WASHINGTON (Reuters) - Two U.S. lawmakers are investigating advertising claims by Wyeth that promote its Centrum Cardio vitamin as a cholesterol-lowering product, according to a letter to the company released on Friday.

Michigan Reps. John Dingell and Bart Stupak are seeking related company documents following television commercials that tout the vitamin as "the only complete multivitamin that can lower cholesterol," according to the lawmakers' letter.

"We are concerned that these statements may be misleading to the general public and that patients with high cholesterol may erroneously substitute Centrum Cardio for a treatment plan prescribed by their physician," the lawmakers wrote.

As Democrats, the two men chair the U.S. House of Representatives Committee on Energy and Commerce and its Subcommittee on Oversight and Investigations, respectively.

Representatives for the company could not be immediately reached for comment.

Centrum Cardio, launched in October 2007, is part of Wyeth's Centrum line of multivitamin products.

On Wyeth's website, the company cites a 2000 U.S. Food and Drug Administration interim rule that allows dietary supplements or foods that provide of 800 milligrams of free phytosterols to claim a possible reduction in heart disease.

A daily serving of Centrum Cardio, or 2 tablets, contains 800 milligrams of phytosterols, it said.