Kelp, a type of large brown seaweed, is renowned for its numerous health benefits and has been used in traditional medicine for centuries. Here's an overview of its health benefits, botanical information, traditional uses, primary compounds, and relevant scientific research.
What is Kelp?
Kelp is a large, brown seaweed that grows in underwater forests along rocky coastlines in cold, nutrient-rich ocean waters. It has long, ribbon-like fronds and air bladders that help it float toward the water's surface to capture sunlight for photosynthesis.
Most Kelp species belong to the order Laminariales. These include species such as Saccharina japonica and Laminaria digitata.
Primary Compounds in Kelp
Iodine: Kelp is one of the richest natural sources of iodine, a vital mineral for thyroid health.
Fucoxanthin: This carotenoid is responsible for the brown color of kelp and possesses antioxidant properties.
Fucoidan: A sulfated polysaccharide found in kelp, fucoidan has various biological activities, including antioxidant and anti-inflammatory effects.
Nitrate: Inorganic versions of this compound found in kelp have been shown to reduce blood pressure.
Health Benefits of Kelp
A Rich Source of Nutrients
Kelp is highly nutritious, containing essential vitamins and minerals such as iodine, calcium, potassium, magnesium, omega-3 fatty acids, and vitamins A, C, and K. These nutrients support overall health and well-being.
Significant Iodine Content
Kelp is particularly notable for its high iodine content, which is essential for thyroid function and the production of thyroid hormones. Adequate iodine intake is crucial for maintaining a healthy metabolism and preventing thyroid disorders.
Antioxidant Properties
Kelp contains various antioxidants, including fucoxanthin, which helps protect cells from oxidative damage caused by free radicals. This may reduce the risk of chronic diseases and support healthy aging.
Supports Weight Management
Fucoxanthin, a compound found in kelp, has been studied for its potential role in promoting weight loss and reducing abdominal fat accumulation. It may also help regulate blood sugar levels and improve insulin sensitivity.
Supports Heart Health
Some studies suggest that components of kelp, such as fucoidan and omega-3 fatty acids, may have cardioprotective effects, including reducing cholesterol levels, lowering blood pressure, and preventing blood clot formation.
Blood Sugar
Studies have found that kelp promotes healthy blood sugar levels. This means helping to regulate insulin levels and balance blood glucose.
Cognition
Kelp species have also been found to help promote cognitive abilities.
Traditional Uses of Kelp
Kelp has been used for centuries in traditional East Asian medicine, particularly in Japan, China, and Korea, for its nutritional and medicinal properties.
It has been traditionally consumed as food, used as a flavoring agent, and incorporated into soups, salads, and other dishes.
In traditional medicine, kelp has been used to support thyroid health, improve digestion, promote hair growth, and enhance overall vitality.
Scientific Research
A study from Canada’s Laval University tested 23 people and found that 500 milligrams of kelp before meals for a week regulated insulin levels and increased insulin sensitivity.
A study from Ireland also found that kelp slowed glucose release from the digestive tract. It also increased insulin sensitivity in this study.
A 2018 study from Northumbria University in the UK tested 60 healthy adults. They found that a combination of kelp and bladderwrack seaweed significantly boosted cognition compared to the placebo group. Those taking the supplement scored significantly highly in cognitive tests according to the researchers.
A 2013 study from Japan’s Hokkaido University found that fucoxanthin from kelp significantly inhibited the growth of cancerous tumors.
A 2025 review of research from the UK’s University of Plymouth analyzed 29 randomized clinical studies, and found that edible algae including kelp species significantly lowered systolic and diastolic blood pressure among 1,583 human participants.
A 2021 clinical study from Japan’s Otsuma Women's University tested 50 people with high body mass index levels. Those taking 6 grams of kelp in tablets per day had significant reductions in body fat percentage compared to the placebo group after five weeks.
A 2020 study from the University of Copenhagen tested 20 people and found that 5 grams of kelp Laminaria digitata and Undaria pinnatifida per day significantly reduced appetite control. It also improved blood sugar control as well.
A 2014 study with 40 healthy people showed that laminaria kelp boosted the growth of probiotic bacteria in the gut.
A number of other studies have shown similar success by kelp in improving health
Scientific References
Aoe S, Yamanaka C, Ohtoshi H, Nakamura F, Fujiwara S. Effects of Daily Kelp (Laminaria japonica) Intake on Body Composition, Serum Lipid Levels, and Thyroid Hormone Levels in Healthy Japanese Adults: A Randomized, Double-Blind Study. Mar Drugs. 2021 Jun 22;19(7):352. doi: 10.3390/md19070352.
Zaharudin N, Tullin M, Pekmez CT, Sloth JJ, Rasmussen RR, Dragsted LO. Effects of brown seaweeds on postprandial glucose, insulin and appetite in humans - A randomized, 3-way, blinded, cross-over meal study. Clin Nutr. 2021 Mar;40(3):830-838. doi: 10.1016/j.clnu.2020.08.027.
Casas-Agustench P, MÃnguez S, Brookes Z, Bescos R. Edible Algae Reduce Blood Pressure in Humans: A Systematic Review and Meta-Analysis of Randomised Controlled Trials. J Hum Nutr Diet. 2025 Aug;38(4):e70095. doi: 10.1111/jhn.70095.
Kumar SR, Hosokawa M, Miyashita K. Fucoxanthin: a marine carotenoid exerting anti-cancer effects by affecting multiple mechanisms. Mar Drugs. 2013 Dec 16;11(12):5130-47. doi: 10.3390/md11125130.
Ko SJ, Kim J, Han G, Kim SK, Kim HG, Yeo I, Ryu B, Park JW. Laminaria japonica combined with probiotics improves intestinal microbiota: a randomized clinical trial. J Med Food. 2014 Jan;17(1):76-82. doi: 10.1089/jmf.2013.3054.