Seeing the light: The outer leaves of lettuces and cabbages are the most nutritious

An article in Current Nutrition & Food Science has pointed out that "open leaf" type lettuces such as romaine are much richer in nutrients than crisp head types, like ice bergs. The main reason for this difference is the ability of the leaves to absorb light, and thereby synthesize more vitamins.

Take a look at the nutrient profile comparison of romaine lettuce to ice-berg.

Nutrition Facts
Lettuce Cos Or Romaine Raw
Serving Size 100g
Calories 17
% Daily Value*
Total Fat 0.3g 0%
Saturated Fat 0.039g 0%
Cholesterol 0mg 0%
Sodium 8mg 0%
Total Carbohydrate 3.3g 1%
Dietary Fiber 2.1g 8%
Sugar 1.2g ~
Protein 1.2g ~
Vitamin A 116% Vitamin C 40%
Calcium 3% Iron 5%
*Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.
Nutrition Facts
Lettuce Iceberg (Includes Cris
Serving Size 100g
Calories 14
% Daily Value*
Total Fat 0.14g 0%
Saturated Fat 0.018g 0%
Cholesterol 0mg 0%
Sodium 10mg 0%
Total Carbohydrate 3g 1%
Dietary Fiber 1.2g 5%
Sugar 2g ~
Protein 0.9g ~
Vitamin A 10% Vitamin C 5%
Calcium 2% Iron 2%
*Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.
Complete nutrient comparison of Romaine vs. Ice-berg/Crisp Head Lettuces

Here we see that romaine contains over 10 times the vitamin A and over 8 times the vitamin C content. Further, the romaine lettuce also contains more protein, dietary fiber, calcium, and iron.

The same phenomenon also holds true for cabbage, take a look at a comparison of Collard Greens (open leaf cabbage) vs. a typical head of cabbage:

Nutrition Facts
Collards Raw
Serving Size 100g
Calories 30
% Daily Value*
Total Fat 0.42g 1%
Saturated Fat 0.055g 0%
Cholesterol 0mg 0%
Sodium 20mg 1%
Total Carbohydrate 5.7g 2%
Dietary Fiber 3.6g 14%
Sugar 0.5g ~
Protein 2.5g ~
Vitamin A 133% Vitamin C 59%
Calcium 15% Iron 1%
*Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.
Nutrition Facts
Cabbage Raw
Serving Size 100g
Calories 25
% Daily Value*
Total Fat 0.1g 0%
Saturated Fat 0.034g 0%
Cholesterol 0mg 0%
Sodium 18mg 1%
Total Carbohydrate 5.8g 2%
Dietary Fiber 2.5g 10%
Sugar 3.2g ~
Protein 1.3g ~
Vitamin A 2% Vitamin C 61%
Calcium 4% Iron 3%
*Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.
Complete nutrient comparison of Collard Greens vs. Cabbage

While the amounts of vitamin C and iron are slightly higher in cabbage, the collards still maintain higher protein levels, about 3 times the calcium, and over 50 times the vitamin A. The rule of thumb is to choose and prepare the outer dark green leaves of all leaf vegetables you consume.