diseases, and more cancer. As life expectancy in developed countries has increased, so too has the incidence of age-related conditions. Happily, investigation into the aging process can benefit us all — no matter what our age.
While some people age healthily, the conclusion of many studies is that, compared with younger people, the elderly are far more likely to contract infectious diseases. Respiratory infections, influenza, and particularly pneumonia are a leading cause of death in people over 65 worldwide. No one knows for sure why this happens, but some scientists observe that this increased risk correlates with a decrease in T cells, possibly from the thymus atrophying with age and producing fewer T cells to fight off infection. Thymus function declines beginning at age 1; whether this decrease in thymus function explains the drop in T cells or whether other changes play a role is not fully understood. Others are interested in whether the bone marrow becomes less efficient at producing the stem cells that give rise to the cells of the immune system.
Researchers at the University of Arkansas are looking at another aspect of why the immune system seems to weaken with age. They studied cell death in mice. They conducted an experiment to compare the lifespan of memory T lymphocytes in older mice with those of younger mice and found that the lymphocytes in older mice die sooner. This suggests that as the lymphocytes die off, the elderly immune system loses its memory for the microbes it is intended to fight and fails to recognize the microbes when they reappear. The body thus becomes less able to mount a vigorous immune response.
A reduction in immune response to infections has been demonstrated by older people’s response to vaccines. For example, studies of influenza vaccines have shown that for people over age 65, vaccine effectiveness was 23%, whereas for healthy children (over age 2), it was 38%. But despite the reduction in efficacy, vaccinations for influenza and S. pneumoniae have significantly lowered the rates of sickness and death in older people when compared with nonvaccination.
Yet other researchers are looking at the connection between nutrition and immunity in the elderly. A form of malnutrition that is surprisingly common even in affluent countries is known as “micronutrient malnutrition.” Micronutrient malnutrition, in which a person is deficient in some essential vitamins and trace minerals that are obtained from or supplemented by diet, can be common in the elderly. Older people tend to eat less and often have less variety in their diets. One important question is whether dietary supplements may help older people maintain a healthier immune system. Older people should discuss this question with a physician who is well versed in geriatric nutrition, because while some dietary supplementation may be beneficial for older people, even small changes can have serious repercussions in this age group.
What about diet?
Like any fighting force, the immune system army marches on its stomach. Immune system warriors need good, regular nourishment. Scientists have long recognized that people who live in poverty and are malnourished are more vulnerable to infectious diseases. Whether the increased rate of disease is caused by malnutrition’s effect on the immune system, however, is not certain. There are still relatively few studies of the effects of nutrition on the immune system of humans, and even fewer studies that tie the effects of nutrition directly to the development (versus the treatment) of diseases.
There are studies of the effects of nutritional changes on the immune systems of animals, but again there are few studies that address the development of diseases in animals as a result of changes in immunity. For example,

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如何提高你的免疫系统
你能做什么？
总体上，你的免疫系统会保护你不受致病微生物有很大的作用。但有时会失败：生殖成功侵入并让你生病。它是可能的介入这一过程并加强你的免疫系统？改善你的饮食？服用某些维生素或中草药制剂？在产生一个近乎完美的免疫反应，希望其他生活方式的改变？
提高免疫力的想法是诱人的，但这样做的能力已被证明是难以捉摸的几个原因。免疫系统是一个系统，不是一个单一的实体。功能好，需要平衡和和谐。仍有很多研究人员不知道免疫系统的错综复杂和相互联系。现在，没有科学证明直接联系生活方式和免疫功能之间的
。但这并不意味着生活方式对免疫系统的影响不神秘，不被研究。相当多的研究人员正在探索影响饮食，运动，年龄，心理应激，草药补充剂，和免疫反应等因素的影响，无论是在动物和人类。虽然有趣的结果出现，到目前为止，他们还只能算是初步的。这是因为研究人员仍在试图了解免疫系统如何工作和如何解释免疫功能测定。下面总结了一些最活跃的研究领域之一为这些话题。在这期间，一般健康的生活方式是开始给你的免疫系统占上风的一个好方法。

免疫的作用。一个健康的免疫系统能打败入侵的病原体，如上图所示，两个细菌引起的淋病是不匹配的大吞噬细胞，称为中性粒细胞，吞噬和杀死他们（箭头所示）。
迈克尔的照片，斯塔恩巴赫，博士的礼貌，哈佛医学院的
采取健康生活策略
你的第一道防线是选择健康的生活方式。以下的一般健康指南是你可以保持你的免疫系统强壮和健康的最好的一步。你身体的每一部分，包括你的免疫系统功能，更好的保护时，免受环境伤害和支持健康生活策略如：
•不抽烟。
•吃多吃水果，蔬菜，全谷物，低饱和脂肪。
•定期锻炼。
•保持健康的体重。
•控制你的血压。
•如果你喝酒，适量饮用。
•得到充足的睡眠。
•采取措施避免感染，例如经常洗手，彻底烹煮的肉类。
•定期医疗检查测试在你的年龄段和风险类别的人持怀疑态度。