Here's which types of lettuce are most popular, why these greens are good for you and what you need to be mindful of as you include more in your diet.

Astronauts Sunita Williams and Butch Wilmore, whose eight-day mission turned into nine months on the International Space Station, are finally heading back to Earth aboard the SpaceX Dragon spacecraft.

Romaine lettuce comes in second at 35% ... more than one of these varieties along with mustard greens, endives, red and green oak leaf and little gem lettuce. While many of these nutrients ...