The body must contend with constant attacks by microscopic organisms. In order to defend against this onslaught, it deploys a wide range of defenses that together are called the immune system.
People with diseases that cause immune deficiency, such as AIDS, fall victim to infectious microorganisms that a healthy person could ward off easily. However, even healthy people get sick from time to time, victims of infections that manage to sneak by the defenses. And some apparently healthy people nonetheless get sick quite often.
If you fall into this latter category, you may wish to find treatments that can strengthen your immune system. Unfortunately, this is easier said than done. To explain why it is so difficult to improve resistance to illness, we need to delve a bit deeper into the nature of immunity.
The immune system consists primarily of various types of white blood cells and the chemicals that they manufacture (such as antibodies). In certain conditions, such as AIDS, many of these white blood cells are damaged or dead. In such cases, the term immune deficiency is clearly appropriate. The circumstance is analogous to an army that lacks, say, guns.
However, careful examination of most people who get frequent colds (or bladder infections or herpes attacks, for example) fails to turn up any visible deficits in the immune system. They have all the immune cells and antibodies they need in roughly the right amounts, and all the various parts appear to work just fine. So why do such people get sick so often? The short answer is, we do not know.
One can hypothesize that in some people the immune system fails to function properly for a relatively subtle, invisible reason, much as a well-equipped army might lose its fighting form due to apathy or disunity. However, keep in mind that even people who develop frequent colds manage to fight off thousands of other infections every day. (If they did not, they would be dead.)
For this reason, an alternate hypothesis comes to mind: that over-susceptibility to a particular type of infection may be caused by something more specific than general immune weakness. As an example, chronically inflamed mucous membranes might lead to frequent colds, since an inflamed mucous membrane may be more porous to cold viruses. Similarly, a woman’s bladder wall might allow particularly easy attachment of bacteria, leading to frequent bladder infections.
In reality, though, these are all speculations. We truly do not know why some people frequently develop minor infections. For this reason, it is very difficult to find a way to fix the problem.
Many natural products are said to boost general immunity. However, while we can scientifically study the effect of a single treatment on a single illness, at the present state of knowledge there is no way we can even know that a treatment strengthens the immune system in general.
Scientists can measure the effects of an herb on individual white blood cell types and note changes in activity, but they do not know how to interpret the results of those measurements as a whole. After all, the immune system is a system, and systems are notoriously complicated to analyze. Current knowledge does not allow us to predict the ultimate effect of fine changes in the parts.
To acknowledge this limitation, scientists tend to use the term immunomodulatory rather than immune-stimulating when they refer to a substance that causes measurable alterations in immune function. This terminology notes a change (modulation), but does not jump to conclusions regarding whether that change is good, bad, or indifferent.
Hundreds or thousands of herbs have immunomodulatory effects, so many that we will make no attempt to list them here. In many cases, these may represent nothing more than the body’s reaction to the herb as a foreign presence—an immune reaction to the herb itself, in other words, with no special benefits. In some cases, observed immunomodulatory effects could indicate an alteration in immune function with potential benefits under certain conditions, but it is as yet impossible to know.
Theoretically, it is possible that some natural substance could boost all aspects of immunity. However, if it did, it would be a highly dangerous substance! The immune system is balanced on a knife edge. An immune system that is too relaxed fails to defend us from infections; an immune system that is too active attacks healthy tissues, causing autoimmune diseases. A universal immune booster might cause lupus, Crohn’s disease, asthma, Graves’ disease, Hashimoto’s thyroiditis, multiple sclerosis, or rheumatoid arthritis, among other problems.
Rather than an immune booster, one might rather prefer a treatment that somehow fine-tunes the immune system. Does such a treatment exist? No one really knows, although claims abound.
There is no doubt that good general nutrition is necessary for strong immunity. However, excessive intake of some nutrients ( zinc, for example) may weaken immunity. For information on which nutrients might be worth taking to improve your nutrition, see the article on general nutritional support. In that section, we also discuss some specific scientific evidence indicating that multivitamin/multimineral supplements may help certain people stay well.
A number of herbs and supplements have shown promise for preventing or treating certain specific infections. For more information, see the articles on bladder infection, colds and flus, diarrhea, fungal infection, herpes infection, middle ear infection, and vaginal yeast infection.
Immunizations are a widely used method for strengthening the immune response to specific illnesses, such as influenza. However, some people (especially seniors) may not respond adequately to immunizations. Certain natural products, such as ginseng, vitamin E, and multivitamin/multimineral supplements may enhance the response.
Echinacea is widely hyped as an immune strengthening herb, but current evidence suggests that regular use of echinacea does not help prevent colds or other infections.2-4 (Echinacea may, however, help colds that have already begun.)
The fungi products active hexose correlated compound (AHCC), coriolus versicolor, maitake, reishi, and shiitake are widely believed in Japan to help support the immune system during cancer treatment. However, there is no reliable evidence to indicate that they are in fact effective.
Substances that enhance the growth of “friendly” bacteria in the large intestine have been studied for their favorable effects on the immune system with mixed results. Probiotics (eg, acidophilus) consist of various bacterial species capable of rebalancing the healthy population of bacteria in the gut. Certain types of starches, called prebiotics, are not fully digested, and therefore, remain in the intestine and “feed” healthy bacteria. There is some evidence that probiotics and, to a lesser extent, prebiotics may lead to a reduction in allergic symptoms and possibly minor infections, especially in children.
There is little doubt that if you live a healthy lifestyle with good nutrition and plenty of exercise, you will approach more closely a state of optimum health. Keep in mind, however, that the key is moderation. Too much exercise (as in marathon running) can weaken the immune system, leading to infections. (If you wish to engage in heavy endurance exercise, vitamin C, beta-sitosterol, and glutamine have shown some promise for preventing the “post-marathon sniffle.”)
Although it is commonly said that high levels of sugar intake weaken immunity, there is no meaningful evidence to support this view. Similarly, while severe alcohol abuse clearly damages immune function, there is no evidence that moderate alcohol consumption increases risk of infections.
Does getting cold cause colds? Possibly, but it has not been proven.
There is also no reliable evidence that reducing intake of dairy products will prevent respiratory infections.
Various alternative therapies are said to be able to enhance overall health and thereby prevent illness in general. These include methods such as acupuncture, Ayurveda, chiropractic spinal manipulation, naturopathy, Reiki, Tai Chi, Therapeutic Touch, traditional Chinese herbal medicine, and yoga. However, there is as yet little to no meaningful scientific evidence to indicate that these methods have any specific positive effect on immunity.
1. Kaleida PH, Casselbrant ML, Rockette HE, et al. Amoxicillin or myringotomy or both for acute otitis media: results of a randomized clinical trial. Pediatrics. 1991;87:466-474.
2. Grimm W, Muller H. A randomized controlled trial of the effect of fluid extract of Echinacea purpurea on the incidence and severity of colds and respiratory infections. Am J Med. 1999;106:138-143.
3. Vonau B, Chard S, Mandalia S, et al. Does the extract of the plant Echinacea purpurea influence the clinical course of recurrent genital herpes? Int J STD AIDS. 2001;12:154-158.
4. Turner RB, Riker DK, Gangemi JD. Ineffectiveness of echinacea for prevention of experimental rhinovirus colds. Antimicrob Agents Chemother. 2000;44:1708-1709.
Last reviewed December 2015 by EBSCO CAM Review Board
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