Not all fruits, vegetables created equally; How to spot most nutritious produce

(CBS News) For thousands of years, Jo Robinson claims in her new book "Eating on the Wild Side: The Missing Link to Optimum Health," farmers have been unknowingly stripping out nutrients in their crops.

Why? Robinson said on "CBS This Morning" it's due to taste and a proclivity for sweetness in our foods: "Unwittingly, we're driven towards sweet and starchy food and away from bitter food," she said. "Many of these antioxidants and phytonutrients are bitter, so generation after generation, we chose things that were less and less bitter, and therefore less nutritious."

So what does that mean for your next grocery trip? Some fruits and vegetables are more nutritious than others. Just walk down the produce aisle and you'll find a variety of salad options -- some with more nutrition than others.

"It's amazing the difference in the nutritional content of the salads in the supermarket," Robinson said. "Iceberg has the least, and then you get to leafy greens -- they're better for you. The best in the store are the ones with leafy greens with some red or brown tints to it."

Arugula, she added, is "beyond lettuce. It's a different species and it is almost a wild vegetable. And that's what I want people to do is learn to find food in the supermarket that's close to these wild plants."

For more with Robinson on more nutritious choices of other fruits and vegetables, watch the video above.