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What is the Immune System?
The immune system is complex and very important for our survival, yet many people don't understand it and only vaguely know of its existence. As a result, they sometimes completely ignore it.
Here are three definitions for the Immune System:
"The bodily system that protects the body from foreign substances, cells, and tissues by producing the immune response and that includes especially the thymus, spleen, lymph nodes, special deposits of lymphoid tissue (as in the gastrointestinal tract and bone marrow), macrophages, lymphocytes including the B cells and T cells, and antibodies." [Merriam Webster Dictionary]
"The system that protects your body from diseases and infections." [Wikipedia]
"The immune system, which is made up of special cells, proteins, tissues, and organs, defends people against germs and microorganisms every day. In most cases, the immune system does a great job of keeping people healthy and preventing infections. But sometimes problems with the immune system can lead to illness and infection." [KidsHealth website]
The immune system, then, is our body's first line of defence against disease, infection, germs, bacteria, and viruses.
How Does the Immune System Work?
When something foreign in the body is detected, the immune system goes to work. Several types of cells work together to recognize anything that doesn't belong in the body. These cells help to produce what are known as antibodies 2.
Antibodies, which are very helpful in keeping you well, have several jobs:
They can activate as a group and assist in killing bacteria, viruses, or infected cells.
They can neutralize poisonous or damaging substances produced by different organisms.
They get help from other types of cells to destroy antigens.
They stay in the body to fight off foreign substances that return to attack the system. 3
Three Types of Immunity
You are born with innate (or natural) immunity which is a type of general, overall protection, simply because you are a human being. There are germs that affect other species but don't harm us. 4 Dogs and cats, for instance, get diseases that humans don't get, and vice versa.
Innate immunity includes the skin and mucous membranes that line the nose, throat, and gastrointestinal tract. They are there early on — to prevent diseases from even getting into your body. The skin, for instance, will begin the healing process as soon as it is cut — and immune cells on the skin will attack any germs that try to invade.
By contrast to innate immunity, adaptive (or active) immunity develops throughout our lives. This occurs as we are either exposed to diseases or we are immunized through vaccination.
Passive immunity is borrowed and lasts for a short time — antibodies in a mother's breast milk, for instance, will give a baby temporary immunity to any diseases the mother has been exposed to.
It may seem as though some people never seem to get sick while others are always getting sick. That is because everyone's immune system is different — and can change as we get older. Older people may become immune to more germs as the immune system comes into contact with more and more of them throughout the years. But some viruses evolve and change from year to year, making our immunity to last year's flu no longer useful for this year's flu.
Disorders of the Immune System
Disorders of the immune system fall into several categories:
- Primary or Acquired Immunodeficiency Disorders: These occur when a part of the system is missing or not working properly — some people are born with this while others acquire it through infection or drugs;
- Acquired or Secondary Immunodeficiencies Disorders: These usually develop after someone has a disease, but they can also be the result of malnutrition, burns, or other medical problems. Certain medicines also can cause problems with the functioning of the immune system;
- Autoimmune Disorders: The body's immune system attacks its own tissue as though it doesn't belong there — there are 80 types of autoimmune disorders;
- Allergic Disorders: The immune system overreacts in response to an antigen but it is not something that affects everyone — people with asthma, eczema, and seasonal allergies are suffering from overactive immune systems; and,
- Cancers of the Immune System: Cancer happens when cells grow out of control; this can happen in the immune system, just as it happens in other areas of the body.
Can Exercise Help your Immune System?
The good news is that there is some research to indicate that regular, moderate exercise helps the immune system because of the physiological changes which occur during exercise. It is believed that during exercise cells that promote immunity circulate through the system more rapidly. After exercising, the body returns to normal within a few hours. However, it is possible that a regular exercise routine may extend periods of immunity.
"Dr. David Nieman, an exercise immunologist at Appalachian State University, is one of the country’s most respected authorities in this area. One of his studies showed that people who walked at 70 to 75 percent of their VO2max for 40 minutes per day reported half as many sick days because of colds or sore throats compared to people who didn't exercise." 5
The bad news is that there is some evidence that too much exercise may negatively affect immunity. "One study found that 90 minutes or more of high-intensity exercise (marathons, endurance races) makes a person more susceptible to illness for up to 72 hours after working out. Researchers think that during high-intensity exercise, the body produces two hormones, cortisol and adrenaline, that ... temporarily weaken the immune system." 6
Should you Exercise when your Immune System is Compromised?
Most doctors, including Dr. David Nieman (quoted in the previous section), recommend the following regarding exercising when you don't feel well:
- If you have a head cold, you can exercise, but don't overtrain.
- If your illness is systemic — that is, it involves other parts, systems, or organs of the body besides the head — don't exercise. Rest instead.
Generally speaking, the advice from doctors is that exercise is usually acceptable "if your symptoms are all "above the neck." As soon as you have signs of respiratory distress, exercising is probably not a good idea.Some physicians have also suggested that engaging in moderate exercise before getting a flu shot could improve your body’s response to the vaccine and enhance your immunity to the flu.
Three different studies conclude:
- "Marathon and triathlon athletes are particularly vulnerable to increased susceptibility to infection, although susceptibility doesn't automatically lead to infection." 7
- For elite athletes and marathoners, there is some indication that exercise can be more susceptible to upper respiratory infection. 8
- Over-training may also adversely affect the immune system. 9
Taking Care of your Immune System
Harvard Medical School recommends five ways to take care of your immune system. They are:
Good hygiene: Wash your hands often — before preparing or eating food and after using the bathroom; cover your mouth and nose when you sneeze; wash and bandage all cuts; do not pick at healing wounds.
Vaccinations: Many infections can be prevented by immunizations. If you travel, be aware of any vaccinations you require before going. Check with your doctor to find out what vaccinations are appropriate for older adults.
Food Safety: A few simple precautions will prevent you from getting sick from food poisoning. Here are the recommendations from the Harvard Medical School:
- Rinse all meat, poultry, and fish before cooking;
- Rinse all fruits and vegetables before cooking or serving;
- Separate raw foods and cooked foods;
- Never use the same utensils or cutting boards with cooked meat that were used with raw meat.
- Cook foods thoroughly; and,
- Defrost foods in the refrigerator or in the microwave.
Healthy Travel: Make sure you have the necessary immunizations. Avoid getting shots in other countries. Remember that some diseases are more common in other countries than in Canada. Make sure you are familiar with the particular health issues of the country you are visiting.
Clean Water: Generally speaking, we can assume the water we drink in Canada is safe, but it doesn't hurt to know where our water is coming from and what, if anything, is being added to it.
If you travel, consider these safety tips:
- Do not consume ice while traveling. Freezing does not kill all infectious microbes.
- Drink only bottled drinks that have secure caps.
- Boil all tap water before drinking;
- Use bottled or boiled water to brush your teeth;
- Do not eat uncooked vegetables;
- Do not eat fresh, uncooked fruit you have not peeled yourself;
- Avoid dairy products (milk may not be pasteurized;.
- Avoid drinking untreated water from lakes and streams, which can contain disease-causing organisms from human or animal waste. If you must drink the water, bring it to a rolling boil for one minute to reduce the chance of infection.
Most of us are guilty of taking our immune system for granted. When we come down with a cold or the flu, we feel as though our immune system has let us down. But, in truth, it's working hard for us, trying to fight off the virus that is attacking our body and wants to take over.
Those of us who suffer from allergies are perhaps more likely to be frustrated with our immune system as it over-works to fight against whatever it believes should not be in our body,yet is actually not a danger to us.
If you are healthy, your immune system will most likely be healthy. Exercise will "keep it in shape," just as exercise helps other systems in your body as well.
Other articles that may interest you:
- Making Energy: How our Bodies Work
- Medications of all Stripes: Use them with Knowledge
- Metabolism, Calorie Intake, and False Promises: Getting Through the Dieting Maze
I am a BCRPA-certified fitness instructor in Vancouver, BC. I teach four classes at the West End Community Centre in Vancouver, BC, mostly designed for the older adult. The Inevitable Disclaimer: Everything published here expresses only my opinion, based on my training and research. What you do with the information is entirely your own responsibility. I am not liable for any injury you suffer that seems to be related to anything you read here. Always consult your doctor before beginning an exercise program. For other articles, return to the table of contents.
These three dots behave exactly like a footnote. Click on them and you will get more information about the topic. ↩
This gets pretty technical. Antibodies are Y -shaped protein molecules which are produced by B cells as a primary immune defense. Each molecule has a unique binding site that can combine with the site of a foreign antigen, such as on a virus or bacterium. That will disable the antigen and signal help from other immune defenses. ↩
This is also how immunizations prevent certain diseases. An immunization introduces the body to an antigen. It doesn't make someone sick, but it does allow the body to produce antibodies that will then protect the person from future attack by the germ or substance that produces that particular disease. ↩
For example, the viruses that cause leukemia in cats or distemper in dogs don't affect humans. ↩