Ever wonder why, when a "bug is going around the office," some people get it and some people don't? After all, everyone in the office is exposed to the same germs, so why do some people come down with a fever and sniffles and others seem to be fine? Even among those who do get sick, there can be a huge difference in the length of the illness. Some people are derailed for two weeks, while others seem to be back at their desk in chipper shape in just under three days. Why?

The answer lies in the strength of the immune system. Think of the immune system like the foundation of your house. If the foundation is made of solid, strong materials, it will stand up to everyday challenges.

How the Immune System Works

Our bodies are constantly exposed to challenges every day in the form of pathogens like viruses and bacteria. But our bodies are exquisitely programmed to fight off these invaders. In the simplest terms, the number one job of the immune system is to identify intruders and get rid of them. The immune system attacks infectious organisms and substances that invade our body and cause disease through a series of steps called the immune response.

The Defenders: Leukocytes

The soldiers in this inner defense army are the white blood cells, called leukocytes. Leukocytes are produced and stored in several areas in the body known as lymphoid organs (the spleen, the bone marrow and the thymus gland). You've probably heard of the lymph nodes, another place where leukocytes are stored. (If you've ever had measles, chickenpox or mumps, you've probably felt the effect of swollen lymph nodes.) Those little nodes (the same ones that were swollen when you had the measles) actually filter the lymph fluid that flows through them; the nodes trap all sorts of pathogens (viruses, bacteria and the like), which are then destroyed by the trusty lymphocytes.

The Invaders: Antigens and Pathogens

A foreign substance that invades the body is known as an antigen. When the immune system detects that antigen, B cells are triggered to produce antibodies, and the T cell "soldiers" come in and "wipe up" the antigens that have been identified. Once your body produces antibodies, they continue to exist forever. That's why if you get sick with chickenpox, you're unlikely to ever get it again. (Your body has plenty of antibodies to the chicken pox virus from its previous exposure.) Immunization is the process of introducing an antigen into the body--not to make you sick, but to trick your body into producing antibodies so you will be able to resist a future attack from that particular pathogen.

The system is like an elegant and beautifully designed army whose purpose is to defend you from things that can make you sick. And like any army, it functions best if it's well nourished. That's where nutrition comes in.

Next Up

Essential vitamins, minerals and fats for your diet.

This section helps you understand how good nutrition can bolster your immune system. You'll also learn about foods that can compromise your immune system and keep your white blood cells from doing their job.

Five Supernutrients to Bolster Your Immune System

Getting enough of these five nutrients will help your immune system do its job better.

Vitamin C

When you get sick, the first vitamin you usually think of is vitamin C. But did you know what vitamin C actually does for the immune system? First of all, it increases antibodies (which, as we saw, is one of the ways the body defends against foreign invaders). Second, it increases something called phagocytosis, which is the Pac-Man-like process of "eating up" the bad guys. And finally, it increases chemotaxis, a technical word meaning the speed with which white blood cells travel to the infection. Vitamin C is plentiful in fruits and vegetables, particularly citrus fruits, red peppers, dark leafy greens, strawberries, kiwi, papaya, broccoli, cabbage and cauliflower.

Zinc

If "C" is the "super immunity" vitamin, then zinc may just be the super immunity mineral. Americans' diets are low in this trace element, according to the Journal of the American College of Nutrition, which reported in 1995 that zinc intake has declined among American adults resulting in widespread immune problems. Zinc levels of vegetarians tend to be lower than those of meat eaters because animal products--meat in particular--provide about 70 percent of the zinc in American diets and because the absorption of zinc from plants is lower than that from animal products. The richest non-meat sources of zinc include whole grains, beans, nuts and nut butters and pumpkin and sunflower seeds.

Vitamin A

Vitamin A is another vitamin that's critical for optimal performance of the immune system. A deficiency of vitamin A increases the severity of bacterial and viral infections. Vitamin A (as beta-carotene) is plentiful in almost any fruit or vegetable with a red coloring: carrots, cantaloupe, melon and guava, for example.

Essential Fats

Essential fats play an important role in supporting the immune system. In addition to strengthening your heart and supporting healthy brain function, essential fats actually increase resistance to infection! Essential fats include:

• Omega-3 fats: Found in sardines and cold-water fish like salmon; also found in flax
• Omega-6 fats: Found in evening primrose oil, borage oil, black currant oil and cold-pressed organic vegetable oils.

Garlic

When it comes to immunity, one food is considered a superfood by just about everyone: garlic. Garlic is literally a global remedy and one of the oldest medicinal foods on the planet. Garlic was used during World War II as Russian penicillin--it neutralizes dozens of bacteria, viruses and fungi. It contains strong antibacterial and antiviral compounds that boost your resistance to stress-induced colds and infections. The key to the astonishingly wide range of health benefits in garlic is a compound called allicin, which is only created when the garlic clove is crushed or chopped. Experts recommend crushing a little raw garlic and combining it with your food shortly before serving. It's a turbo-charger for the immune system!

Sugar and Trans Fats

Some foods--like excess sugar and trans fats--depress immunity. Studies have shown that downing 75 to 100 grams of a sugar solution (about 20 teaspoons of sugar, or the amount that is contained in two average 12-ounce sodas) can suppress the body's immune responses. Remember our discussion of leukocytes, the white blood cells that make up the bulk of the body's immune soldiers? Well, the leukocytic index is a measure of how many organisms one white blood cell can eat in an hour. The average leukocytic index in the USA (and remember, "average" is not necessarily very healthy) is about 13.9. Within 15 minutes of eating 100 grams of refined carbohydrates (sugar), the leukocytic index drops to about 1.4! It's hard to come up with better proof of how high sugar intake can depress the immune system!

Turbo-Charge Your Immune System

You can turbo-charge your immune system with nutrition by doing the following:

• Get plenty of essential fats.
• Get plenty of vitamin C on a daily basis--more when you feel a cold coming on.
• Make sure you get plenty of zinc.
• Drink plenty of water--eight full glasses a day is best.
• Eat garlic on a regular basis.
• Take digestive enzymes with each meal if you're over 40.

Moving Forward

We've looked at the immune system from a nutritional standpoint. In Lesson 2 you'll take a look at the way your thoughts, feelings and moods actually impact the performance of your immune system--it's the exciting new science of psychoimmunology.

For now, be sure to complete the quiz and assignment for the lesson, then stop by the Message Board to share questions, thoughts, tips and experiences with your instructors and fellow students.

In the last lesson, you learned how the immune system works and how it can protect you from a host of pathogens which could easily lead to ill health. You also learned how to make it stronger with nutrition. But would you be surprised to know that your thoughts and feelings can do the same thing?

NK Cells and Interleukins

Remember lymphocytes from Lesson 1? Lymphocytes are a particular kind of white blood cell. One special subset of cells are called NK Cells--Natural Killer Cells--which have an extremely important role to play in defending your body against pathogenic intruders. These NK cells are actually the body's first line of defense. They inject invading pathogens with small granules, and they can attack two or more invaders at the same time. The NK cells are stimulated by hormones called interleukins. And interleukins are in turn stimulated when you are:

• Excited
• Happy
• Exercising
• Satisfied
• Pursuing your bliss
• Generally enjoying life

Isn't that amazing? When you're happy, active and engaged, you're actually sending a message to your body to increase the very hormones that stimulate the activity of one of your body's best defense mechanisms! No wonder it's easier to get sick when you're run-down and depressed. What we think, feel and do:

• Affects hormones (endocrine system)
• Affects neurotransmitters (chemicals in the brain that are responsible for how we feel)
• Affects immunity

The Power of Connection

One of the strongest predictors for a long and healthy life is connections with other people. It's long been known that married men live longer than single men, and people with connections in a community--through family, friends, church or any other nexus--live longer and have fewer markers for serious illness. The very act of caring for something outside yourself--even when that something is an inanimate object--can exert a powerful affect on your body's ability to remain healthy.

One well-known study illustrates this dramatically. Researchers gave elderly residents of a local nursing home a houseplant. They told half the residents that they were in control of the plant's care and feeding; the other half were told that a staff person would come into their room and take responsibility for the plant's well-being. Six months later, 30 percent of the residents in the latter group had died, compared to only 15 percent of the group that was responsible for the plant's care. Can you imagine? A 50 percent reduction in death--just due to caring about something outside yourself.

Next Up

Stress and your immune system.

The relationship between stress and immunity is a complicated one. Some stress is actually good for us -- it "primes" us to be stronger and more able to adapt to the little bumps in the road that we all encounter in our daily life, whether those bumps be physical or mental. But continued, unremitting stress depresses our immune system measurably. Stress produces a hormone called cortisol. Cortisol is an essential hormone in our bodies and is also known as the "flight or fight" hormone. Nature designed us to produce cortisol when immediate action was needed--such as when our ancestors had to run from a woolly mammoth or pick up a club and fight a saber-toothed tiger. But a shot of cortisol was meant as a turbo-charger, a way of firing up the body's engine for immediate action. It was never meant to be elevated 24/7. While cortisol is needed for every cell in the body, our overstressed lifestyles produce far more of it than we need. Here's what cortisol does to immunity:

• It destroys T-cells.
• It causes T-cells to be released before they mature.
• It shrinks the thymus gland (one of the essential immune system glands where leukocytes are stored).

The Sources of Stress

There are five main sources of stressors in modern life:

• Biological: bacteria, viruses, yeast, mold, fungi
• Environmental: Noise, lack of sunlight, pollution
• Emotional: Anger, hostility, resentment, fear
• Social: Crowding, crime, prejudice
• Family: Divorce, separation, death, college

Because of the connection between stress and health, stress management should be a cornerstone of a healthy, empowered lifestyle. Finding ways to "lower the temperature" with pleasant activities like long walks, time with friends, warm baths, interaction with animals and so on isn't just relaxation--it's actually making an investment in your health by normalizing your levels of stress hormones.

Next up

Optimism vs. pessimism...and how both affect your immune system.

Although the studies on optimism and immunity don't always show a beneficial effect, by and large most research shows that optimists live longer than pessimists. At one landmark study at the Mayo Clinic in Minnesota, it was found that those with a positive attitude and outlook on life live on average 19 percent longer than those who are miserable. Other research has put the difference in lifespan between optimists and pessimists at a whopping seven years!

"Optimists and pessimists differ markedly in how long they will live." -- Dr. Martin Seligman, University of Pennsylvania, author of Learned Optimism: How to Change Your Mind and Your Life

Optimists have:

• Better immune function
• Higher levels of T-cells
• More active immune systems
• Fewer infectious diseases

Pessimists have:

• Worse immune function
• Lower levels of T-cells
• Twice as many visits to doctors
• Twice as many infectious diseases

So what can you do to strengthen your immune system and extend your life? Here's a list of things that can help you as well as almost anything on the planet.

• Monitor your cynical thoughts
• Examine situations reasonably
• Put yourself in other people's shoes
• Learn to laugh at yourself
• Learn to relax
• Practice trust
• Learn to listen
• Practice forgiveness

Five Golden Rules for a Healthier Immune System

If you want to boost your immune system and live a healthy, happy and long life, follow these golden rules:

1. Take care of yourself with optimal nutrition.
2. Take care of others.
3. Nurture your inner dreams.
4. Share and be generous.
5. Always practice gratitude and forgiveness.

Combined with the five nutritional tactics you learned in Lesson 1, these principles will enhance your everyday quality of life as well as help your immune system do what it's designed to do--defend you!

Moving Forward

We've looked at the immune system from a nutritional standpoint as well as from a psychological point of view. Scientists now believe that our thoughts, feelings and moods actually impact the performance of our immune system, whether positively or negatively. Hopefully, this lesson has given you a lot to think about. Which of the five sources of stress impact you the most? What positive changes can you start making today in your emotional patterns--in other words, how you respond to the stress in your life?

Be sure to complete the quiz and assignment for the lesson, then stop by the Message Board to share questions, thoughts, tips and experiences with your instructors and fellow students.