What's good for you can cause you to do not-so-good things.
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It's hard not to feel just a little bit virtuous after choosing an antioxidant-rich smoothie or, say, the omega-3-rich salmon choice on a steak house menu. There's an almost irresistible connection between making the "right" choice and a tiny feeling of pride.

But pride can cometh before a fall: namely, a fall into the spell of the "health-halo" effect, a phenomenon that leads us—even those experienced with nutrition numbers and claims—to overestimate the value of a food by casting it in a virtuous light because of one narrow attribute. As more and more foods get labeled and associated with health benefits, the problem only grows.

Problem? Well, health halos, according to Brian Wansink, PhD, who heads up the Food and Brand Lab at Cornell University, can get you to eat more food than you intended. One of Wansink's studies found that when people opted for a low-fat snack, they ended up eating 90 more calories compared to people who selected regular snacks.

This is perhaps not surprising: The low-fat label is the Mother Teresa of all health halos, often used on snacks and sweets that may be quite high in calories or sodium.

This is not to say, of course, that some foods don't deserve their good-for-you reputation, and in many cases a low-fat food is a better choice. This is especially true when it comes to low-fat or fat-free milk, yogurt, and other dairy products. But marketers have long used the low-fat label for its halo effect.

A similar thing happens when "organic" is added to a label. People who ate organic cookies in another Wansink study thought the treats contained 40 percent fewer calories than the exact same cookies without the organic label.

It appears that many health claims can have an unintended halo effect. For example, "trans-fat-free" is an important benefit to everyone who wants to avoid manipulated fats that are implicated in cardiovascular disease. Yet researchers studying the trans-fat claim found that, in the case of crackers, it created such a bright halo that people in one study thought that a meal featuring the crackers was lower in calories than the same meal without the crackers—even though the crackers added 100 calories.

The effect appears to be real, but it doesn't mean that health claims lead to obesity. Nor does it mean that the "no trans fat" claim is bad. But it highlights the complex relationship between food, language, and the dozens of choices we make every day.

We want to know what's in our food, and we want a labeling system that encourages healthy choices. But labels don't substitute for knowing the basic principles of good nutrition and for cultivating an amused appreciation of the power that language has over our appetites. The halo effect also reinforces the wisdom of the "real foods" approach to eating—for having a reasonable portion of the real thing rather than reflexively opting for the sugar-free or low-fat versions.

Taste can also point the way. I'd much rather savor a small square of luscious dark chocolate than eat a jumbo bar of sugar-free candy. I prefer a pat of real butter on my toast or vegetables over reduced-fat margarine. I toss salads with olive oil and vinegar instead of low-fat bottled dressing.

Of course, that dark chocolate is packed with fat and calories, and "savoring" is another piece of critical language, implying moderation. Keep an eye on portions while keeping pleasure part of the picture.

How have you experienced the health-halo effect? E-mail us at letters@CookingLight.com.