The Dublin man was on a unusual diet that involved large intakes of water, no meat and alternative health supplements.
Luke McGuire (26), who never drank or took drugs, was found collapsed on the ground in the back garden of his family home at Oakley Road in Ranelagh on June 2, 2011.
An inquest into his death heard from his father Brian that he was following a "very low protein" vegetarian diet of raw vegetables, fruit and potatoes.
Dublin Coroner's Court heard the diet was developed by Robert Young, an alternative medicine advocate in California.
Mr McGuire told the court that his son mentioned "feeling weird" prior to his death.
"The next morning he said to me that he was taking these salts, and that he thought they were making him feel ill in some way and that he felt thirsty," Mr McGuire said.
Luke had purchased the salts -- labelled pHour Salts and PuripHy -- through Mr Young's website, the court heard.
The salts "help you maintain the alkaline integrity of your cells, organs, and body", according to the website, while the other product is described as "water purification in a bottle".
On June 2, Luke came into the kitchen and he seemed fine, the court heard.
He then went out to the back garden. Twenty minutes later, his mother, Marie Rooney, found him lying on the ground. His father and a family friend started CPR, but he never recovered and he was later pronounced dead at St James's Hospital, the court heard.
Pathologist Dr Ciaran O Riain said that the most significant finding at the autopsy was tonsillar herniation due to swelling in the brain. He attributed the swelling to hyponatraemia -- an electrolyte disturbance caused by lower than normal sodium levels -- which he said may be related to water intoxication.
Coroner Dr Brian Farrell said that the deceased may have had a chronic low sodium situation that "tipped over" on the day of his death. He adjourned the inquest until November 8.
Mr Young was not available for comment last night.