The word digest implies something good. If you digest a thought, it means you carefully deconstruct it in your mind. This can lead to a better understanding. When you digest food, you break it down into a form your body can absorb and use as energy. The problem with cigarettes is that it's more about ingestion than digestion. Your body takes in a large amount of chemicals and carcinogens with each puff, and what doesn't leave your mouth or nose through exhalation stays there for a while. Our internal organs, blood and cells simply aren't built to process cigarette smoke.
When you smoke, the first thing that happens is a mix of gases is released around your eyes, nose and throat. This happens within the first few seconds. Your eyes may water, your nose might run and your throat will most likely become irritated. Tiny hairs called cilia work to clean your bronchial tubes and lungs of nasty foreign matter. They're the street sweepers of the body. Smoking paralyzes and can even kill the cilia so they can't sweep. If you smoke, the cilia that you don't kill wake back up and get out the brooms. When smokers wake up coughing, it's because the cilia are hard at work again. Then the first cigarette of the day paralyzes the poor little guys again, and the hacking cough ceases. It's no wonder that smokers in the early days didn't realize it was bad for them. If a cigarette stops the morning cough, it must be a good thing, right?
Deep inside the lungs, cigarette smoke damages the floating scavenger cells that work to remove foreign particles from the lungs' tiny air sacs, called alveoli. A lot of what you inhale turns to tar. This tar isn't unlike what you might use to pave a road or shingle a house. Only about 30 percent of cigarette tar is sent back into the air through exhalation -- the rest sticks to your throat and lungs like saltwater taffy. Besides being disgusting, tar kills healthy lung cells. A pack-a-day smoker ingests a full cup of tar into his or her lungs every year.
The myth of low-tar cigarettes is just that -- a myth. Cigarette manufacturers poke tiny little holes in the filter to "reduce" the amount of tar you ingest. Sounds good, right? Unfortunately, your fingers block most of these holes when you hold a cigarette, and low-tar smokers end up inhaling more deeply to achieve the nicotine hit they crave.
The chemicals in cigarette smoke are pretty much immediately absorbed into your bloodstream. From here they go straight to your heart and from there, everywhere else in your body. Your heart begins to beat faster as soon as you light up, as much as 10 to 25 beats per minute. That adds up to 36,000 extra beats per day. Smoke can also cause an irregular heartbeat, or arrhythmia. The oxygen level in your blood is reduced because the carbon monoxide produced when you smoke tricks the body into thinking that it's oxygen. (For more on this trick, read How does smoking starve your heart of oxygen?.) Problem is, your body's cells still need oxygen, so your heart goes into overtime to supply it.
If you continue to smoke regularly, your senses of taste and smell will slowly fade, thanks to the tar that coats your tongue and nasal passages. You probably won't even realize it's happening and may only notice what you've been missing when you quit. Most smokers who quit report a noticeable change in how their food tastes and smells.