Dr. Sanjay Gupta: Did it surprise you when you first got these results back?
Kimber Stanhope: I would have to say I was surprised because when I saw our data, I started drinking and eating a whole lot less sugar. I would say our data surprised me.
So imagine, for these healthy young people, drinking a sweetened drink might be just as bad for their hearts as the fatty cheeseburgers we've all been warned about since the 1970s. That's when a government commission mandated that we lower fat consumption to try and reduce heart disease.
Dr. Sanjay Gupta: So with the best of intentions, they say, "Time to reduce fat in the American diet?"
Dr. Robert Lustig: Exactly. And we did. And guess what? Heart disease, metabolic syndrome, diabetes and death are skyrocketing.
Dr. Lustig believes that's primarily because we replaced a lot of that fat with added sugars.
Dr. Robert Lustig: Take the fat out of food, it tastes like cardboard. And the food industry knew that. So they replaced it with sugar.
Dr. Sanjay Gupta: This idea that sugar increases this particularly bad LDL, the small dense particles that are associated with heart disease. Do most doctors-- do they know this?
Dr. Robert Lustig: No, they do not know this. This is new.
And it turns out, sugar has become a major focus in cancer research too. Lewis Cantley, is looking at the connection.
Dr. Sanjay Gupta: If you limit your sugar you decrease your chances of developing cancer?
Lewis Cantley: Absolutely.
Cantley, a Harvard professor and the head of the Beth Israel Deaconess Cancer Center, says when we eat or drink sugar, it causes a sudden spike in the hormone insulin, which can serve as a catalyst to fuel certain types of cancers.
Lewis Cantley: What we're beginning to learn is that insulin can cause adverse effects in the various tissues. And of particular concern is cancer.
Why? Nearly a third of some common cancers -- including breast and colon cancers -- have something called insulin receptors on their surface. Insulin binds to these receptors and signals the tumor to start consuming glucose.
Lewis Cantley: This is your body...
Every cell in our body needs glucose to survive. But the trouble is, these cancer cells also use it to grow.
Lewis Cantley: So if you happen to have the tumor that has insulin receptors on it then it will get stimulated to take up the glucose that's in the bloodstream rather than go into fat or muscle, the glucose goes into the tumor. And the tumor uses it to grow.
Dr. Sanjay Gupta: So you've just seen that tumor turn blue which is essentially reflective of glucose going into it.
Lewis Cantley: That's right.
Dr. Sanjay Gupta: So these cancers, much in the same way that muscle will say, "Hey, I'd like some of that glucose, the fat says, "I would like some of that glucose," the cancers have learned how to do this themselves as well?
Lewis Cantley: Yes. So they have evolved the ability to hijack that flow of glucose that's going by in the bloodstream into the tumor itself.
Lewis Cantley's research team is working on developing drugs that will cut off the glucose supply to cancer cells and keep them from growing. But until there's a breakthrough, Cantley's advice? Don't eat sugar. And if you must, keep it to a minimum.