1
00:00:00,351 --> 00:00:06,320
Not surprisingly, the secrets of aging lie deep in the molecular biology of individual cells.

2
00:00:06,320 --> 00:00:14,338
There are admittedly several theories of aging, but one has emerged as the most compelling and best supported by impressive new evidence.

3
00:00:14,338 --> 00:00:21,894
This does not mean the theory necessarily accounts for all aging changes, but many authorities believe it explains a major part.

4
00:00:21,894 --> 00:00:33,106
It is called the free radical theory of aging, and it goes this way: Aging occurs when cells are permanently damaged by continual attacks from chemical particles called free radicals.

5
00:00:33,166 --> 00:00:44,413
Simply, the cellular damage accumulates over the years, until the totality of destruction reaches the point of no return — diseases clustered at the end of life and eventually death.

6
00:00:44,446 --> 00:00:57,163
This, then — the perpetual but futile struggle of individual cells to stay alive and function normally, in the face of chemical disintegration — is the genesis of aging and all its consequences.

7
00:00:57,181 --> 00:00:59,297
Oxygen is what it is all about.

8
00:00:59,318 --> 00:01:03,160
Ironically, the stuff that gives us life eventually snuffs it out.

9
00:01:03,160 --> 00:01:12,014
The ultimate life force lies in tiny cellular factories of energy, called mitochondria, that burn nearly all the oxygen we breathe in.

10
00:01:12,014 --> 00:01:13,598
But breathing has a price.

11
00:01:13,599 --> 00:01:20,767
The combustion of oxygen that keeps us alive and active spews off by-products called oxygen free radicals.

12
00:01:20,767 --> 00:01:24,287
They have Dr. Jekyll and Mr. Hyde characteristics.

13
00:01:24,287 --> 00:01:27,356
On the one hand, they help guarantee our survival.

14
00:01:27,357 --> 00:01:36,435
For example, when the body mobilizes to fight off infectious agents, it generates a burst of free radicals to destroy the invaders very efficiently.

15
00:01:36,435 --> 00:01:56,536
On the other hand, free radicals, including the pervasive superoxides created by respiration, careen out of control through the body, attacking cells, turning their fats rancid, rusting their proteins, piercing their membranes and corrupting their genetic code until the cells become dysfunctional and sometimes give up and die.

16
00:01:56,536 --> 00:02:02,832
These fierce radicals, built into life as both protectors and avengers, are potent agents of aging.