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What are the potential health benefits of Seaweed?

Edible seaweed includes varieties such as nori, hijiki, wakame, arame and kombu, dulse, kelp and sea lettuce; most of which originate from Japan or Japanese traditional cuisine. Not only do these seaweeds have many health benefits they also make good snacks and tasty additions to many recipes. Seaweeds are also included in many supplement formulas and exist as individual supplement forms as well. Evidence is coming to light that seaweed can support and may prevent conditions such as breast cancer, premenstrual syndrome, asthma and obesity, to name a few. Its health benefits are attributed to its strong antioxidant function and ability to assist in the body’s detoxification processes [i]. That said, seaweed should only be consumed in moderation due to its high iodine content and the effects this mineral has on thyroid balance. It can be possible to have too much of a good thing.

How to Use Seaweed

Seaweed is a versatile ingredient and can be used in many dishes from soups (especially miso soup) and salads. It is also a great alternative to salt when used in the form of flakes to top food, it contains a much broader range of minerals as well as adding a lovely savoury flavour.

Most of the edible seaweeds are now available in UK supermarkets, Nori is one of the most common as it is used for rolling sushi.

Seaweed salad is a Japanese staple and it compliments many flavours of Japanese cuisine including ginger, soy, sesame and fresh spring onion.

The protein present in some seaweeds, contain all the essential amino acids. This means seaweed can help ensure you get the full range of amino acids as part of a varied diet [ii].

Antioxidants, Vitamins and Minerals:

Antioxidants help protect our bodies from free radical damage, which can lead to severe health problems including cardiovascular disaese and neurodegenerative diseases such as Alzheimer’s[iii] [iv]. Antioxidants in seaweed include beneficial plant compounds such as carotenoid pigments; fucoxanthin and phlorotannins, which are polyphenols only found in brown seaweeds [v].

Fucoxanthin is said to have 13.5 times the antioxidant capacity when compared to vitamin E [vi].

Additionally, the overall content of vitamins A, C and E in seaweeds is found to be quite high and these vitamins possess antioxidant properties. Furthermore, a balanced level of these vitamins are needed in the body as they help to recycle each other in the body, making the antioxidant action more potent. Other valuable nutrients in seaweed include vitamins B1 and B2, folate, zinc, sodium, calcium, copper, manganese and magnesium.

Fibre and Polysaccharides:

Prebiotics are non-digestible, selectively fermented compounds that stimulate the growth or activity of beneficial gut microbiota [vii]. Fibre and prebiotic polysaccharides contained in seaweed support gut function and a healthy balance of microbiota in the microbiome. It’s estimated that you have more bacteria cells in your body than human cells [viii]. The fibre content of sea is up to 75% of the total weight [ix].

What are the specific therapeutic benefits of Seaweed?

Thyroid Function:

The iodine content of seaweed benefits thyroid function. Below is the average iodine content of three different dried seaweeds [x]:

  • Nori: 37 mcg per gram
  • Wakame: 139 mcg per gram
  • Kombu: 2523 mcg per gram

Seaweed also contains an amino acid called tyrosine, which is used alongside iodine to make two key hormones that help the thyroid gland function properly [xi].


Seaweeds are specifically used to treat tumours in Traditional Chinese Medicine and Japanese folk medicine. Daily consumption of seaweed has been proposed as a factor in explaining lower postmenopausal breast cancer incidence and mortality rates in Japan [xii].

Rat studies show mekabu and wakame to have breast cancer preventative effects [xiii] [xiv].

Weight Balance and Metabolism:

The high fibre content of seaweed supports satiety, helping you feel fuller for longer and slowing the uptake of glucose to the bloodstream in order to avoid imbalanced blood sugar levels.

Seaweed is also considered to have effects against obesity. In particular, several animal studies suggest that a substance in seaweed called fucoxanthin may help reduce body fat [xvi] [xvii] [xviii].

Intriguingly, seaweed has become a research focal point for new ways to support people who are at risk of diabetes [xix]. An eight-week study in 60 Japanese people revealed that fucoxanthin, a substance in brown seaweed, may help improve blood sugar balance [xx].

Heart Disease:

Seaweed is a good source of soluble fibre and contains long-chain omega-3 fatty acids, both are crucial for heart health [xxi] [xxii].

In addition, several animal studies report that the sulphated polysaccharides found in seaweed may have the ability to reduce blood pressure and prevent blood clotting [xxiii] [xxiv] [xxv].

Immune system:

Some studies show that seaweed may help to boost your immune system by fighting viruses and preventing them from getting into your system [xxvi] [xxvii].


Heavy Metal Toxicity:

Seaweed can absorb and store minerals in concentrated amounts from its environment [xxviii] [xxix]. For this reason it is commonly used as a ‘heavy metal detox’. Although, clinical evidence to this effect is currently limited, seaweed from an organic and reputable source is likely not to pose a threat itself in terms of heavy metal content [xxx] [xxxi].


Seaweed may interfere with certain medications. Seaweed contains a high amount of potassium, which can be harmful to individuals with kidney disease. Seaweed also contains vitamin K, which could interfere with blood-thinning medications such as Warfarin.

Recommended For

Blood Sugar Balance , Cardiovascular Health / Cardiovascular Disease (CVD) , Detoxification , High Blood Pressure (Hypertension)

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