Iceberg lettuce is 95.6% water, and a cup of it shredded (72 g) has 10 calories. That is why it carries a name as the vegetable with no nutrition. The reputation is half right: per 100 g, romaine has about 4 times the vitamin K (102 against 24.1 µg), nearly 5 times the folate (136 against 29 µg) and about 17 times the vitamin A (436 against 25 µg), according to USDA data.
It is also not empty. A 100 g serving of iceberg gives 20% of the daily value for vitamin K and 7% for folate, with crunch and volume for 14 calories. In a large US study that scored 52 fruits and vegetables by their link to blood markers of heart and metabolic health, iceberg or head lettuce ranked in the top five.
Few trials have tested lettuce itself, and almost none say they used iceberg. Many studies below cover leafy greens as a group, and each card says so. Lettuce is eaten raw and has been linked to food poisoning outbreaks, so washing and storing it properly is covered below too.
Health benefits of iceberg lettuce
The top findings from 14 studies, strongest evidence first
What the stars mean
- Strong. Several randomized trials, pooled in a meta-analysis, point the same way, or regulators (FDA or EFSA) have approved the claim.
- Moderate. Good randomized trials support it, but there are fewer of them, or their results vary.
- Limited. Small, short or single trials, or mixed results. Promising, but it needs confirmation.
Population and lab studies get no stars: they show a link or a mechanism, not proof.
How we rate evidence →- ★Lower blood pressure for hours, with high-nitrate lettuceIn 19 healthy adults, 50 g of high-nitrate lettuce (530 mg) lowered the top number (4.9 mm Hg systolic) for 3 to 6 hours. Lettuce with 3 mg of nitrate was the comparison, and it was a one-time effect in young, healthy people.
- ★Smaller blood sugar rise after a fatty mealIn 16 healthy young men, adding 100 g of lettuce to a fatty meal lowered the 4-hour blood sugar response (361.9 against 385.7 mg/dL). Blood fats did not change.
- ★Better carotenoid absorption with oil on saladIn 7 people eating a mixed salad, a fat-free dressing gave almost no carotenoid absorption. A dressing with 28 g of canola oil gave the most. This was a mixed salad, not lettuce alone.
- Population studyLinked to fewer hip fractures in womenIn 72,327 women, eating a serving of lettuce or more a day went with a 45% lower risk of hip fracture. The comparison group ate one or fewer a week.
- Population studyLinked to a healthy metabolic profileOf 52 fruits and vegetables scored by their link to 14 heart and metabolic blood markers, iceberg or head lettuce ranked in the top five.
All 14 studies, strongest evidence first
Adding 100 g of lettuce to a fatty meal lowered the blood sugar response in healthy men, but not blood fats
Randomized crossover trial in 16 healthy young men who ate a moderately high-fat meal with lettuce, watercress or added cellulose as the control. The 4-hour blood glucose curve was lower with lettuce (361.9 against 385.7 mg/dL), and insulin also fell. Cholesterol, triglycerides, TNF-alpha and IL-6 did not differ. The abstract does not name the lettuce type, and people with cardiometabolic risk factors were not tested.
50 g of lettuce grown to be high in nitrate lowered systolic blood pressure by 4.9 mm Hg over the next 3 to 6 hours
Double-blind crossover trial in 19 healthy adults aged 22 to 31. They ate 50 g of lettuce with 530 mg of nitrate or lettuce with 3 mg of nitrate and more phenolic compounds, both grown by changing the fertilizer. The blood pressure drop tracked the rise in saliva nitrate. It was a one-time effect in young, healthy people, and the abstract does not name the lettuce type.
Lettuce juice with about 200 mg of nitrate a day for 14 days lowered gum inflammation in people with gingivitis
Double-blind placebo-controlled trial in 44 periodontal patients who drank 100 ml of lettuce juice three times a day, with nitrate (23 people) or without it (21). The gingival index fell to 0.3 against 0.5 on placebo, and saliva nitrate was higher. Plaque did not change. It tests the nitrate in a juice, not lettuce leaves.
Eating 250 g of fresh lettuce raised blood antioxidant capacity, but lettuce kept in sealed packaging did not
Crossover study in 11 healthy volunteers. After fresh lettuce, plasma antioxidant potential over 6 hours rose by 1.3 mmol/L against 0.1 mmol/L for the same lettuce stored in modified-atmosphere packaging at 5°C, and blood vitamin C rose from 10.9 to 12.7 mg/L. It measured blood markers, not health, and the abstract does not name the lettuce type.
Salads eaten with a fat-free dressing gave almost no carotenoid absorption, while 28 g of canola oil gave the most
Crossover trial in 7 people who ate three salads of spinach, romaine lettuce, cherry tomatoes and carrots with dressing holding 0, 6 or 28 g of canola oil. Alpha-carotene, beta-carotene and lycopene barely appeared in the blood with the fat-free dressing and rose with each step up in fat. It was a mixed salad, not lettuce alone, in very few people.
A lettuce extract capsule taken for 4 weeks improved sleep time and sleep efficiency in adults with poor sleep
Randomized placebo-controlled trial in adults aged 30 to 65 with poor sleep quality, taking two capsules a day of a lettuce extract (not the vegetable). Sleep time on polysomnography was about 359 minutes against 322 on placebo, and sleep efficiency 87% against 80%. The funder, Uni Bio Inc, says it had no part in the design or the analysis.
In three large US cohorts, iceberg lettuce ranked among the five fruits and vegetables with the best metabolic profile
Analysis of 207,241 people followed for 32 years. Of 52 fruits and vegetables scored by their link to 14 blood markers of heart and metabolic health, 19 counted as high quality, and iceberg or head lettuce was in the top five. People whose intake held a larger share of such items had an 11 to 16% lower risk of major chronic disease. That result belongs to the group of foods, not to iceberg alone.
Women who ate a serving of lettuce or more a day had a 45% lower risk of hip fracture than those who ate one or fewer a week
Nurses’ Health Study cohort of 72,327 women aged 38 to 63, with 270 hip fractures over 10 years. Lettuce was the food that gave the most vitamin K. The numbers come from a 1984 food questionnaire, the abstract does not name the lettuce type, and a link cannot prove cause.
Among 485,403 older Americans, those who ate the most vegetables had a 28% lower risk of liver cancer, an effect driven mainly by lettuce and cruciferous vegetables
NIH-AARP cohort followed for a median 15.5 years, with 947 liver cancers and 986 deaths from chronic liver disease. The top fifth of vegetable intake also had a 39% lower risk of dying from chronic liver disease, and lettuce was linked to it as well. The abstract gives no lettuce-only figures, and fruit showed no link.
Eating about 1.3 servings a day of green leafy vegetables went with slower cognitive decline, equal to being 11 years younger
Prospective study of 960 adults aged 58 to 99 in the Memory and Aging Project, followed for 4.7 years on average. It covers green leafy vegetables as a group, not lettuce alone, from food questionnaires, adjusted for age, education, activity, smoking and more. Higher intakes of vitamin K, lutein, folate and nitrate each went with slower decline too.
Green leafy and cruciferous vegetables were linked to a 16% lower risk of cardiovascular disease
Meta-analysis of 8 studies of green leafy vegetables, which included cruciferous types, with a relative risk of 0.84 (range 0.75 to 0.94). It covers the group, not lettuce alone, and observational studies cannot show cause.
Green leafy vegetables were linked to a 14% lower risk of type 2 diabetes, but vegetables overall were not
Systematic review of prospective cohorts. Six studies qualified and four gave separate data on green leafy vegetables, with a hazard ratio of 0.86 (range 0.77 to 0.97). Fruit, vegetables and fruit and vegetables combined showed no significant benefit. The authors say it needs further study.
In Singapore, dark green leafy vegetables were not linked to the risk of type 2 diabetes
Cohort of 45,411 adults with 5,207 cases. The top fifth against the bottom had a hazard ratio of 1.05 (range 0.96 to 1.15). An updated meta-analysis of 11 studies found a borderline link for green leafy vegetables (0.91, range 0.84 to 1.00), which the authors call not convincing.
Rats fed a diet of 20% lettuce for 3 weeks absorbed 37% less of the cholesterol in their food
Study in rats, not people. The lettuce diet also lowered the LDL to HDL ratio and liver cholesterol, and eating lettuce raised blood vitamin C and vitamin E within 2 hours. The abstract does not name the lettuce type, and human trials are needed.
Who should be careful with iceberg lettuce
Most people can eat iceberg lettuce freely. Take a little care if one of these applies:
- Raw leafy greens and food poisoning. CDC lists unwashed lettuce among the riskier foods, and children under 5, adults 65 and older, pregnant women and people with weakened immune systems are more likely to get seriously ill. Of 20 multistate outbreaks traced to vegetable row crops from 2017 to 2020, CDC tied romaine to 7 and iceberg to 2 (1 confirmed, 1 suspected).
- Warfarin. Iceberg has less vitamin K than romaine (24.1 against 102 µg per 100 g), but a cup still gives 14% of the daily value. You do not need to avoid it; hospital leaflets ask people on warfarin to keep their vitamin K foods steady from week to week.
How to choose, store and eat iceberg lettuce
- With oil in the dressing: in a 7-person trial of a mixed salad, a fat-free dressing gave almost no carotenoid absorption and 28 g of canola oil gave the most.
- Mixed with darker greens: per 100 g, romaine has 102 µg of vitamin K and 136 µg of folate, against 24.1 and 29 µg in iceberg.
- Whole head or bagged: for a head, CDC says to discard the outer leaves, rinse the rest under running water and dry it; bags marked ready to eat or triple washed need no rinsing.
Pick a firm head rather than a hard one, since Oregon State University Extension says hard heads get more brown russet spotting. Head lettuce keeps 2 to 3 weeks at 32°F and about half as long at 38°F, so use a cold fridge (FDA says 40°F or below) and keep it away from apples and pears, which make the spotting worse. Residues are no reason to skip it: in USDA tests in 2024, none of 708 head lettuce (iceberg) samples had a residue above the legal limit.
Sources
- Safer food choices. CDC.
- Summary of possible multistate enteric (intestinal) disease outbreaks in 2017 to 2020. CDC.
- Listeria outbreak linked to leafy greens, February 2023. CDC. Advice on preparing leafy greens at home.
- Outbreak of E. coli infections linked to leafy greens. CDC. 2020. Advice not to soak greens.
- Selecting and serving produce safely. FDA.
- Dietary advice for patients taking warfarin. Cambridge University Hospitals NHS Foundation Trust.
- Lettuce. Oregon State University Extension.
- Pesticide Data Program annual summary, calendar year 2024. USDA Agricultural Marketing Service.
- Lettuce, cos or romaine, raw (SR Legacy, FDC ID 169247). USDA FoodData Central.
- Brown MJ, Ferruzzi MG, Nguyen ML, et al. Carotenoid bioavailability is higher from salads ingested with full-fat than with fat-reduced salad dressings as measured with electrochemical detection. Am J Clin Nutr. 2004.
- Herman KM, Hall AJ, Gould LH. Outbreaks attributed to fresh leafy vegetables, United States, 1973-2012. Epidemiol Infect. 2015.
- Zhang G, Chen Y, Hu L, et al. Survey of foodborne pathogens, aerobic plate counts, total coliform counts, and Escherichia coli counts in leafy greens, sprouts, and melons marketed in the United States. J Food Prot. 2018.
History of iceberg lettuce
Lettuce is one of the oldest salad crops. A 2021 genome study of 445 Lactuca samples found that cultivated lettuce was first domesticated near the Caucasus, marked by the loss of seed shattering. The earliest known pictures of lettuce farming come from ancient Egypt, around 2680 BC, where the plant was linked to the fertility god Min, and early lettuce may have been grown for its seed oil as much as for its leaves.
The Romans named it lactuca, from the Latin word for milk, because cut stems ooze a white latex, and the English word came through Old French. Serving a lettuce salad before the meal became a tradition under Emperor Domitian (81 to 96 AD). In 1586 the botanist Joachim Camerarius described the three basic types still sold today: head, loose-leaf and romaine (cos). Columbus carried lettuce to the Americas in the late 15th century.
Iceberg is a young type. Wikipedia credits the seed company Burpee with creating it in 1894, and it quickly became the most common lettuce in the western United States. Where the name came from is disputed. The popular story is crushed ice in shipping crates, while a modern Burpee CEO has said it refers to the crisp texture and icy-white outer leaves.
The train made it a star. Growers in California’s Salinas Valley shipped iceberg east in ice-cooled rail cars, because a head stays crisp for weeks when kept near 32°F. In the 1950s vacuum cooling let growers cool lettuce in the field and replaced ice-cooling in packing houses, and trade writers say iceberg was the most commonly eaten lettuce in the United States by then.
Then bagged salad changed the market. USDA says head lettuce (iceberg, butter, Boston and Bibb) peaked at 28.6 pounds per person in 1989 and fell 54% to 13.2 pounds by 2017, while romaine and leaf lettuce rose from 3.3 pounds in 1985 to 12.5 pounds in 2017. USDA credits the growing popularity of prepackaged, ready-to-eat salad greens.
Sources
- Wei T, van Treuren R, Liu X, et al. Whole-genome resequencing of 445 Lactuca accessions reveals the domestication history of cultivated lettuce. Nat Genet. 2021.
- Lettuce. Wikipedia.
- Iceberg lettuce. Wikipedia.
- What’s the story behind the name “iceberg” lettuce?. AOL.
- A brief history of lettuce. HortiDaily. 2018.
- Lettuce. Oregon State University Extension.
- Romaine and leaf lettuces almost as popular as head lettuce. USDA Economic Research Service. 2019.
Frequently asked questions about iceberg lettuce
Is iceberg lettuce good for you?
Yes, as a low-calorie food that adds crunch and some vitamin K, though it is less nutrient-rich than darker lettuces. Raw iceberg has 14 calories, 1.2 g of fiber and 24.1 µg of vitamin K (20% of the daily value) per 100 g. Women who ate a serving of lettuce or more a day had a 45% lower risk of hip fracture in a US cohort, but that is a link, and no trial here tested iceberg for health.
Is iceberg lettuce as healthy as romaine?
Not quite, because romaine has more of most vitamins. Per 100 g, romaine has 102 µg of vitamin K against 24.1 µg, 136 µg of folate against 29 µg, 2.1 g of fiber against 1.2 g, and 17 calories against 14 (USDA data). Both are low in calories and iceberg is not empty, so mixing in darker greens is an easy fix.
How many calories and carbs are in iceberg lettuce?
A cup of shredded iceberg (72 g) has 10 calories, and 100 g has 14. It has about 3 g of carbohydrate per 100 g, of which 1.2 g is fiber and 2 g is sugars, leaving about 1.8 g of net carbs. A cup has about 1.3 g of net carbs.
Is iceberg lettuce good for weight loss?
No study here tested iceberg for weight loss. It has 14 calories and 95.6 g of water per 100 g, so it fills a plate cheaply, which helps only when it replaces higher-calorie foods. Dressing, cheese and croutons can add far more calories than the lettuce.
Is iceberg lettuce safe to eat?
For most people yes, but raw lettuce has caused outbreaks, so wash and chill it. US reports to CDC from 1973 to 2012 counted 606 outbreaks tied to leafy vegetables, with 20,003 illnesses and 19 deaths; norovirus caused 55% of those with a known cause, Shiga toxin-producing E. coli 18%, and 85% involved food from restaurants or caterers. In a US survey of 14,183 leafy green samples from 2009 to 2014, E. coli O157:H7 turned up in 0.01%, and none was found in the iceberg samples. CDC advises extra care for children under 5, adults 65 and older, pregnant women and people with weakened immune systems.
How do you wash iceberg lettuce?
Discard the outer leaves, rinse the rest under running water while gently rubbing the leaves, and dry them with a clean cloth or paper towel. CDC says not to soak leafy greens in a sink or bowl, because germs can spread from leaf to leaf, and FDA advises against soap or produce wash. No washing removes all germs, and bags labeled ready to eat, triple washed or no washing necessary do not need rinsing.
Does lettuce help you sleep?
Not as a salad, as far as the evidence here shows. A 4-week placebo-controlled trial of a lettuce extract in adults with poor sleep found about 359 against 322 minutes of sleep time on polysomnography, but it used a concentrated capsule and was funded by a company, Uni Bio Inc. No trial here tested eating iceberg lettuce for sleep.
Is iceberg lettuce good for blood sugar?
It can fit, but the evidence is thin. In 16 healthy men, 100 g of lettuce in a fatty meal lowered the 4-hour blood sugar curve, and a pooled analysis linked green leafy vegetables to a 14% lower risk of type 2 diabetes. A large Singapore cohort found no link, and its updated meta-analysis was called not convincing. Iceberg has about 2 g of sugars per 100 g. If you have diabetes, check portions and choices with your care team.