Mohamed Fahmy's declaration came as he pleaded not guilty to what his family has described as a "ridiculous" set of charges.
"It's physically fine, but psychologically unbearable," Fahmy yelled to reporters present.
Fahmy was working for satellite news broadcaster Al Jazeera English when he was arrested along with two colleagues — Australian Peter Greste and Egyptian Baher Mohamed — at the end of December.
The trio are being tried as part of a group of 20 individuals who authorities say worked for the Al Jazeera network and allegedly threatened national security. At least 12 of those are being tried in abstentia.
The proceedings come amidst a crackdown against the Muslim Brotherhood, an Islamist group which Egypt's military-led government branded a terrorist organization after the July ouster of former president Mohamed Morsi.
The Egyptian government has claimed Al Jazeera is biased towards the Brotherhood — an allegation the Qatar-based broadcaster has vigorously denied.
Thursday's trial proceedings in Cairo got underway after hours of delay and lasted only 40 minutes before the case was adjourned until March 5.
Despite the short proceeding, Fahmy's brother said his family was optimistic.
"There's no case, it's built on nothing. We're positive there's no evidence against him," Adel Fahmy told The Canadian Press from Cairo.
"We're positive that things will get resolved eventually, but we're hoping that it's not one of those cases that will drag on for months."
Fahmy's family said the Canadian journalist's morale was high as the trial got underway because he believed the Egyptian justice system would eventually dismiss his case.
"He knows that this is the phase of this whole story where the truth will prevail," Fahmy's brother said. "It's the most important phase."
Fahmy's brother said lawyers working on the case have asked for Fahmy and his colleagues to be released on bail, although a decision on the request has yet to be delivered.
Fahmy's parents — who travelled to Cairo from their home in Montreal weeks ago — and his brother weren't allowed into the courtroom for Thursday's proceedings because they lacked proper passes. But staff from the Canadian Embassy were allowed in.
The Department of Foreign Affairs has said "senior Canadian officials" have raised Fahmy's case with Egyptian authorities and have requested a "fair and expeditious trial."
Fahmy's family moved to Canada in 1991. He lived in Montreal and Vancouver for years before eventually moving abroad for work, which included covering stories for the New York Times and CNN.
Meanwhile, Fahmy's employer expressed disappointment that he and his colleagues weren't released on Thursday.
"The charges against our staff are baseless, unacceptable, and wholly unjustified," Al Anstey, managing director of Al Jazeera English said in an email.
"What is going on in Egypt right now is a trial of journalism itself, so it is critical that we remain resolute in calling for freedom of speech, for the right for people to know, and for the immediate release of all of Al Jazeera's journalists in detention in Egypt."
Anstey called on observers to keep up the pressure on Egypt to release the journalists, and called for a global day of action on Feb 27.
"Journalism is not a crime," he said.
Egyptian prosecutors allege that 20 Al-Jazeera employees set up a media centre for the Muslim Brotherhood in two suites in a luxury hotel.
A statement by the prosecution said the defendants "manipulated pictures" to create "unreal scenes to give the impression to the outside world that there is a civil war that threatens to bring down the state" and broadcast scenes to aid "the terrorist group in achieving its goals and influencing the public opinion."
Fahmy, Al Jazeera's acting bureau chief in Cairo, has been singled out.
An official from the high state security prosecution team investigating the case said Fahmy was an alleged Brotherhood member, led the media operation that "fabricated" footage and broadcast it with the "aim of harming Egypt's reputation."
— with files from the Associated Press