Of all the lettuce options, iceberg is the top choice of consumers, according to the USDA Economic Research Service. Although it supplies fewer nutrients than other types, such as green leaf lettuce with double the calcium and B vitamins, iceberg still delivers fiber and most essential nutrients and is especially high in vitamin K. When you add tomatoes, you boost all the nutrients, especially vitamin C and vitamin A.
Iceberg lettuce and tomatoes contain vitamin A in the form of four carotenoids: alpha-carotene, beta-carotene, lutein and zeaxanthin. All four are antioxidants, but alpha- and beta-carotene can be converted into the type of vitamin A that’s essential for vision and healthy skin. Lutein and zeaxanthin provide antioxidant protection to the retina and may help prevent age-related macular degeneration. Tomatoes are one of the best sources of another carotenoid, lycopene, an antioxidant that may lower the risk of prostate cancer. One cup of shredded iceberg lettuce and four slices of tomato deliver 37 percent of the recommended daily intake of vitamin A. The tomatoes contribute 68 percent of the total amount.
One cup of iceberg lettuce and four slices of tomatoes provide 20 percent of the recommended daily intake of vitamin K, with the lettuce responsible for 70 percent of the total amount. Vitamin K is needed for the production of four proteins that participate in the process of blood clotting. Vitamin K also regulates bone building and may lower your risk of cardiovascular disease by inhibiting calcifications in blood vessels, according to research published in the June 2009 issue of the “American Journal of Clinical Nutrition.”
Free radicals are molecules that damage healthy cells and cause inflammation if not neutralized by an antioxidant. Vitamin C is one of our most important antioxidants, because it protects cells throughout the body and can neutralize a variety of free radicals. It’s also essential for the production of collagen, the connective tissue that supports skin and other tissues. One cup of shredded iceberg lettuce with four slices of tomatoes delivers 16 percent of the recommended daily intake for men and 19 percent for women. If you’re pregnant or breast-feeding, you need more vitamin C. Women who are pregnant get 17 percent of their daily value, while those who are breast-feeding get 12 percent from the same size serving.
Everyone requires folate for healthy red blood cells, but women who may become pregnant and children especially need it for the creation of DNA and the growth of new cells. In addition to supporting growth spurts in childhood and adolescence, folate prevents birth defects of the brain and spinal cord that occur during the first 30 days of pregnancy, when many women aren't aware they're pregnant. Including sufficient folate as part of a regular daily diet helps ensure an adequate supply to support a baby. One cup of shredded iceberg lettuce and four slices of tomatoes provide 9 percent of the recommended daily intake.
- USDA Nutrient Data Laboratory: Lettuce, Iceberg, Includes Crisphead Types, Raw
- USDA Nutrient Data Laboratory: Tomatoes, Red, Ripe, Raw
- USDA Economic Research Service: Commodity Spotlight -- Lettuce In and Out of the Bag
- Linus Pauling Institute: Carotenoids
- USDA National Nutrient Database for Standard Reference: Lycopene Content of Selected Foods
- American Journal of Clinical Nutrition: Vitamin K Supplementation and Progression of Coronary Artery Calcium in Older Men and Women
- University of Ohio: Fact Sheet -- Folate
- Institute of Medicine: Dietary Reference Intakes
- Harvard School of Public Health: Vitamin K
- National Academies Press: Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids
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