Apr. 27—Ancient indigenous communities of the Pacific Northwest were once thought to subsist almost solely on salmon, however such a regimen underestimates the complexity of ancient diets and could have caused sickness, according to new research led by Washington State University.
WSU Anthropologist Shannon Tushingham, lead author of a paper published in the American Journal of Anthropology in early April, said diets that are rich in lean protein can produce a potentially fatal imbalance called "protein toxicity," sometimes known as "rabbit starvation."
While the physiological effect can get a little complicated, Tushingham said, too much of a reliance on lean protein without other macronutrients like fat and carbohydrates would not only have been unhealthy but obscures sophisticated cultural solutions indigenous communities developed for maintaining nutritional balance through cold winters.
"They were experts at this, they knew what they needed to collect over the course of the spring and the summer and the fall and it wasn't just salmon," Tushingham said. "If they only relied on salmon, it would be bad for the health of their families, especially for pregnant nursing mothers and young children ... and elders."
Tushingham said human beings have a limit for how much lean protein they can consume before they cross the line into toxicity. In order to maintain nutritional balance, she said communities in the Pacific Northwest supplemented their protein consumption with a variety of strategies.
This included harvesting nuts and root plants like acorns and camas, extracting important nutrients from bone marrow, trading for fat with other indigenous peoples or even dipping dried salmon into the fat of other marine mammals like whales, seals and sealions.
Tushingham said she and her co-authors' work seeks to bring together nutritional knowledge with indigenous and archaeological data to develop a more realistic scenario for what ancient diets may have been like. She said these revelations aren't limited to communities of the Pacific Northwest but can be applied to people studying ancient communities around the globe.
"You see this in surveys of worldwide hunter-gatherers — we brought that information together, and it seems that all over the world, no matter how much diet changes, that people really seem to observe this protein limit," she said. "They're getting additional calories in different ways and it can be through additional fats or additional carbohydrates."
Tushingham was careful to say there is no "perfect diet" however it is clear that cultures around the world developed strategies for balancing their nutrition that depended heavily on the traditions of their communities and the conditions where they lived. Because of migratory patterns that brought them deep inland, she said there's no denying salmon were a key component to ancient indigenous diets for a staggering number of communities in the west. However, she said, they, like other cultures around the world, found ways to ensure their food consumption was variegated enough to keep people healthy and then passed that knowledge down through generations for thousands of years.
"This will not be a surprise to indigenous people ... they have all these really ingenious strategies and what we call ancestral nutrition knowledge," she said. "This is something that they developed over thousands of years, they fine-tuned these strategies and especially in northern areas, it's quite remarkable how they were able to achieve these things."
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