RALEIGH – The financial challenges and practical problems embedded in America’s health care system are so daunting that few politicians feel they can be candid about them without running into a political buzzsaw.

Many resort to vague promises of a free lunch, of some fantastic arrangement in which everyone will be “covered” by a government-run insurance plan that will deliver everyone the medical services they desire while costing less than the current system. They square the circle by arguing that if the new government monopoly expands access to preventive care, it will pay for itself by averting costly diseases in the future.

The argument sounds plausible. But it is contradicted by the vast preponderance of the evidence about the net financial benefits of preventive medicine.

This is not even a controversial proposition any more among health care experts. They know preventive care doesn’t, on balance, pay for itself. They know that under the current system, patients frequently receive tests costing thousands of dollars that discover too few diseases needing intervention to justify those costs. Some of the tests are ordered defensively, so medical providers aren’t as vulnerable to tort lawsuits. Others are ordered because they are confer medical benefits on some patients while seeming not to cost much because of the peculiarities of third-party payment of medical bills.

The influential policy journal Health Affairs just published another survey of the literature. Here’s the abstract:

Over the four decades since cost-effectiveness analysis was first applied to health and medicine, hundreds of studies have shown that prevention usually adds to medical costs instead of reducing them. Medications for hypertension and elevated cholesterol, diet and exercise to prevent diabetes, and screening and early treatment for cancer all add more to medical costs than they save. Careful choices about frequency, groups to target, and component costs can increase the likelihood that interventions will be highly cost-effective or even cost-saving.

As you can see, the proper conclusion from the data is not that we shouldn’t try to find ways to prevent debilitating or deadly diseases. And there are some targeted interventions that, given the government’s already substantial role in health care finance, probably save money for taxpayers over the long run, particularly when the interventions are inexpensive.

The proper conclusion is that expansive government “reforms” of health care cannot be funded by phantom savings from preventive care. If you hear a politician saying that, you can be sure that he is either misinformed or disingenuous.

Hood is president of the John Locke Foundation