7. Radicals in Action

As everyone knows, genetics research grabs most of the headlines in medical science today. Yet even the most astounding advances in genetics will require a thorough understanding of biochemistry in order to be used effectively. A "quieter" revolution is occurring in biochemistry, where scientists are finding that most abnormalities in the body result in increased free radical activity, and most of the symptoms, metabolic disturbances and damage caused by disease, are created by oxidative stress. Here are some "little picture" examples of this new understanding:

• If a respiratory enzyme that is crucial for energy release is missing, whether due to poor nutrition or a genetic fault, the electrochemical potential of the process will be diverted to free radical exchanges. This chaotic oxidation will further block metabolism by destroying other enzymes.²⁴

• If levels of the electrolyte potassium are too low or too high, large numbers of free radicals will emerge and cause most of the symptoms of these potentially fatal imbalances.²⁵

• If an infection occurs, the virus or bacteria will cause free radical damage in its attempt to feed off the body. The immune system dramatically increases radical activity to fight back. This oxidative stress stimulates the production of the prostaglandins, leukotrienes, and interleukins. They make the body feel "sick," and generate more radicals to add to the symptoms and damage of illness.²⁶

• During exercise, oxidative stress increases sharply. As the cells begin to lose their power to generate energy, they also lose their ability to make and recycle antioxidants to combat oxidative stress. This, in turn, accelerates the breakdown of energy metabolism. Radicals can damage metabolism in both direct and indirect ways. For instance, radicals inside the cells disable the sulfur-bearing proteins that transport calcium ions within the cell.^{27, 28} The failure of calcium ion transfer is a cardinal sign of muscle exhaustion and may be directly involved in the process of cramping and tying up.²⁹

Other molecules (such as hydrogen peroxide and singlet oxygen) encourage radical-forming reactions. They are called proradicals because they spontaneously create superoxide, the radical that initiates oxidative chain reactions. Oxygen itself, which makes up 1/5 of the air your horse breathes and lives in, is by far the most abundant of the proradicals.

Oxygen is the "fire" that burns most of our energy, the universal activator required for thousands of essential biomolecular reactions. Oxygen has tremendous chemical power–to feed life, but also to damage and destroy it, when the "fire" rages out of control, and oxidizing radical exchanges overwhelm the body's antioxidant supplies.