Introduction: What is Sea Lettuce?
Sea Lettuce vs. Other Seaweeds
Nutritional Breakdown
Functional Compounds
Source List
Introduction: What is Sea Lettuce?
Sea Lettuce (Ulva lactuca) is a vibrant green leafy seaweed that thrives in diverse climatic conditions across the globe. Its mild, vegetal umami flavor and delicate texture make it a versatile ingredient that complements a variety of food applications.
Sea Lettuce’s superpower is that it is a multifunctional nutritional powerhouse.
- It has dense, complete, nutrition, with protein content up to 25% dry mass and a complete amino acid profile.
- Its unique functional benefits are specifically beneficial for gut health due to the presence of the hydrocolloid ulvan and its high dietary fiber content.
- This has the added benefit of making sea lettuce highly digestible, which increases the bioavailability of nutrients relative to other seaweeds.
- Most importantly, unlike other seaweeds, it is safe to consume without micronutrient toxicity risks and has a mild, highly palatable flavor.
Known as aosa in Japan and parae in Korea, sea lettuce has long been a staple in East Asian cuisines because of its multifunctional nutritional properties and mild flavor. In Japan, it is commonly used as a base for the umami-rich seasoning furikake, as a powdered topping for fried dishes like okonomiyaki, or blended with nori to create sushi sheets and seaweed snacks. It also features in soups, seaweed salads, and pickled side dishes.A related seaweed, known as Ulva prolifera or Gamtae in Korea and aonori in Japan, is highly prized for its culinary uses. Gamtae is valued for its bright green color, delicate aroma reminiscent of an ocean breeze mixed with white truffle, and unique flavor profile—a mild briny umami with a sweet and bitter finish. This complex, yet mild flavor has made gamtae a favorite among leading restaurants in Korea and worldwide. Nutritionally, Gamtae has a very similar profile to sea lettuce, given that they are closely related biologically. As such, gamtae and sea lettuce may be used interchangeably in functional food or nutrient supplementation applications.
Sea Lettuce vs. Other Seaweeds
| Protein Content |
Up to 30%; complete amino acid profile |
Up to 5%; incomplete amino acid profile |
Up to 5%; incomplete amino acid profile |
Up to 40%; incomplete amino acid profile |
Up to 16%; incomplete amino acid profile |
| Iodine Levels (mcg/kg) |
43,000 |
232,700 |
93,900 |
45,800 |
680,000 |
| Unique Functional Compounds |
Ulvan, Prebiotic Fiber, Polyphenols |
Fucoidan, Fucoxanthin |
Fucoidan, Fucoxanthin |
Porphyran |
Fucoidan, Phlorotannins, Laminarin |
| Digestibility & Bioavailability |
High, due to presence of Ulvan and prebiotic fiber |
Moderate, due to presence of indigestible alginates |
Moderate, due to presence of indigestible alginates |
High, due to lower insoluble fiber content |
Low, due to high presence of alginates |
| Flavor Profile |
Mild, neutral, savory, vegetal |
Strong, fishy, savory, earthy |
Mild, slightly sweet, vegetal |
Mild, savory, distinctive |
Strong, earthy, fishy |
Nutritionally, sea lettuce is a standout powerhouse of protein and essential micronutrients. When grown in nitrate-rich environments, it boasts a protein content of up to 25% that includes all nine essential amino acids. It is particularly rich in iodine, iron, magnesium, calcium, zinc, vitamin B12, vitamin A, and vitamin C, all in levels that are beneficial but not toxic, providing substantial health benefits.
| Protein (g) |
5 |
50 |
9.76% |
| Total Fat (g) |
1 |
78 |
0.74% |
| Total Carbohydrate (g) |
2 |
275 |
0.59% |
| Dietary Fiber (g) |
6 |
28 |
21.82% |
| Sodium (mg) |
595 |
2,300 |
25.89% |
| Vitamin A (mcg) |
38 |
900 |
4.24% |
| Vitamin C (mg) |
14 |
90 |
15.56% |
| Folic Acid (mcg) |
10 |
400 |
2.50% |
| Vitamin B12 (mcg) |
6 |
2.4 |
232.50% |
| Magnesium (mg) |
704 |
420 |
167.67% |
| Phosphorus (mg) |
68 |
1,250 |
5.44% |
| Potassium (mg) |
435 |
4,700 |
9.26% |
| Calcium (mg) |
606 |
1,300 |
46.60% |
| Iron (mg) |
45 |
18 |
250.17% |
| Zinc (mg) |
1 |
11 |
9.09% |
| Iodine (mcg) |
900 |
150 |
600.00% |
| Manganese (mg) |
1 |
2.3 |
32.61% |
| Selenium (mcg) |
3 |
55 |
4.85% |
| Copper (mcg) |
175 |
900 |
19.44% |
*source: MariTide Aquatech LLP. Data was compiled across 27 commercially available nutrition labels and peer-reviewed papers.
**source: FDA. Daily recommended dose for adults. Specific needs vary across demographics and activity levels.
Sea lettuce is also rich in Ulvan, a water-soluble prebiotic hydrocolloid (i.e. a form of soluble fiber) that supports gut health by enhancing the growth of beneficial gut bacteria. Additionally, it also contains antioxidant polyphenols, carotenoids, phytosterols, and essential fatty acids among other functional compounds.
| Ulvan (Sulfated Polysaccharide) |
Highly abundant |
Moderately bioavailable; enhanced by gut fermentation. |
Prebiotic, supports gut health, boosts immunity, antioxidant, antiviral, and antibacterial properties. |
| Bioactive Peptides |
Released during digestion or processing. |
High bioavailability when consumed in enzymatically digested forms. |
Antihypertensive, antioxidant, reduces oxidative stress, supports cardiovascular health. |
| Polyphenols and Flavonoids |
Present in smaller quantities compared to terrestrial plants. |
Highly bioavailable; absorbed through the gut. |
Antioxidant, reduces inflammation, supports heart and overall cellular health. |
| Essential Fatty Acids |
Contains small amounts of Omega-3 and Omega-6. |
Readily absorbed; similar to other plant-based sources. |
Anti-inflammatory, supports brain and cardiovascular health. |
| Phytosterols |
Naturally occurring in the cellular structure of sea lettuce. |
Moderate bioavailability; absorbed in the intestine. |
Lowers cholesterol levels, supports cardiovascular health. |
| Vitamins (C, A, B12) |
Rich in bioactive forms like Vitamin C, beta-carotene, and B12. |
High bioavailability; supports diverse metabolic pathways. |
Antioxidant, supports immune function, skin health, and vision. |
| Minerals (Iodine, Magnesium, Iron, Zinc) |
High in essential trace minerals in bioavailable forms. |
Highly bioavailable; iodine, in particular, is well absorbed. |
Supports thyroid function, enzymatic activity, red blood cell production, and immune system. |
| Antimicrobial Compounds |
Naturally occurring; specific mechanisms under research. |
Active at surface contact and in the gut. |
Antibacterial and antifungal properties, particularly beneficial for gut and skin health. |
| Carotenoids (Lutein, Beta-carotene) |
Present in moderate quantities as natural pigments. |
Readily absorbed; fat-soluble. |
Supports eye health, reduces age-related macular degeneration risk, and acts as an antioxidant. |
The bioavailability of these functional compounds is generally high and increases if pre-processed by blanching or fermentation. These specific prebiotic, immunity-boosting, and antioxidant properties of sea lettuce make it stand out compared to other functional foods.
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