NutriDex

The Supplement Research Compendium
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romaine-lettuce

A crisp, ultra-low-calorie leafy green delivering outsized vitamin K, vitamin A, folate, and the eye-protective carotenoids lutein and zeaxanthin.

Moderate evidence 🥦Vegetables

✚ Updated · How we grade evidence

Evidence tier
Moderate
Research weight
Citations
8 verified / 8
Classification
Vegetables
❝
What the evidence says. Several controlled trials; effects real but modest or context-dependent.

Nutrition per serving 1 cup shredded, raw (47 g)

47gSERVING
  • Sugars 0.6 g1%
  • Fibre 1 g2%
  • Protein 0.6 g1%
  • Other 44.8 g95%
What's in one serving, by weight — average composition (USDA).
Vitamin C2%Fiber4%Potassium2%Folate16%Vitamin A23%Vitamin K40%Vitamin B62%Manganese3%
One serving as % of the adult daily requirement (FDA Daily Values). The bold outer ring = 100% of a day's needs.
8 kcal0.6 g protein1 g fiber0.6 g sugar
NutrientPer serving% daily value
Vitamin C1.9 mg2%
Fiber1 g4%
Potassium116 mg2%
Folate64 µg16%
Vitamin A205 µg23%
Vitamin K48 µg40%
Vitamin B60.04 mg2%
Manganese0.07 mg3%
Copper0.02 mg3%
Vitamin E0.06 mg0%
Magnesium6.6 mg2%
Calcium16 mg1%

Composition data: USDA FoodData Central ↗

What is romaine-lettuce?

romaine-lettuce is a vegetable used for supports blood-pressure regulation via dietary nitrate. NutriDex grades the human evidence as Moderate. Romaine is a nutrient-dense, water-rich leafy green: a single shredded cup is roughly 8 kcal yet supplies meaningful vitamin K, provitamin-A carotenoids, and folate. As one of the higher-nitrate leafy greens, it shares the bioactive profile (dietary nitrate, lutein/zeaxanthin, vitamin K, folate) tied in human studies to lower cardiovascular risk, slower cognitive decline, and reduced progression of age-related macular degeneration. The strongest randomized evidence is indirect, coming from inorganic-nitrate and lutein/zeaxanthin trials rather than romaine itself; whole-diet leafy-green data are observational but consistent.

Purported Benefits

✓Supports blood-pressure regulation via dietary nitrate
✓Rich in eye-protective lutein and zeaxanthin
✓Linked to slower age-related cognitive decline
✓Very low calorie, high water and folate
✓Associated with lower cardiovascular disease risk

Dosing & Compounds

Typical Dose
Standard serving: 1 cup shredded, raw (47 g). Eat whole (with skin where edible); favour whole fruit over juice.
Active Compounds
dietary nitrateluteinzeaxanthinbeta-carotenevitamin K1 (phylloquinone)folatekaempferol

Safety & Cautions

High in vitamin K (about 48 ug per cup), which can interfere with warfarin and similar anticoagulants — keep intake consistent if on these drugs. Leafy greens including romaine have been recurrent sources of E. coli and Listeria outbreaks, so wash thoroughly and observe recalls. Oxalate content is low to moderate. Otherwise very well tolerated. Educational only — always check with your doctor or pharmacist before combining romaine-lettuce with any medicine.

Key Studies

Meta-analysis of prospective cohorts Pollock RL 2016 ✓ Full text
Higher green leafy and cruciferous vegetable intake was associated with a 15.8% lower incidence of cardiovascular disease (RR 0.842, 95% CI 0.753-0.941).
Systematic review & meta-analysis of RCTs Siervo M et al. 2013 ✓ PubMed
Across 16 crossover trials (n=254), inorganic nitrate/beetroot supplementation reduced systolic BP by -4.4 mm Hg (95% CI -5.9 to -2.8; P<0.001), with a dose-response relationship.
Meta-analysis of prospective cohorts Li M et al. 2014 ✓ Full text
Pooling 10 articles (24,013 cases; 434,342 participants), each 0.2 serving/day increase in green leafy vegetables was associated with a lower type 2 diabetes risk (RR 0.87, 95% CI 0.81-0.93).
Randomized controlled trial Jackson JK et al. 2020 ✓ Full text
In 243 adults aged 50-70 with elevated SBP, 5 weeks of leafy-green vegetables or matched inorganic nitrate pills (300 mg/d) did not significantly lower 24-h ambulatory systolic blood pressure versus low-nitrate control.
Randomized controlled trial (long-term follow-up) Chew EY et al. (AREDS2 Report 28) 2022 ✓ PubMed
Over 10 years in AREDS2 (n=4203), lutein/zeaxanthin versus no lutein/zeaxanthin reduced progression to late age-related macular degeneration (HR 0.91, 95% CI 0.84-0.99; P=0.02).
Randomized controlled trial Bondonno CP et al. 2022 ✓ PubMed
A 12-week increase in nitrate-rich vegetable intake lowered ambulatory systolic blood pressure in (pre)hypertensive middle-aged and older adults compared with control.
Prospective cohort Blekkenhorst LC et al. 2017 ✓ PubMed
In 1226 older women over 15 years, women in the highest tertile of vegetable-derived nitrate intake had lower atherosclerotic vascular disease mortality (HR 0.53, 95% CI 0.33-0.86) versus the lowest.
Prospective cohort Morris MC et al. 2018 ✓ Source
In 960 older adults over ~4.7 years, the highest green-leafy-vegetable quintile (~1.3 servings/d) showed slower cognitive decline (beta=0.05 standardized units/y; P=0.0001), equivalent to being ~11 years younger.
8 sources cited · 8 verified Search all studies on PubMed ↗

Common questions about romaine-lettuce

What is romaine-lettuce used for?

romaine-lettuce is most often taken for Supports blood-pressure regulation via dietary nitrate, Rich in eye-protective lutein and zeaxanthin, Linked to slower age-related cognitive decline, Very low calorie, high water and folate. A crisp, ultra-low-calorie leafy green delivering outsized vitamin K, vitamin A, folate, and the eye-protective carotenoids lutein and zeaxanthin.

Does romaine-lettuce work — what does the evidence say?

Moderate evidence. Several controlled trials; effects real but modest or context-dependent. Romaine is a nutrient-dense, water-rich leafy green: a single shredded cup is roughly 8 kcal yet supplies meaningful vitamin K, provitamin-A carotenoids, and folate. As one of the higher-nitrate leafy greens, it shares the bioactive profile (dietary nitrate, lutein/zeaxanthin, vitamin K, folate) tied in human studies to lower cardiovascular risk, slower cognitive decline, and reduced progression of age-related macular degeneration. The strongest randomized evidence is indirect, coming from inorganic-nitrate and lutein/zeaxanthin trials rather than romaine itself; whole-diet leafy-green data are observational but consistent.

What is the typical dose of romaine-lettuce?

Standard serving: 1 cup shredded, raw (47 g). Eat whole (with skin where edible); favour whole fruit over juice.

Is romaine-lettuce safe? Any cautions or side effects?

High in vitamin K (about 48 ug per cup), which can interfere with warfarin and similar anticoagulants — keep intake consistent if on these drugs. Leafy greens including romaine have been recurrent sources of E. coli and Listeria outbreaks, so wash thoroughly and observe recalls. Oxalate content is low to moderate. Otherwise very well tolerated.

How many studies support romaine-lettuce?

NutriDex cites 8 sources for romaine-lettuce, graded "Moderate".

Cite this page
APA

Peh, D. (2026). romaine-lettuce: Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 26 Jun 2026, from https://nutridex.info/s/romaine-lettuce

BibTeX
@misc{nutridex_romaine_lettuce,
  author       = {Peh, Daryl},
  title        = {romaine-lettuce: Benefits, Dosage, Side Effects \& Evidence},
  year         = {2026},
  howpublished = {NutriDex --- The Supplement Research Compendium},
  url          = {https://nutridex.info/s/romaine-lettuce},
  note         = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-06-26}
}

For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.

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