It’s a commonly held misconception that lettuce is nutritionally vacant, a sort of crunchy placeholder for calories, or a vehicle for other salad ingredients. Quite the contrary, lettuce is a fascinating and diverse food with several unique varieties and a long history in human diet. In all of its varieties, lettuce carries significant nutritional value mostly in the form of vitamins, minerals, fiber and even protein. A strong dose of lettuce in your diet can support your immune system, strong bones, healthy blood pressure and provides antioxidants connected to reducing free radicals and reduced risk of some diseases.
Lettuce has been in use by humans since as far back as ancient Egypt, when its seeds were harvested for oil, and it was the sacred plant of the reproduction god. Since then, it’s been cultivated and developed into its many varieties, used as a medicinal plant and eventually as the dietary staple that it is today. In China, lettuce has been cultivated since the 5th century, and has come to represent good luck, served on birthdays and holidays. Today, Americans eat about 33 pounds of lettuce per person per year.
Actually a member of the Asteraceae family, along with the daisy and the sunflower, the name is derived from the Romans’ name for it lactuca, based on the Latin lac for milk. This is because of the milky white substance that comes from its stems. Its scientific name is lactuca sativa. The plants vary in size and shape, but generally range from 6 to 12 inches in height. It’s a robust plant that grows well in cool weather. While there are seven main cultivars of lettuce, four are most common—leaf, romaine/cos, crisphead (iceberg) and butterhead.
Lettuce is also one of those foods that fold seamlessly into regular diet, whether as the base of a salad, topping for sandwiches, or even in smoothies. Contrary to popular criticism of America’s most popular lettuce, iceberg, every form of lettuce has nutritional value. That said, all lettuces are not created equal, with romaine generally leading the pack in health benefits. You can follow a rough rule of thumb that the greener in color a lettuce variety is, the more nutritional value it will offer. The following is a breakdown of the most popular varieties of lettuce, and the nutritional value they offer.
Nutritional Levels of The Different Varieties of Lettuce
Romaine lettuce is the hot new kid on the lettuce block. Not that new, really, but for years iceberg was far and away the most popular lettuce in America. In recent years, demand for romaine has doubled and iceberg demand has steadily declined. Part of that can probably be attributed to the Caesar salad, which calls for romaine as the main ingredient. But Americans have also become enamored of romaine’s heartier nutritional value.
Romaine is crisp, slightly bitter and marked by long, narrow leaves with a large rib. This is what gives the lettuce its crunchiness that is the hallmark of a good Caesar.
First off, like all lettuce, romaine is very low in calories, with an entire head only providing 100, making it so popular for salads. But you might be surprised to find out that romaine lettuce, like all lettuce, contains protein. Romaine is also a complete protein, meaning it contains all of the essential amino acids.
Romaine is loaded with vitamins, with one of its biggest strengths being vitamin K. This vitamin is closely tied to the blood’s ability to clot, but also the activation of a protein that contributes to bone health. It’s also an excellent source of vitamin A, which is actually a family of nutrients that helps with vision, the immune and inflammatory systems and cell growth. Another big plus for romaine is folate, which aids red blood cell growth, circulation, cell production, and nervous system health. Romaine also has high levels of vitamin C, more than other varieties.
But the list of nutrients in romaine lettuce is quite long, including iron, molybdenum, potassium and B vitamins. And like all lettuce, it’s a great source of fiber. For those looking to boost their health with a great variety of lettuce, consider switching to romaine. It’s packed with benefits, and most agree it offers the strongest health benefits of all the varieties. In fact in all but a handful of categories, romaine has higher content per serving than its relatives.
Leaf, Green and Red
Also known as looseleaf lettuce, green leaf and red leaf lettuces differ from other varieties because of their ruffly, colorful leaves that grow in loose, bushy and open heads. Red leaf is known for its bronze or purplish edges that add a splash of color to a dish. They are milder in flavor than other lettuce varieties and softer than an iceberg or romaine.
One thing to note, while red leaf is more vibrant in appearance, green leaf edges it out in every major nutritional category, except for iron. All in all, green leaf is by most accounts the second-healthiest lettuce, after romaine. Red leaf is close to iceberg at the bottom of the heap.
Green leaf lettuce has similar health benefits as romaine, such as fiber, iron, calcium, magnesium, phosphorous and potassium. But it has some unique benefits. For example, while romaine delivers more vitamin A, green leaf has more vitamin K, offering 105 percent of the recommended daily intake per serving. This is the highest vitamin K content per serving of any of the main lettuce types. And while romaine still beats it in terms of vitamin C content, green leaf come in second among the popular varieties.
Also called butter lettuce, this delicate, soft variety is often overlooked for its heartier relatives. The two main members are Boston and Bibb lettuce, and grow in small, fluffy heads. Bibb lettuce is usually the pricier of the two. Butter lettuces have a smooth, silky texture, hence the name, and must be handled carefully so as to not damage the soft leaves. They also have one of the shortest shelf lives of all kinds of lettuce. Because the leaves resemble little round cups, they are often used for display in dishes.
Butter lettuce is more nutritionally valuable than iceberg and even red leaf, but ranks below romaine and green leaf in most categories. However, it has a handful of strengths where it even bests its popular big brother romaine. Butterhead’s biggest advantage over its relatives is as a source of protein, with 0.74 grams per cup serving. It also has the most calcium, iron and potassium compared to the other top varieties. It’s lacking in the vitamin C category, though, tying poor old iceberg and just beating crummy red leaf.
Pulling up the rear, our dear friend iceberg. America’s favorite lettuce, a crunchy whitish sheet found on burgers coast to coast. A densely packed, firm sphere in the bottom drawer of every home refrigerator. The basic ingredient in $2.50 side salads at every chain restaurant and cafeteria in the country.
But let’s not be too hard on old iceberg. For one, that tight, crunchy texture is beloved for a reason. It adds a fresh and juicy heft to otherwise squishy sandwiches. And don’t forget the trendy wedge salad, which capitalizes on the robust architecture of a chunk of iceberg to cradle other delicious foods like bacon and blue cheese.
Nutritionally speaking, iceberg is guilty as charged as one of the lamest types of lettuce (it does, however, blow away the competition as a source of water!). But to be fair, iceberg beats out fancy red leaf in almost every major category. It’s biggest strength is fiber. That crunch comes from its tough, sturdy leaves that deliver almost a gram per cup serving. It’s also second to butterhead in terms of protein.
And while iceberg’s not the largest source of nutrition compared to other kinds of lettuce, it’s still is a great way to get vitamin K, vitamin A, iron, magnesium and potassium. And it remains low in calories and basically completely lacking fat or cholesterol.
Let’s say, however, that even a big head of romaine isn’t going to satisfy your nutritional desires. There are several great lettuce alternatives that have grown increasingly popular over the years, both in salads and as garnish.
Kale, for example, is riding high in culinary popularity, and packs a massive punch of vitamins K, A, C, calcium, folate and potassium. It also has an intense flavor and texture. Greens such as collards, turnip greens and mustard greens have undergone a renaissance in popularity, with similar health benefits to kale.
And probably the most common lettuce alternative would be spinach, that Popeye power source that makes for a heartier salad, and also outperforms lettuce in some of the same key vitamin categories.