I always thought that eating  a lot of sugar cause diabetes.

Um, it's a bit more complicated than that.

Diabetes is really common.

One in 10 people have it.

And   tens of thousands of people die from it every  year.

And according to a study done by the CDC,   by 2050 one in three Americans could have  diabetes if things keep going the way they are.

If you have diabetes that's not kept in check,  you have way too much sugar, specifically   glucose in your bloodstream.

So it would be  logical if eating a lot of sugar caused it.

To understand how sugar in your blood and sugar  you eat are related, let's start at the beginning:   with how you process sugar.

You eat something, say  an apple, and as you digest it, you're breaking   down the larger sugars in that apple like sucrose  into smaller ones like fructose and glucose,   which then get into your blood.

As blood glucose  levels rise.

Your pancreas starts producing the   hormone, insulin.

Insulin, and glucose travel  through your bloodstream to your cells.

Insulin binds to its specific insulin  receptor first.

And that sends a signal,   telling your cells to let glucose in.

Your  cells use that glucose to produce energy,   energy that keeps your muscles moving, your  brain working, and a lot of other important   processes that keep you alive.

With diabetes,  this whole process is thrown out of whack.

But how it's thrown out of whack  depends on the type of diabetes.

In type one, your immune system destroys cells  in your pancreas that produce insulin.

With   less insulin available to bind to receptors on  your cells, less glucose gets in and you're left   with a bunch of glucose in your blood.

Type two  diabetes is way more common than type one.

It's   actually around 90% of all diabetes cases.

In type  two, your pancreas is producing insulin, but your   cells aren't responding to it.

Usually because the  signal telling your cells to let glucose in just   isn't getting through.

this is called insulin  resistance.

With insulin resistance, your pancreas   has to make more and more insulin to keep up with  rising blood glucose levels.

For a while that   might work okay.

And the amount of sugar in your  blood will stay relatively normal, but over time,   your pancreas can't keep up.

And just like with  type one, you'll be left with a bunch of glucose   in your blood.

Gestational diabetes is the type  of diabetes someone gets when they're pregnant,   just like with type two, the pregnant  person becomes insulin resistant.

And I   actually didn't know this before doing  research for this video, but between 30   and 50% of people with gestational diabetes go on  to develop type two within the following decade.

So why is a lot of glucose in your blood a bad  thing?

First, if there's a lot of glucose in   your blood, chances are not enough glucose is  getting into your cells, which is a problem.

Second, having too much sugar in your  blood can also damage your blood vessels,   which means your blood won't circulate as well.

And that puts you at risk for a heart attack,   stroke or kidney damage, as well as nerve and  vision problems.

Your kidneys try to solve that   problem by releasing any extra glucose into  your urine, bringing a bunch of fluids from   your tissues with it, which is why most people who  are starting to realize they might have diabetes   report feeling thirsty and also needing to pee all  the time.

As the disease progresses, the symptoms   become more serious.

People often have trouble  recovering from infections or healing wounds, and   further down the line.

There's more of a risk for  the things I just mentioned, like kidney damage.

Diabetes is a diagnosed based on  how much glucose is in your blood.

So it would seem logical that a diet with tons of  sugar must cause it, this is a more controversial   topic than you might think.

There are no  human studies that prove eating tons of sugar   causes type two diabetes, because it would be  unethical for scientists to give people diabetes.

But there are studies showing that having a  bunch of sugar in your diet can cause insulin   resistance, which remember can lead to type two  diabetes.

In one of those studies scientists put   volunteers on a diet where for 10 weeks, 25% of  the calories in their diet came from glucose or   fructose sweetened beverages.

Interestingly, they  found that volunteers on the high fructose diet   had increased glucose and insulin in their blood  and they were less sensitive to insulin.

They   didn't see that for the high glucose diet.

And it's not clear exactly why there's still   a lot of work going on to figure all this out.

One thing that is very clear is that obesity   is the greatest risk factor for developing  type two diabetes and sugar plays into that.

If you're eating more sugar than your body can  turn into energy, that sugar will be stored   as fat and extra fat, especially fat in your  abdominal cavity around a bunch of your organs   can cause inflammation.

Some research has  shown that inflammation makes our cells   resistant to insulin and that resistance  can actually lead to more inflammation.

And that leads to more insulin resistance, which  as you now know, can lead to higher and higher   levels of sugar in your blood.

But a lot of  sugar in a person's diet can still increase   insulin resistance.

Even if the person doesn't  gain weight for people with type two diabetes,   healthier eating and exercise can sometimes be  enough to manage it, but more likely a doctor   will prescribe different medications to keep blood  sugar at a reasonable level.

There's also so much   research that's focused on preventing diabetes and  its complications and even trying to reverse it.