In a previous article, I argued that a recent drop in the body temperatures of the Tsimane people of Bolivia was caused by the introduction of vegetable oil to a mostly starch diet. Native Americans used acorns as a staple starch, but they removed the oil form them before eating. However, they often added animals fats, most commonly bear fat, to their starches.
Acorn oil is not THAT high in polyunsaturated fat and acorns aren’t that oily, but if the acorn is a staple of your diet you could still manage to consume enough PUFA to affect your metabolic rate. This would have led you to be very cold in the North American climate. I suspect the Native Americans knew this.
First hand reports show clearly that Native Americans were removing acorn oil, both in California and on the East coast.
The acorn was a staple across the US. East coast Native Americans grew corn and beans and often made cakes that combined two or all three of these. Native Californians never took up agriculture. They lived in a paradise where a year round supply of acorns could have been gathered in just a few weeks in the fall.1 Acorns were the primary staple of the Native Californian.
Acorns are mostly starch, with a protein content below 10% and typically are around 8% oil, although some species have as much as 18% oil.2
Acorn oil is similar in composition to avocado or olive oil, but with a little more linoleic acid.3,4 It varies a little by species, but the predominant fat is always oleic acid, an 18 carbon monousaturated fat (MUFA). It has from 16-22% linoleic acid, an omega-6 polyunsaturated fat (PUFA), depending on the species. It has 2% or less of omega 3 alpha-linolenic acid.
Most acorns are high in tannins, making them bitter. The tannins are typically removed by either leaching them out by pouring water over them a numbers of times or by boiling them in several changes of water.
Lets look at California first. I find this passage to be particularly illuminating.1
California Native Americans knew which species of acorns were oilier and they used hot water to leach out the tannins of the oilier varieties, instead of cold water! This removed the oil. What is more extraordinary about this observation is that Native Americans didn’t have steel kettles before European contact, so water was boiled by heating stones in fires, then using wooden paddles to add the hot stones to water in woven baskets. That is a lot of extra work to go through if the end result is a loss of caloric value. Presumably the Native Californians wouldn’t have done this without a good reason.
John Smith wrote this about the preparation of acorns in Virginia.5
It’s unclear exactly how long “half the day” is, but what IS clear is that the oil (oyle) was removed from the acorns by boiling and used as an ointment rather than being consumed.
Starch Plus Fat
It is often suggested in the keto diet community that combining starch with fat is a particularly fattening food combination. Perhaps Native Americans simply didn’t want to eat a combination of starch and fat? Seemingly not. Consider this description of Native American corn cakes.6 I’ve seen other descriptions of similar cakes combining corn and acorn meal.
Or “rye” cakes buttered with deer suet.5
Or “potatoes” with bear grease.6
The potatoes would have been tubers of the arrowhead plant, a very common wetland plant that grows throughout the entirety of the US. The arrowhead tubers are very high quality, starchy tubers, much like a potato.
“Sagittaria is an aquatic plant with tuberous roots that can be eaten like potatoes. Lewis and Clark found it at the mouth of the Willamette and considered it equal to the potato, and valuable for trade. Indian women collected it in shallow water
from a canoe, or waded into ponds or marshes in the late summer and loosened the roots with their toes. The roots would rise to the top of the water where they were gathered and tossed into floating baskets. Tubers are baked in fire embers, boiled, or roasted in the ashes. Tubers are skinned and eaten whole or mashed.”7
- 1.Mayer P. MIWOK BALANOPHAGY: IMPLICATIONS FOR THE CULTURAL DEVELOPMENT OF SOME CALIFORNIA ACORN-EATERS. Berkeley; 1976. https://digitalassets.lib.berkeley.edu/anthpubs/ucb/text/arfs015-001.pdf
- 2.Bainbridge D. Use of Acorns for Food in California: Past, Present, Future. PSFRES; 1987. https://works.bepress.com/david_a_bainbridge/43/
- 3.Lopes IMG, Bernardo-Gil MG. Characterisation of acorn oils extracted by hexane and by supercritical carbon dioxide. European Journal of Lipid Science and Technology. Published online January 2005:12-19. doi:10.1002/ejlt.200401039
- 4.Kaplan M, Kokten K, Bengu AS, Kardes YM, Das A, Sekerci AD. Fatty Acid Composition of Different Quercus Species. Chem Nat Compd. Published online March 2019:313-315. doi:10.1007/s10600-019-02675-x
- 5.Smith J. The Voyages and Discoveries of Captain John Smith in Virginia. Oxford; 1612.
- 6.Adair J. The History of the American Indians; Particulary Those Nations Adjoining to the Mississippi, East and West Florida, Georgia, North and South Carolina, and Virginia. London; 1755.
- 7.NRCS U. Broadleaf Arrowhead. USDA; 2003. https://plants.usda.gov/plantguide/pdf/cs_sala2.pdf