Seaweed Nutrition Facts and Health Benefits
Mark Stibich, PhD, FIDSA, is a behavior change expert with experience helping individuals make lasting lifestyle improvements.
Mia Syn, MS, RDN is a registered dietitian nutritionist with a master of science in human nutrition. She is also the host of Good Food Friday on ABC News 4.
Verywell / Alexandra Shytsman
Seaweed has been popular in Asian cuisine for centuries, and it’s starting to catch on in the West as well. Although seaweed offers several promising health benefits, it also carries potential pollutants from the ocean to your plate. If you’ve heard mixed advice on the pros and cons of eating seaweed, here’s some information to help clarify the facts.
Seaweed Nutrition Facts
The following nutrition information is provided by the USDA for 1 cup (80g) of raw wakame seaweed.
- Calories: 36
- Fat: 0.5g
- Sodium: 698mg
- Carbohydrates: 7.3g
- Fiber: 0.4g
- Sugars: 0.5g
- Protein: 2.4g
There are a little over 7 grams of carbohydrate in 1 cup of raw seaweed. Of this, less than 1 gram comes from fiber and sugar combined. Seaweed contains various polysaccharides that act as antioxidants, providing numerous health benefits.
Raw seaweed is very low in fat with a 1/2 gram per cup.
A 1-cup serving of raw seaweed provides 2.4 grams of protein.
Vitamins and Minerals
Seaweed is rich in several vitamins and minerals including calcium, potassium, vitamin C, folate, beta carotene, and vitamin K. The sodium content of seaweed varies based on the brand and preparation method but can be up to 698 milligrams per cup (raw). Some species of edible seaweeds also provide vitamin D and B12, two essential nutrients that can be hard to come by in plant foods. Seaweed is also a good source of iodine.
In addition to vitamins and minerals, seaweed provides unique plant compounds that have been linked to promoting good health and disease prevention.
May Protect Against Asthma
Data reviewing the 2013–2016 Korea National Health and Nutrition Examination Survey (KNHANES) discovered that lower intakes of seaweed and seafood were associated with higher rates of asthma. Because asthma is an inflammatory disease, it’s hypothesized that the polyunsaturated fats and vitamins found in these foods are protective. Although more research is needed to confirm a cause and effect benefit, introducing seaweed during pregnancy and early childhood appears to be beneficial.
Reduces Risk of Osteoporosis
Oxidation from free radicals is associated with a host of health issues, including the weakening of bones. Seaweed contains antioxidant compounds, called fucoidans, which are shown to prevent bone breakdown by free radicals. Specifically, fucoidans protect osteoblasts (the cells responsible for building bone) against apotosis, or cell death, that may otherwise be induced by oxidative stress. Seaweed also provides vitamin K and calcium, two key nutrients for bone strength.
May Aid Cancer Prevention
The fucoidans in seaweed have also been studied for cancer prevention. While human clinical trials are limited, fucoidan’s ability to influence programmed cell death shows promise as a potential supplement to traditional cancer treatments. Like other vegetables, seaweed is also a source of antioxidants (like vitamin C and beta carotene). These compounds are known for cancer prevention qualities, especially when consumed as part of a nutrient-dense eating plan (rather than just supplementation).
Promotes Heart Health
Seaweed is a good source of soluble fiber, especially dulse seaweed and kombu which provide 5 to 6 grams per serving. Soluble fiber binds to cholesterol, pulling it out of the body through waste. In addition to reducing cholesterol, seaweed can also help lower blood pressure levels due to its potassium content (just watch out for added sodium). Finally, the folate in seaweed keeps homocysteine levels down (a sign of inflammation), reducing the risk of stroke.
Supports Weight Loss
The main form of soluble fiber found in seaweed is alginate. Studies show that alginate improves satiety by delaying gastric emptying, which can lead to a reduction in subsequent food intake.
Additionally, seaweed contains protein, which is also known to produce feelings of fullness. Seaweed offers ample nutrients and flavor for a minimal number of calories. Seaweed wraps, soups, or salads can be a good choice to help keep hunger pangs at bay while trying to lose weight.
Allergies exclusively to seaweed are not commonly reported, but they are possible. Shellfish allergies and iodine allergies more likely to occur. Shellfish allergies can be very dangerous so using caution around any possible source of cross-contamination (including seaweed) may be advised. If someone is allergic to iodine, the natural iodine content of seaweed would be a trigger. Speak to an allergist if you suspect that you have a seaweed allergy.
As a natural source of vitamin K, seaweed may interfere with the anticoagulant effects of blood thinners like Coumadin (warfarin). Maintaining a consistent intake of foods that are high in vitamin K will help your doctor determine the correct dosage of medication for you.
Depending on where seaweed is sourced, it may contain high levels of heavy metals like mercury and arsenic. Varying the types of seaweed you eat, avoiding hijiki seaweed (which is known to be high in arsenic), and limiting your intake to three times per week can help you reduce heavy metal exposure from seaweed. Many U.S.-based companies test for heavy metals so check on the label for testing.
There are many different color variations of edible seaweed that come from different species. Nori, or purple laver, is a dark-colored seaweed used to wrap sushi. This is one of the most nutritious types of seaweed with a high protein and nutrient content.
Aonori, or green laver, is cultivated in Japan and sometimes referred to as “sea lettuce.” Kombu (in Japan) and haidai (in China) is another type of dried seaweed. A type of red algae with leathery fronds is called Dulse. Dulse is commonly chewed as a raw snack in Ireland or cooked with potatoes. Other edible variations of seaweed include winged kelp, Irish moss, sea grapes, mozuku, and hiziki.
When It’s Best
Seaweed can be eaten raw or dried, depending on the variety. You may be able to find more popular varieties, like nori, in your local supermarket, but other types of seaweed can be harder to come by. Asian grocery stores are likely to offer a fuller selection.
Storage and Food Safety
Fresh seaweed should be handled the same way other leafy greens are handled. Wash fresh seaweed under running water before consuming or preparing. Store fresh seaweed in the refrigerator.
Dried seaweed should be placed in an airtight container after opening. Follow the expiration dates listed on the package for maximum freshness. Looking for a reputable food company online or at the grocery store will help you avoid heavy metals and other toxins.
How to Prepare
The easiest way to eat seaweed is by using dried seaweed wrapper (nori), the kind you find in sushi restaurants. Use it to wrap almost anything. You can also break into pieces and sprinkle dried seaweed flakes onto a salad or other dishes for a nutritional boost. Seaweed is also popular in Asian soups, such as miso soup.
Seaweed is a nutritious protein source with minimal calories. A cup of cooked seaweed provides over 5.5 grams of protein and lots of vitamins.