Kelp, a type of brown algae belonging to the seaweed family, has long been a dietary staple in Asian cultures and is now gaining recognition worldwide for its impressive nutritional profile and potential health benefits. While often used as a synonym for seaweed, kelp specifically refers to brown algae from the Laminariaceae family. The kelp most often used in Japanese dishes, including miso soup and udon, is kombu. This article explores the various aspects of kelp, from its nutritional composition and potential health benefits to its uses and potential risks.
What is Kelp?
Kelp refers to a group of large brown seaweeds with around 30 different species found in oceans worldwide. True kelps belong to the genus laminaria, family Laminariaceae, while giant kelps belong to the genus macrocystis, family Lessoniaceae, and bladder kelps belong to the genus nereocystis, family Lessoniaceae. These seaweeds thrive in shallow, underwater forests, requiring sunlight as an energy source and a hard surface (not sand) on which to grow. Kelp grows quickly. In fact, giant kelp is one of the world's fastest-growing plants, growing as much as 300 feet (100 meters) in a single year.
Nutritional Powerhouse
Kelp boasts an impressive nutritional profile, making it a valuable addition to a balanced diet. Seaweed contains ten times as many minerals as plants grown in soil, and people who eat seaweed seldom have mineral deficiencies. Unlike plants that receive their nutrients from root structures, kelp absorbs vitamins and minerals from its surroundings. Kelp is rich in umami; the fifth lesser-known taste alongside sweet, sour, bitter, and salty. Umami gives food a savory or meaty flavor.
A 100-gram serving of kelp (3.5 ounces) contains a good source of many key vitamins and minerals. Besides iodine and iron, kelp is a rich source of calcium, folate, magnesium, and vitamin K.
A one-ounce serving of dried kelp (about the weight of a slice of bread) contains these nutritional values:
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- Calories: 68
- Protein: 5 grams
- Fat: 1 gram
- Carbohydrates: 11 grams
- Fiber: 0 grams
- Sugar: 0 grams
Potential Health Benefits of Kelp
Due to its rich nutrient content, kelp offers a wide range of potential health benefits, including:
Thyroid Health
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. In general, seaweed is one of the best sources of iodine you can eat. Brown seaweed, compared to red or green, tends to be higher in iodine. In the human body, Iodine is important to make thyroid hormones triiodothyronine (T3) and thyroxine (T4). Eating foods high in iodine can help prevent hypothyroidism, a condition in which the thyroid doesn’t make enough T3 and T4.
Diabetes Control
Kelp contains a mineral called vanadium that could help people with Type 2 diabetes. Early studies using animals and humans have shown that it can help regulate blood sugar. Researchers need to find out more about how vanadium behaves in the body before it will be available on the market. Scientists are also investigating fucoxanthin, a substance in brown algae that could help with weight management, which is important for people with diabetes.
Prevention of Anemia
Kelp is moderately rich in iron, which is necessary to prevent the iron deficiency known as anemia. If you have anemia, your body’s tissues don't get enough oxygen because of a shortage of red blood cells. Menstruating women are especially at risk of anemia, which can cause fatigue, weakness, dizziness, and other symptoms.
Bone and Muscle Health
Kelp is also a rich source of vitamin K and fucoidan. An individual serving of kelp can provide you with almost a quarter of the daily recommended intake of vitamin K. One of the main roles of vitamin K is that it helps strengthen bone density. Kelp’s high magnesium levels also offer health benefits to professional athletes. Not to mention the fact that magnesium is well-known for supporting sleep quality, kelp can reportedly enhance energy when you exercise and help muscles recover after you finish a workout. Seaweed also contains other electrolytes, including sodium, potassium, and calcium.
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Digestive Health
Kelp powder is high in dietary fiber and can help support digestive health. The fiber content in kelp powder assists with regularity.
Hair and Nail Health
Kelp powder contains minerals such as iodine, zinc, and iron, which help maintain healthy hair and nails. Iodine, in particular, supports thyroid function, the system that regulates metabolic health and hair growth. Kelp powder also contains vitamins A, C, E, and B, which all help to strengthen skin, nails, and hair.
Skin Health
The skin is the largest organ in the body and requires a lot of nutrients to stay healthy. Essential vitamins, minerals, and antioxidants found in seaweed can support skin health and help protect skin cells from damage. Because of its high nutritional value, kelp powder has the potential to help with inflammation, support irritated skin, and aid acne breakouts.
Energy Levels
Kelp powder is high in nutrients such as iron, magnesium, and iodine, which all support energy balance. Magnesium also aids in the conversion of food into energy, which ultimately fuels the body's cells. Kelp powder also contains B-complex vitamins, which aid in energy intake and metabolism.
Brain Function
The brain requires a diet rich in various vitamins and minerals to function properly, and kelp powder contains several of these nutrients. Kelp powder contains iodine, omega-3 fatty acids, and antioxidants, which can all help the brain function. Omega-3 fatty acids help with memory and cognitive function while also supporting mood and helping with age-related cognitive decline. Antioxidants help the brain by supporting the body’s natural defenses, and the high content of these nutrients in kelp powder can help support brain function.
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Weight Management
Kelp may aid weight management in several ways. For one, seaweed is a low-fat and low-calorie food source that is fairly filling. A 2012 study found that, when combined with an energy- or calorie-restricted diet, alginate supplementation was associated with greater support for body composition goals in individuals seeking healthy weight management. Kelp also contains a protein known as fucoxanthin, which has been shown to contribute to burning fat tissue. 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.
Anti-Inflammatory Properties
An overactive immune system frequently contributes to inflammation by flooding the body with harmful hormones and free radicals. Because kelp possesses anti-inflammatory properties, it may help with inflammation in the body. Additionally, kelp is full of healthy nutrients, including vitamin K, vitamin A, vitamin B-12, calcium, iron, and magnesium. While each supports your health in different ways, many of these vitamins also aid your body’s natural defenses. According to a study in the journal Marine Drugs, kelp contains phytonutrients that may help reduce inflammation, a possible contributor to chronic diseases like arthritis and Alzheimer’s disease.
How to Incorporate Kelp into Your Diet
Kelp is available in various forms, making it easy to incorporate into your diet:
- Fresh or Frozen: 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.
- Dried: Most consumers eat dried kelp or kelp noodles. Kelp is sometimes marketed under the Japanese name, kombu.
- Powder: Powdered kelp is a brown seaweed that has been dried and processed into a powder.
- Noodles: Kelp noodles are one of the most recent creative commercial uses of this food. The appearance comes from peeling the brownish outer layer of dried kelp. The inside, which is white, is then mixed with water and sodium alginate to form a dough-like mixture. Kelp noodles are similar to tofu in that they don’t taste like much. Kelp noodles are crunchy and can be used directly out of the package to add texture to salads or stir fry's or as a finishing element to a dish.
Kelp can be eaten fresh, dried, cooked, added to smoothies and sauces as a powder, or served on food as dried granules. In Japan, dried kelp has been a staple in dashi broth, which is a combination of bonito flakes (dried, smoked tuna) and dried kelp. It also rehydrates well and can be added to soups and stir-fries. Since kelp comes from the ocean, cooking it fresh with similar ingredients is a good place to start. This means pairing it with seafood such as oysters or clams. Kelp is versatile, though.
Potential Risks and Side Effects
While kelp offers numerous health benefits, it's important to be aware of potential risks and side effects:
Iodine Overload
Ingesting large amounts of kelp powder increases the amount of iodine in your body. High levels of iodine may cause your thyroid gland to produce too much thyroid hormone. Side effects associated with the overproduction of the thyroid hormone include sweating, fatigue, loose stools, and unintended changes in body mass.
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. If you already have hyperthyroidism, it can make your condition worse.
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.
The recommended daily allowance for adults is 150 milligrams of iodine and between 220 to 290 milligrams for people who are pregnant or lactating, according to the American Thyroid Association.
Heavy Metals
Several types of sea kelp contain high levels of arsenic. Consuming too much kelp powder may elevate the arsenic levels in your body, which may lead to arsenic toxicity. Symptoms of arsenic toxicity include an upset stomach, heart rate irregularities, kidney damage, breathing difficulties, numbness, tingling, and seizures, among other things.
Kelp may contain harmful metals, including cadmium, lead, aluminum, and other heavy metals. This is more likely if you eat a lot of kelp from areas of contaminated ocean water. The heavy metals in kelp are usually below toxic levels, but some people worry about exposure to them, especially to arsenic.
Things to Watch Out For: Heavy metals are a concern with kelp products. Kelp can contain aluminum, cadmium, arsenic, and lead. Kelp is more likely to contain these elements when harvested from areas with industrial development. The heavy metals in kelp are usually below toxic levels, but some people worry about exposure to them, especially to arsenic.
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)
Contraindications
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 is generally considered safe for most people to consume in moderation. However, people with certain risk factors should not take kelp, including women who are pregnant or breastfeeding, people being treated for thyroid issues, and people taking certain medications.
Kelp Supplements
As a supplement, kelp is used as a natural source of iodine. But the average laminaria-based supplement might contain large amounts of iodine. This can cause decreased thyroid function (hypothyroidism) or increased thyroid function (hyperthyroidism). Some supplements may also contain arsenic. There isn’t enough information to know if kelp supplements are safe.
Kelp comes in powder and capsule form. Follow the instructions on the package for the correct dose. Talk with your doctor before taking any types of supplements.
You should also be careful to read the labels on any supplement products that contain kelp powder. Any sea kelp supplements with more than 500 mcg should be avoided. Pay attention to the packaging on the supplement for specific dosage information.