The potato industry recently scored a big victory, in what sounds at first like a familiar story of Big Ag winning out over public health.

Eight years ago, over allegations of insufficient nutritional value, potatoes were excluded from a government program that helps pregnant women and young children improve their diets.

The rationale was that aid recipients in the Women, Infants, and Children program already ate plenty of white potatoes, a widely consumed vegetable in the U.S.

But in February, potatoes were back on the menu after a fierce multiyear lobbying campaign by the National Potato Council. Nutritionist Marion Nestle and other progressive reformers called foul, denouncing the change. “Really?” Nestle scoffed. “I have a hard time believing that WIC recipients are suffering from lack of potatoes in their diets.”

Several watchdog groups and the national WIC advocacy group opposed the change, too. “It’s disappointing that politics has trumped science,” Margo Wootan, director of nutrition policy at the Center for Science in the Public Interest, told reporters.

But did science really lose? In this case, the potato industry had science on its side, the outcry from nutritionists notwithstanding. Despite the common belief that potatoes are nutritionally null, a report released in February by the Institute of Medicine, an independent nonprofit, shows that white potatoes are an inexpensive source of potassium, fiber, and other needed nutrients, and one that people actually enjoy eating.

The takeaway from the potato controversy is not that lobbyists sometimes base their campaigns on real science. Rather it’s that the David-and-Goliath narrative of science versus Big Ag may be blinding us to another, even bigger problem: the fact that there is often very little solid science backing recommendations about what we eat.

Most of our devout beliefs about nutrition have not been subjected to a robust, experimental, controlled clinical trial, the type of study that shows cause and effect, which may be why Americans are pummeled with contradictory and confounding nutritional advice.

Nutritional bad guys that have fallen from grace in the national consciousness—white potatoes, eggs, nuts, iceberg lettuce—have been redeemed years later. Onetime good guys, like margarine and pasta, have been recast as villains. Cholesterol is back in the probably-won’t-kill-you column after being shunned for 40 years, as of the latest nutritional advice from the Dietary Guidelines Advisory Committee in February. (That advice was still too timid, according to Cleveland Clinic cardiologist Steve Nissen, who also wants the nutritional guidelines to admit our best evidence suggests fat isn’t bad for you either).

And then there’s salt—don’t eat too little, says the newest research. You could die.

Amid the growing concern that nutritional advice to avoid high-fat food led to overconsumption of carbohydrates and caused spikes in illnesses like Type 2 diabetes, more and more scientists are starting to worry publicly that the basis of our dietary advice is scientific quicksand.

How potatoes were born again is a telling example of the uncertain foundation of nutrition. Potatoes had a bad rap in part because they are usually eaten deep fried, but even when they are not, they have a high glycemic index, according to prominent Harvard nutritionist Walter Willett.Steffi Loos/DAPD/Associated Press

A high GI means that foods quickly turn into sugar (glucose) in the body and may eventually lead to heart disease and other illnesses, especially among diabetics, according to an analysis of data from the Nurse’s Health Study at Harvard, which Willett oversees.

He placed potatoes in the same naughty group as candy in his influential 2005 book Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating. One of his studies concluded that white potatoes are worse than soda, leading the L.A. Times to dub spuds public enemy No. 1 in 2011.

So how, just a few years later, did white potatoes return to the list of healthy foods?

The IOM committee found a lack of evidence supporting claims that the tubers are unhealthy. WIC only pays for fresh produce, or frozen or canned fruits and veggies with nothing added, so there is no worry women in the program are using their vouchers for potato chips.

No one contests the positives of potatoes—much needed micronutrients and fiber—and there isn’t enough proof, they found, that the GI is important to health. So white potatoes got the green light.

Willett calls the IOM potato report “myopic,” because other vegetables have the same needed nutrients as potatoes without the possible dangers of high GI foods that his studies have shown.

And because micronutrient deficiency isn’t our biggest dietary problem, Willett told me in a recent email exchange, “obesity is likely to be of greater concern.”

In other words, why take the risk on a possible downside to eating potatoes when you don’t need to?

Written by Heather Tirado Gilligan and published by SLATE, April 18, 2015.

FAIR USE NOTICE: This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a ‘fair use’ of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U. S. C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www. law. cornell. edu/uscode/17/107. shtml“