Sunday, November 25, 2007

SEX SLEEP EAT DRINK DREAM

A Day in the Life of Your Body

By Jennifer Ackerman

Houghton Mifflin. 253 pp. $25

Scientific studies of food, sex and sleep are inevitably delicious. Take the finding that eating butter and fat reduces sensitivity to pain. Or the discovery that men are more attracted to photos of women in the fertile phase of their menstrual cycles. Or the finding that women who ate chocolate every day during pregnancy had babies who tended to smile and laugh more.

Science writer Jennifer Ackerman, a contributor to National Geographic and the author of two previous books, scoops up these and many other tantalizing tidbits in Sex Sleep Eat Drink Dream, loosely organized as a day in the life of the body. The book progresses from a 5:30 a.m. wake-up through a day of work, food, exercise, cocktails and sex, with each activity launching forays into the scientific corpus.

Ackerman's approach is most engaging -- and least gimmicky -- when she describes how the body's abilities and internal priorities shift during the day. She notes, for instance, that testosterone production in men tends to spike around 8 a.m., but the amount of sperm per ejaculation peaks in the afternoon, making this an excellent time for baby-making. We may hustle to the gym before work, but exercise is physiologically easier in the late afternoon: Our body temperatures are higher, our airways more open, and our capacity for building muscle mass greater. "Most sports records are set between 3 p.m. and 8 p.m.," she reports. Also in the early evening, the body's tolerance for alcohol hits a high, "just in time for the cocktail hour."

Ackerman nicely explores the implications of circadian rhythms for medical care, as well. She points out, for instance, that at night some kinds of cancer treatments seem to be more effective -- and cause fewer side effects -- a difference that clinicians ought to pay more attention to.

For much of the book, though, her approach is to pile one wondrous finding atop another: how soothing music increases productivity in dairy cows, how laughter improves heart health, and how walnuts, salmon and cold-water sardines can improve mood. Unfortunately, she rarely differentiates between rigorous studies and lightweight ones. (Research on the basic underpinnings of circadian rhythms appears in top journals, but the only citation for that study of music and dairy cows is a newspaper called the New Indian Express.) Ackerman's tidbits, it seems, aren't always as meaty as they are delicious.

-- Amanda Schaffer is a science and medical columnist for Slate.