Why is lettuce rarely cooked?

Cooking lettuce is not as unusual as you think. It's kind of trendy to grill romaine,

and iceberg lettuce is often cooked in Chinese cuisine, both in soups and stir-fries.

There is a recipe for braised lettuce in Julia Child's Mastering the Art of French Cooking,

and Lidia Bastianich, who specializes in Italian cuisine, recently did a stuffed and cooked lettuce (escarole) on her show.

First of all, visual similarity has little to no importance in cooking. The way an item is handled depends on its texture, taste, flavor and interaction with other ingredients, and it is rare that these are connected among similar looking substances. When it happens, it is because they are related chemically, physically or biologically, not because they look alike.

Now on to the lettuce, and why we don't need to cook it. There are a few reasons why we cook vegetables.

1. Because they are too hard to chew comfortably. That one doesn't apply to lettuce, it has very tender leaves. In fact, once you cook it, it goes not from hard to soft (as does a, say, carrot), but from tender to limp. On the other hand, it can be useful for cabbage. Try to wolf down a salad made from cabbage only, especially if you are a medieval peasant with no access to a mandoline (so your wife didn't cut it up in 2.5 mm stripes, but hacked as good as she could with whatever knife she had). It is possible, but requires much more jaw work than spooning coleslaw.

2. Because we want to mellow their taste. Joe's answer covers this, there isn't much reason to mellow the taste of lettuce.

3. Because we want to neutralize toxins or irritants. Plants like beans and potatoes come to mind in this category, but this doesn't apply to lettuce (neither to cabbage).

4. To kill off germs. Traditionally, this hasn't been a concern with most vegetables.

5. Because we like a filling, warm meal. This is by no means a universal preference, but the more you get into the North, the more likely it is that the main meal is served warm. Cabbage makes for an excellent main meal for said peasant - easy to grow in abundance, relatively carbohydrate rich, especially before starchy crops like potatoes and maize got widespread. It is also easily preserved for the winter (and after imperfect home fermentation, the taste mellowing part becomes important). So it is frequently cooked to soups or casseroles. Lettuce, on the other hand, is not really a main meal. It has much less calories per volume, and also per unit of cultivated land. So it is eaten in addition to the main, filling meal, not as a main part of it. So there is no need to make it warm too. Note that there are examples for cooked leaf soups without much calories, but these are poor man's food, and made from leaves usually foraged, not cultivated (nettle, sorrel, dock). They are used more as a diversion against hunger than actually stilling it, when there are no resources for better (= more caloric) food. They do deliver micronutrients though. I don't know why lettuce isn't commonly used this way, but I suspect that there is no wild lettuce in the places where nettle and sorrel are eaten. Of these, only spinach seems to have survived the cultural shift to centralized food production.

6. Because it is a structural part of some cooked dish. Other answers mention wrappers. Its shape lets it be used in this way, but it is a poor wrapper, both tastewise and in terms of durability, leaf size and thermal isolation. Wherever you live, you are likely to have a better wrapper lying around.

As the other answers mention, it does get cooked from time to time. But it is more of a whim, or a wish for diversity I guess. None of the usual reasons for cooking other vegetables applies to it. You can still cook it if you want to, but it is better suited for a fresh salad appilcation.

Much of the lettuce produced in the U.S. (e.g., iceberg) is effectively just crunchy water; they've bred so much of the taste out of it that it's used for texture and not for flavor. As cooking changes the texture, it then provides no contribution to the finished dish.

For those recipes that do incorporate cooked lettuce, it tends to be:

• lettuce with a stronger flavor (tends to be bitter), such as romaine, endive, escarole, chicory or radicchio.
• lettuce with a firm texture, such as romaine, endive and radicchio.
• cooked a short period of time. (grilled or added to soups or stir fries towards the end; not cooked to the point where it gets completely limp)

... and, as mentioned, lettuce can be cooked to soften, then used as a wrapper. I personally prefer cabbage for this, but it's useful for dishes where the cabbage might overwhelm the flavor of the filling.

There are a bunch of great answers, but I think to me, the most important part is that most lettuces are just gross after you cook them. They go from crisp and refreshing to soft, mushy and sometimes stringy. Obviously, there are exceptions as others have mentioned but simply put, most of your salad lettuces just don't produce a nice cooked product.

In Sicily we cook Roman lettuce, three ways that are my favourites are: 1. Take the whole leafs and boil in water for about 10 min with just a pinch of salt, drain (not completely) and serve as a side seasoned with just olive oil and a squeeze of lemon juice. 2. Same process of boiling though cut in to half and add little pasta towards the end, serve with just olive oil. (I would have this every time I needed a little detox) 3. Cut in to small pieces and sauté with onions (I also like to add nutmeg, black pepper and walnuts though pine nuts are more of a Sicilian touch) this makes for an amazing vegan pasta sauce. Unless you add some Parmesan :) as a topping my mom would always do toasted breadcrumbs.

It loses its crispiness, and its refreshing leafy lively taste. So this product transform into something else other than that one has come to expect of lettuce.