From your first moments on earth to your golden years, the 37 trillion cells that make up your body are in continuous flux, constantly multiplying.
Your body creates 2 million new red blood cells every second, replacing dead cells and nourishing your tissues.
Your muscle cells regenerate as you move. The lining of your gut is constantly shedding and regrowing. And every month or two your skin cells completely turn over.
But all that constant growth comes a cost.
To continuously multiply, your cells have to divide. When they do that they copy your genes — all 3 billion letters of your genetic code.
Cells copy your genes really accurately. There are even special proteins that check for errors and fix mistakes.
But during the copying your cells do make occasional errors, known as mutations.
Things outside your body causes mutations too.
Like smoke from cigarettes or bad air quality. That can cause mutations in the lungs and many other tissues including the mouth, kidneys, and bladder.
Skin cells suffer mutations caused by uv radiation from the sun
and alcohol causes lots of mutations, too.
So within our dynamic bodies, trillions of errors, those mutations, accumulate in our genes every day.
While the vast majority of the mutations might go unnoticed, some mutations build up and cause cells to keep dividing out of control. This is what we call cancer.
Remember those proteins that check your genetic code for errors?
If mutations happen on the genes for those proteins, more errors get through, allowing faulty cells to copy like crazy.
Most cells can recognize if they’re malfunctioning, and actually kill themselves to protect the body.
If mutations harm the genes that drive that cell suicide, cells can also multiply unchecked.
Scientists say when several of those mutations occur at once, cells can form tumors.
A tumor a quarter inch in size is made of hundreds of millions of cancer cells.
Given the constant threats to our cells, what prevents us from being full of tumors?
First, you can thank your amazing immune system. It finds and destroys cancer cells throughout the body.
While you’ve been watching this video, in fact, your immune system probably detected and killed scores of malfunctioning cells.
Then there’s benign tumors. They don’t spread and cause few problems.
When cancers become malignant and spread to new tissues, they do the most harm.
There are more than one hundred types of cancer.
It’s a double-edged sword: Our constantly dividing cells, throughout our bodies, make us who we are. It’s how we grow, heal, and age.
But cancer is so common and devastating because it hijacks that essential process.
The big challenge scientists are working to answer is to understand how cancer does that hijacking.
Once scientists solve that mystery more people can live longer, healthier lives.
Meantime, its up to us to do what we can to care for our bodies.