The plant looks like a small bush, hooded or open, spherical or elongated, of a bright green or light greenish color tending to light yellow, sometimes with shades of pink, wine, red, etc. on part of the leaf or on its entirety. The leaves have a very different shape, appearance and color depending on the cultivated varieties; there is no lack, for example, of varieties with reddish leaves, such as the Lollo rosso and the Red salad bowl.
The color of the leaves also changes according to the location in the head: the external ones are darker, while inside they are almost totally clear (due to the lower concentration of chlorophyll). In a similar way, the crunchiness of the same is greater towards the heart, while outside the leaves are more tender even if thick.
Lettuce for cultivation comes from wild species, such as the alpina, perennis, serriola etc., which colonize the Mediterranean regions. It is distinguished from the latter by the unmistakable leaf structure and its differentiation (which occurred in antiquity) has mainly affected Southern Europe.
Lettuce is the “leafy vegetable” that occupies the largest cultivation area of the peninsula (about 24,500 ha – ISTAT 2002), which is why it is considered one of the most important food and agricultural products in Italy. With regard to so much diffusion, lettuce is often (and erroneously) called “salad” (a noun that should indicate the recipe, not the ingredient).
There are numerous varieties of lettuce, which develop optimally at various times of the year. Considering them all, lettuce is available all year round.
As can be seen from the table below, lettuce is a low-calorie vegetable, with an energy prevalence of carbohydrates (simple carbohydrates) compared to proteins and lipids.
The few peptides it contains are of low biological value and have no nutritional value. Fatty acids, even more deficient, are mainly unsaturated. Cholesterol is absent and small amounts of phytosterols emerge.
In lettuce, the fiber is present in good quantities and is the main pseudo-nutrient.
This vegetable is also very rich in water, a very important aspect in the nutrition of athletes and the elderly (both at risk of dehydration), as well as of the obese (which benefits from the satiating power obtained from the fiber-water combination).