Nabhan provides a new analysis and new context to a number of facts that I was already aware of. Here are a few examples from his wide-ranging points:
- Fava beans cause severe anemia in some individuals whose origins are in the Eastern Mediterranean. Nabhan examines the genes that cause this reaction, and explores the results:
- Fava-bean sensitive families are more malaria resistant.
- Bio-active elements in herbs and plants (for example, sage) used in cooking the beans contribute to the positive aspect of this genetically-based sensitivity.
- Diabetes affects large numbers of Native Americans, Hawaiians, and Austrailians when they give up their traditional way of life. Nabhan provides evidence about this:
- Desert plants, a major part of the traditional diet, contain slow-release carbohydrates, which protect the plants themselves in times of drought. Diabetes-prone individuals, in eating these plants, received protection from their weakness until introduction of a western diet.
- The change was much too rapid for any genetic adaptation to respond: “half a century ago, … more Indians were dying each year of accidental snake bite than of diabetes.” (p. 163)
- Herdsmen used cattle for meat and dairy products in northern Europe. In part animal food compensated for the lack of vegetation due to the short growing season. Variations between this and other populations resulted:
- Development of a genetic ability to digest lactose conferred benefits on these groups: their herds became a more effective year-round food supply. (Outside of Europe far fewer people are able to digest lactose.)
- The northern diet lacks greens because of the short growing season. A high level of heart attacks (compared to Mediterranean peoples) may be the result, as greens provide folic acid and other heart protectives.
- Domestic animals polluted the water supply, making it favorable to develop alcoholic beverages. Specific genes make some individuals less susceptible to alcoholism: these genes are more common in descendants of northern Europeans. Because alcohol consumption reduced bacterial disease, the alcohol-resistance genes conferred an advantage to members of this society -- another complicated adaptation of genes interacting with diet.
- Strong, bitter flavors – like chili pepper and some types of greens – are tasted more prounouncedly by some individuals whose tongues have more taste receptors. In contrast, less sensitivity may enable some population groups to use hot seasoning and greens more. Advantages of using hot spice may be to preserve food from bacterial contamination, and to profit from the high vitamin content.
Each chapter is focused on a different group and the interaction of their genetic makeup with the foods in their traditional diet. Obviously, it’s easier to look at groups who were most recently living in the traditional way, like people on islands in the Mediterranean or Southwestern Indian tribes. On the whole, the book makes a really interesting point about how people adapt to their environment.