ANOTHER BATCH OF SETTLED SCIENCE THAT HAS UNRAVELED: The Growing Food Fight over the Government’s Nutrition Guidelines.

For decades, the government has advised Americans on what they should eat. The advice isn’t just advisory; it drives everything from school lunches and agricultural subsidies to marketing for those bowls of candy we call breakfast cereal. But the science behind this enterprise has always been shaky. . . .

In 1988, the surgeon general issued a report declaring ice cream to be a “comparable” public health threat to cigarettes. The science was settled. Except it wasn’t. If you’ve been paying any attention, you’ve seen the stories about how fat isn’t necessarily bad for you, while carbs are the real enemy. Studies have found that more milk fat in your diet correlates with less heart disease. Who’s right? I lost nearly 50 pounds in part by cutting out carbs. That’s clear enough for me, but it’s also clear there’s a lot we don’t yet understand. . . .

“There’s a lot of stuff in the guidelines that was right 40 years ago but that science has disproved. . . . Sometimes the scientific community doesn’t like to backtrack,” David McCarron, the incoming chairman of the Medical Nutrition Council at the American Society of Nutrition, told the Washington Post. There’s no shortage of lessons here, well beyond this food fight. Even when everyone’s intentions are good, politics can get in the way of science. Scientists are not immune to fads and groupthink just because they claim to speak for science. Special interests work the refs, but the refs often have an agenda as well. Winners of policy fights hate to lose — or admit they’re wrong. And people who shout about a settled consensus are often only shouting to drown out those who might disagree.

Maybe the government shouldn’t be telling us what to eat.