Americans spend $3.5 billion yearly on doctor's visits and nonprescription treatments for their one billion yearly colds, many caused by viruses such as the rhinovirus.

Here are 10 simple, smart, and inexpensive ways you and your family can shorten the length and severity of a cold or flu by increasing the strength of your virus-fighting immune system.

This is the season to be happy, jolly, and merry — not miserable with a cold or flu!

1. Don't eat a lot of dairy. Yes, foods like milk and cheese are filled with bone-building calcium. But their proteins can also make existing phlegm thicker and more irritating to the throat and sinus passages, which worsens uncomfortable upper respiratory symptoms like stuffiness and coughing, and sets the stage for a post-cold throat or sinus infection. It's okay to have some dairy, but don't overdo it during colds.

2. Skip the soda. The nine teaspoons of sugar in the average 12-ounce can of soda suppresses immune function by 30 percent for up to three hours — just the opposite of what you want to do when you have a cold or flu.

3. Use a nasal rinse. Coughing out mucus or blowing your nose is your body's way of getting rid of billions of bacteria and viruses so your immune system doesn't have to kill them in hand-to-hand combat. One easy way to help your body get rid of those bugs is with a nasal rinse, which washes out more than 90 percent. You can rinse your nose with a neti pot from your local health food store or drugstore, a product that will likely include the salts to make the rinse. Or you can make the rinse at home, either sniffing it from the palm of your hand, or (lying down) squirting an eyedropper of the rinse into each nostril. After rinsing your nose, blow gently. A recipe for the homemade rinse is to mix 1/2 teaspoon salt per cup of lukewarm water. You can add an optional pinch of baking soda to make it more soothing.

4. Drink a lot of water. Drinking warm water (hot tea or hot water with a squirt of lemon for flavor) loosens the mucous, so it can be coughed out.

5. Inhale steam. This is a great tip for colds that have turned into bronchitis. Just take a hot shower, and take a few deep breaths. This will loosen the mucous so you can cough it out.

6. Suck on zinc lozenges. An analysis of several studies shows that using zinc lozenges during a cold can reduce its duration by 42 percent — in other words, the length of a typical cold is cut nearly in half. The keys to cold-shortening success when using zinc lozenges are the type and amount used. Use zinc acetate. And suck on lozenges that deliver at least 70 mg of zinc a day.

7. Keep Oscillococcinum on hand. Oscillococcinum is a homeopathic remedy that can help ease the symptoms of the flu (or the flu-like symptoms of a cold), such as chills, fever, achiness, and just plain old feeling bad (malaise). The remedy also speeds healing. For it to work, you need to take it early in the infection, as soon as you have any symptoms.

8. Don't forget vitamin C — 1,000 to 8,000 mg daily. Even after you've gotten a cold, taking vitamin C still helps and can shorten its duration.

9. Get 8 hours of sleep a night. Experiments show that depriving an animal of sleep suppresses its immune system. Don't experiment on yourself! Your immune system is sleep-sensitive, too. Aim for 8 hours nightly.

10. For cough medicine, try dark chocolate! You heard me right! A two-ounce square of dark chocolate can suppress coughs as effectively as cough medicines. (Dark chocolate contains at least 75 percent cacao.) Use the chocolate if you have a dry cough, which just irritates your lungs. A wet, productive cough that gets rid of mucous shouldn't be suppressed.