THE MOST IMPRESSIVE EVIDENCE favoring plant-based diets is the way that so many food factors and biological events are integrated to maximize health and minimize disease. Although the biological processes are ex- ceptionally complex, these factors still work together as a beautifully choreographed, self-correcting network. It is exceptionally impressive, especially the coordination and control of this network. Perhaps a couple of analogies might help to illustrate such a process. Flocks of birds in flight or schools of fish darting about are able to shift direction in a microsecond without bumping into each other. They seem to have a collective consciousness that knows where they are go- ing and when they will rest. Colonies of ants and swarms of bees also integrate varying labor chores with great proficiency: But as amazing as these animal activities are, have you ever thought about how their behaviors are coordinated with such finesse? I see these same charac- teristics, and more, in the way that the countless factors of plant-based foods work their magic to create health at all levels within our body, among our organs and between our cells and among the enzymes and other sub-cellular particles within our cells. For those unfamiliar with biomedical research laboratories, the walls of these labs are often covered with large posters showing thousands of biochemical reactions operating within our bodies. These are reactions that are known; far more remain to be discovered. The interdependence of these reactions with each other is especially informative, even awe- some in its implications. 361
362 THE CHINA STUDY An example of a very small portion of this enormous network of re- actions is the effect of vitamin D and its metabolites on several of the diseases discussed in this book. This particular network illustrates a com- plex interconnection between the inner workings of our cells, the food we eat and the environment in which we live (Chart Cl). Although some of the vitamin D present in our bodies may come from food, we can usually get all that we need from a few hours of sunshine each week. In fact, it is our ability to make our vitamin D that leads to the idea that it is not a vitamin; it is a hormone (i.e., made in one part of our body but function- ing in another part). The sun's UV rays make vitamin D from a precursor chemical located in our skin. Provided we get adequate sunshine, this is all the vitamin D we need.I We can, of course, also get vitamin D from fortified milk, certain fish oils and some vitamin supplements. The vitamin D made in our skin then travels to our liver, where it is converted by an enzyme to a vitamin D metabolite. This metabolite's main function is to serve as the body's storage form of vitamin D (while remaining mostly in the liver but also in body fat). The next step is the crucial one. When needed, some of the stor- age form of vitamin D in the liver is transported to the kidney, where another enzyme converts it into a supercharged vitamin D metabolite, which is called 1,25 D. The rate at which the storage form of vitamin D is converted to the supercharged 1,25 D is a crucial reaction in this network. The 1,25 D metabolite does most of the important work of vitamin D in our bodies. This supercharged 1,25 D is about 1,000 times more active than the storage vitamin D. Supercharged 1,25 D only survives for six to eight hours once it is made. In contrast, our storage vitamin D survives for 2 twenty days or more. , 3 This demonstrates an important principle typi- cally found in networks like this: the far greater activity, the far shorter lifetime and the far lower amounts of the 1,25 D end product provide a very responsive system wherein the 1,25 D can quickly adjust its activi- ty minute-by-minute and microsecond-by-microsecond as long as there is sufficient storage vitamin D to draw from. Small changes, making a big difference, can occur quickly. The relationship between the storage form of vitamin D and the supercharged 1,25 D is like having a large tank of natural gas buried in our yard (storage vitamin D) but carefully using only a very tiny amount of gas to light the burner at our stovetop. It is critical that the amount and timing of gas (1,25 D) coming to our stovetop be carefully
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