It’s hard to find, she discovers. In people who have a strong family history of heart disease, treating high cholesterol does decrease mortality, on average. But for those who don’t have that predisposition, it doesn’t. Colonoscopies have not been proved more effective at reducing deaths from colon cancer than other, cheaper, less-invasive tests. Sometimes procedures cause more trouble than they prevent. Mammograms, for instance, detect tumors that might never be fatal, and can lead to over-treatment, which carries its own risks. The insight is counterintuitive—although finding diseases early on should prolong lives, the screenings we undergo don’t seem to lower mortality rates overall—and Ehrenreich decides that she will no longer get most preventive care.
She is just as clear-eyed about other approaches to delaying our decay—exercise, diet, meditation. Though she became a “fitness devotee” herself in middle age, she finds symptoms of cultural malaise rather than health benefits in the fitness and diet obsessions of the past 40 years. Wellness programs do little to reduce companies’ immediate health-care costs, and the pursuit of fitness, Ehrenreich argues, is often simply one more “class cue.” Workouts easily become just that—work, another demand for self-discipline, competition, and control. Ironically, when she reached her 70s, her knees began giving her trouble not from age-appropriate arthritis but from overexertion.
Turning from her critique of preventive medicine and fitness culture as death-postponement strategies, Ehrenreich is even more unsettled by research indicating that our immune system is not the magical “protective cloak” she learned about in graduate school. What really gets her rethinking her scientific beliefs is the evolving story of the macrophage—the specialized white blood cell that she always thought of as her good shepherd “through the valley of the shadow of death.”
Macrophages have traditionally been understood as one of our crucial first-line defenses against disease. They are found throughout our body—in our bones, brain, lymph nodes, lungs, and breasts—and circulate in our blood. They look like the amoebas we learned about in high school, those slippery, one-celled, independent creatures that move by stretching out and contracting, and eat by wrapping themselves around their prey, invaginating and absorbing it. The usual story went like this: Whenever macrophages find threats to our well-being in our midst—bacteria, viruses, fungi, or cancer cells—they kill them and eat them by engulfing and absorbing them. Ehrenreich assumed that keeping her immune system—and valiant macrophages—strong through exercise, diet, and positive thoughts was the key to not getting sick, not getting cancer, not getting old.
But research around the turn of the millennium suggested a different view. Macrophages do not always kill our cancer cells; sometimes they even help them grow and spread. They escort certain cancer cells through the tight walls of our blood vessels, and protect them as they circulate in our bloodstream, looking for a congenial new home. When such a site is found—in a bone or breast, liver or lung—macrophages then support those cancer cells as they mature into the metastases that will go on to kill us.