What Is Sea Moss (Irish Moss)? A Complete Scientific Guide
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- Definition
- Benefits
- Weight Loss
- Side Effects
- Forms
- How to Select
- Dosage
- FAQ
- Definition
- Benefits
- Weight Loss
- Side Effects
- Forms
- How to Select
- Dosage
- FAQ
Note: The U.S. Food and Drug Administration (FDA) does not approve supplements for safety or effectiveness. Talk to a healthcare professional about whether a supplement is the right fit for your individual health, and about any potential drug interactions or safety concerns.
If you pay attention to superfoods and supplements hyped online, you may have encountered sea moss, sometimes referred to as Irish moss.
Sea moss, used for centuries in traditional folk medicine, has made the leap to TikTok, with celebrity fans like Kim Kardashian and Hailey Bieber extolling its therapeutic powers.
But can sea moss really benefit your health? Here’s what you should know.
Overview
What Is Sea Moss?
Sea moss (Chondrus crispus) is a species of red algae that grows on North Atlantic coastlines. It’s a small, spiky, or frilly seaweed that typically resembles red leaf lettuce, though it can vary in color from yellow-green to dark purple.[1]
Current marketing claims about the healthfulness of sea moss focus on its wealth of vitamins, minerals, polyphenols (natural plant compounds with antioxidant and anti-inflammatory properties), and fiber, says Jamie McManus, MD, chair of medical affairs, health sciences, and education for Shaklee Corporation, a producer of nutritional supplements.
Some producers of sea moss supplements also claim it can promote weight loss.
Potential Health Benefits of Sea Moss
Research on the health benefits of sea moss is limited. Most studies focus on seaweed generally and not sea moss specifically, says Robin Foroutan, RDN, a registered dietitian with the Morrison Center in New York City. Carrageenan, a gelatinous compound that is the main component of sea moss, also gets scrutiny.[2]
But given that people around the world have used sea moss as a treatment for hundreds of years, she says, it’s worth a closer look. “When a food has been around medicinally that long, there’s potentially some truth to it, even if we don’t have the research to support it. ”
It’s important to note that any data on the health benefits of sea moss comes primarily from animal and laboratory studies, which don’t necessarily translate to human health. What’s more, some of the purported impacts are only theoretical, requiring further research.
May Improve Gut Health
Studies focusing on sea moss supplements suggest that they may benefit gut health, says Kristin Kirkpatrick, RDN, a dietitian at the Cleveland Clinic Wellness Institute in Denver. Sea moss is rich in fiber and probiotics (beneficial bacteria) that may support healthy digestion.[3]
May Help Fight Infection
A healthy gut is linked to a robust immune system. By supporting gut health, sea moss might boost immunity.[3]
What’s more, sea moss could theoretically soothe mucus membranes in the respiratory and digestive tracts because of its gelatinous texture, Foroutan says. Mucus membranes produce mucus, which fight infection by helping trap and remove germs from the body.[4]
May Boost Heart Health
Adding seaweed to your diet could potentially help reduce the risk of cardiovascular disease, thanks to algae’s high fiber content and antioxidants.[5]
Fiber has been found to help lower blood pressure and cholesterol levels, benefiting heart health.May Lower Likelihood of Certain Cancers
One laboratory study found that compounds extracted from sea moss inhibited the growth of some human cancer cells.[6]
Such anticancer properties may be attributed to the antioxidants in carrageenan.[7]
Human studies, however, are needed to confirm the potential role of sea moss in cancer prevention and treatment.
May Fight HPV
According to a review of existing scientific literature, carrageenan found in red algae may help protect against human papillomavirus (HPV) infections and complement other preventive HPV therapies, such as vaccines. However, studies exploring this potential connection yielded conflicting results; more research is needed.[8]
May Promote Healthy Skin
Sea moss appears to be growing in popularity as an ingredient in natural skin-care products, though research into this use is lacking.
The nutrients and compounds in seaweed — including sea moss — may help treat acne and have antifungal properties, says Karan Lal, MD, a board-certified dermatologist with Schweiger Dermatology Group in Hackensack, New Jersey.[9]
Amino acids in the moss, such as arginine, may also benefit the skin by promoting anti-aging effects, Dr. Lal says.[10]
May Help Thyroid Function
“[Sea moss] is rich in iodine, among other vital nutrients,” says Kristin Gillespie, RD, a registered dietitian based in Virginia Beach, Virginia.
Iodine is essential for thyroid function. Specifically, iodine helps the thyroid gland produce hormones that affect metabolism. Women who are pregnant and people who follow a vegan or dairy-free diet are more likely to have trouble getting enough iodine. In pregnancy and infancy, thyroid hormones support the healthy development of the brain and bones.[11]
Even though sea moss is high in iodine, it’s important to point out that research hasn’t specifically looked at how taking a sea moss supplement might improve thyroid health. Speak to your physician about ways to manage your thyroid health.
Potential Weight Loss Effect
While no clinical studies identify sea moss as a weight loss remedy, the algae does have some qualities that may theoretically support weight loss. More human research is needed to confirm.
Fiber is satiating, Foroutan says. That means it can help you feel full for longer and reduce the likelihood that you’ll overeat — but this effect hasn’t been specifically studied in sea moss.[12]
Potential Risks and Side Effects of Sea Moss
While occasionally eating sea moss raw is unlikely to harm you, it’s always best to consult with your healthcare provider before trying a supplement.
“Honestly, these supplements shouldn’t be needed if you are consuming a general healthy diet that is rich in a variety of food types,” says Gillespie. “This supplement is not without risks, so it is better to reap nutritional benefits from whole food sources instead.”
Risks
Because of its potentially high iodine content, people with thyroid conditions should discuss the use of sea moss with their healthcare provider, says McManus. “While iodine is essential for normal thyroid function, excess iodine intake can lead to under- or over-functioning,” she says.
Most Americans get enough iodine in their diet. While it’s difficult to overdo it through food alone, people who are managing conditions that affect thyroid function (such as Graves’ disease, Hashimoto’s disease, or thyroiditis) should avoid iodine supplementation unless medically necessary.[13]
In fact, taking iodine-rich supplements like sea moss could worsen hypothyroidism (a condition signified by an underfunctioning thyroid), and may interact with your thyroid medications, such as levothyroxine.[14]
Always ask your doctor before taking these supplements, especially if you’re taking other herbs, supplements, or medications.Even if you don’t have thyroid disease, it’s important to follow daily allowances for iodine, says Jessica Cho, MD, an internal medicine physician in private practice in Los Angeles. Currently, the National Institutes of Health’s recommended average amount is 150 micrograms per day for adults. (If you are pregnant or lactating, that amount increases to 220 or 290 micrograms, respectively.)[11]
If you and your healthcare provider determine that sea moss is safe for you, have them help you select a quality supplement (more on that later). The FDA does not fully regulate supplements’ safety or quality, so finding a third-party-tested product is essential.
Here’s why: “Depending on where the sea moss is sourced from, it can accumulate heavy metals from their presence in our oceans,” says McManus. “Be sure you are dealing with reputable sources that test for heavy metals.”
Side Effects
“Research on the effect of carrageenan is conflicting and sparse, but some research has suggested a connection between carrageenan and unpleasant side effects, including inflammation and digestive problems such as bloating,” says Gillespie.[15]
Forms of Sea Moss
Sea moss supplements come in numerous forms, including:[3]
- Capsules
- Gummies
- Powders
- Gel
- Whole dried sea moss (sold as red seaweed or red algae)
You can buy sea moss capsules, gummies, and powders at supplement stores or at some health food stores. As for whole red seaweed, certain health food stores and online vendors carry it. You can even make sea moss gel at home from dried sea moss.
Different forms of sea moss supplements may contain additional ingredients or preservatives. Opt for products that contain the fewest additives so you can maximize sea moss’s potential benefits.
How to Select Sea Moss
Choose a reputable brand that provides detailed information on iodine content, as well as specifics on quality testing and sourcing, and which also follows good manufacturing practices, says McManus.
To do so, check the label for approvals from USP, NSF, or ConsumerLab. This means the product has undergone third-party testing for quality and purity.
Dosage of Sea Moss
No safe dosage has been established for sea moss gel capsules. One study concluded that consuming up to 4 grams per day of red seaweed or sea moss was unlikely to pose any adverse health effects. At the other end of the spectrum, researchers also found that consuming 286 grams of Irish moss per day could lead to excess iodine intake.[16]
If you’d like to add sea moss capsules to your health routine, consult an integrative physician or a registered dietitian-nutritionist. “Again, there is limited human research, so [if it’s recommended by your health provider] I would suggest starting out with a small dose and see how you react,” says McManus.
The Takeaway
- Sea moss is rich in vitamins, fiber, and antioxidants, which are purported to support heart, gut, immune, and thyroid health. But more research (particularly involving human subjects) is needed to better establish these effects.
- While sea moss is generally considered safe in moderation, eating too much could lead to iodine overload, digestive issues, or contamination risks from ocean pollutants.
- Talk to your doctor before trying a sea moss supplement, especially if you have an underlying thyroid condition or take medications.
FAQ
What is sea moss good for? Sea moss itself hasn’t been widely studied for potential health benefits. But like other plant foods, seaweed is rich in fiber and minerals, all of which may potentially boost your immunity, as well as contribute to a healthy heart and digestive system.Can you take sea moss every day? It’s unclear if that’s safe, so check with your healthcare team. One potential risk of taking too much sea moss is excess iodine exposure, which may be risky for people with thyroid disease.What’s the difference between sea moss and Irish moss? Sea moss is another name for Irish moss, and the scientific name for both is Chondrus crispus. But importantly, these are not the same as “seaweed.” As these terms may be used interchangeably, it’s important to know each one if you’re looking for Irish moss or sea moss specifically in a product or supplement.Can you drink sea moss? Sea moss is available in powder form, which may be added to water to drink as a beverage. Some supplement powders may also be added to foods.Does sea moss help you lose weight? While some research has found potential anti-obesity effects of seaweed in animal studies, such studies need to be replicated in humans for confirmation and are not specifically focused on sea moss.Additional reporting by Laura McArdle and Kathleen Ferraro.
EDITORIAL SOURCESEveryday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.SourcesResources- Irish Moss. Britannica. April 2, 2025.
- Pacheco-Quito EM et al. Carrageenan: Drug Delivery Systems and Other Biomedical Applications. Marine Drugs. November 23, 2020.
- 8 Potential Health Benefits of Sea Moss. Cleveland Clinic. January 6, 2025.
- Immune System. Cleveland Clinic. October 20, 2023.
- Valado A et al. Bioactivity of Carrageenans in Metabolic Syndrome and Cardiovascular Diseases. Nutraceuticals. December 2, 2022.
- Torres MD et al. Chrondrus crispus Treated With Ultrasound as a Polysaccharides Source With Improved Antitumoral Potential. Carbohydrate Polymers. December 2021.
- Lomartire S et al. An Overview to the Health Benefits of Seaweeds Consumption. Marine Drugs. June 15, 2021.
- Cassandra L et al. Carrageenan as a Preventative Agent Against Human Papillomavirus Infection: A Narrative Review. Sexually Transmitted Diseases. July 2021.
- López-Hortas L et al. Applying Seaweed Compounds in Cosmetics, Cosmeceuticals and Nutricosmetics. Marine Drugs. September 29, 2021.
- Dini I. The Potential of Algae in the Nutricosmetic Sector. Molecules. May 11, 2023.
- Iodine. National Institutes of Health: Office of Dietary Supplements. May 1, 2024.
- Dietary Fiber: Essential for a Healthy Diet. Mayo Clinic. December 11, 2024.
- Thyroid Disease. Cleveland Clinic. March 25, 2024.
- Hypothyroidism: Should I Take Dietary Supplements? Mayo Clinic. July 9, 2024.
- Liu F et al. Food-Grade Carrageenans and Their Implications in Health and Disease. Comprehensive Reviews in Food Science and Food Safety. June 19, 2021.
- Darias-Rosales J et al. Risk Assessment of Iodine Intake From the Consumption of Red Seaweeds (Palmaria palmata and Chondrus crispus). Environmental Science and Pollution Research. August 15, 2020.
Justin Laube, MD
Medical Reviewer
Justin Laube, MD, is a board-certified integrative and internal medicine physician, a teacher, and a consultant with extensive expertise in integrative health, medical education, and trauma healing.
He graduated with a bachelor's in biology from the University of Wisconsin and a medical degree from the University of Minnesota Medical School. During medical school, he completed a graduate certificate in integrative therapies and healing practices through the Earl E. Bakken Center for Spirituality & Healing. He completed his three-year residency training in internal medicine at the University of California in Los Angeles on the primary care track and a two-year fellowship in integrative East-West primary care at the UCLA Health Center for East-West Medicine.
He is currently taking a multiyear personal and professional sabbatical to explore the relationship between childhood trauma, disease, and the processes of healing. He is developing a clinical practice for patients with complex trauma, as well as for others going through significant life transitions. He is working on a book distilling the insights from his sabbatical, teaching, and leading retreats on trauma, integrative health, mindfulness, and well-being for health professionals, students, and the community.
Previously, Dr. Laube was an assistant clinical professor at the UCLA Health Center for East-West Medicine and the David Geffen School of Medicine at UCLA, where he provided primary care and integrative East-West medical consultations. As part of the faculty, he completed a medical education fellowship and received a certificate in innovation in curriculum design and evaluation. He was the fellowship director at the Center for East-West Medicine and led courses for physician fellows, residents, and medical students.
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Kristeen Cherney, PhD
Author
Kristeen Cherney, PhD, is a freelance writer, essayist, author, and poet with more than 15 years of health writing experience for digital platforms such as Healthline, The Mighty, and LiveStrong. She’s covered nutrition, women’s and children’s wellness issues, as well as specialized topics ranging from diabetes and thyroid disease to anxiety, depression, asthma, allergies, and skin conditions. With a doctorate in English (rhetoric and composition), Dr. Cherney focuses her academic scholarship on the intersection between disability and literacy. She also holds a Master of Arts in English and a Bachelor of Arts in communication.Cherney has contributed to the books The Wiley Handbook on Violence in Education: Forms, Factors, and Preventions, Composing in Four Acts: Readings for Writers, and Georgia State University's Guide to First-Year Writing, as well as to scholarly journals like Praxis, the Journal of Teaching Writing, and the Journal of Dracula Studies.Cherney enjoys running, meditating, hiking, and paddleboarding.See full bio
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Emma Penrod is a journalist based in western Utah who covers science, business, and government policy with an eye toward environmental and economic justice. Her stories have been published by many outlets, including Newsweek, Sierra magazine, Insider, The Weather Channel, and the High Country News. In her spare time, Emma enjoys writing histories, gardening, and cooking vegetarian dishes.
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