07 April 2008

Aldat the yak hunter and how he got enough vitamin C

I am still reading Sven Anders Hedin’s My Life as an Explorer (1925) (previous posts about that book are here and here). During his travels in Asia, Hedin encountered and interacted with many characters who lived in the wilderness more or less isolated from the society. One of them was a man named Aldat in Tibet in circa 1900.

This Aldat was of Afghan descent. He spoke Persian. He had an eagle nose, a short beard, and eyes full of melancholy. He was a yak-hunter by profession, and lived alone in the mountains all year round. His food consisted of the flesh of the wild yak, and his drink was snow-water. His possessions were limited to the clothes on his body, a fur robe, a rifle, and ammunition. In the summer, his brothers would come up, with donkeys, to fetch the skins of the yaks he had killed.
My first reaction to this account was of disbelief. How can one survive only on meat and water? Wouldn’t the person eventually develop scurvy from lack of vitamin C? To satisfy my curiosity, I did some reading and then some calculations.

The 1st piece of information I needed was how much vitamin C yak meat can provide. But I assumed that information would be difficult to find and I didn’t bother to search for it; instead, I substituted beef for yak meat. According to the USDA Nutrient Database, a 100-gram portion of cooked beef tongue provides 1.3 mg vitamin C and 284 kcal energy, while a 100-gram portion of cooked beef liver provides 1.9 mg vitamin C and 191 kcal energy. In comparison, 30% fat broiled ground beef has 0 mg of vitamin C per 100 g of meat.

Next, I needed to know how much daily food energy Aldat would have required. Luckily, a paper by Rodahl (1954) had the answer. According to Rodahl, trappers in Greenland could maintain their body weight on an average of 3,000 kcal per day, energy requirements of adult Eskimos in Greenland were estimated to be 2,800 to 2,900 kcal per day and the U.S. infantrymen stationed in Alaska consumed a mean of 3,200 kcal per day with no weight change. Although Rodahl cites some higher values of energy consumption by people engaged in more strenuous activities, for example, arctic miners and explorers, I will assume that the daily energy intake requirement of Aldat, who lived in a cold climate and was probably physically active most of the day, was 3000 kcal.

I can now calculate that Aldat could have fulfilled his energy requirement by eating everyday about 1 kg of yak tongue or about 1.5 kg of yak liver. Assuming that the vitamin C contents of yak body parts are similar to those of cows, Aldat would have gotten about 13 to 29 mg of vitamin C every day from eating tongues and liver. We have good reason to assume that he may have indeed eaten tongues, because, according to Hedin, tongues, along with kidneys and hearts, were considered to be the best parts of a yak’s flesh.

Finally, I needed to know if, say, about 10 mg vitamin C per day would have been enough to prevent Aldat from getting scurvy. The answer came from a paper by Carr & Frei (1999), who, citing another paper, state that 10 mg of vitamin C per day can prevent scurvy.

Therefore, Aldat could have avoided scurvy on his yak-only diet. That conclusion notwithstanding, Aldat wasn’t a healthy individual. He joined Hedin’s team as a hunter, but 2 months into a difficult expedition over the mountains of Tibet, he got sick. He suffered from headaches, nose-bleeds, delirium, low body temperature and his feet turned black. He died within 3 weeks.

Hedin apparently never figured out what had driven Aldat to the lonely mountains.
Aldat was charmingly mysterious. He was like a disguised prince in a fairy-tale. He answered all questions briefly and correctly, but did not speak unless questioned. He was never seen to smile or laugh, or to talk with the other men. It was as though he were fleeing from a great sorrow, and sought solitude, danger, and the hard, adventurous struggle against the wolves and the storms.

Anitra C. Carr and Balz Frei. 1999. Toward a new recommended dietary allowance for vitamin C based on antioxidant and health effects in humans. Am. J. Clinical Nutrition, 69: 1086 - 1107.

Kaare Rodahl. 1954. Nutritional Requirements in Cold Climates
J. Nutr. 53: 575-588. pdf


Deniz Bevan said...

I'm not sure if the Vitamin C absorbed from meat is enough to prevent malnutrition and scurvy. Probably part of the reason has to do with how the body "uptakes " vitamin C - the C in oranges or green vegetables is probably more easily absorbed for instance (there's a reason for this but I can't explain it offhand). Also, he would, of course, need all sorts of other vitamins and minerals. Unless he was in the habit of eating whatever greens or grains the yaks were feasting on, then his diet would certainly be lacking all sorts of nutritional elements.
I find this stuff really interesting. There was a Canadian who lived on his own like this somewhere in the wilderness (either BC or the Territories) - but he died only a few years ago; that is, he probably ate all kinds of canned foods as well, and didn't rely only on game.
It's still possible to get scurvy in this day and age - a friend of a friend, while in University, moved out on his own and subsisted on the single-young-man diet of pizza, burgers, coke and beer, etc. His teeth began loosening and he felt weak and dizzy. The doctors diagnosed scurvy. Presumably they told him to go have dinner at his parents' house more often :-)

Dave Coulter said...

That 1.5 kg daily (!) dose of liver would have sent me back into town. Ugh!

Snail said...

Deniz, the doc should have probably prescribed a daily dose of yak tongue !


Yak liver pizza would have been even better.

Dave Coulter said...

Check please. (urp)