If we really are what we eat, then we are a strange bunch of folks after all.

That’s the diagnosis from journalist and author Frederick Kaufman. In his gastronomic exploration “A Short History of the American Stomach,” he starts with the Puritans — who seemed to like fasting and vomiting as much as buckled headwear — moves on to the “kosherization of America” and concludes with today’s chip- and soda-wielding television viewers mesmerized by Rachael Ray whipping up a popcorn ball.

In a Feb. 22 lunchtime speech at San Francisco’s Commonwealth Club, the Jewish journalist, author and English professor at City University of New York expounded on food for thought (about food).

He explored the universe of raw milk covens (he infiltrated one in Manhattan), fad diets of the 19th century and cowboy eating contests (two men, 50 yards of cow intestine and a lot of spare time). In an interview afterward, he marveled at the prevalence of kosher food in America.

While that may not help an observant Jew find a nice place to eat in Kanakee, Ill., it makes a big difference at the supermarket.

“I believe the latest statistic is that $500 billion is spent yearly at [American] grocery stores. Of that, $170 billion is spent on kosher products. That’s an astounding statistic,” he said.

That’s putting it mildly. How is this possible when Jews make up 2 percent of the population? Is there one guy out there buying billions of dollars’ worth of Hebrew National hot dogs just for the joy of it?

Not quite, said Kaufman, whose German Jewish relatives arrived in Virginia before the Revolutionary War. First of all, it’s not just Jews buying kosher — Seventh-Day Adventists, Muslims, vegetarians, health food enthusiasts and “people who want a bit of ethnic spritz” pick up kosher products. Indeed, 28 percent of consumers have knowingly bought a kosher product in the past year. No doubt more have done it unknowingly.

Although the several thousand dollars required to acquire kosher certification may pull rent money away from a corner deli, it’s chump change to companies such as Coca-Cola, which went kosher in 1937, he said.

Major food producers have noticed their market share rise modestly after ensuring that their products are kosher — modest gains that translate into millions in revenue.

But that’s not all, he said.

When Coke, Snickers or Campbell’s Soup goes kosher, it means every ingredient in the can or bar has to be kosher too.

“The real effect of kosherizing America is one step down from the finished product to the level of ingredients. If you’re a sugar purveyor in this country and you’re preparing for an order from Snickers, you better have sugar that’s certified kosher,” he said.

“That means all the sugar in America is certified kosher and almost everything on the ingredient level that can be certified kosher is certified kosher.”

But there are some kosher ingredients that aren’t even ingredients. Confused? Don’t’ worry. So is nearly everyone else, he said.

He recalled a recent trip to Fugelbakken, Denmark, with Rabbi Menachem Genack to ensure that enzymes used in food production were certified kosher.

“Enzymes are the great little secret of food production in America today,” said Kaufman with a laugh.

Used even in “all-natural” products that tout their simplicity, the enzymes stimulate production — “they’re in every hot dog bun in America” — and are then removed and reused. And since they are not in the finished product, the enzymes are not required to be listed as ingredients.

They do need to be certified kosher, though, and the big boxes of enzymes shipped to the United States have “KOSHER” emblazoned upon the sides. The boxes heading to Sudan, on the other hand, don’t carry the big label — “but they’re kosher anyway,” said Kaufman.

“A Short History of the American Stomach,” by Frederick Kaufman (208 pages, Harcourt, Inc., $23)