Getting Seaweed back on our Plates

Getting Seaweed back on our Plates

Welcome ocean lovers!

Whether it’s surfing the waves, open water swimming, kayaking to secluded coves or walking our beautiful coastal paths on a glorious sunny day, we can all appreciate the magic of the sea and it’s beguiling ways. As well as feeding our minds and our soul the sea has long been a bountiful provider of a nutritious and health giving food. As an island nation we are abundant in the maritime magic which is seaweed; a nutrient dense sea vegetable regularly consumed until roughly 50-100 years ago and also used for medicinal properties and as a fertiliser on the land. A lot has changed in our dietary habits in the last 50 or so years and seaweed has certainly not been on the menu in most households as we have moved to a highly processed and more meat based diet. Most of us will have heard, or possibly tried laver seaweed (Porphyra Umbilicalis) in the form of laverbread which was traditionally eaten in Ireland, Scotland and Wales as a healthy and accessible food in coastal communities. Welsh laverbread (Bara Lawr) was given the prestigious name of Welsh caviar and there are records of laver being harvested and used to make laverbread near St David’s, Pembrokeshire around 1693. Outside laverbread our only other culinary connection with seaweed is possibly in the form of sushi, a food strongly associated with Japanese culture and highend restaurants. Seaweed also risen to the ranks of a superfood and celebrity status through the likes of Jamie Oliver and Heston Blumenthal, but where does it fit into a normal diet for the majority of us and what of its’ role as a nutritional and functional food?

A functional food ‘delivers additional or enhanced benefits over and above their basic nutritional value’.

As a Registered Nutritional Therapist living on the beautiful coast of Pembrokeshire I advocate for a rich and varied diet especially with a background of locally grown and sustainably produced. Seaweed has the ability to become part of the Holy Grail of sustainable nutrition which we are espousing as part of our commitment to both feed the planet and preserve our environment. So let us take a deep dive into the nutritional and functional qualities of seaweed to unravel it’s mysteries and acknowledge it’s power.

Minerals and vitamins

Some seaweeds have 10 to 100 times more minerals and vitamins per unit of dry mass than any other plants or animal foods. There really is an incredible range of nutrients from the fat soluble vitamins A, D, E, K to the water soluble vitamins C, B1, B2, B9, B12 plus minerals such as calcium, iron, iodine, magnesium, phosphorus, potassium, zinc, copper, manganese, selenium. The available content of vitamins and minerals in seaweed will vary though by species and environmental factors.

The first health claim often touted is the abundant supply of iodine in seaweed. To understand how to use seaweed as part of our diet we really need to address this potent mineral and how it can bring health but also recognise how it can be a potent inhibitor of thyroid function. So what are the things we need to consider to get the balance right?

Seaweeds can be a good dietary source of iodine but they can also be a source of excessive iodine. Iodine is an essential micronutrient which is required for the synthesis of thyroid hormones and this is particularly important during pregnancy when production of thyroid hormones are needed for the neurodevelopment of the baby. The UK has traditionally been considered iodine-sufficient but there is now concern that iodine insufficiency may be present particularly in pregnant women and women of childbearing age. Furthermore, a recent survey in the UK found that iodine deficiency was found in more than two-thirds of schoolgirls aged 14- 15 years.

The recommended iodine intake for adults (>12 years) is 150 µg/day. However, during pregnancy and lactation, the requirement for iodine rises from 150 to 250 µg of iodine per day. The safe upper limit for iodine is approximately 600 µg/day for adults (>12 years) and pregnant women but there is a red flag in the case of those who are chronically iodine deficient as they may react adversely to levels lower than this if the thyroid has adapted to low iodine levels. It is also not advisable to consume a lot of seaweed or supplement with kelp when taking thyroid medication.

The background to determining how much seaweed we can eat will also be dependant on the inclusion of other iodine rich food in our diet; so if we eat a lot of shellfish, fish, milk, dairy and eggs then we are likely to require less iodine in food from seaweed and should apply more caution. However, for vegans and vegetarians who avoid these foods then seaweed can be a really beneficial form of iodine to supplement their diet. In this respect I am talking about a wholefood source and not a supplement. Seaweed also has a delayed release of iodine so it can remain available in the body longer for continuous use. This can be beneficial when the body needs it but it is also why prolonged use at high levels can cause toxicity.

It is important that products have adequate labelling to demonstrate iodine content or to provide information to estimate iodine content. Much like other food we should get into the habit of understanding the nutritional content of the food we eat so we can inform ourselves about meeting our dietary requirements. Applying the guidelines for recommended daily allowance and recognising the safe upper tolerance levels, plus acknowledging if we have a background risk e.g. Thyroid disease can inform our choice to eat seaweed in a safe and healthy manner. Once we have a handle on this then we are free to enjoy the other amazing nutraceutical applications of seaweed!


Researchers have demonstrated seaweeds can contain between 5%–47% protein as dry mass. Red seaweeds such as dulse (Palmaria palmata) and laver (Porphyra aver) may present a great opportunity as a low-cost, nutrientdense option to compete with protein crops such as soya. Healthy, alternative protein sources are important for vegans and vegetarian and a more sustainable option to soya.

Healthy Fats

Another great benefit from seaweed is the contribution of healthy fats. Most lipids in seaweed are polyunsaturated, composed of omega 3 fatty acids such as docosahexaenoic (DHA) and eicosapentaenoic acid (EPA). The presence of such healthy fats is associated with benefits for reducing depression in the elderly and lowering the inflammatory markers for diabetes and Cardiovascular disease.

Benefits for the gut

An exciting new area of research is looking at the potential of seaweeds to boost the human gut microbiome. What we are talking about is the nutritional benefits for our gut bacteria from specific carbohydrates in seaweeds which are called polysaccharides. These can be fermented by the gut microbiota to provide a prebiotic effect which is beneficial for our health .

Some of these polysaccharides have generated a plethora of research due to their potential health benefits. One of the most notable is Fucoidan. Fucoidan is a sulphated polysaccharide primarily found in brown seaweed. Oral preparations made using fucoidan to treat mice with IBD such as ulcerative colitis and Chrons disease have shown a significant effect on reducing the inflammatory response. Some of the benefits from other complex polysaccharides in seaweed may be achieved through a positive modulation of the gut microbiome and an increase in beneficial bacteria. It has to be noted that the main body of research is in vitro and animal studies but clinical trials are now under way to look at how fucoidan can be used in the treatment of IBD.

Impact on chronic disease

Epidemiological studies comparing Japanese and Western diets have suggested a lower incidence of obesity and chronic conditions such as cancer, hyperlipidaemia and coronary heart disease (CHD) may be linked to the consumption of seaweed.

Other dietary and lifestyle factors will also impact the incidence of chronic disease but at this time seaweed is definitely becoming a focal point for scientific research; so let’s look at why it may be having some a positive impact on weight and chronic disease.

In a study looking at the dietary habits of 923 Japanese patients who had undergone surgery for colorectal cancer, those who consumed a Western style diet, high in red meat, sugar, carbohydrates and refined oils had a significantly higher risk of colorectal cancer than those who consumed a traditional diet with seaweeds, vegetables, fruits and fish. When Chinese, Japanese and Filipino women emigrated from Asia to the United States a population based study demonstrated a 6 fold increase in breast cancer after approximately 4 years. This may be attributed to other lifestyle factors and possibly a move from a traditional diet which is more protective against breast cancer.

The Okinawans in Japan enjoy the longest life expectancies in the world and have a high dietary intake of fish, soy, and seaweed. Research has shown that some components in seaweed such as carotenoids, peptides, and dietary fibres may positively impact markers for total cholesterol, blood glucose levels, lower blood pressure and body weight. This suggests that seaweed may have a protective effect against cardiovascular disease but a direct association has not been measured.

There is also some data which points to bioactive compounds in seaweed which can positively impact weight. Dietary fibres such as alginate which are isolated from the cell wall of brown algae have been promising in trials for weight management. In a 4 week trial an alginate drink was reported to significantly reduce energy intake in participants who were overweight and obese and could help with weight loss as part of a healthy diet. A bioactive compound in seaweed called Fucoxanthin which is a carotenoid produced by brown algae, was used in supplementary form over 4 weeks for obese participants. The results were a reduction in body weight, BMI, and abdominal fat by acting on both the visceral and subcutaneous fat. Lastly, there may be potential for the use of seaweed for those with Type 2 Diabetes. A seaweed supplement containing dried sea tangle and sea mustard 3 times a day with a daily consumption of 48g was given to participants with Type 2 Diabetes over 4 weeks. The results showed a positive impact on glycaemic control, lowering blood lipid markers and increased antioxidant levels. Edible seaweed are also low in calories and rich in dietary fibre, unsaturated fatty acids, minerals and vitamins which makes them suitable for helping managing diabetes.


On a personal note as a practicing Nutritional Therapist, many clients present with inadequate levels of iodine and this is generally in association with low selenium. The basis for this is a 3 day food diary which clients must complete to generate an approximate intake of macro and micronutrients. Therefore, for clients where contraindications do not apply, seaweed as a wholefood can be a great option. Supplements should be used with caution and I would strongly recommend getting professional advice before supplementing.

There is such an incredible wealth of data now on the health benefits from seaweed that hopefully it will change the image of this humble and overlooked sea vegetable. I think it is hard not be taken aback by the lower incidence of chronic disease in Asian countries where seaweed has been a part of their traditional diet. Sadly, this is also changing and when we look at the impact of migration from East to West I would not be championing the West in this scenario!

Changing our dietary habits is critical to a healthier society and eating not just plant based but also sea-based is a very exciting alternative. We have an epidemic of chronic illnesses which are a huge burden on society and the NHS and seaweed is showing incredible potential as low calorie, high fibre, antioxidant rich and nutrient dense food. At this time we also need more research with human trials to identify how to specifically use extracts of seaweed as appropriate nutraceuticals.

We need to connect again with our own indigenous seaweeds and how can we incorporate them into dishes we can enjoy, make it a savoury sprinkle on our meal rather than salt, get fancy with some homemade sushi, use it in a ‘good to go’ early morning smoothie, bake it in our bread or do as Richard Burton and put some Welshman’s caviar with your bacon and cockles or perhaps a crafty seaweed gin!

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