Lettuce: Nutrition by Type, Vitamin K and Washing Advice

Lettuce is the most familiar salad green, but the common types differ more than their mild taste suggests. In USDA SR Legacy data, a shredded cup of butterhead has about 56 micrograms of vitamin K, 47% of the FDA Daily Value, while a shredded cup of iceberg has 17 micrograms, or 14%. This guide compares lettuce nutrition across butterhead, green leaf, red leaf, iceberg and romaine, covers lettuce vitamin K with the NIH and MedlinePlus advice for people who take warfarin, and sums up what CDC and FDA say about washing salad greens.

Peptide Labs does not sell lettuce or lettuce products. This article is general nutrition information, not medical advice.

Types of lettuce in USDA data

USDA SR Legacy lists five raw lettuce entries, each matching a type sold in most stores:

• Butterhead: includes Boston and bibb types; soft, loose heads of tender leaves.
• Green leaf: loose, frilly, mild leaves.
• Red leaf: the same loose leaves with red or bronze tips.
• Iceberg: includes crisphead types; tight, pale, very crisp heads. See our iceberg lettuce guide.
• Romaine (cos): tall heads with sturdy ribs and darker outer leaves; see our romaine lettuce guide.

Peppery or bitter leaves such as arugula, endive and radicchio have their own USDA entries. For spinach, kale and the wider group, see our leafy greens guide.

Lettuce nutrition per cup (USDA SR Legacy)

The table ranks the five types by vitamin K per shredded cup, using the cup weight USDA gives for each entry. Percentages are of the FDA Daily Values used on food labels.

FDA label guidance counts 20% of the Daily Value or more in a serving as high and 5% or less as low. By that FDA yardstick, a shredded cup of butterhead, romaine, green leaf or red leaf is high in vitamin K, and romaine is also high in vitamin A. In USDA data every type is low in fiber and potassium per cup, and none tops 10 calories per shredded cup.

Comparing types of lettuce gram for gram

USDA cup weights differ: a shredded cup of red leaf weighs 28 grams and one of iceberg 72 grams. Comparing equal weights removes that effect.

Gram for gram in USDA data, red and green leaf carry the most vitamin K, romaine by far the most folate and vitamin A, and green leaf the most vitamin C. Iceberg is lowest on almost every line except water.

Is lettuce healthy?

As a food, lettuce is mostly water and very low in calories in USDA data, and the leafy types supply vitamin K and vitamin A. The Dietary Guidelines for Americans place romaine in the dark-green vegetable subgroup and iceberg in the other vegetables subgroup. This guide attaches no health promises to lettuce. Two points deserve care, covered below: vitamin K for people on warfarin, as NIH and MedlinePlus describe it, and raw produce safety, as CDC describes it.

Lettuce and blood thinners

NIH’s Office of Dietary Supplements explains that vitamin K is needed to make proteins involved in blood clotting, and per USDA cup most lettuce types supply a third or more of the FDA Daily Value. The same NIH fact sheet says vitamin K can have a serious and potentially dangerous interaction with anticoagulants such as warfarin, and that people taking warfarin need to keep their vitamin K intake consistent, because sudden changes can increase or decrease the anticoagulant effect. The same ODS fact sheet names iceberg lettuce, along with spinach, broccoli and some vegetable oils, among the most common sources of vitamin K in the US diet.

MedlinePlus, in its warfarin information, advises eating consistent amounts of vitamin K-containing food on a week-to-week basis, not eating large amounts of leafy green vegetables, and talking to your doctor before you make any changes in your diet. The point MedlinePlus and ODS make is steadiness, worked out with the clinician who oversees your warfarin. Per USDA cup, switching from iceberg to butterhead or romaine roughly triples the vitamin K in a salad. Our vitamin K in foods guide lists other greens.

Folate in lettuce

USDA SR Legacy gives a shredded cup of romaine 64 micrograms DFE of folate, 16% of the FDA Daily Value, and NIH’s folate fact sheet lists the same figure. The other types carry 10 to 40 micrograms DFE per USDA cup. Our folate food list ranks other sources.

Lettuce and E. coli: what CDC and FDA report

CDC has investigated several E. coli outbreaks tied to raw greens. In a 2017 outbreak, CDC reported 25 people infected with the outbreak strain of E. coli O157:H7 in 15 states; nine were hospitalized, including two who developed hemolytic uremic syndrome, a type of kidney failure, and one death was reported from California. CDC said information from ill people pointed to leafy greens as the likely source, and the investigation was not able to identify a specific type.

In a 2020 outbreak, CDC counted 40 people in 19 states, 20 hospitalized and 4 with hemolytic uremic syndrome, with no deaths. CDC wrote that epidemiologic and traceback evidence showed greens were the likely source, but investigators were unable to identify a specific type or brand, because people reported eating a variety of greens and because different greens are often grown, harvested and processed together. Of 23 ill people interviewed, 22 reported eating or maybe eating greens, including spinach (16) and romaine lettuce (15), and CDC noted that several farms of interest were identified but no single ranch was a common source. CDC says symptoms often include severe stomach cramps, diarrhea (often bloody) and vomiting.

Oxalate in lettuce

In Table 5 of a 2023 review in the journal Foods, raw lettuce measured 0.3 milligrams of total oxalate per 100 grams in a 2002 study, while a 2007 study of vegetables eaten in Korea, compiled in the same review table, reported 40, both far below spinach and chard in that review. Our low oxalate vegetables list has the full table, and our oxalates guide explains who needs to think about oxalate.

How to choose, wash and store lettuce

• Choosing: FDA advises choosing produce that is not bruised or damaged and says pre-cut items such as bags of lettuce belong in the refrigerator or on ice.
• Outer leaves: CDC advises discarding outer leaves and any torn or bruised ones, and FDA says to remove the outermost leaves of a head of lettuce.
• Washing: CDC advises washing your hands with soap and water before and after preparing greens, then rinsing the leaves under running water while gently rubbing them. FDA says there is no need for soap or a produce wash.
• No soaking: CDC says not to soak greens in a sink or a bowl of water, because germs can spread from one leaf to the others.
• Bagged greens: CDC says greens labeled ready to eat, triple washed or no washing necessary do not need washing again, and notes that washing removes some germs and dirt but not all germs.
• Drying and storing: CDC advises drying greens with a clean cloth or paper towel. Keep lettuce cold and loosely wrapped in the crisper drawer.
• Cooking: CDC notes that the safest produce is cooked; romaine can be grilled, and most types can be wilted into soups.

Frequently Asked Questions

Questions about a label? Contact us or read our Buyer’s Guide. Food comes first; follow the label and ask a healthcare provider before starting a supplement, especially if you take medicines, are pregnant or have a health condition. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Last reviewed October 2026.

Related guides: Low Oxalate Vegetables: A List From Published Lab Values, Iceberg Lettuce: USDA Nutrition, Calories and Is It Healthy?, Romaine Lettuce: USDA Nutrition, Romaine vs Iceberg and Safety, Leafy Greens: USDA List of Dark Greens, Spinach vs Kale and Tips.