" To experience a food science miracle, go to Canada. Buy a 5.5-ounce bag of Family’s Best brand sour cream and onion (crème sur et oignon) potato chips. Bring them back. Watch closely as a belly-bloating 250-calorie serving drops to 150 calories. Total fats slim down from 16 grams to 9 and sodium lightens by 150 mg per serving.

It’s not all such good news. The chips that offered 20 percent of your daily needs of vitamin C in the Great White North provide only 10 percent in the Land of the Free. And fiber drops from 2 grams to 1.

Most of the changes result from differences in official serving sizes. In the States, a serving of chips is just 1 ounce, “about 12 chips,” according to the nutrition label. In Canada, it is 1.8 ounces. (Mysteriously, their label says that is “approximately 30 chips.” Go figure.) In any case, the Canadians come closer to the 5 ounces I can easily eat in a 15-minute car trip.

But one miraculous trans-border transmogrification can not be explained so easily. It involves trans-fats. In Canada, a serving provides a third of a gram of trans-fats. That little number might convince health-conscious parents to put the bag back on the store shelf, perhaps next to the insecticide.

But why bother? They could turn those toxic tasties into harmless indulgences by carrying them just a few kilometers south. Pass through customs and look again — the bag of chips is trans-fat free. “0g,” says the label.

American consumers, who see Canadian nutrition labels about as often as they play hockey, have no way to know that their label is lying. Zero grams is not the same as .2 grams or even .1 grams.

How can it make sense to punish responsible, label-reading consumers (all 3 of us!) by hiding the truth?

As it turns out, plenty of sense. In the words of President Herbert Hoover, the business of the “American people” is business. And the “American people” includes Mr. Cape Cod, Ms. Granny Goose and their uncle, Mr. Frito Lay.

Thanks to the miracles of monocultures, genetic engineering, and industrial irrigation, there are way too many potatoes. If the Food and Drug Administration needs to tell a little white lie to get you to eat your vegetables, who are you to complain?

Think about it in terms of who benefits. You buy some chips — the growers and chip companies make a buck and you get the satisfying crunch of a salty snack between your jaws. Win-win. Later, you come down with heart disease. The cardiologist makes a buck and the gross domestic product gets the satisfying crunch of your life savings between its jaws. Win-win!

The reason this beautiful synergy fails in Canada is that that country’s government has, despite the best efforts of its homegrown conservatives, aligned itself with public health. This alliance even holds up against the power of agribusiness, which is no weaker on the vast prairies of Saskatchewan than it is on the great plains of our Dakotas.

The difference arises from Canada’s single-payer health insurance system. Americans like to argue that their insurance system is better even though we pay 5 times as much for overhead, our infant mortality is off the industrialized world’s charts, and our insurers think it’s their job to put the “prevent” into preventive care. At least we can get an MRI on 2 days’ notice, if we have a few grand to spare, right?

Americans don’t realize how public health insurance scheme helps put Canada’s government on the same side as its people when it comes to public health. In Canada, there is no question as to whether seatbelt laws are a good idea. Taxpayer money covers everyone’s health care. I have an obvious financial stake in keeping my neighbor’s forehead away from his windshield. If he ends up like Humpty Dumpty, I will have to pay the king’s horses and men for their hopeless efforts.

Sure, the same is true in the States. We also pay for our neighbors’ mistakes. But here, the cost is broken up among individual insurance plans, various types of taxes, and even the workers comp insurance paid by our employers. The system in Canada makes the connection between neighbors much more obvious.

Which brings us back to the magic potato chips. The Canadian half of the shiny label reflects a somewhat more realistic version of the real world because the Canadian government pays for every case of heart disease. It has every reason to tell consumers the truth about their food.

This might also explain why Canadian cigarette packages have for years carried the world’s most disturbing full-color warnings.

A government by, of, and for the people — the one in Washington, D.C. — should do everything it can to at least help its citizens learn about the health consequences of their actions. Unfortunately, so long as “the people” includes such citizens as Mr. Cod, Ms. Goose, and Mr. Lay, government will need a little nudge in order to do right by those of us with a pulse. Single-payer health care installs that nudge into the political system.

Alas, the result could be a less wonderful world. No longer will Canadian parents be able to spare their childrens’ health simply by carrying junk food south of the border. Is the health of all Americans worth the loss of this miracle?