As we head toward winter and into flu season, it seems like a good time to consider the importance of our immune system, and particularly the role of antioxidants in maintaining an effective immune system.
The Immune System – How It Works
Self and non-self
A healthy immune system can recognize the body’s own cells as “self,’’ and foreign cells as “non-self.” When immune defenders encounter foreign cells or organisms with markers that say “non-self,” they quickly launch an attack.
Anything that can trigger this immune response is called an antigen. An antigen can be a virus, or part of a microbe such as a molecule. Tissues or cells from another person (except an identical twin) also carry non-self markers and are defined as foreign antigens; this explains why organ transplants may be rejected.
Autoimmune diseases occur when the immune system mistakes self for non-self, and attacks the body’s own cells or tissues. Examples include some forms of arthritis and diabetes. In other cases, the immune system responds to a harmless substance such as ragweed pollen, resulting in an allergy; the ragweed pollen is an allergen (see the May 2009 newsletter).
Structure of the immune system
The organs of the immune system are located throughout the body, and are called lymphoid organs because they contain lymphocytes, small white blood cells that are key players in the immune system. Lymphocytes originate in the bone marrow (soft tissue in the hollow centre of bones) as do all blood cells. Cells mature in the thymus, located behind the breastbone, which are known as T lymphocytes or T cells (“T” for thymus). B lymphocytes, or B cells mature into plasma cells, which make and release antibodies.
Lymphocytes can travel throughout the body using the blood vessels. They can also travel through a system of lymphatic vessels (carrying a clear liquid called lymph) that closely parallels the body’s veins and arteries. This system includes lymph nodes which are concentrated in the neck, armpits, abdomen and groin. Each lymph node contains specialized compartments where immune cells congregate, and where they can encounter antigens.The spleen is located at the upper left of the abdomen. It serves as a meeting ground where immune defenses confront antigens.
The body’s immune response
Infections range from the common cold to debilitating conditions to life-threatening diseases. Disease causing microbes – pathogens – trying to get into the body must first get past the body’s external defenses, usually the skin or cells lining the body’s internal passageways.
The skin is generally penetrable only through cuts or tiny abrasions. Microbes entering the nose often cause the nasal surfaces to secrete more protective mucus, and can trigger a sneeze or cough reflex to force the microbes out. The stomach contains a strong acid that destroys many pathogens that are swallowed with food.
If microbes survive these defenses, they then have to find a way through the walls of the digestive, respiratory, or urogenital passageways to the underlying cells. These passageways are tightly lined with epithelial cells covered in a layer of mucus, effectively blocking the transport of many pathogens into deeper cell layers. Mucosal surfaces also secrete immunoglobulin A (IgA), which is often the first antibody to encounter the invading microbe. Underneath the epithelial layer, a number of other types of immune cells each lie in wait for specific types of microbes.
How Can We Care for Our Immune System?
It’s important to keep our immune system working well, and to know how we can help it function better. A number of key strategies for general good health are very important:
- Sufficient exercise – Keeping fit and active helps the body to circulate lymph throughout the body. Thirty minutes of moderate exercise a day can help the immune system to perform its job efficiently.
- Healthy and balanced diet – Good nutrition is fundamental to strengthening the immune system (see March 2009 Newsletter). Avoidance of sugar and ‘bad’ (saturated or trans) fats is important.
- Sufficient amounts of quality sleep – Too little sleep or poor quality sleep weakens the immune system, making us more susceptible to disease.
- Good hygiene habits – One of the best ways to maintain our health is to stop potentially harmful cells from entering the body mainly through the eyes, mouth and nose. Of course, the best thing we can do is to wash our hands regularly, especially before eating and after using the toilet.
- Emotional health – It’s important to find ways to reduce stress levels and learn to relax! Ongoing stress places a strain on the immune system. Laughter has positive effects on the immune system. Other stress reducing activities such as yoga and meditation are helpful.
- Healthy weight – Being either overweight or underweight can adversely affect the body’s ability to fight illness. Note that yo-yo dieting also has a negative impact on the immune system.
- Practice prevention – Look at your family’s and your own medical history to see where there are weaknesses, and take necessary steps to prevent future illness. Take an active role in, and look after all aspects of your health.
In particular, antioxidants can play an important role in dealing with another threat to our immune system – oxidation, and the formation of free radicals.
A common example of oxidation is a slice of apple turning brown when exposed to air. However, when the apple is dipped in water containing lemon juice (an antioxidant), it will not turn brown – the oxidation is prevented.
Free radicals are natural by-products of oxygen metabolism in the body that may contribute to the development of chronic diseases such as cancer and heart disease. Antioxidants work by significantly slowing or preventing damage from oxygen caused by free radicals that can lead to cell dysfunction and the onset of disease. Antioxidants may also improve immune function and thereby lower our risk for infection and cancer.
Fruits and vegetables are major dietary sources of antioxidants. Common antioxidants include beta-carotene, lutein, lycopene, selenium, vitamin A, vitamin C and vitamin E. There are many, many more. Besides benefitting many diseases, they can also slow down the aging process. A few examples follow:
- Broccoli contains lutein which has been shown to reduce the risk of the “wet” type of macular degeneration. It contains phytochemicals that may have cancer-fighting properties.
- Carrots contain beta-carotene which is not only good for the eyes, but has also been demonstrated to reduce the likelihood of dying from cardiovascular disease by 20%.
- Dietary flavenoids, a type of antioxidant, may help keep your brain sharper as you age. This provides us with yet another reason to eat lots of fruit and vegetables.
- Selenium may also help protect the aging brain, decreasing cognitive decline. Foods high in selenium include seafood, lean meat and poultry, low-fat dairy products and whole grains.
- Pomegranate and mangosteen juice have higher antioxidant activity than many other fruit juices. A study showed that regular consumption of pomegranate juice may serve to both prevent and reverse atherosclerosis, a major component of cardiovascular disease, as well as lower blood pressure and reduced oxidation of LDL (‘bad’ cholesterol).
- Green tea may lower the risk of colorectal cancer, according to a study of Chinese women. Those who reported regular green tea drinking at the beginning of the study were 37% less likely to develop colorectal cancer, and those who were life-time green tea drinkers had a 57% lower risk.
- Antioxidants from dark, leafy greens protect against cataracts – this includes spinach, kale and collard greens, which contain the antioxidants lutein and zeaxanthin. Exposure to ultraviolet radiation from sunlight and oxidative stress are main risk factors for cataracts.
I can recommend supplements that are rich in a wide variety of antioxidants – please feel free to contact me at email@example.com. Also, please see the September Newsletter for information on Silver Shield, should your immune system need help, whether it’s dealing with a virus or bacteria.
The suggestions and recommendations in this newsletter are not intended to be prescriptive or diagnostic. The information is accurate and up to date to our knowledge, but we are not responsible for any errors in our sources of information.
References and Notes:
- National Institute of Allergy and Infectious Diseases. Understanding the Immune System – How it Works. U.S. Department of Health and Human Services, National Institutes of Health. NIH Publication No. 07-5423, 2007.
- Immune system boosters. http://www.nativeremedies.com/ailment/immune-system-boosters-info.html
- Dietary Supplement Fact Sheet: Selenium. Office of Dietary Supplements, NIH Clinical Center, 2009. http://ods.od.nih.gov/factsheets/Selenium_pf.asp
- What is an antioxidant? American Dietetic Association. 2006, http://www.eatright.org/cps/rde/xchg/ada/hs.xsl/home_9660_ENU_HTML.htm
- Broccoli and beyond! Tufts University Health & Nutrition Letter. 2008;26(4):4-5.
- To cut risk of heart-disease death, try eating more carrots. Tufts University Health & Nutrition Letter. 2008;26(2):8.
- Dietary flavenoids may help keep your brain sharper as you age. Tufts University Health & Nutrition Letter. 2007;25(7):6.
- Selenium may help protect aging brain. Tufts University Health & Nutrition Letter. 2007;25(3):1-2.
- Aviram M, Rosenblat M, Gaitini D et al. Pomegranate juice consumption for 3 years by patients with carotid artery stenosis reduces common carotid intima-media thickness, blood pressure and LDL oxidation. Clin Nutr 2004;23:423-433.
- Aviram M, Rosenblat M, Gaitini D et al. Corrigendum to “Pomegranate juice consumption for 3 years by patients with carotid artery stenosis reduces common carotid intima-media thickness, blood pressure and LDL oxidation” [Clin. Nutr. 23 (2004) 423-433] Clin Nutr 2008;27:671.
- Ross SR. Pomegranate – Its role in cardiovascular health. Holist Nurs Pract 2009;23:195-197.
- Green tea may lower colorectal cancer risk. Tufts University Health & Nutrition Letter. 2007;25(7):8.
- Antioxidants from dark, leafy greens protect against cataracts. Tufts University Health & Nutrition Letter. 2005;23(1):2.