"I leave Riot Foods with my head held high and integrity intact," Kamins told shareholders in the letter.
"I no longer want to live life as an addict the way I have been, and I hope that in regards to my relationship of leading Riot Foods, that this is just a see you later, and not a goodbye."
Kamins father, Trevor, is now standing in as managing director of Riot while the board reviews its options. Co-founder Art Green has also committed to be more involved in the business.
"We have an excellent and dedicated operational manager and sales manager and together with the staff, the business continues to operate at the high level that it always has done," Trevor said.
Last month, Riot announced it needed $1 million in a matter of weeks or risk being sold.
Kamins wrote that after several weeks of looking to raise the money needed to secure Riot's future, the company had been granted permission to launch an equity crowding campaign on Pledge Me.
"No one but a few close friends were aware of my addiction, and understandably, there is now doubt from the board and shareholders as to whether the public equity process should continue."
The crowdfunding round is no longer visible on the Pledge Me site, but at this stage it is unclear whether it was removed due to cancellation or due to completion of the fundraising round.
The Herald has approached Pledge Me for further information.
Riot Foods had faced significant challenges with its Ascot Rd factory after the alleged destruction of the facility by an unnamed "fumigation/sterilisation company" and so had missed its production date, Kamins said in October.
"Essentially a company came in to make final preparations to open the facility, that's where we will be making our dried beef product, and something happened in that process, and effectively all of our brand new production equipment was destroyed as well as a lot of damage to the flooring," he said.
Riot Foods had to rebuild the production facility, one of two it has in Auckland, Kamins said. He would not disclose how much the company spent on the rebuild.
"This has significantly impacted the cashflow and profitability of Riot Foods. The inability to produce at this site, and the significant management focus on the recovery has impacted on our sales and related profitability."
Issues with the factory delayed Riot's planned re-launch of its biltong and other Clean Paleo product ranges, along with its nut butter brand Poppy and Olive and Better Balls, into the Australian and Asian markets.
He said he was devastated by the situation the business was in.
Riot Foods was founded in 2014 by Kamins and TV personality Art Green, a year after setting up flagship food brand Clean Paleo. It has since acquired other food brands, including Poppy and Olive, in April 2017.
If you'd like confidential advice and support to get help for yourself or someone you know in regard to addiction, contact the Alcohol Drug Helpline: general freephone 0800 787 797, text 868.