I never had a chemistry kit when I was a kid. It was my least favorite subject in school and killed my grade point average. I doubt that I retained a single chemistry fact or principle five minutes beyond final exams.

Yet when it comes to the care and feeding of my own body, I have become something of a chemistry expert.

Brief background: I was born with digestive problems that persisted chronically throughout childhood. I was constantly sick growing up, with two or three bad colds a year. I missed most of 5th grade with mono. I was hospitalized when I was 14 with ulcerative colitis so severe that the doctors told my parents that nothing could be done and they should prepare for my death.

Two weeks of hospital food and removal from the stresses of my life and I improved enough to be released from the hospital. I had learned two important lessons: first, the doctors didn’t know why I was sick or why I improved; second, my condition changed from day to day depending for the most part on diet.

Even while I was struggling in chemistry class, I had begun a long-range chemistry experiment with the simplest of protocols: pay attention to what I was eating and drinking each day and then, starting with the next morning’s trip to the bathroom, pay attention to my results, including the condition of my hair and skin. If the results were less than ideal, I would consider changing something in my diet.

Or: input chemicals; observe outputs; reassess and make adjustments to inputs. Repeat daily.

We are exposed to astounding amounts of pollution. Over 80,000 chemicals have been introduced into our society since 1900, and only 550 have been tested for safety. According to the US Environmental Protection Agency (EPA), about 2.5 billion pounds of toxic chemicals are released yearly by large industrial facilities. And 6 million pounds of mercury are poured into our air every year.

In fact, a recent government survey — “The National Report on Human Exposure to Environmental Chemicals” issued in July 2005 — found an average of 148 chemicals in our bodies. And those were only the ones for which they tested . . . The Environmental Working Group examined the umbilical cord blood of children just as they emerged from the womb. They found 287 industrial chemicals, including pesticides, phthalates, dioxins, flame-retardants, Teflon, and toxic metals like mercury. — Dr Mark Hyman

Highschool chemistry 101: chemical A mixed with chemical B results in X; chemical B mixed with chemical C results in Y; and chemical C mixed with chemical A results in Z. Most chemicals are reactive — when mixed with one or more other chemicals they result in new substances with different properties.