Kelp, a type of seaweed belonging to the order Laminariales, thrives in nutrient-rich coastal waters in temperate and subtropical zones worldwide. It’s not a plant but brown algae that grows in forests near shorelines. Kelp is a subgroup of seaweed encompassing several genera, with Laminaria hyperborea being the most common in the United States. This article delves into the multifaceted uses of kelp, its potential health benefits, and the possible side effects associated with its consumption in tablet form.
What is Kelp?
Kelp has multiple applications, including its use as a food source, a colloidal gel in products like toothpaste and ice cream, a botanical medication, and a source of nitrogen and phosphate in fertilizer. The constituents of kelp include salts of alginic acid (laminaric acid: 25%), carbohydrates (laminarin, mannitol, fucoidan, and others: 55%), and minerals and trace elements typically found in coastal waters. Kelp is particularly rich in iodine but can also absorb other metals and minerals from the ocean, such as calcium, iron, mercury, lead, cadmium, and even arsenic.
Nutritional Profile and Potential Benefits
Kelp is low in calories and high in nutrients. As it grows, kelp absorbs minerals from the sea, making it one of the most nutrient-rich edible plants: 100 grams (g) of raw kelp contains 43 calories and 0.56 g of fat.
A half-cup serving of fresh kelp contains:
- 17 calories
- Less than 1 gram of fat
- 0. 52 grams of fiber
- 0. 64 grams of protein
Kelp is also a good source of some vitamins and minerals. In terms of your percent daily value (DV), kelp contains:
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- 26 micrograms of vitamin K (22% DV).
- 72 micrograms of folate (18% DV).
- 48 milligrams of magnesium (12% DV).
Vitamins and Minerals
Sea kelp is a source of vitamins, macronutrients, and minerals. Kelp absorbs nutrients from its marine environment, making it rich in vitamins, minerals, and trace elements. Kelp is an excellent source of vitamin K, supplying 82% of your daily value per serving, per the USDA. Vitamin K is required for proper blood clotting and bone metabolism. Folate is an important nutrient for pregnant people to help prevent birth defects. A serving of kelp supplies 180 micrograms, or 45 percent of your DV, making it a good source of the nutrient. Kelp also contains the B vitamins riboflavin, pantothenic acid, and thiamine, required for proper metabolism and energy production. Plus, you'll get some vitamin C and vitamin E, which help fight oxidative damage to your cells. Kelp has 168 milligrams of calcium, which is more than many vegetables, including collard greens and kale, according to UCSF Medical Center. Your body needs calcium to maintain strong bones and muscle function. Kelp also has high amounts of magnesium, offering 121 milligrams or 29 percent DV per serving. Magnesium benefits include maintaining muscle and nerve function and regulating blood pressure. Kelp is also a good source of iron, boasting 2.8 milligrams, or 16 percent of the DV, per serving. Iron helps you maintain healthy blood cells. It also has some manganese, potassium and zinc, which may help fight oxidative stress in the body.
Thyroid Health
Kelp contains iodine, which plays a crucial role in producing thyroid hormones and managing metabolism, among other effects. Your thyroid requires iodine to function properly. Your body does not manufacture iodine, so it's important to get it through your diet. If you don’t have enough iodine, your thyroid won’t produce enough of some necessary hormones, a condition known as hypothyroidism. Kelp contains iodine and can prevent hypothyroidism. Severe iodine deficiency can result in an enlarged thyroid gland, known as goiter, according to the NIH. A moderate iodine deficiency can also cause low IQ in infants and children and impaired cognitive ability in adults. Kelp is a natural source of Iodine, an essential one in thyroid hormone production.
Weight Management
Kelp contains the natural fiber alginate, which can act as a fat blocker, stopping the absorption of fat in the gut. Seaweed has a number of compounds that may have anti-obesity benefits. A natural fiber derived from kelp called alginate may help block fat absorption in the intestines by 75 percent, according to a March 2014 study in Food Chemistry. The researchers suggest it may be a viable treatment option for people with obesity.
Antioxidant Properties
Like other seaweeds, kelp contains antioxidants like carotenoids and polyphenols. Antioxidants suppress the negative effects of free radicals, which are unstable molecules that can damage your cells. Seaweeds like kelp contain antioxidants, which may help reduce disease-causing free radicals and lower your risk of conditions like cancer and heart disease.
Other Potential Benefits
Research from 2021 suggests that kelp may be linked to a lower chance of developing heart disease, type 2 diabetes, digestive tract issues, and bone-related conditions. Kelp may improve sensory receptors. It may also promote healthy nails and blood vessels, aid in digestion, and ease constipation. It may also reduce hair loss and help with diabetes and weight management. Kelp may treat gastrointestinal ulcers and reduce the risk of breast cancer.
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Gut Health
Kelp is a good source of prebiotics. Your gut includes millions of microorganisms that help you absorb nutrients and fight illnesses. But you have to feed these tiny organisms so they can do this critical work for you. Kelp is a good source of prebiotics.
Bone Health
Kelp contains good amounts of vitamin K, which is a key nutrient for bone health. Vitamin K is important for proper bone mineralization, which makes your bones stronger. Research has found that people who don’t get enough vitamin K have a higher risk of breaking a bone.
Forms of Kelp and Ways to Incorporate It into Your Diet
It’s best to consume kelp in its natural form. Kelp is available fresh or frozen, but it can be hard to find unless you live in an area where it’s grown or harvested. Most consumers eat dried kelp or kelp noodles. Kelp is sometimes marketed under the Japanese name, kombu. Kelp comes in powder and capsule form. You can purchase fresh or dried kelp in many markets, and it adds a savory flavor to dishes. Kelp is popular in Japanese cuisine, but it fits into many different cooking styles. It’s leafy, nutritious and tastes yummy in a variety of savory dishes.
Here are some ways to incorporate kelp into your diet:
- Kelp Noodles: Try swapping out your pasta for this low carb alternative, or use kelp to create a tasty kelp noodle salad.
- Seaweed Snacks: Seaweed snacks are crunchy morsels of umami flavor. While these chips can be found at most grocery stores, you can also make your own.
- Kelp Seasonings: Kelp seasonings are available in convenient shakers. They add a great flavor to stir-fries, marinades, and even popcorn.
- Soup: One of the most common ways to use kelp is in soups. Whether you’re making a kelp stock or miyeok-guk (seaweed soup), kelp-infused soups are an excellent way to get a bowl full of nutrients. A bowl of miyeok-guk is also a Korean birthday tradition.
- Kelp Powder: This nutrient-dense powder can be used in a variety of recipes. Add it to your favorite morning smoothie, or mix it into your salad.
- Desserts: Try this recipe for kelp carrot cake, whip up seaweed pudding, or bake some seaweed salt-speckled cookies.
- Salads: Add strips of rehydrated kelp to a veggie salad.
- Sprinkle dried kelp powder: Sprinkle dried kelp powder into homemade soup or hummus.
- Roast Chicken: Tuck fresh kelp and your favorite herbs in with a roast chicken before cooking.
- Dried kelp flakes: Use dried kelp flakes in place of salt on eggs, rice or even popcorn.
Potential Side Effects and Precautions
While kelp is generally recognized as safe, it is important to be aware of potential side effects and take necessary precautions.
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Iodine Overdose
Eating too much kelp can cause iodine overdose. Eating large amounts of kelp could cause an iodine overdose. Kelp supplements often contain several thousand times the daily recommended limit of iodine, which can do more harm than good. Kelp supplements can come with some serious health risks, and excessive amounts of iodine can cause harm to the thyroid.
For adults, the FDA recommends a dietary intake of 150 micrograms (mcg) of iodine per day. The recommended daily amount of iodine for adults is 150 micrograms, according to the National Library of Medicine. Pregnant or breastfeeding people need 50 percent more. One pound of raw kelp can contain up to 2,500 mcg of iodine, so make sure you’re reading your packages and monitoring how much you eat. In theory, eating too much iodine could lead to iodine poisoning. Adults should not consume more than 1,100 micrograms (mcg) of iodine daily because it can cause vomiting, stomach burns and other harmful side effects. Most people can eat a small amount of kelp without side effects, but don’t consume more than one serving per day.
Too much iodine may worsen the symptoms of hypothyroidism in patients with abnormal thyroid glands, especially if a lack of iodine is not the primary cause of the under-active thyroid, according to the Mayo Clinic.
Both hyperthyroidism and hypothyroidism have been linked to too much kelp intake. This is due to its high amount of iodine. Abnormal thyroid function has also been linked directly to too much use of kelp supplements.
Heavy Metal Contamination
Kelp can absorb other metals and minerals from the ocean, such as calcium, iron, mercury, lead, cadmium, and even arsenic. Kelp may contain harmful metals, including cadmium, lead, aluminum, and other heavy metals. It is more likely to contain these elements when harvested from areas with industrial development. Sea kelp supplements can also be particularly high in arsenic. High levels of arsenic are toxic and carcinogenic in nature. Kelp supplements have been reported to cause side effects like diarrhea, nausea and overall body weakness.
Interactions with Medications
Certain medications, drugs and vitamins can interact with kelp supplements. Harmful side effects can result from taking kelp together with:
- Digoxin (Lanoxin)
- Potassium supplements
- Potassium-sparing diuretics such as triamterene (Dyrenium, Maxzide, Dyazide), amiloride and spironolactone (Aldactone)
- Thyroid medicines such as levothyroxine (Levoxyl, Synthroid), liothyronine (Cytomel), liotrix (Thyrolar), and thyroid (Armour Thyroid)
- Blood thinners such as warfarin
Precautions
- Talk with your doctor before taking kelp supplements if you have a thyroid disorder, an allergy to iodine, kidney or liver disease.
- Women who are pregnant or breastfeeding shouldn’t use kelp supplements.
- If you’re being treated for thyroid issues, you shouldn’t take kelp.
- You also shouldn’t use it if you take certain heart medicines.
- If you need an X-ray with a contrast media, talk to your doctor. You may have to stop taking kelp one month before your X-ray. You may not be allowed to take it again until the contrast medium leaves your body.
Kelp and Liver Health
While kelp is generally recognized as safe, it has not been formally assessed for hepatic adverse effects or elevations of serum aminotransferase, alkaline phosphatase, or bilirubin levels. However, despite common use, there have been no published case reports of liver injury convincingly attributed to kelp. Large case series of liver injury due to herbal and dietary supplements do not mention or list kelp as a possible cause.