Blumenthal's investigation focuses on Enviga, a green-tea drink that contains caffeine, calcium and a green tea extract known as epigallocatechin gallate, or EGCG. Coke says EGCG speeds up metabolism and increases energy use, especially when combined with caffeine.
An Enviga Web site claims that the drink's blend of green tea and caffeine burns more calories than it contains and can help drinkers maintain an ideal weight. According to a Nestle study, young people who drank three of the 12-ounce beverages a day burned an average of 106 calories.
Blumenthal said he's demanded copies of all scientific studies, clinical trials, tests and papers that prove the calorie-burning claim by next week.
"Promise of wondrous weight loss must be supported by science, not magic," he said.
Calls were placed to Coke and Nestle seeking comment.
A nonprofit watchdog group, the Center for Science in the Public Interest, filed suit last week against Coke and Nestle over their Enviga claims.
"There is no clear evidence that what's in Enviga will help you control your weight," said CSPI senior nutritionist David Schardt in a press release. "You'd be much better off giving up non-diet soda, which costs nothing to do, or by joining a gym, which is typically less expensive than paying for 3 cans of Enviga a day."
Coke officials had called the threat of a lawsuit a "meritless publicity stunt."