Why Medical Advice Seems to Change So Frequently
By Aaron E. Carroll for The New York Times
Medical scientists and academics must publish their research to advance. Medical organizations must release health recommendations to remain relevant. News organizations feel they must report on research and recommendations as they are released. But sometimes it’s hard to separate what’s truly a medical certainty from what is merely solid scientific conjecture.
I thought about this recently when the National Institute of Allergy and Infectious Diseases expert panel changed course and recommended that we start giving babies peanut powder or extract in food before they are six months old rather than make sure they go nowhere near it. The panel said this is good advice, especially if the babies are at higher risk for developing an allergy.
I’ve written about the research supporting these new recommendations before. A recent well-designed study showed that infants exposed to peanut protein developed significantly fewer peanut allergies than those who were not. The measurement, called number needed to treat (N.N.T.), was powerful: For every seven infants exposed to peanut protein, one fewer developed allergies. In the high-risk population, for every four infants exposed, one fewer became allergic. Those numbers are stunning.
But it’s important to remember that the earlier recommendation wasn’t made in the Dark Ages. As recently as 2000, the American Academy of Pediatrics declared that children at risk for allergies be given no peanuts until they were 3 years old. It’s not unrealistic to think that this might have increased the number of children with peanut allergies, not decreased them.
This isn’t an isolated incident. As a pediatrician, I’m more aware of the academy’s recommendations than those of some other medical organizations, and I’ve taken to The Upshot to discuss their statements on car seats on planes, the use of retail clinics and where babies should sleep. In each case, I’ve expressed concerns that the recommendations, which were not supported by strong evidence, may be doing more harm than good.
The American Academy of Pediatrics isn’t acting in bad faith, though, nor is it alone. Recommendations from other medical organizations for mammograms, which weren’t supported by well-designed randomized controlled trials but for years went unchecked, are now being scaled back because of concerns that they may be leading to bad outcomes without compensating benefits.
Recommendations for prostate cancer tests are facing a similar fate. Hormone replacement therapy, recommended widely before the early 2000s, almost went away after the Women’s Health Initiative Study. Today, recommendations argue that we’re not using that therapy widely enough, perhaps leading to deaths.
But nowhere is this recommendation whiplash more disorienting than in nutrition. Recommendations pushing low-fat diets may have led to an increase in carbohydrate consumption, which many experts now believe may have made the obesity epidemic worse. Coffee was considered a potential carcinogen, until overwhelming evidence led to its recognition as part of a healthy diet. You were told you should never miss breakfast, you should drink more water and you should use natural sweeteners like honey. Except none of those things are well supported by science.
Often recommendations are born out of a need to do more for more people. If something works for one group, we tend to believe that it should work for more. People at high risk for breast or prostate cancer may need to be screened for the diseases. Expanding that screening to people at low risk, however, yields more false positives than true revelations. Hormone replacement therapy most likely benefits some women, especially younger women and those who have had a hysterectomy. Others get the same side effects or harms with little benefit.
Other times, recommendations consider only the upside and fail to consider the potential pitfalls. This would apply to recent sleep recommendations, which may (and I stress may) benefit babies but also might hurt them and parents in other ways.
But most often, recommendations fail because they aren’t supported by high-quality research. They have only observational trials behind them, not the full weight of randomized controlled trials. Too many times, organizations have been burned when the associations we see don’t translate to causal changes in the more strict randomized controlled trials.
Unfortunately, when it comes to food, the problems run together. Pick any food fad, be it low-fat, low-carb, gluten-free or peanut avoidance, and you’ll see the markers. Some people benefit from avoiding certain foods, so organizations proclaim that all people will benefit. They have observational studies that support their beliefs, and if other such studies contradict them, well, those can be ignored. Few consider the downsides of these changes, until years later, when we look back and wonder what we were thinking.
There’s growing evidence that simple lifestyle changes may be more influential than many medical interventions. That advice, though, is bland and nonspecific. Get some exercise. Don’t smoke. Don’t drink too much. Don’t be obese. And try to eat a bit better. But none of them advocate drastic change or abstinence in any one nutrient or food. Moderation may not only feel right; it may be right, too.
This was the thinking behind my food recommendations years ago. It’s the philosophy behind many of my recent columns as well. Of course, if everyone started applying common sense to these issues, I’d have a lot fewer columns to write.
I’d be willing to make that sacrifice, though, if you’d all — medical professionals and everyone else — be willing to be more thoughtful and skeptical of what we “know” to be right.
Article courtesy of Aaron E. Carroll for The New York Times.