Sea Moss: Everything You Need to Know
Tina Horne / Getty Images
Irish moss on the sandMedically reviewed by Elizabeth Barnes, RDN
Sea moss is also known as Irish moss—a type of red seaweed that grows along the European and North American continents on the Atlantic coast. Its scientific name is Chondrus crispus (C. crispus).
In general, seaweeds are rich sources of proteins and minerals. They also contain fiber and plant chemicals that may promote good health.
Aside from general health support, there are several other health claims for sea moss. But most available research is either in vitro studies (not tested in a living organism) or in vivo studies (tested on animals). For this reason, there isn't enough data to support these other health claims for sea moss. What's more, there are safety concerns with sea moss.
This article discusses what you should know about sea moss—some of its health claims, side effects, and interactions.
Dietary supplements are not regulated the way drugs are in the United States, meaning the Food and Drug Administration (FDA) does not approve them for safety and effectiveness before products are marketed. Whenever possible, choose a supplement tested by a trusted third party, such as U.S. Pharmacopeia (USP), ConsumerLab.com, or NSF. However, even if supplements are third-party tested, they are not necessarily safe for all or effective in general. Therefore, talking to your healthcare provider about any supplements you plan to take and asking about potential interactions with other supplements or medications is essential.
Supplement Facts
Active Ingredient(s): Carrageenan, proteins, fiber, minerals, and plant chemicals
Alternate Names(s): Sea moss, Irish moss, Chondrus crispus, C. crispus, red seaweed, red algae
Legal Status: Legal as a food
Suggested Dose: May vary based on the amount of iodine in the specific source of sea moss, other iodine sources in your diet, age, and medical condition
Safety Considerations: Possible safety concerns, with special considerations for children, pregnant people, and breastfeeding people
Nutrition
Five grams—about one-third cup—of dried seaweed contains the following nutrients in kilocalories (kcal), grams (g), milligrams (mg), and micrograms (mcg):
Energy: 11 kcal
Protein: 1.6 g
Total lipid (fat): 0.2 g
Carbohydrates: 2.6 g
Fiber: 0.3 g
Sugars: 0.15 g
Calcium: 18.6 mg
Iron: 1.25 mg
Magnesium: 24.1 mg
Phosphorus: 4.3 mg
Potassium: 62 mg
Sodium: 28.8 mg
Vitamin C: 0.25 mg
Choline: 3.2 mg
Vitamin A: 0.7 mcg
Vitamin E: 0.25 mg
Vitamin K: 1.25 mcg
Health Claims of Sea Moss
Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or healthcare provider. No supplement is intended to treat, cure, or prevent disease.
Most research on sea moss is either in vitro lab or in vivo animal studies. There are very few human clinical trials on sea moss.
While more extensive research is necessary, people might use sea moss for various—often overstated—health claims.
Digestive System Support
One of sea moss's health claims may include digestive system support. Data from a rat animal study suggested that sea moss may have some prebiotic effects. A diet with sea moss may encourage the growth and activity of "good" bacteria that naturally exist in your body.
While sea moss seemed to support gut health in this animal study, a review article hinted at the opposite effects of carrageenan—a substance in sea moss. According to this review article, carrageenan triggered worsening inflammatory bowel disease (IBD) symptoms. A carrageenan-free diet may relieve IBD symptoms.
Since the evidence is mixed, further, extensive research is necessary.
Until more data is available, healthcare providers may recommend limiting how much sea moss and carrageenan you take.
Thyroid Health Support
Supporting thyroid health is another potential health claim for sea moss. This might be because sea moss contains iodine, an essential nutrient your body uses to make thyroid hormones. These hormones help with bodily functions, including weight regulation, temperature, and energy levels.
While the iodine amount in 3 to 4 g of dehydrated (dried) sea moss per day is likely safe, people might typically use larger quantities for seaweed-based recipes.
One article suggested reports of iodine-induced hypothyroidism (underactive thyroid) were not considered significant.
Hyperthyroidism-induced by iodine is possible. Hyperthyroidism (overactive thyroid) has been shown to increase with iodine supplementation, which is a concern. Moreover, there was also a report of thyrotoxicosis (a thyroid storm) with sea moss in people with hyperthyroidism. Thyrotoxicosis is a life-threatening condition of too much thyroid hormone.
Thyroid effects are more likely to affect infants, unborn fetuses, and older adults over 65.
If you're using sea moss, a healthcare provider may want to monitor your iodine levels closely.
Immune System Support
Sea moss's other potential health claim is immune system support. And in animal studies of rats and roundworms, results suggested some positive effects of sea moss on the immune system (the body's defense system).
In a review article, however, carrageenan—a substance in sea moss—triggered some inflammation (swelling). Inflammation is typically a response from the immune system against something foreign or harmful—like an infection. But too much inflammation can cause more harm than good. There are also reports of severe allergic reactions to carrageenan.
What's more, sea moss contains a lot of iodine. Too much iodine might result in an autoimmune thyroid condition. An autoimmune condition is when your immune system attacks parts of your body by mistake. In this case, it's attacking your thyroid, which can lead to hypothyroidism.
Since currently available evidence is mixed, further extensive research is necessary. And until more information is available, healthcare providers may recommend limiting how much sea moss and carrageenan you take.
What Are the Side Effects of Sea Moss?
Like many medications and natural products, side effects are possible with sea moss.
Common Side Effects
There is little information about the common side effects of sea moss, but carrageenan—a substance in sea moss—is on the Food and Drug Administration's (FDA) list of substances added to food.
Generally, the amount of iodine in 3 to 4 g of sea moss daily is likely safe. But if you have higher than normal iodine levels, some symptoms may include:
Burning mouth or throat sensation
Aside from high iodine symptoms, weight loss might be another side effect, a marketed health claim for sea moss. But it's likely overstated, similar to many other health claims for sea moss.
If you're experiencing these symptoms, seek guidance from a healthcare provider immediately.
Severe Side Effects
In general, there is limited information on the safety of sea moss. But some severe possible side effects may include:
Severe allergic reaction: A severe allergic reaction is a serious side effect possible with any medication or food. There are reports of severe allergic reactions to carrageenan, a substance in sea moss. If you're having a severe allergic reaction, symptoms may include breathing difficulties, itchiness, and rash.
Iodine poisoning: Since sea moss has iodine, there is a chance that you might take too much iodine. If your iodine levels are dangerously high, you may experience a weak heartbeat and coma. High iodine levels may also lead to hypothyroidism. Too much iodine might also result in a life-threatening condition of thyrotoxicosis in people with hyperthyroidism. Symptoms of thyroid problems may include weight changes and excessive tiredness.
Metal toxicity: Generally, seaweed may have toxic metals—like lead and mercury—based on where they grew. Symptoms of lead or mercury toxicity may include headaches and changes in thinking.
Arsenic poisoning: Arsenic poisoning is also possible with seaweeds—like sea moss. Short-term symptoms of arsenic poisoning may include nausea and diarrhea, but longer-term exposure might result in developing diabetes (high blood sugar) and cancer.
IBD flare-up: Carrageenan may trigger an IBD flare-up. Symptoms of a potential IBD flare-up may include stomach pain, diarrhea, and rectal bleeding.
If you're having a severe allergic reaction or if any of your symptoms feel life-threatening, call 911 and get medical help right away.
Precautions
A healthcare provider may advise against sea moss if any of the following applies to you:
Severe allergic reaction: Avoid sea moss if you have a known allergy to it or its components (ingredients or parts), such as carrageenan. Ask a pharmacist or healthcare provider for a complete list of the ingredients if you're unsure.
Pregnancy: Sea moss is rich in iodine. Too much iodine may lead to side effects in anyone, including pregnant or breastfeeding people. Too much iodine may also negatively affect an unborn fetus.
Breastfeeding: High levels of iodine in breast milk may negatively affect nursing infants. High amounts of iodine might result in hypothyroidism or hyperthyroidism. And this risk is higher for the fetus and newborns. Before trying sea moss, discuss the benefits and risks with a healthcare provider.
Adults over age 65: Some older adults may have a greater likelihood of medication side effects. So, older adults should use caution with sea moss, which is rich in iodine. And large amounts of iodine may increase the risk of hypothyroidism, especially in older adults.
Children: Since sea moss is rich in iodine, use caution. Too much iodine will likely lead to side effects in anyone. What's more, too much iodine raises the risk of hypothyroidism. And this risk is further increased in children, especially newborns. Talk with a healthcare provider if you're considering sea moss for your child.
IBD: Carrageenan may worsen IBD symptoms. If you have IBD, healthcare providers may recommend avoiding sea moss, which contains carrageenan.
Thyroid conditions: The high iodine amounts in sea moss might raise the risk of hypothyroidism. There was also a report of thyrotoxicosis in people with hyperthyroidism (overactive thyroid). Thyrotoxicosis (thyroid storm) is a life-threatening condition of too much thyroid hormone. Healthcare providers may recommend against sea moss if you already have a thyroid condition or are at risk for thyroid problems.
Dosage: How Much Sea Moss Should I Take?
Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs.
There are very few human clinical trials on sea moss. For this reason, there are no guidelines on the appropriate dosage of sea moss for any condition.
Generally, 3 to 4 g of dried sea moss daily is likely safe in adults.
The specific dose may vary based on the amount of iodine in the specific source of sea moss, other iodine sources in your diet, your age, and your medical condition.
If you take sea moss, follow a healthcare provider's recommendations or label instructions.
What Happens If I Take Too Much Sea Moss?
There is little information about the safety, toxicity, and overdoses of sea moss in humans.
However, symptoms of overdoses with sea moss are likely similar to its potential common and serious side effects—but excessive and severe. For example, too much iodine in sea moss might result in a coma or thyroid problems.
For context, 3 to 4 g of dried sea moss per day likely contains a safe amount of iodine. The recommended amount of iodine is 150 mcg per day for most adults. Children usually need less, and pregnant or breastfeeding people typically need more.
Aside from possible iodine poisoning, some sea moss products contain toxic substances—like lead, mercury, and arsenic. So, poisonings from these substances are also possible.
If you suspect you're experiencing life-threatening side effects, seek immediate medical attention.
Interactions
There is limited information about possible medication interactions with sea moss.
Possible interactions are based on the health claims or potential side effects of sea moss. Use caution when taking sea moss with the following:
Amiodarone (for irregular heart rhythm): Amiodarone contains significant amounts of iodine. Taking more iodine could cause serious adverse effects.
Immune support medications: In general, sea moss might affect the immune system. For this reason, caution should be used with other medications—like Humira (adalimumab)—that affect the immune system.
IBD medications: The carrageenan in sea moss might trigger an IBD flare-up. This means that sea moss might work against IBD medications, such as Humira.
Thyroid medications: Sea moss is rich in iodine. Too much iodine is linked to thyroid problems. So, sea moss might work against thyroid medications, such as Tapazole (methimazole).
It is essential to carefully read a supplement's ingredients list and nutrition facts panel to know which ingredients and how much of each ingredient is included. Please review this supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications.
Similar Supplements
Sea moss might have effects on digestion, thyroid, and immune health.
Other potentially similar supplements may include:
Ashwagandha: Ashwagandha may also interact with thyroid medications. For this reason, it's typically not recommended for people with thyroid problems.
Echinacea: Echinacea has a health claim of immune system support, and echinacea might slightly decrease your chances of getting a cold. But there isn't any evidence to support that echinacea can reduce the number of days you experience symptoms—if you already have a cold.
Peppermint oil: Peppermint oil might be effective at relieving some irritable bowel syndrome (IBS) symptoms, such as stomach pain and gas.
Probiotics: Some probiotics may relieve IBS symptoms, but different probiotic products might have different effects. So, the evidence isn't overwhelmingly conclusive yet.
Soy: Potential uses of soy may include high blood pressure, high cholesterol, and menopausal symptoms. But this supplement may also affect your thyroid function if you have low iodine levels.
Sources of Sea Moss & What to Look For
There are several sources of sea moss, but health nutrition guidelines typically place more importance on food sources to improve the diet.
Although food sources—like iodized salt—are preferable over sea moss, there still might be a place for supplements for some people. People with vegan or vegetarian diets are likelier to experience iodine deficiency.
But before trying sea moss, talk with a healthcare provider.
Summary
Sea moss is a red seaweed with claims that it may affect digestion, thyroid, and immune health. Since further extensive research is necessary, these health claims are likely overstated.
What's more, there are several safety concerns with sea moss.
For these reasons, it's essential to ensure the diagnosis and treatment of your medical conditions is completed on time.
Before you take sea moss, you should ask a pharmacist or healthcare provider about the safety of taking sea moss in light of other medications you take, as well as if sea moss may be beneficial to take.
Frequently Asked Questions
What is the most common dosage form of sea moss?
Sea moss is available in a few different dosage forms—with capsules being the most common.
What are the negative effects of sea moss?
Sea moss has the potential for numerous adverse effects, including a severe allergic reaction, inflammatory bowel disease flare-up, iodine poisoning, thyroid problems, metal toxicity, and arsenic poisoning.
Who should not take sea moss?
Healthcare providers may recommend against sea moss if you have thyroid problems or inflammatory bowel disease (IBD). You should also avoid sea moss if you have a severe allergic reaction to it or any of its components (ingredients or parts).
How do I take sea moss safely?
To safely take natural medications—like sea moss—inform a healthcare provider and pharmacist about any medications you take. This includes over-the-counter (OTC), herbal, natural medicines, and supplements.
A pharmacist or healthcare provider can help you prevent possible interactions and side effects. They can also ensure you’re giving sea moss a fair trial at appropriate doses.
