When Luke and I wrote our first Stock Report in January titled “Who doesn’t love the Napa Valley?,” we had convinced ourselves the foolproof test of greatness as a chef would be a willingness to forego easier bouillon and make stock from scratch. That’s why we named our column The Stock Report.

Well, in six months of living in Napa, we found that the more telling indicator of a truly extraordinary chef is that he or she insists on serving only traditional fats and oils.

Traditional fats and oils are more expensive than industrial, as much as 10 times the cost, and price is a pretty reliable mark of an ingredient’s quality. But the reason I’m writing this letter to Napa’s chefs is to raise awareness that a growing number of scientists, doctors, and other health care practitioners believe traditional fats are part of a healthy diet and the industrial fats may be toxic.

Unfortunately, we’ve met few chefs who make this distinction.

Traditional oils include olive, coconut, peanut, grapeseed, almond, avocado, walnut and a few others. (Ideally, they will be processed traditionally, too.) Traditional fats include butter and animal fats like lard and beef fat (tallow).

Industrial oils include canola, corn, soy, sunflower, cottonseed, safflower and rice bran. Industrial fats include margarine, shortening and solid deep-fryer fats.

At the 30 or so Napa restaurants we’ve enjoyed to date, when we asked our waiter if the salad dressings and grilled veggies were made using olive (traditional) or canola (industrial) oil, most had no idea. When the server has no idea if the restaurant uses an ingredient that costs 10 times as much as the alternative, that’s either because they aren’t using it, there’s a major communication gap, or someone’s not doing their job.

Two servers, at Hog Island Oyster Company and Kitchen Door, gave us an emphatic “no” to the question of industrial oil use. A third, at Go Fish (now Brassica, still owned by Cindy Pawlcyn) told us, “We don’t allow canola oil on the premises.”

The rest, it turned out, were using canola or a blended oil containing mostly canola, which we believe contributes to the development of heartburn.

Most of the chefs I’ve met personally who stick to traditional fats downplay this preference, almost apologetically explaining that they use just a little. But there’s no need to apologize. As long as you don’t reuse them over and over, then the fats you are using will not cause health problems. The kind your competition uses will.

You don’t have to take my word for it. Multiple lines of research are all converging around the idea that traditional fats and oils are actually healthy, including epidemiological, laboratory research, and — most important — clinical observations.

I am a member of the American Society of Bariatric Physicians, and at least half of the practitioners who attend our meetings employ some version of a low-carb, high-fat diet because that’s the kind of diet that produces results: weight loss, blood pressure, cholesterol and blood sugar control, and other beneficial effects.

What’s more, many people with digestive and autoimmune diseases have, on their own, adapted some version of a low-carb, high-fat diet and experienced dramatic improvement. I tell my patients that choosing skim and low-fat promotes depletion of necessary nutrients including lecithin, choline, biotin, and phospholipids, and others currently being sold to dieters as supplements.

I suspect more than two of Napa’s fine eateries make using only quality fats and oils a priority. But the trouble is these are hard to find. I’m writing today in hopes that these chefs may make themselves better known for this choice.

There is a huge movement away from the industrial food chain that encompasses not just Alice Waters and Michael Pollan fans, but also dieters, fitness enthusiasts, working moms and more. They are adherents to one or more industrial-food-free popular diets such as the Paleo Diet, the Atkins Diet, the Dukan Diet, the Low-Carb High-Fat diet, and the GAPS Diet.

Right now, many are sticking to these diets for health reasons — and because industrial oils are not disclosed on menus, avoiding them becomes so cumbersome they’d prefer to limit themselves to food made in their own kitchens.

As more restaurants make it known they are using traditional oils and fats, I believe an eager audience will emerge.

This will be our last Stock Report because Luke and I are embarking on our next book, tentatively titled “The Napa Paradox.”

If you are a chef interested in real food and you’d like to participate by lending a recipe we can credit to you, please contact us through our website.

Cate Shanahan, M.D., is a family physician with Queen of the Valley Medical Associates and can be reached at 251-3681. Luke Shanahan is a food and health writer and aspiring cook. Their books include “Deep Nutrition: Why Your Genes Need Traditional Foods” and “Food Rules: A Doctor’s Guide to Healthy Eating.” Learn more at DrCate.com.