Anthropology P380: Prehistoric Diet and Nutrition
Lecture 2: Biological constraints on human nutrition
Vitamin C is an example of a biological constraint on our nutrition that not only reflects our evolutionary background, and demonstrates how evolutionary change has had an impact on specific nutritional requirements, but also shows how culture can be at odds with what our bodies are adapted for.
Ascorbic acid is important for the transport of hydrogen within and between cells (cellular respiration), which is particularly important for the development of collagen in connective tissues, the formation of dentine, and the absorption of iron. In other words, it is essential for survival, but only needed in small amounts.
Symptoms of Vit C deficiency include impaired wound healing (collagen), dental defects (dentin formation) and SCURVY = sore/swollen joints leading to hemorrhages throughout the body, swollen and bleeding gums, and anemia... But this is almost unknown in the natural world because most mammals don't need a dietary source of Vitamin C -- they make it themselves.
Most mammals can synthesize Ascorbic Acid from a form of glucose, using an enzyme called L-Gulano-Lactone oxidase. Location of synthesis varies phylogenetically: done in kidney among amphibians, reptiles, lower birds (chickens & pigeons & owls), in kidney AND liver in some birds (e.g. myna bird) and in LIVER in most other birds and mammals. (Transition in synthetic site associated with evolution of temperature regulatory mechanism & change from cold-blooded to warm-blooded vertebrates). But this enzyme is ubiquitous throughout nature... suggesting evolved early in primitive forms of life.
Exceptions =
- humans and other primates
- guinea pigs,
- Indian fruit-eating bat,
- and a frugivorous bird, the Redvented Bulbul.
This is a potentially lethal mutation, unless you live in a tropical forest and eat alot of fresh fruit & vegetables, so this is an ancient evolutionary legacy. Humans are dependent on Vitamin C = strong selection pressure! Linus Pauling has extended this argument to claim that we need very large doses of Vit C (read about this in "Food and Cooking" book chapter)
Scurvy is rare in industrialized societies today, and uncommon among tropical hunters and gatherers. but it was "a serious health menace" in 15-16th century western Europe -- The Age of Discovery -- sea-men on long voyages and city dwellers in winter.
Syllabus | Readings | Lectures | Assignments | Quiz Site
Human Origins and Evolution in Africa Home Page
Jeanne Sept's Personal Home Page
Last updated: 19 January, 1998
URL: http://www.indiana.edu/~origins/teach/P380syll.html
Comments: sept@indiana.edu
Copyright 1998 Jeanne Sept
