By now most everyone has seen ads from the Corn Refiners Association, claiming that our fears about high-fructose corn syrup are misplaced. Since our kids will soon be loading up on Halloween treats laden with the substance, it’s a good time to consider why so many people find corn sweeteners so scary.

Just this month, researchers from Loyola University’s Stritch School of Medicine in Chicago took a look at the link between kidney disease and high-fructose corn syrup. Using data from nearly 9,400 adults in the National Health and Nutrition Examination Survey from 1999 to 2004, they tracked consumption of sugary soft drinks, a major source of high-fructose corn syrup in the United States, and protein in the urine, a sensitive marker for kidney disease. They found that overall, people who drank two or more sugary sodas a day were at 40 percent higher risk for kidney damage, while the risk for women soda drinkers nearly doubled.

In June, the Journal of Hepatology suggested a link between consumption of high-fructose corn syrup in sodas and fatty liver disease.

And this summer, a small study published in The Journal of Nutrition suggested that fructose may make people fatter by bypassing the body’s regulation of sugars, which means it gets more quickly converted to fat than do other sugars.

Many scientists hypothesize that high-fructose corn syrup has contributed to rising obesity rates, although others say there is no solid evidence to support the theory. The corn refiners agree, dedicating a Web site to the “sweet surprise” of high-fructose corn syrup.

But we do know that foods made with high-fructose corn syrup are heavily processed and typically lack any meaningful nutritional value. And while the jury is out on the real effect high-fructose corn syrup has on obesity, we do know it’s a threat to the health of the planet.

As writer Michael Pollan told The Washington Post earlier this year, high-fructose corn syrup “may be cheap in the supermarket, but in the environment it could not be more expensive.”

Most corn is grown as a monoculture, meaning that the land is used solely for corn, not rotated among crops. This maximizes yields, but at a price: It depletes soil nutrients, requiring more pesticides and fertilizer while weakening topsoil.

“The environmental footprint of high-fructose corn syrup is deep and wide,” writes Pollan, a prominent critic of industrial agriculture. “Look no farther than the dead zone in the Gulf [of Mexico], an area the size of New Jersey where virtually nothing will live because it has been starved of oxygen by the fertilizer runoff coming down the Mississippi from the Corn Belt. Then there is the atrazine in the water in farm country — a nasty herbicide that, at concentrations as little as 0.1 part per billion, has been shown to turn male frogs into hermaphrodites.”