Into the Wild: did a neurotoxin kill Chris McCandless?

January 6, 2014, 5:01 pm

In April 1992, Chris McCandless, aka “Alexander Supertramp,” hiked into the Alaskan wilderness with no map, no compass, and no means of communicating with the outside world. A 24-year-old from Fairfax, Virginia, he had graduated with honors with a double major (history, anthropology) from Emory University in Atlanta. However, as chronicled in Jon Krakauer’s book Into the Wild, he then took off on an odyssey of self-discovery that led to Alaska. Four months later, his body was discovered by hunters who came across the abandoned bus that served as his shelter. He had died 19 days before, on August 18, 1992. He had lost about 50% of his body weight — his remains weighed just 67 pounds.

For a while, McCandless managed to live off the land, shooting duck, porcupine, and other animals, and foraging for plants. But by July, his diary entries — recovered after his death — turned bleak:

“extremely weak . . . fault of potato seed . . . much trouble just to stand up . . . starving . . . great jeopardy”

By this time, McCandless was too debilitated to walk to safety, especially since the river he had easily crossed coming in had turned into a raging cataract with the spring thaw.

As the above excerpt demonstrates, McCandless attributed his frail condition eating the “potato seed.” But what was that.

The eskimo potato is Hedysarum alpinum, also called the “alpine sweetvetch.” The roots are said to taste like carrot, and are an important source of food for animals, and also for native Alaskans. At the time McCandless trekked into the wilderness, the entire plant was thought to be non-toxic.

When he initially wrote about McCandless for Outside magazine in an article called “Death of an Innocent,” Jon Krakauer attributed McCandless’s weakened condition to his having mistaken Hedysarum mackenzii ( aka wild sweet pea) for H. alpinum. Following traditional wisdom, Krakauer believed that the seeds of the H. mackenzii were poisonous and that McCandless had made a tragic error in plant identification.

However, by the time his book was published, Krakauer had second thoughts and believed it unlikely that McCandless had confused the two species, and that contrary to common wisdom, seeds of H. alpinum might in fact contain a toxic alkaloid. He sent samples to the University of Alaska for analysis. No alkaloids were identified.

So the cause of McCandless’s weakened condition and death remained a mystery. But recently, as described in a fascinating blog post on The New Yorker website, a tantalizing clue came from a paper called “The Silent Fire” by Ronald Hamilton. Hamilton recalled that during World War II, the town of Vapniarca in the Ukraine was the site of a concentration camp. At that camp, prisoners were fed bread made from flour made from Lathyrus sativus, the “grass pea”.  This is a member of Febaceae, the same family that contains H. alpinum.

Many prisoners at Vapniarca were stricken with lathyrism, a degenerative neurological disease characterized by weakness and paraylsis of the lower limbs. The responsible neurotoxin is the glutamate analogue β-oxalyl-L-α,β-diaminoproprionic acid (ODAP), which is an amino acid (not an alkaloid). According to Spencer & Schaumburg’s text Experimental and Clinical Neurotoxicology (2nd edition):

Factors associated with disease [i.e., lathyrism] onset are physical work, coldness, exhaustion, malnutrition and, sometimes, fever.

Hoffman points out that lathyrism occurs most frequently in young men, and that the preconditions of physical work, exhaustion, and malnutrition fit McCandless’s situation exactly. ODAP, being a glutamate analog, overstimulate motor neurons of the lower extremities, depleting them.

Thus, Hoffman speculated that by looking for alkaloid toxins, Krakauer may have missed the boat completely, since the culprit might have been ODAP, a protein. To test his hypothesis, Hoffman sent seeds from H. alpinum and H. mackenzii to Indiana University of Pennsylvania for analysis. Results suggested that ODAP was present in both, in fact in higher concentrations than found in the L. sativus plant itself.

The methodology used in these tests has been challenged. Further analysis, using the more specific mass spectometry, is planned. Perhaps, eventually, we will know the real answer as to what killed Chris McCandless.

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