Is sugar toxic?
Source: The New York Times Magazine; YouTube video of Robert Lustig's lecture "Sugar: The Bitter Truth"
Research is conclusively showing that the consumption of fructose in high-fructose corn syrup (HFCS) and sucrose (i.e., refined sugar) are harmful to the body and are contributing causes for obesity, diabetes, heart disease, and some cancers.
The harmful effects of fructose are not due to the quantities consumed, but to how the body metabolizes it—fructose from sugar and HFCS are metabolized mainly by the liver instead of by cells in the body. If consumed in sufficient quantities—roughly 200 calories per day—fructose can affect one’s insulin resistance and liver fat production.
Although sugar is a carbohydrate, the fructose in sugar sets it apart from carbohydrates in foods such as bread, rice, and potatoes, which break down upon digestion to glucose alone and have less harmful effects on insulin resistance.
Further research on the topic and long-term studies are needed to yield more definitive answers regarding the quantity of fructose-filled foods the human body can consume prior to seeing negative effects.