Kale has become synonymous with health, so it's no surprise that the produce aisle is packed with salad blends that boast about their kale content. Just one loosely packed cup of this hearty green contains 24 milligrams of calcium, 78 milligrams of potassium, 19 milligrams of vitamin C, as well as vitamins A and K; and you get all that good stuff for just eight calories.

But while these prepackaged blends could cut your prep time, they may not be the best option if your goal is to work more kale into your diet. We purchased three samples of three Dole salad mixes with a kale claim, separated the kale from the other ingredients, and measured the amount of kale in each package.

We found that while they all contain plenty of healthful greens—including some with radicchio, spinach, and chard—we didn't find much kale. Here's how they compared:

Pre-packed kale blends don't always contain a lot of kale.

Dole Power Up Greens Spring Mix & Greens

This 4 1/2-ounce package of greens had an average of just 3/4 ounce of kale. Still, this mix and other "Dole Power Up" blends might be good options if you're looking to bump up your intake of green vegetables in general, as they contain other dark leafy greens. One serving (about 3 cups) has 20 calories and gives you 70 percent of your daily vitamin A, 15 percent of your daily vitamin C, 10 percent of your daily calcium, 130 percent of your daily vitamin K, and 2 grams of fiber. Average price paid: $3.47.

Dole Chopped Salad Kit Sunflower Crunch

This blend contained the least amount of kale—an average of 1/4 ounce out of the 9 1/2 ounces of greens in a package; or about 2 percent by weight. After sorting through the greens, our testers found mostly romaine lettuce and green cabbage. Other ingredients in the mix—including bacon, sunflower seeds, and dressing—hike up the calorie, fat, and sugars content. Just one serving of the prepared salad has 180 calories, 13 grams of fat, and 9 grams of sugars. Average price paid: $3.66.

Dole Power Up Greens Baby Kale & Greens

This mix contained the most kale—but it still wasn't much, just one ounce in a 4 1/2-ounce package. The other greens include spinach and chard. Still, it's a nutritious blend. For just 20 calories per 3-cup serving, you get 80 percent of your daily vitamin A, 25 percent of your daily vitamin C, 20 percent of your daily calcium, 230 percent of your daily vitamin K, and 2 grams of fiber. Average price paid: $3.69.

The Bottom Line

To get kale's benefits—it has more calcium, fiber, potassium, and vitamins A, E, and K than many other greens—skip the salad mixes. Your best bet is to purchase packages containing 100 percent kale or a bunch of kale fresh from the produce section and make your own salad blend.

Editor's Note: This article was adapted from the June 2016 issue of Consumer Reports on Health.