The Puritans held that reminders of mortality had an edifying effect on the living, which is why they sometimes would illustrate even literature for young children with drawings of death’s-heads and skeletons. Something of the same spirit seems to animate our ever-advancing movement for mandatory public health. The Food and Drug Administration has just floated the idea of requiring cigarette packs to carry rotating pictures that would include corpses — yes, actual corpses — as well as close-ups of grotesque medical disorders that can afflict smokers.

New York City Mayor Michael R. Bloomberg’s superactivist Health Department has begun public ad campaigns about the health risks of everyday foods, including a controversial YouTube video portraying soda drinkers as pouring globs of shimmery yellow fat into their open mouths and — just out — an ad showing an innocent-looking can of chicken-with-rice soup as bursting with dangerous salt. Whether or not you live in New York, you’re likely to be seeing more of this sort of thing because the mayor’s crew tends to set the pace for activist public-health efforts nationwide; the Obama administration, for example, picked Bloomberg lieutenant Thomas R. Frieden to head the influential Centers for Disease Control and Prevention.

Why should government use our own tax dollars to propagandize and hector us about the risks of salted snacks, chocolate milk or the other temptations of today’s supermarket aisle? The Bloomberg-Obama camp seems to feel that government dietary advice is superior to other sources of information we might draw on because (1) it’s more objective, independent and pure of motive and (2) it can draw on better science. Private food advertising itself, of course, is suspect from the start: Advertisers have a product to sell and are not in business to tell both sides of the story. But few of us depend primarily on ads as a source of health advice: Our family, friends and doctors warn us that certain foods tend to pack on the pounds or put us at risk of other bad outcomes, and if we don’t listen to them, there’s a vast popular culture of written and broadcast health-and-diet advice putting out a similar message.

The thing is, public health activists in high places have a product to sell, too. Just before the election, the New York Times ran an eye-opening piece based on an open-records request seeking background on how the city had planned its soda-as-dripping-fat gross-out campaign to scare consumers away from sugary beverages.

Some highlights of the paper’s findings:

• Staffers at the Health Department were sharply divided about whether the proposed ads went beyond the available science in demonizing sweet drinks. The city’s health commissioner, Dr. Thomas A. Farley, overruled three subordinates, including his chief nutritionist, to push things forward.

• “The scientists, [the city’s nutritionist] said, ‘will make mincemeat of us.’ ” “Basic premise doesn’t work,” said a Columbia professor of pediatrics and clinical medicine whom the city consulted.

• “ ‘The science absolutely weakens our potential for mass distribution,’ [the program’s campaign manager] wrote.”

• After some tinkering: “I think this is broad enough to get away with,” wrote the city’s nutritionist of the final video.

Enough to get away with. As Gothamist​.com summed up, “[I]n the end, it was decided that going viral was more important than going accurate.”

Incredibly, New York City’s latest ad, on salt in processed foods, is even worse. It shows a can of soup bursting at the seams with table salt, whole mounds and piles of it. The city’s underlying point is not 100 percent off-base — healthful in most other ways, conventional canned soup is a relatively salty food — but the actual amount of salt in a can is more like 1 teaspoon, not the third of a cup or more depicted in the city’s ridiculously exaggerated photo. Not to put too fine a point on it, but the Bloomberg soup ad is built on a visual lie.

What would happen if a private advertiser tried to get away with imagery as misleading as this? Well, in 1970, in a case still taught in business schools, Campbell’s got caught manipulating the soup pictures in its ads; its photographers had put marbles at the bottom of the bowl so that the pleasing vegetables would be more visible on top. The Federal Trade Commission filed a deceptive-advertising complaint to make the company stop.

If you’re expecting today’s federal government to chide New York City for its graphic falsehoods, think again. Last month, the federal Centers for Disease Control — headed by Bloomberg’s own Dr. Frieden — announced a $412,000 grant to assist the city in its anti-salt efforts. For everyone’s own good, of course.