Why doctors’ advice is so often wrong, and how it affects us

Tiffany Mcleod followed the advice to the letter. She has food allergies, and was worried her children might too. Her doctor recommended she avoid eating nuts while pregnant or breastfeeding, and to keep the kids away from them until the age of three.

“You want to do what’s best for your child,” she says. “And you figure that your doctor knows what that is.”

Her doctor was following American Academy of Pediatrics (AAP) guidelines issued in 2000. But by 2008, AAP had backed off from this recommendation. Then last year, it reversed course. A large study had found that regular exposure to peanuts from four months of age reduces the risk of allergy by about 80 per cent. McLeod, who lives in Texas, in the United States, had both of her babies in the years between the changing advice. She learned the hard way that her youngest has a life-threatening allergy.

“We had to rush her to the emergency room. It was extremely scary,” she says.

It would be comforting to think the drastic change in advice with peanut allergy is unique. But this type of medical about-face isn’t rare. A recent analysis of research published in one medical journal over 10 years identified a whopping 146 such reversals. To be clear, this is not just the process of upgrading advice as better evidence comes in. These are practices that became routine before we learned they didn’t actually work. And worse, before we knew if they could cause harm.

In the era of evidence-based medicine you might assume most of your doctor’s advice is based on information obtained through rigorous testing. But it is becoming clear that is often far from the case. Fortunately, people are now shining a light on the problem, and devising ways to fix it.