WASHINGTON — NFL commissioner Roger Goodell did not acknowledge a connection between head injuries on the football field and later brain diseases while defending the league’s policies on concussions before Congress on Wednesday.

That frustrated several members of the House Judiciary Committee, including the committee chairman, Michigan Democrat John Conyers, when Goodell told him the NFL isn’t waiting for that debate to play out and is taking steps to make the game safer.

‘‘I just asked you a simple question. What is the answer?’’ persisted Conyers.

Goodell replied by saying a medical expert could give a better answer than he could. But some House members complained later that Dr. Ira Casson, chairman of the NFL’s committee on concussions, had not testified.

Rep. Linda Sanchez, D-Calif., gave Casson some exposure anyway, playing a clip of a TV interview in which he denied evidence of a link between multiple head injuries in NFL players with brain disorders such as dementia and Alzheimer’s.

Sanchez said that reminded her of tobacco companies denying a link between smoking and health damage in the 1990s.

Goodell testified alongside new NFL Players Association leader DeMaurice Smith, who said the union ‘‘has not done its best in this area. We will do better.’’ Both men did agree to turn over players’ medical records to the committee.

In addition, Conyers wants information on head injuries from the NCAA, high schools and medical researchers to better understand football’s health risks.