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Romaine lettuce, also called cos lettuce, is the tall, crisp lettuce with long, sturdy leaves and a pale, crunchy rib that forms the base of a Caesar salad. It is mostly water and very low in calories, yet one shredded cup supplies about 40% of the Daily Value for vitamin K and 23% for vitamin A in USDA data, far more than the same amount of iceberg. Below are the USDA romaine lettuce nutrition facts, a romaine vs iceberg comparison, how romaine stacks up against other lettuces and greens, what the romaine E. coli outbreaks were about, and how to wash and store it.
Peptide Labs does not sell romaine lettuce or lettuce products. This article is general nutrition information, not medical advice.
Key Takeaways
- One cup of shredded raw romaine (47 g) has about 8 calories, 1.0 gram of fiber, 40% DV for vitamin K and 23% DV for vitamin A in USDA data.
- The Dietary Guidelines place romaine in the dark-green vegetables subgroup and iceberg in the other vegetables subgroup.
- CDC linked romaine to three multistate E. coli O157:H7 outbreaks in 2018 and 2019.
- FDA advises rinsing heads of lettuce under plain running water, no soap or produce wash, and removing the outermost leaves.
- People taking warfarin should keep vitamin K intake from foods like romaine consistent and talk to their clinician before changing their diet.
Romaine lettuce nutrition per cup
The table uses the USDA FoodData Central SR Legacy entry for raw cos or romaine lettuce (FDC 169247), converted to USDA’s portion weight for one cup shredded (47 grams), next to the values per 100 grams. The percent Daily Value (%DV) uses the FDA Daily Values printed on Nutrition Facts labels.
| Nutrient (raw romaine) | 1 cup shredded (47 g) | % DV | Per 100 g | % DV |
|---|---|---|---|---|
| Calories | 8 | Not applicable | 17 | Not applicable |
| Carbohydrate | 1.5 g | 1% | 3.3 g | 1% |
| Fiber | 1.0 g | 4% | 2.1 g | 8% |
| Total sugars | 0.6 g | No DV | 1.2 g | No DV |
| Protein | 0.6 g | 1% | 1.2 g | 2% |
| Vitamin A | 205 mcg RAE | 23% | 436 mcg RAE | 48% |
| Vitamin K | 48 mcg | 40% | 102.5 mcg | 85% |
| Folate | 64 mcg DFE | 16% | 136 mcg DFE | 34% |
| Vitamin C | 1.9 mg | 2% | 4.0 mg | 4% |
| Potassium | 116 mg | 2% | 247 mg | 5% |
| Calcium | 16 mg | 1% | 33 mg | 3% |
| Iron | 0.5 mg | 3% | 0.97 mg | 5% |
Three nutrients stand out. Vitamin K is the largest: a shredded cup gives about two-fifths of the Daily Value in USDA data, which is why romaine appears in our guide to vitamin K in foods. Vitamin A comes from carotenoids; USDA lists about 5,226 micrograms of beta-carotene per 100 grams of romaine, a pigment covered in our beta-carotene guide, plus lutein and zeaxanthin, which our lutein guide explains. And folate is high for a lettuce, about a third of the Daily Value per 100 grams; our methylfolate guide covers the difference between food folate and supplement forms.
Romaine is about 95% water by weight. A whole head, about 626 grams in USDA’s portion data, comes to roughly 106 calories. Fiber is modest per cup; for foods that add more, see our guide to fiber-rich foods.
Romaine vs iceberg: nutrition side by side
Romaine vs iceberg is the most common lettuce question, and USDA data give a clear answer on vitamins. Both are low in calories and high in water, but romaine carries much more vitamin A, vitamin K and folate. The table compares one shredded cup of each, using USDA portion weights (iceberg packs more densely, so its cup weighs more).
| Per 1 cup shredded, raw (USDA FDC ID) | Romaine, 47 g (169247) | Iceberg, 72 g (169248) |
|---|---|---|
| Calories | 8 | 10 |
| Fiber (% DV) | 1.0 g (4%) | 0.9 g (3%) |
| Total sugars | 0.6 g | 1.4 g |
| Vitamin A (% DV) | 205 mcg RAE (23%) | 18 mcg RAE (2%) |
| Vitamin K (% DV) | 48 mcg (40%) | 17 mcg (14%) |
| Folate (% DV) | 64 mcg DFE (16%) | 21 mcg DFE (5%) |
| Potassium (% DV) | 116 mg (2%) | 102 mg (2%) |
| Water per 100 g | 94.6 g | 95.6 g |
The Dietary Guidelines for Americans reflect the same split: romaine lettuce is listed in the dark-green vegetables subgroup, while iceberg lettuce is listed with “other vegetables” such as celery, cucumber and onions. That does not make iceberg a bad food. It is crisp, mild and hydrating, and many people simply eat more salad when they like the lettuce. Our sibling guide to iceberg lettuce covers it in detail.
How romaine compares with other lettuces and greens
Romaine sits in the middle of the salad aisle. Green and red leaf lettuces have a little more vitamin K per 100 grams, romaine has the most folate of the lettuces, and spinach and kale outscore every lettuce on most vitamins and minerals. Values are per 100 grams of the raw leaves.
| Per 100 g, raw (USDA FDC ID) | Calories | Fiber (% DV) | Vitamin A (% DV) | Vitamin K (% DV) | Folate (% DV) |
|---|---|---|---|---|---|
| Romaine (169247) | 17 | 2.1 g (8%) | 436 mcg (48%) | 102.5 mcg (85%) | 136 mcg (34%) |
| Iceberg (169248) | 14 | 1.2 g (4%) | 25 mcg (3%) | 24.1 mcg (20%) | 29 mcg (7%) |
| Green leaf (169249) | 15 | 1.3 g (5%) | 370 mcg (41%) | 126.3 mcg (105%) | 38 mcg (10%) |
| Red leaf (168431) | 13 | 0.9 g (3%) | 375 mcg (42%) | 140.3 mcg (117%) | 36 mcg (9%) |
| Butterhead, Boston or Bibb (168429) | 13 | 1.1 g (4%) | 166 mcg (18%) | 102.3 mcg (85%) | 73 mcg (18%) |
| Spinach (168462) | 23 | 2.2 g (8%) | 469 mcg (52%) | 482.9 mcg (402%) | 194 mcg (49%) |
| Kale (168421) | 35 | 4.1 g (15%) | 241 mcg (27%) | 389.6 mcg (325%) | 62 mcg (16%) |
If you want a deeper look at darker greens, our guide to greens compares many of them, and our kale guide shows why kale stands out for vitamin C and calcium.
Romaine lettuce benefits: what the evidence supports
There are no clinical trials of romaine itself, so the honest case for romaine lettuce benefits rests on its USDA nutrient profile and its place in the vegetable group. In plain terms, romaine adds vitamin K, vitamin A, folate, some fiber and a lot of water for very few calories. Claims that romaine melts fat, cleanses the liver or balances hormones are not supported by evidence. Is romaine lettuce healthy? Yes, as part of an overall eating pattern rich in vegetables, which is how the Dietary Guidelines frame it. For other watery, low-calorie produce, see our guides to cucumber and low-calorie snacks. If you are eating smaller meals on a GLP-1 medicine, our GLP-1 diet guide explains how bulky vegetables fit in.
Romaine lettuce E. coli outbreaks: what happened
Lettuce is usually eaten raw, so there is no cooking step to kill germs that reach the leaves in the field or during processing. CDC investigated three large multistate outbreaks of E. coli O157:H7, a Shiga toxin-producing strain, linked to romaine:
- Spring 2018: 210 people in 36 states got sick, 96 were hospitalized, 27 developed hemolytic uremic syndrome (HUS), a type of kidney failure, and 5 died. CDC named romaine from the Yuma, Arizona, growing region as the likely source.
- Fall 2018: 62 people in 16 states and Washington, DC, got sick, 25 were hospitalized and 2 developed HUS, with no deaths. Romaine from the Central Coastal growing regions of northern and central California was implicated.
- Fall 2019: 167 people in 27 states got sick, 85 were hospitalized and 15 developed HUS, with no deaths. Romaine harvested in the Salinas Valley, California, was implicated.
Each outbreak was declared over once the contaminated lettuce was off the market. During an active outbreak, follow the current CDC and FDA notices, which name the product, brand or growing region to avoid. CDC lists the symptoms of this kind of E. coli infection as diarrhea that can be bloody, severe stomach cramps and sometimes vomiting or a low fever. Call a doctor for diarrhea that lasts more than two days, bloody stools, a high fever or signs of dehydration such as very little urine, dark urine or dizziness. HUS is a medical emergency; CDC lists warning signs such as peeing much less, unusual paleness, unexplained bruising and extreme tiredness.
How to wash, store and use romaine
- Hands first: FDA advises washing your hands with soap and water for 20 seconds before and after preparing produce.
- Whole heads: remove the outermost leaves, cut away bruised or damaged parts, then rinse the leaves under plain running water while rubbing gently. FDA says there is no need to use soap or a produce wash. Dry with a clean towel or salad spinner.
- Bagged romaine: FDA says produce labeled pre-washed or ready-to-eat can be used without further washing. If you rinse it anyway, keep it away from unclean surfaces and utensils.
- Storage: keep cut or bagged romaine in a clean refrigerator at 40 degrees Fahrenheit or below, as FDA advises, and throw out leaves that are slimy or smell off.
- Uses: Caesar salads, lettuce wraps, sandwiches and tacos, or halved hearts briefly grilled. Creamy dressings add calories and sodium, so check the Nutrition Facts label.
Warfarin, vitamin K and salads
Warfarin (Coumadin) works by opposing vitamin K, and the NIH Office of Dietary Supplements describes the interaction as serious. People taking warfarin are not usually told to avoid greens; they are told to keep vitamin K intake consistent from week to week, because a sudden jump or drop can change how the medicine works. Because a cup of romaine supplies 40% of the Daily Value for vitamin K in USDA data, switching from iceberg to big romaine salads is the kind of change to discuss with your clinician or anticoagulation clinic first.
Frequently Asked Questions
Is romaine lettuce healthy?
Yes, as part of a vegetable-rich diet. USDA data show romaine is very low in calories and supplies vitamin K, vitamin A, folate and some fiber.
How many calories are in romaine lettuce?
About 8 calories per shredded cup (47 g) and 17 per 100 grams in USDA data. A whole head is roughly 106 calories.
Romaine vs iceberg: which has more nutrients?
Romaine. Per cup, it has about 11 times the vitamin A, nearly 3 times the vitamin K and 3 times the folate of iceberg in USDA data.
Is romaine lettuce a dark leafy green?
Yes. The Dietary Guidelines for Americans list romaine lettuce in the dark-green vegetables subgroup; iceberg is in the other vegetables subgroup.
Why has romaine lettuce been linked to E. coli?
It is eaten raw, so germs on the leaves are not killed by cooking. CDC linked romaine to three multistate E. coli O157:H7 outbreaks in 2018 and 2019.
Do I need to wash bagged romaine?
FDA says produce labeled pre-washed or ready-to-eat can be used without further washing. Rinse whole heads under running water without soap.
Can I eat romaine if I take warfarin?
Usually yes, but keep your vitamin K intake consistent and talk to your clinician before making big changes to how much you eat.
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 food allergy. 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: Iceberg Lettuce: USDA Nutrition, Calories and Is It Healthy?, Leafy Greens: USDA List of Dark Greens, Spinach vs Kale and Tips, Foods High in Vitamin K: USDA List, K1 vs K2 and Warfarin Notes, Lettuce: Nutrition by Type, Vitamin K and Washing Advice.