Seaweed

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].

Cell-Protective:

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].

Safety

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].

Interactions:

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.

[i] RefsCorsetto, P. A. Montorfano, G. Zava, S. et al. (2020). ‘Characterization of Antioxidant Potential of Seaweed Extracts for Enrichment of Convenience Food’. Antioxidants (Basel, Switzerland), 9(3), 249.

[ii] Wong, K.H. & Cheung, P.C.K. ‘Nutritional evaluation of some subtropical red and green seaweeds: Part I — proximate composition, amino acid profiles and some physico-chemical properties’. Food Chemistry. 71, (4) pp.475-482.

[iii] Bakir, S. Catalkaya, G. Ceylan, F.D. et al. (2020) Role of Dietary Antioxidants in Neurodegenerative Diseases: Where are We Standing? Current Pharmaceutical Design. 26(7): pp.714-729.

[iv] Sunkara, A. & Raizner, A. (2019) ‘Supplemental Vitamins and Minerals for Cardiovascular Disease Prevention and Treatment’. Methodist Debakey Cardiovascular Journal. 15: pp.179–184.

[v] Rengasamy, K.R. Mahomoodally, M.F. Aumeeruddy, M.Z. et al. (2020) ‘Bioactive compounds in seaweeds: An overview of their biological properties and safety’ Food and Chemical Toxicology. 135:111013.

[vi] Mikami, K. & Hosokawa, M. (2013). ‘Biosynthetic pathway and health benefits of fucoxanthin, an algae-specific xanthophyll in brown seaweeds’. International journal of molecular sciences,(7), pp.13763–13781.

[vii] Holscher, H. D. (2017). ‘Dietary fiber and prebiotics and the gastrointestinal microbiota’. Gut Microbes, 8(2), 172–184.

[viii] Sender, R. Fuchs, S. & Milo, R. (2016) ‘Revised Estimates for the Number of Human and Bacteria Cells in the Body’. PLoS Biology. 14(8):e1002533.

[ix] O'Sullivan, L. Murphy, B. McLoughlin, P. et al. (2010). ‘Prebiotics from marine macroalgae for human and animal health applications’. Marine drugs, 8(7), 2038–2064.

[x] Sheng, T.Y. Hung, H.H. Lin, T.C. et al. (2014) ‘Analysis of iodine content in seaweed by GC-ECD and estimation of iodine intake’. Journal of Food and Drug Analysis. 22, 2, pp189-196.

[xi] Kapil, U. (2007). ‘Health consequences of iodine deficiency’. Sultan Qaboos University Medical Journal, 7(3): pp.267–272.

[xii] Teas, J. Vena, S. Cone, D. L. et al. (2013). 'The consumption of seaweed as a protective factor in the etiology of breast cancer: proof of principle’. Journal of applied phycology, 25(3), 771–779.

[xiii] Funahashi, H. Imai, T. Mase, T. et al. (2001) ‘Seaweed prevents breast cancer?’ Japanese Journal of Cancer Research. 92(5): pp.483-7.

[xiv] Funahashi, H. Imai, T. Tanaka, Y. et al. (1999) ‘Wakame seaweed suppresses the proliferation of 7,12-dimethylbenz(a)-anthracene-induced mammary tumors in rats’. Japanese Journal of Cancer Research. 90(9): pp.922-7.

[xv] Kim, E.K. & Ju, S.Y. (2019) ‘Asthma and Dietary Intake of Fish, Seaweeds, and Fatty Acids in Korean Adults. Nutrients’. 11(9): pp.2187.

[xvi] Montero, L. Pilar, A. Camargo, Ibáñez, E. et al. (2018) ‘Phenolic Compounds from Edible Algae: Bioactivity and Health Benefits’, Current Medicinal Chemistry. 25(37).

[xvii] Shirosaki, M. Koyama, T. (2011) ‘Laminaria japonica as a food for the prevention of obesity and diabetes'. Advanced Food and Nutrition Research. 64:199-212.

[xviii] Maeda, H. Hosokawa, M. Sashima, T. et al. (2005) ‘Fucoxanthin from edible seaweed, Undaria pinnatifida, shows antiobesity effect through UCP1 expression in white adipose tissues’. Biochemical and Biophysical Research Communications. 332(2): pp.392-7.

[xix] Montero, L. Sánchez-Camargo, A Ibáñez, E. et al. (2018) 'Phenolic Compounds from Edible Algae: Bioactivity and Health Benefits. Current Medical Chemistry. 25(37): pp.4808-4826.

[xx] Mikami, N. Hosokawa, M. Miyashita, K. et al. (2017). ‘Reduction of HbA1c levels by fucoxanthin-enriched akamoku oil possibly involves the thrifty allele of uncoupling protein 1 (UCP1): a randomised controlled trial in normal-weight and obese Japanese adults’. Journal of nutritional science, 6, e5.

[xxi] Cardoso, S. M. Pereira, O. R. Seca, A. M.et al. (2015). ‘Seaweeds as Preventive Agents for Cardiovascular Diseases: From Nutrients to Functional Foods’. Marine drugs, 13(11): pp. 6838–6865.

[xxii] Lordan, S. Ross, R. P. & Stanton, C. (2011). ‘Marine bioactives as functional food ingredients: potential to reduce the incidence of chronic diseases’. Marine drugs, 9(6): pp.1056–1100.

[xxiii] Brown, E.S. Allsopp, P.J. Magee, P.J. et al. (2014) ‘Seaweed and human health’. Nutrition Reviews. 72(3): pp.205-16.

[xxiv] Ku, C.S. Yang, Y. Park, Y. et al. (2013) ‘Health benefits of blue-green algae: prevention of cardiovascular disease and nonalcoholic fatty liver disease'. Journal of Medicinal Food. 16.

[xxv] Ikeda, K. Kitamura, A. Machida, H. et al. (2003) ‘Effect of Undaria pinnatifida (Wakame) on the development of cerebrovascular diseases in stroke-prone spontaneously hypertensive rats’. Clinical and Experimental Pharmacology and Physiology. 30(1-2): pp.44-8.

[xxvi] Myers, S. P. O'Connor, J. Fitton, J. H. et al. (2011). ‘A combined Phase I and II open-label study on the immunomodulatory effects of seaweed extract nutrient complex’. Biologics : targets & therapy, 5, pp.45–60.

[xxvii] Okolie, C.L. Rajendran, S.R, Udenigwe, C.C. et al. (2017) ‘Prospects of brown seaweed polysaccharides (BSP) as prebiotics and potential immunomodulators’. Journal of Food Biochemistry. 41:e12392

[xxviii] Zava, T. T. & Zava, D. T. (2011). ‘Assessment of Japanese iodine intake based on seaweed consumption in Japan: A literature-based analysis’. Thyroid research, 4, 14.

[xxix] Circuncisão, A. R. Catarino, M. D. Cardoso, S. M. et al. (2018). ‘Minerals from Macroalgae Origin: Health Benefits and Risks for Consumers’. Marine drugs, 16(11) pp. 400.

[xxx] Rubio, C. Napoleone, G. Luis-González, G. et al. (2017) ‘Metals in edible seaweed’. Chemosphere. 173: pp.572-579.

[xxxi] Circuncisão, A. R. Catarino, M. D. Cardoso, S. M. et al.(2018). ‘Minerals from Macroalgae Origin: Health Benefits and Risks for Consumers’. Marine drugs, 16(11), pp.400.