More evidence is needed to support a report, compiled by a government-sponsored team and confectionery giant Meiji Co., which concluded that chocolate is good for the brain, the Cabinet Office said Thursday.

The January 2017 report has faced criticism that there was insufficient data for the claim.

"Additional tests should be conducted as comparative data is needed. (The project team) should have been more careful in releasing the report," the Cabinet Office told a panel of experts.

The report said eating cacao-rich chocolate for four weeks could expand the cerebral cortex and enhance learning ability.

But the report did not compare test subjects who ingested chocolate with those who did not. Additionally, the sample size was limited to only 30 subjects, fanning criticism that it was too small to be valid.

Last month, the Cabinet Office said the report was "announced prematurely" after reviewing it from last May with the help of brain scientists.

The research was conducted by a team led by Yoshinori Yamakawa of NTT Data Institute of Management Consulting Inc. under the Impulsing Paradigm Change through Disruptive Technologies Program.

The program is supported by the government to encourage "high-risk, high-impact" research and development.

"I am sorry for causing trouble. I regret creating misunderstanding," Yamakawa said.

A member of the expert panel criticized the team for announcing their results before writing a research paper on the subject.

Yamakawa is one of 16 project managers for the governmental program encouraging innovation. A total of ¥3.3 billion ($31 million) has been allocated to projects he led since 2014.