While iceberg lettuce is still the favorite salad green in the U.S., the rise of ready-to-eat packaged salad greens has contributed to increased romaine and spinach consumption. Both are more nutrient dense than than iceberg lettuce, which is mostly water. But what about spinach versus romaine? Is one healthier than the other? Spinach and romaine are both high in certain nutrients.
Vitamin A is important for many body functions, including vision, growth and development, red blood cell production, and immunity. The recommended daily allowance, RDA, is 3000 IU for men and 2333 IU for women. Spinach has 2813 IU per cup and romaine has 4094 IU per cup.
VItamin K is important for blood clotting and bone and cell growth. The the adequate intake, AI, for Vitamin K is 120 micrograms for men and 90 micrograms for women. Spinach has 145 micrograms per cup and romaine has 48 micrograms per cup.
Carotenoids are naturally-occurring pigments made by plants. Beta carotene, lutein, and zeaxanthin are a few of the 600 known carotenoids. Diets high in carotenoid-rich fruits and vegetables are associated with reduced risk of cardiovascular disease and some cancers. Lutein and zeaxanthin in particular are associated with eye health. There is no RDA for beta-carotene, lutein, or zeaxanthin, though studies show that 6mg of lutein and zeaxanthin might be needed for beneficial effects. Spinach has 1688 micrograms of beta carotene and 3659 micrograms of lutein and zeaxanthin per cup. Romaine has 2456 micrograms of beta carotene and 1087 micrograms of lutein and zeaxanthin per cup.
Potassium is an essential dietary mineral. It acts as an electrolyte, meaning it's capable of conducting electricity. Normal body functions, including regular heart beats and proper body hydration, depend on regulation of potassium concentrations both inside and outside of cells. The AI for potassium is 4700 milligrams per day for both men and women. Spinach has 167 milligrams per cup and romaine has 116 milligrams per cup. As a comparison, a medium banana has 422 milligrams.