Sea Grapes (Umibudo): Nutrients, What Research Shows and Safety
Sea grapes (umibudo, Caulerpa lentillifera) as a food: what farm analyses found, raw-food safety, salt and iodine gaps, and what lab and small human studies do and do not show.
Content last updated . This page has not been medically reviewed.
Sea grapes, called umibudo in Japan, are a green seaweed, Caulerpa lentillifera. They look like tiny strings of green beads and are eaten whole, usually fresh or packed in brine. [2] People eat them for their pop-in-the-mouth texture and for general nutrition. This page keeps the food apart from extracts and from hype, and it is honest about what we could not find: there is no USDA entry, and we found no human trial on health outcomes.
Read this first
- No USDA entry for this food. The numbers below come from farm and lab analyses, and they differ a lot from farm to farm. [1]
- Eaten raw, so handling matters. Sea grapes are often eaten uncooked. In a 2025 study, fresh sea grapes carried coliform bacteria and a bacterial count until they were treated. [3] Vibrio germs, which cause most infections from raw shellfish and from seawater in wounds, can be serious for people with liver disease, diabetes, cancer, weakened immunity or who take stomach-acid medicine. [5] We did not find a source that tested sea grapes for Vibrio. [2]
- Iodine, arsenic and other metals: Proper evidence not found for sea grapes in the sources we read. Other seaweeds range from very low to very high iodine, so do not assume. [8] Ask a clinician if you have thyroid disease, are pregnant or breastfeeding, or take thyroid medicine. [9] [10]
- Allergic reaction to any food: trouble breathing or swelling of the face or throat is an emergency. Call 911 (or your local emergency number).
- Evidence in one line: sea grapes are a food with an interesting nutrient profile; claims about cholesterol, cancer or stomach germs come from lab and animal work only. [11] [12] [13]
What is in it (no USDA values)
USDA FoodData Central (SR Legacy) has no entry for sea grapes, so we cannot give USDA numbers. The figures below are from published analyses of the seaweed itself. They are not a nutrition label and they vary with growing site, harvest and processing.
| Measure | What the source found | Form and source |
|---|---|---|
| Water | About 95% in fresh sea grapes | Fresh, Thailand [2] |
| Protein | 8.70% to 18.57% of sample, depending on farm (Dapeng lowest, Daya highest) | Samples from Guangdong, China; the abstract does not state fresh or dry basis [1] |
| Protein, dry weight | About 4.9% fresh sea grapes, and about 11% to 18% after brining | Dry weight, Thailand [2] |
| Fat | Up to 5.10% at the highest farm | China [1] |
| Total sugar | About 32.5% to 32.9% at two farms | China [1] |
| Dietary fiber | About 4.1% of dry weight fresh, and about 12% to 18% after brining | Dry weight, Thailand [2] |
| Ash (minerals and salt) | About 65.6% of dry weight in fresh sea grapes | Thailand [2] |
| Iodine, sodium, potassium, arsenic | Not reported in the abstracts and papers we read for this species | Proper evidence not found |
The high ash figure means that much of the dry weight is minerals and salts from seawater, which is why dried or desalted weights look different from fresh. [2] A related species (Caulerpa cylindracea, not sea grapes) from the Adriatic was about one third salt by dry weight, and its authors advised desalting before eating. [6] We mention it only as a reminder that Caulerpa seaweeds can hold a lot of salt; it may not apply to sea grapes.
Plant compounds: one rat study used a carotenoid and peptide extract of Caulerpa sea grapes. That is a lab and animal result, not a statement about eating the whole food. [11]
What research says
| Health goal | What the sources found | Strength of evidence | What was studied |
|---|---|---|---|
| Blood sugar after a meal | Noodles made with 2.5% or 5% sea grape powder gave a lower glycemic index (47 and 43) than the control in 10 healthy volunteers. [4] | Promising but limited (tiny study, noodles, not whole sea grapes) | Powder in noodles, 10 healthy adults |
| Cholesterol and weight | Extracts and polysaccharides lowered blood fats and weight gain in rats and mice. [11] [14] | Lab or animal only | Extracts and polysaccharides, rodents |
| Cancer | A polysaccharide from sea grapes killed colon cancer cells in a dish and slowed tumor growth in mice. [12] | Lab or animal only. No human data found | Purified polysaccharide |
| Stomach germ (H. pylori) | A water extract slowed growth of the germ in lab tests. [13] | Lab or animal only | Extract in a dish |
| General nutrition | Protein, fiber and minerals vary greatly with farm. [1] [2] | Composition data, not health outcomes | Seaweed samples |
| Thyroid, immunity, "detox" | Proper evidence not found in the sources we read | Insufficient evidence | Not applicable |
Eaten as food vs taken as extract. The one human result is for powder baked into noodles. The cholesterol, cancer and germ results use purified or concentrated extracts that people do not get from eating a bowl of sea grapes. [11] [12] [13]
How much is a normal serving
We did not find an official serving size for sea grapes from USDA, the Japanese food composition tables or another health body. The glycemic index study mixed sea grape powder into noodles at 2.5% and 5%, which is a research recipe and not a recommendation. [4] This is information, not a prescription. Because iodine in sea grapes is not measured in the sources we read, we cannot say how much is "safe" for someone who must limit iodine.
Safety, allergy and medicines
- Raw-food bacteria. Fresh sea grapes had a measurable bacterial load and coliforms before a seawater plasma treatment removed them in the lab. [3] A brining study found the bacterial count dropped after salting but rebounded in some samples by week 12, and some samples grew mold. [2] That study did not test for Vibrio, E. coli or Salmonella. [2]
- Vibrio. CDC says most vibriosis comes from raw or undercooked shellfish, or from wounds exposed to coastal water. It does not mention seaweed. [5] Higher-risk groups include people with liver disease, cancer, diabetes, HIV or thalassemia, those on immune-suppressing treatment, and those taking stomach-acid medicine. [5]
- Salt. Brined sea grapes were stored in salt at 10% to 30%. [2] The study authors said desalting before eating may cut nutrients. [2] People on a low-sodium diet should check the label and ask a clinician. We did not read a sodium value for sea grapes.
- Iodine and thyroid. Iodine values for other seaweeds are very different: a 2025 Korean survey found sea tangle (a kelp) averaged 2,432 mg per kg dry weight. [8] Sea grapes are not kelp, and we have no iodine number for them. Official upper levels for adults are 1,100 mcg a day (Health Canada, 2025), lower for children. [9] People with thyroid disease or on thyroid medicine, pregnant or breastfeeding people and children should ask a clinician. [9] [10]
- Metals. A New Caledonia survey of 17 seaweeds found all exceeded the European total arsenic limit for food additives, and named Caulerpa oligophylla among five judged safe. That is a different species, so it does not tell us about sea grapes. [7] See the heavy metals page.
- Caulerpenyne and other natural toxins: Proper evidence not found in the sources we read.
- Allergy: we did not find a source on sea grape allergy. Seaweed is not fish or shellfish. For hives with trouble breathing, or swelling of the face or throat, call 911. See food allergy basics.
- Medicines, warfarin, kidney disease: Proper evidence not found for sea grapes. Ask a pharmacist.
Choosing, storing and food safety
- Buy from a seller that keeps sea grapes cold and sealed. In a 2025 study, quality fell after 48 hours of storage in weight, fat oxidation and pigment. [3]
- Brined products may stay stable for weeks, but the brining study saw bacteria and mold in some samples, and stated food-safety monitoring is needed. [2]
- Do not rely on folklore about rinsing in tap water or fresh water. We did not find a source on it.
- If you are in a higher-risk group for Vibrio, ask your clinician whether raw sea products are right for you. [5]
Related pages
Health connections for Sea Grapes (Umibudo)
What research links to eating or drinking this food, and how strong the evidence is. Many studies are observational or use juice, powder, oil or extracts rather than the food as eaten; each card says which.
Sea grapes as a food: nutrient content varies by farm
Not enough evidenceProtein ranged from 8.7% to 18.6% between farms in one Chinese analysis, and fresh sea grapes are about 95% water. There is no USDA entry.
Supplements: Composition data only; no health outcome is claimed.
Sea grapes and blood sugar after a meal
Preliminary or mixedNoodles with 2.5% or 5% sea grape powder had a lower glycemic index than the control in 10 healthy volunteers.
Supplements: Whole sea grapes were not tested.
Iodine, arsenic and metals in sea grapes: data gaps
Not enough evidenceNo iodine, arsenic or metal values for sea grapes were found. Other seaweeds range from low to very high iodine.
Supplements: Not applicable.
Sea grapes and cholesterol: rodent studies
Lab or animal research onlyAn extract and a polysaccharide lowered blood fats and weight gain in rats and mice.
Supplements: Extracts are not the food.
Sea grapes and cancer: lab cells and mice
Lab or animal research onlyA polysaccharide killed colon cancer cells in a dish and slowed tumors in mice. No human data found.
Supplements: No human evidence.
Sea grapes extract against H. pylori in the lab
Lab or animal research onlyA water extract slowed growth of H. pylori in lab tests.
Supplements: No human evidence.
Connected topics
Open a group to see how each topic connects and how strong the evidence is.
Health goals (1)
- Blood Sugar BalancePreliminary or mixed
One tiny study (10 people) found a lower glycemic index for noodles made with sea grape powder. Not enough to say sea grapes help blood sugar.
Body systems (2)
- Blood Sugar SupportPreliminary or mixed
Same small noodle study; whole sea grapes were not tested.
- Digestive SystemDocumented risk
Raw sea grapes carried bacteria in a lab study, so handling matters. CDC describes vibriosis as a gut infection from raw shellfish or coastal water but does not mention seaweed.
Biomarkers (1)
- Blood GlucosePreliminary or mixed
Blood glucose after eating noodles with sea grape powder was lower than the control in 10 healthy volunteers.
Documented risks and interactions (2)
- Raw sea grapes and food safety. Fresh sea grapes carried coliform bacteria in a lab study; CDC describes Vibrio risks from raw shellfish and coastal water but does not mention seaweed.
- Sea grapes, brine and salt. Sea grapes are stored in 10% to 30% brine; the authors noted desalting may reduce nutrients. No sodium value was read.
Frequently asked questions
Are sea grapes safe to eat raw?
They are a traditional raw food, but a 2025 study found bacteria on fresh sea grapes until treated. [3] CDC's Vibrio page does not mention seaweed, and we found no sea grape Vibrio test. [5] [2] Buy from a careful seller and keep them cold.
Do sea grapes have iodine?
We did not find an iodine measurement for sea grapes. Other seaweeds range widely, so we cannot say. [8] Ask a clinician if iodine matters for you. [9]
Do sea grapes lower cholesterol or fight cancer?
Only in lab and animal studies using extracts or purified polysaccharides. [11] [12] We found no human trial.
Are sea grapes high in salt?
Brined sea grapes are stored in 10% to 30% salt. [2] We did not read a sodium value, so check the label and the seller.
Is it an allergen?
We found no source on sea grape allergy. Any food can cause a reaction. Call 911 for trouble breathing or swelling of the face or throat.
References
- Zhou W, Wang Y, Xu R, Tian J, Li T, Chen S. Comparative Analysis of the Nutrient Composition of Caulerpa lentillifera from Various Cultivation Sites. Foods 2025 (abstract read via Europe PMC). Read 2026-10-24.
- Pan-utai W, Satmalee P, Saah S, Paopun Y, Tamtin M. Brine-Processed Caulerpa lentillifera Macroalgal Stability: Physicochemical, Nutritional and Microbiological Properties. Life (Basel) 2023 (full text). Read 2026-10-24.
- Than HAQ, Do NK, Tran MAN, Nguyen TT, Pham TH, Khacef A. Postharvest treatment of sea grapes (Caulerpa lentillifera) using cold plasma activated seawater. Food Res Int 2025 (abstract read via Europe PMC). Read 2026-10-24.
- Syakilla N, George R, Matanjun P. The potential of noodles incorporated with green seaweed Caulerpa lentillifera as a low-glycaemic food. J Appl Phycol 2025;37(4):2965-2974 (abstract read via Europe PMC). Read 2026-10-24.
- CDC. About Vibrio. Page dated 14 May 2024. Read 2026-10-24.
- Iveša N, et al. Caulerpa cylindracea: first insight into its nutritional potential. Foods 2025 (abstract read via Europe PMC; a different species). Read 2026-10-24.
- Lagourgue L, et al. Assessment of contaminant concentrations and nutritional value of New Caledonian seaweeds. Mar Pollut Bull 2025 (abstract read via Europe PMC). Read 2026-10-24.
- Lee Y, Park HJ, Jo M, Ha KS, Mok JS. Analysis and risk assessment of total iodine content in edible seaweeds in South Korea. Foods 2025 (abstract read via Europe PMC). Read 2026-10-24.
- Health Canada. Dietary reference intakes tables: reference values for elements. Page dated 2025-11-19. Read 2026-10-24.
- Taylor PN, et al. What endocrinologists should know about iodine: population deficiency, individual excess and misinformation in the United Kingdom. Clin Endocrinol 2026 (abstract read via Europe PMC). Read 2026-10-24.
- Kurniawan R, et al. Carotenoid and peptide supplementation from Caulerpa sp. (sea grapes) extract mitigate metabolic syndrome in cholesterol-enriched diet rats. Diabetol Metab Syndr 2025 (abstract read via Europe PMC). Read 2026-10-24.
- Wen Q, et al. Molecular mechanisms underlying the anti-colon cancer effects of Caulerpa lentillifera polysaccharides. Int J Biol Macromol 2025 (abstract read via Europe PMC). Read 2026-10-24.
- Thacharoen C, et al. Metabolomic profiling and anti-Helicobacter pylori activity of Caulerpa lentillifera extract. Mar Drugs 2025 (abstract read via Europe PMC). Read 2026-10-24.
- Long H, et al. Polysaccharide from Caulerpa lentillifera alleviates hyperlipidaemia through altering bile acid metabolism mediated by gut microbiota. Int J Biol Macromol 2025 (abstract read via Europe PMC). Read 2026-10-24.