What does it mean to grow old? The simple answer, from the perspective of physics, is the passage of time. And in physics, as time passes things tend to deteriorate or break down. That process is called entropy.

The difference between the physical perspective and the biological world is that living organisms have the ability to either slow down the deterioration process, or in some cases, even reverse it.

Unfortunately, there are a lot of things working against us — including environmental dangers such as:

• Pesticides
• Herbicides
• Fungicides
• Industrial chemicals
• Ultraviolet rays
• Excessive heat
• Trauma
• Fluoridation of drinking water
• Mercury vapor in the air
• Aluminum in the air and water

The first three are the most ubiquitous and dangerous, but there are thousands of others. All these forms of environmental exposure cause inflammation.

A great deal of research suggests that inflammation — especially chronic, low-level inflammation — accelerates aging.

Other things can tear our bodies down as well, including infections, stress (both physical and mental), lack of sleep, deficiencies in nutrients, and less commonly, genetic disorders. A poor diet — like the typical Western diet — is a leading factor in poor response to aging.

Unfortunately, most members of the medical establishment treat proper nutrition as an afterthought. Your doctor may mumble something about controlling fat intake or losing weight, but then he or she will spend more time scribbling prescriptions or trying to convince you that you have a condition for which there is no known treatment.

There are a number of theories about aging, the most popular being the free radical theory and the telomere theory — both of which are related.

The very fact of living necessitates the production of high levels of free radicals, which are reactive particles that can damage a number of essential biological tissues, including DNA, cell membranes, and mitochondria.

When a person is healthy, his or her antioxidant network is able to neutralize most of these destructive particles. But that's not usually the case.

In fact, most people produce more oxygen and nitrogen free radicals than their bodies can handle.

When critical parts of cells and tissues are damaged significantly by free radicals, they begin to break down. This can lead to detrimental conditions such as:

• Kidney failure
• Poor eyesight
• Hearing difficulties
• Heart failure
• Cancer
• Intestinal disorders
• Liver failure
• Defective immunity
• Poor cognition (thinking and memory)

In most cases, this destructive process takes place over the course of decades, accelerating as a person reaches his or her advanced years.