When billionaire Elon Musk was a 17-year-old college student at Queen’s University in Kingston, Ontario, he had a brief stint where he only spent a dollar a day on food — and he successfully got by.

“My threshold for existing was pretty low,” he tells Neil deGrasse Tyson in a 2015 interview on the podcast StarTalk. “So I figured I could be in some dingy apartment with my computer and be okay and not starve.”

The CEO of SpaceX and Tesla describes how, from a young age, he focused on things that would affect the future of humanity, like electric cars, solar power and sustainable consumption. So shortly after he moved to Canada from South Africa, he tried this experiment to figure out if could really live spending so little on food.

As it turned out, a $30 CAD monthly grocery budget proved sufficient.

“You sort of just buy food in bulk at the supermarket,” he says, though he admits that “you get really tired of hot dogs and oranges after a while.” Pasta and green peppers were staples of his, too.

Of course, this was a few decades back, and Musk warns against trying it at home. “I would not encourage anyone to live on $1 a day,” he tells Business Insider. “That would not be super fun. Also, I did this back in 1990, so a dollar went a lot further back then. Would be much harder to do that today.” Indeed, $1 CAD from back then is now worth $1.64 U.S., with inflation and accounting for the 1990 conversion rate.

Still, the experiment offers some perspective on how much you need to spend just to get by. Canadians dished out $8,784 CAD on food in 2016, or $571.47 U.S. a month, whereas the average American spent just over $600 U.S. a month. After accounting for inflation, Musk, by contrast, spent less than $50 U.S.

For recommendations on how to keep your weekly food budget low, check out how CNBC Make It reporter Kathleen Elkins got by on a “cash diet,” spending just $30 U.S. a week on groceries.

After her experiment, Elkins described having a new awareness of how she spends money, not unlike Musk, who also says he came away with some insight.

“This was an important psychological-philosophical anchor for you, not to put words in your mouth,” Tyson tells him. “But that’s a starting point to launch anywhere you want to go.”