There is speculation that 24-year-old Christopher McCandless inadvertently poison himself when he died in the abandoned bus in the wilderness 17 years ago. In one of Chris’s final journal entries he mentions beautiful blueberries—than can be found in the autopsy report. John Krakauer author of "Into the Wild," believes McCandless died upon eating the seeds of Hedysarum alpinum, a edible plant commonly known as wild potato. Collecting some near the area where he died, Krakauer sent the seeds to the University of Alaska Fairbanks chemistry department for testing.
At first, lab testing appeared positive for poison. But a more extensive analysis the next year -- examining additional seeds that UAF graduate student Ed Treadwell harvested near Fairbanks -- prompted department of chemistry chairman Tom Clausen to conclude that the seeds weren't poisonous after all.

"There were no toxins," Clausen said. "And we looked at everything -- roots, seeds, stems and leaves."

After receiving the lab results, Krakauer's theory is that McCandless possibly confused wild sweet pea -- which local guidebooks have long listed as poisonous -- with wild potato.

Krakauer was aware of that possibility, but he dismissed it in his book after concluding that McCandless probably knew the difference between the two plants -- since he'd been eating wild potato roots for weeks.

“The leaves look almost identical unless you examine them from below,” Pratt, a wildflower expert says. The underside of the wild potato leaf has small veins on it; the underside of the sweet pea leaf doesn't. "He could have made a mistake," claims Pratt.

So is the poisoning theory in the movie as unlikely as the poisoning theory in the book?
Location matters when you test the toxicity of flora, Pratt says. A plant that isn't poisonous in one spot can easily be poisonous in another -- if the soil it's growing in is saturated with something toxic.
Dr. Clausen who analyzed the potato seeds for Jon Krakauer said he hasn't seen any evidence yet that the plants McCandless ate were poisonous.