Food is America’s official national obsession.

But what exactly deserves to be called “food” is up for debate in Michael Pollan’s latest book, “In Defense of Food: An Eater’s Manifesto.”

After giving us glimpses into America’s feedlots, food-processing plants, organic factory farms and small local farms in 2006’s “The Omnivore’s Dilemma,” Pollan is back with a 200-plus-page sequel featuring his own take on Americans’ nutritional pitfalls, diseases and how to eat right in America.

His slightly academic, heavily annotated and thoroughly indexed book tackles not where food comes from in America, but “what to eat” in this food-crazed country.

Answer: “Eat food. Not too much. Mostly plants.”

It turns out eating whole foods, instead of “food substance” products, isn’t just healthy, it’s eco-friendly.

Also, eating meat as a “side dish” and focusing more on plant-derived food, Pollan argues, can actually be a green act and not just from an animal-rights point of view. (Let’s not forget: This is the man who took us on a wild boar hunting trip in which he shot his own pig dead with the sole purpose of eating it, which he did.)

“In most but not all cases,” Pollan writes, “the best ethical and environmental choices also happen to be the best choices for our health – very good news indeed.”

Having skimmed the book a bit – I do plan to read it all – I think his most interesting and hilarious chapters might be “Escape from the Western Diet” and “Eat Food: Food Defined” in which he offers numerous all-caps points for guidance.

Don’t eat anything your great-grandmother wouldn’t recognize as food. Imagine walking the supermarket aisle with your great granny and showing her Go-Gurt Portable Yogurt, Pollan suggests, adding, “Is a product like Go-Gurt Portable Yogurt still a whole food? A food of any kind? Or is it just a food product?” He also adds: “‘Don’t eat anything incapable of rotting’ is another personal policy you might want to consider adopting.”

Avoid food products containing ingredients that are a) unfamiliar, b) unpronounceable, (c) more than five in number, or that include d) high-fructose corn syrup. Pollan uses the ridiculously long ingredients list for the oxymoronic Sara Lee’s Soft &Smooth Whole Grain White Bread to illustrate his point. “Monoglycerides I’ve heard of before, but ethoxylated monoglycerides?”

Avoid food products that make health claims. Don’t forget, Pollan reminds us, that trans-fat-rich margarine was one of the first industrial foods to claim it was healthy or at least healthier.

Shop in the peripheries of the supermarket and stay out of the middle.

Get out of the supermarket whenever possible. Instead, try farmers markets and CSA shares.

Eat mostly plants, especially leaves. “In all my interviews with nutrition experts, the benefits of a plant-based diet provided the only point of universal consensus,” Pollan writes.

If you have space, buy a freezer. Fill it with a ¼, ½ or a whole pastured steer from a local farmer. “A freezer will also encourage you to put up food from the farmers market, allowing you to buy produce in bulk when it is at the height of its season.”

Pay more. Eat less. “The American food system has for more than a century devoted its energies to quantity and price rather than to quality. … Not everyone can afford to eat high-quality food in America, and that is shameful; however, those of us who can, should. … Another important benefit of paying more for better-quality food is that you’re apt to eat less of it.”

Well, I’m not sure I believe that last point. Quality food tastes so much better, I’m apt to eat much, much more of it! I’d wager, however, that high-quality, expensive food is wasted far less often.

“In Defense of Food” should hit bookstores in hardback Jan. 1.