“A herb from the sea” – the health benefits of Kelp

The health benefits of marine algae and seaweeds have long been understood by Eastern medicine, and their inclusion in Eastern diets has been associated with a reduced incidence of certain chronic diseases. Kelp, which includes a variety of seaweeds, is often referred to as “a herb from the sea” and is found across the oceans of the world. A specific form of brown kelp, a member of the Fucaceae  family, is Ascophyllum nodosum which is found in the North Atlantic. Recently the properties and therapeutic benefits of this particular species of kelp have become more understood.

Health benefits of Kelp

Kelp is naturally nutrient dense and contains a broad spectrum of micronutrients including mineral trace elements, vitamins, carotenoids and prebiotics. However, it is perhaps best known for its rich iodine content, which means it is of great potential benefit for the health of the thyroid gland.

The thyroid is the master metabolic gland within the body, and without it our bodies would not be able to convert nutrients into energy. It requires four iodine ions and a tyrosine molecule to produce the thyroid hormone T4 (one iodine ion is then lost and T4 is converted to the more active T3).  If there is a deficiency of iodine the thyroid gland may struggle to produce adequate levels of thyroid hormone(s), having a negative impact on metabolism and potentially leading to primary hypothyroidism1.

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A study has shown that supplementation with powdered kelp restores normal thyroid function and urinary iodine levels in patients with iodine deficient hypothyroidism2.

The normal function of the thyroid is essential for all systems of the body as it is responsible for the metabolism of every cell in the body. It is also therefore particularly important for cognitive and neurological function. Studies have found significant associations between low levels of free triiodothyronine (T3), poor performance, and increased mortality13.

Dietary sources of Iodine

Although iodine is present in small amounts in vegetables and wholegrains, the main sources are fish, dairy products and eggs, therefore there have been concerns over iodine deficiency in vegans. Therefore, sea vegetables such as kelp are an excellent vegan source of iodine and should be considered an important part of vegan diets.

As well as being a rich source of iodine Ascophyllum nodosum is also recognised for having a high content of polyphenols, particularly phlorotannins, as well as phenolic acids, and flavonoids4. These phytonutrients have been shown to have specific therapeutic benefits on many aspects of physiology. Studies suggest that potential mechanisms of action of these phytonutrients include: antioxidant capabilities, blood sugar regulation, cognitive support, immune stimulation, regulation of blood lipids and weight management.


The phytonutrients within brown seaweeds such as Ascophyllum nodosum, have been shown to possess antioxidant properties. A study comparing the antioxidant capabilities of red, green and brown marine algae and seaweeds showed that radical scavenging activity was highest from brown seaweed and the activity was correlated to the high polyphenol content5.

In vitro research into phlorotannin fragments showed that following digestion and fermentation, although the antioxidant capacity of phlorotannins was reduced, their anti-genotoxic activity and cell growth inhibitory effect in colon cells was maintained and enhanced, indicating that phlorotannins potentially exert a strong beneficial effect in the colon6.

As well as antioxidant capabilities, polyphenolic extracts from Ascophyllum nodosum have demonstrated further benefits to cardiovascular function. In vivo studies have found decreased blood total cholesterol and glycated serum protein levels compared with untreated diabetic mice, and it also normalised the reduction in liver glycogen levels that occurred in diabetic animals5.

Ascophyllum nodosum may be of further benefit for diabetic patients as it has strong α-glucosidase and mild α-amylase inhibitory activities that correlate with its phenolic content.

The inhibitory effects on these enzymes slows down the digestion of carbohydrates and therefore can help to stabilise blood sugar levels. Overall, findings suggest that brown seaweed extracts may limit the release of simple sugars from the gut and thereby alleviate postprandial hyperglycaemia7. This property also suggests it has potential for use in weight management by improving satiation during a meal leading to reduced calorie intake8 and may help to maintain insulin homeostasis by reducing insulin release and thereby increasing insulin sensitivity9.

This postprandial reduction of glucose and insulin may partly be responsible for improved cognitive function following the consumption of a meal containing seaweed10 (seaweed consumption led to significant improvements on cognitive tests including accuracy on digit vigilance and choice reaction time).

It is well known that phenolic compounds (such as polyphenols found in Ascophyllum nodosum) have individual benefits to cognitive function. The mechanisms of action for brain heath are not completely understood but theories include:

  • Increased cerebral blood flow, which follows on from data showing declines in cerebral blood flow in ageing
  • Modulation of glucose metabolism
  • Improved insulin sensitivity
  • Polyphenols stabilise membranes, reduce inflammation and exert antioxidant activity

Phlorotannin-rich Ascophyllum nodosum has further demonstrated anti-ageing properties. It was tested for effects on oxidative stress, inflammation, and cell senescence, all of which are associated with ageing. Extracts were found to have beneficial effects on all of these, by preventing reactive oxygen species and LPS-induced TNF-α and IL-6 release as well as increasing nuclear SIRT1 activity in epithelial cells11. Phlorotannins isolated from brown seaweeds have shown interesting bioactive properties including anti-cancer, anti-inflammation, anti-oxidant, anti-allergic, anti-wrinkling and hair growth promotion properties.

There may also be a benefit to oral health as a study identified that daily intake of the algae Ascophyllum nodosum as an adjunct to customary oral hygiene showed a major reduction of supragingival calculus (tartar) formation and reduced plaque formation. In addition, the calculus in the algae group was characterised by a more porous and less solid structure and was easier to remove than the calculus in the control group12.

Note: research is carried out on extracts of the species of Kelp Ascophyllum nodosum, which contains a higher concentration of polyphenols such as phlorotannins than the whole seaweed.

Kelp sources

Kelp grows in seas and oceans all over the world and therefore is reasonably well available.  However, the source of kelp and other seaweeds is important to investigate due to the pollution of many of the Earth’s waters. Cytoplan’s Organic Kelp is grown in the seas surrounding the Outer Hebrides, it is certified as 100% organic, guaranteed free of all pollutants and is certified by the Nutritious Food Seaweed BDA standards.

When kelp is picked, this stimulates further regrowth, therefore the quicker it is harvested, the faster it grows, and this ability supports the small community that harvests it. Our kelp supplement comes in capsules and contains three species of bladderwrack seaweed; Ascophyllum nodosum, Pelvetia canaliculata and Focus spiralis. Organic kelp can be taken in the capsule or can be used as a culinary ingredient (open capsule and sprinkle on meals).

Key takeaways

  • Kelp is a rich source of iodine and therefore supports normal thyroid function and thus cognitive health and energy production
  • Kelp also contains traces of every known mineral and element
  • A particular species of kelp, Ascophyllum nodosum has a high polyphenol content particularly of phlorotannins which have many beneficial properties such as antioxidant and anti-inflammatory capabilities, maintenance of glucose and lipid homeostasis, cognitive support as well as supporting dental health
  • Cytoplan kelp is 100% organic, free of pollutants and supports a community in the Outer Hebrides where it is harvested

If you have any questions regarding the topics that have been raised, or any other health matters please do contact me (Helen) by phone or email at any time.

helen@cytoplan.co.uk, 01684 310099

Helen Drake and the Cytoplan Editorial Team

Relevant Cytoplan Products

Organic Kelp – 400mg per capsule, providing 280ug Iodine, capsules containing three species of bladderwrack seaweed; Ascphyllum nodosum, Pelvetia canaliculata and Focus spiralis. Those on thyroid medication should consult their doctor before taking this product.

Thyroid SupportContains kelp 300mg (providing iodine 150ug), manganese 2.67mg, selenium 56.75ug, chromium 13ug, L-Tyrosine 400mg. Those on thyroid medication should consult their doctor before taking this product.


  1. Azizi F, Mehran L, Hosseinpanah F, Delshad H, Amouzegar A. Primordial and Primary Preventions of Thyroid Disease. Int J Endocrinol Metab. 2017;15(4):e57871. doi:10.5812/ijem.57871
  2. Takeuchi T, Kamasaki H, Hotsubo T, Tsutsumi H. Treatment of Hypothyroidism due to Iodine Deficiency Using Daily Powdered Kelp in Patients Receiving Long-term Total Enteral Nutrition. Clin Pediatr Endocrinol. 2011;20(3):51-55. doi:10.1297/cpe.20.51
  3. Agregán R, Munekata PES, Franco D, Dominguez R, Carballo J, Lorenzo JM. Phenolic compounds from three brown seaweed species using LC-DAD–ESI-MS/MS. Food Res Int. 2017;99(Pt 3):979-985. doi:10.1016/j.foodres.2017.03.043
  4. Sachindra NM, Airanthi MKWA, Hosokawa M, Miyashita K. Radical scavenging and singlet oxygen quenching activity of extracts from Indian seaweeds. J Food Sci Technol. 2010;47(1):94-99. doi:10.1007/s13197-010-0022-4
  5. Corona G, Coman MM, Guo Y, et al. Effect of simulated gastrointestinal digestion and fermentation on polyphenolic content and bioactivity of brown seaweed phlorotannin-rich extracts. Mol Nutr Food Res. 2017;61(11):1700223. doi:10.1002/mnfr.201700223
  6. Lordan S, Smyth TJ, Soler-Vila A, Stanton C, Ross RP. The α-amylase and α-glucosidase inhibitory effects of Irish seaweed extracts. Food Chem. 2013;141(3):2170-2176. doi:10.1016/j.foodchem.2013.04.123
  7. Mayer MA, Finlayson G, Fischman D, et al. Evaluation of the satiating properties of a nutraceutical product containing Garcinia cambogia and Ascophyllum nodosum extracts in healthy volunteers. Food Funct. 2014;5(4):773. doi:10.1039/c3fo60631g
  8. Paradis M-E, Couture P, Lamarche B. A randomised crossover placebo-controlled trial investigating the effect of brown seaweed ( Ascophyllum nodosum and Fucus vesiculosus ) on postchallenge plasma glucose and insulin levels in men and women. Appl Physiol Nutr Metab. 2011;36(6):913-919. doi:10.1139/h11-115
  9. Haskell-Ramsay C, Jackson P, Dodd F, et al. Acute Post-Prandial Cognitive Effects of Brown Seaweed Extract in Humans. Nutrients. 2018;10(1):85. doi:10.3390/nu10010085
  10. Dutot M, Fagon R, Hemon M, Rat P. Antioxidant, Anti-inflammatory, and Anti-senescence Activities of a Phlorotannin-Rich Natural Extract from Brown Seaweed Ascophyllum nodosum. Appl Biochem Biotechnol. 2012;167(8):2234-2240. doi:10.1007/s12010-012-9761-1
  11. van Dijken JW V., Koistinen S, Ramberg P. A randomized controlled clinical study of the effect of daily intake of Ascophyllum nodosum alga on calculus, plaque, and gingivitis. Clin Oral Investig. 2015;19(6):1507-1518. doi:10.1007/s00784-014-1383-2
  12. Gussekloo J, Exel E van, Craen AJM de, Meinders AE, Frölich M, Westendorp RGJ. Thyroid Status, Disability and Cognitive Function, and Survival in Old Age. JAMA. 2004;292(21):2591. doi:10.1001/jama.292.21.2591

Last updated on 8th February 2018 by cytoffice


5 thoughts on ““A herb from the sea” – the health benefits of Kelp

  1. I trained as a Macrobiotic chef many years ago. Sea vegetables are key to that diet and Japanese diet in general.
    When used properly they can be delicious!

    1. Hi John, thank you for your question. Kelp contains a broad spectrum of minerals, including magnesium, trace elements, vitamins and carotenoids. However I would not be able to describe it as a rich source as the magnesium is not declared on the label. Thanks, Clare.

  2. Can you hep me please, not sure if you can take to many supplements at present i take; zinc/copper, calcium, eyecyt, magnesium, wholefood & vit C. All yours and vit D 4000ius. All herbal 1 a day. I am also considering taking a fish oil & a prebiotic.
    Buy taking all these it is proving very expensive.

    1. Hi Anne,
      You may find it more economical to purchase one of our multivitamin/mineral products such as Foundation Formula. For more personalised advice, we offer a free appraisal of your health, together with advice on lifestyle, diet and supplements via our health questionnaire. Please follow this link to the questionnaire if you would like to take advantage of this service
      Kind regards,

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