As mounting evidence leads to the tart truth that sugar is a toxic substance and fueling America’s biggest health problems, more medical experts are going sugar-free, and more policymakers are seeking ways to clamp down on its consumption.

Next week in Chicago, delegates to the American Medical Association — a group that creates much of the country’s medical advice — will vote on whether taxing sugar-sweetened beverages would be an effective way to reduce their consumption.

Such news is bittersweet: bitter because Americans love their sugar. Sweet because just one dietary change — eliminating added sugars — could reverse America’s deadliest and costliest ills, including obesity, diabetes, high blood pressure, heart disease and many cancers, experts say.

The United States now spends three out of every four health-care dollars treating these diseases, according to the authors of a recent article in Nature, which said that because of sugar’s potential for abuse — coupled with its toxicity and pervasiveness in the Western diet — it should be controlled like alcohol and tobacco.

Last month, New York Mayor Michael Bloomberg touted a plan to ban supersized soft drinks in restaurants and movie theaters, citing the sugary drinks’ ill effects on health — and wallets.

That same week, the Food and Drug Administration quashed a petition from the Corn Refiners Association asking permission to change the much-maligned name of high-fructose corn syrup to the more innocuous “corn sugar.”

In the Nature article, scientists from the University of California-San Francisco blamed sugar consumption — which has tripled in the past 50 years — not only for the world’s obesity epidemic, but also for 35 million deaths a year worldwide.

Refined sugars and starches are a metabolic problem because humans weren’t made for today’s Western diet, said Dr. Devendra Mehta, a pediatric gastroenterologist at Orlando Regional Medical Center.

“The pancreas wasn’t made to handle high doses of unrefined sugars,” said Mehta, 52, who cut sugar from his diet five years ago. “The strain is manifesting itself as disease. Our ancestors didn’t have a lot of refined foods, and nothing in boxes, and they didn’t have metabolic diseases.”

As soon as you eat sugar or fructose, the pancreas responds by secreting insulin, which converts dietary sugar into glycogen, a fuel tissues can use.

However, when the body doesn’t need the fuel immediately — and it often doesn’t — insulin parks glycogen in cells where it is stored as fat, Wood said.

The stress on the pancreas makes the insulin-producing beta cells wear down. As they do, diabetes develops. The stress also puts people at risk for inflammation, which contributes to cardiovascular disease, he said.

“Cancer is also fed quite well under a nice supply of the growth-promoting hormone insulin,” said Wood, which is why certain cancers track with diabetes.