Caffeine and sugar are two well-known ingredients in Coca-Cola — but many soda drinkers may not realize the fizzy beverage also contains salt.

But why add salt into a sugary drink? To make consumers thirsty and ready to buy more, says Dr. Robert Lustig, professor of pediatric endocrinology at the University of California, San Francisco.

“They know what they're doing. Do you have to put salt in Coke?” he says. “The fact is, you don't have to put salt in soda. So this is by design.”

This is part of what Lustig calls “the Coca-Cola conspiracy” and it’s contributing a dangerous sugar problem in the U.S.

Nutrition experts are increasingly sounding the alarm on sugar, with some comparing its adverse health effects to smoking.

Sugar consumption can trigger a number of chronic diseases including Type 2 diabetes, heart disease and cancer — even leading some teenage soda-drinkers to need liver transplants, Lustig says. People get addicted to sugar the same way they do drugs, alcohol, gambling and social media, he says.

This problem isn’t an easy one to fix because food companies, like Coca-Cola, are profiting off Americans’ sugar addictions, he says.

“The only way we are going to fix this problem is when there are more votes than dollars,” he says.