IOC member Anita DeFrantz says ice cream was the reason the U.S. junior rowing team got sick in August and answers whether she would let her child swim in the Rio waters. (1:53)

An International Olympic Committee member is pointing to a food choice as a culprit for a stomach illness that spread through the U.S. junior rowing team.

Anita DeFrantz, an IOC member since 1986 and bronze medalist in rowing at the 1976 Olympic Games, told ESPN's Mike & Mike on Thursday that eating ice cream led to 13 rowers on the 40-member U.S. team coming down with a stomach illness in August during the World Rowing Junior Championships -- a trial run for next summer's Olympics in Rio de Janeiro.

"It wasn't the lagoon that was the problem," DeFrantz said. "What they did, unfortunately, is they just decided to go to the beach, or the bay, and they went swimming in the bay. And to top it off, they decided to have some ice cream afterward."

DeFrantz said differences in ingredients and sanitation of food internationally led the rowers to get sick.

USRowing CEO Glenn Merry said the ice cream theory was new to him and added that the precise cause of the illness that affected the junior rowers was still "a bit of a mystery'' despite diligent efforts to solve it.

"I don't know that it's accurate,'' Merry said of DeFrantz' comments. "I have not seen Anita's interview, and I don't know where she drew that information.''

Merry said that after rigorous follow-up with the junior team, his medical and coaching staff has been unable to pinpoint "what the differentials were. ... It's very difficult to say that it was the lake or not the lake. We had one athlete who flipped her single scull and ingested some water who did not get sick and other athletes that did get sick. Part of our process was to determine whether they followed our [sanitation and diet] protocols.

"We're befuddled that we had such a high incidence of illness compared to other teams at the same competition.''

Merry said he doubts any alternative venues will be considered, and his organization is focused on how best to inform and protect athletes who make the Olympic team.

The event was held amid rising concerns about the water quality at venues for the Rio Olympics, now less than a year away.

On July 30, The Associated Press published an independent analysis of water quality that showed high levels of viruses and, in some cases, bacteria from human sewage in all of Rio's Olympic and Paralympic water venues, including the Rodrigo de Freitas Lake, where the rowing competition took place.

DeFrantz said testing closer to the time of the Games will indicate the true safety of the water.

Information from The Associated Press contributed to this report.