Fat-free salad dressings aren't all they're cracked up to be, according to research published in the American Journal of Clinical Nutrition. It turns out that key nutrients in vegetables, such as beta-carotene and lutein, aren't absorbed without fat.

Iowa State University, Columbus researchers tested blood samples after people ate salads with three different salad dressings, containing 0, 6 or 28 grams of canola oil. The dressing with the most fat produced the highest degree of nutrient absorption.

Another study at Ohio State University, Ames, found that adding 2.5 tablespoons of avocado to salads or salsa increased nutrient absorption dramatically, for example, by 13.6 times for beta-carotene, which protects against heart disease, and by 4.3 times for lutein, necessary for eye health. Other research has shown that some fat in a meal leaves you more satisfied.

Bottled Dressings: Good and Bad

That said, you don't need unhealthy fat, often found in bottled dressings as saturated or trans ("hydrogenated" or "partially hydrogenated") fats. Also, avoid sky-high levels of sodium, unhealthy sweeteners, or additives such as artificial flavors, colors, texture enhancers and preservatives. Look for olive-oil based dressings without artificial ingredients -- real seasonings and herbs taste better.

As an alternative, making your own dressing doesn't have to be complicated. Extra virgin olive oil and balsamic vinegar are always a good bet. Or, use avocado combined with lemon or lime juice.

Adding too much dressing -- even if it's healthy -- also isn't good. To avoid the pitfall, try this:

1. Buy flavorful dark greens, preferably organic ones. Tasteless greens are an invitation to overdo the dressing.

2. Don't just pour dressing onto your salad plate. Put the greens, alone, in a big bowl and drizzle the dressing over them, gently -- they can't swim. Toss lightly but thoroughly until the leaves are evenly coated, then add the rest of your salad vegetables and toss a couple more times. This way, your salad will have more flavor.

If washing a big bowl is too much bother, you can always find your nearest 99-cent store, buy a bunch of cheap bowls and toss them in the trash when you're done. Just kidding.