The health benefits of... seaweed

The health benefits of seaweed

Slimy, slippery seaweed has been heralded as the new, must-have superfood. So is it truly healthy or just media hype? Read on to discover the nutritional profile of the most common varieties, plus inventive ways to put it to use in your own cooking...

Despite its recently trendy, superfood status, seaweed has been used all over the world for thousands of years, but has most notably been a prominent part of Asian diets for the longest period of time, particularly in Japan, Korea and China. There are thought to be over 10,000 species of seaweed, reflecting its immense diversity, both in flavour and nutritional properties. The most popular seaweed species are nori, which is dried in sheets and widely used to make sushi. Other common varieties include dulse, arame, wakame, kelp and spirulina. Sea vegetables also have a long history in ancient medicine, folklore, farming and food growing in Europe, particularly in Ireland.


Nutritional benefits

Square sheets of dried seaweed

Sea vegetables are full of nutrients. Coming in a multitude of colours, textures, shapes and sizes, all types contain a rich supply of minerals, most prominently calcium, copper, iodine and iron. They are also rich in protein, fibre and vitamins, specifically vitamin K and folic acid, while being low in calories and fat.

Thanks to their impressive nutritional profile, seaweeds are beneficial to health, and are thought to help the body fight illness and disease. The Japanese have one of the highest life expectancies in the world, and one significant, standout dietary habit is their regular consumption of seaweeds. Seaweeds contain a molecule known as fucoidans, which are believed to be responsible for these impressive health benefits, contributing not just to overall life expectancy, but also to immunity and cardiovascular function.

A 2011 review of 100 studies on the benefits of seaweeds, published in the American Journal of Agricultural and Food Chemistry, reported seaweeds may be used to help lower blood pressure and promote heart health.

The quest for umami – or the fifth taste – by chefs and foodies alike has highlighted another key component of seaweeds – their high glutamate content, an amino acid, necessary for normal brain function. Dashi, a traditional Japanese broth, heralded as the ‘mother’ of umami, has seaweed as a core ingredient. Research suggests that it’s the high glutamate content of certain seaweeds that provides the umami flavouring. 

Safety warning

Such high concentration of certain nutrients may be problematic for some, for example, overconsumption of vitamin K can interfere with blood thinning medications. Certain seaweeds have high potassium contents, which might cause issues for those with kidney problems. While the iodine content makes it especially beneficial for thyroid health, consuming too much iodine can have the opposite effect. If you are taking any of the aforementioned medication, have a relevant medical condition or have any concerns speak to your GP.

What to do with seaweed

Kelps are usually dried into sheets and added to a dish during cooking, or are soaked in water to soften them before eating.
Kombu is a brown kelp, favoured for its strong, mineral-rich flavour and often used in soups.
Arame, another species of kelp, has a mildly sweet flavour and firm texture, that makes it an appealing addition to many dishes – even baked goods. Sometimes sold as flakes or granules, seaweeds are increasingly used as a salt substitute. Kelp noodles, which do not require cooking, are a good gluten-free alternative, being low in calories but high in calcium.
Dulse is a seaweed with a softer, chewy texture. It is commonly eaten in dried form as a snack, as a healthy alternative to fried crisps.

Where to get it

Explore Asian supermarkets and experiment with some of the varieties on the shelves. If you’re feeling adventurous, buy a few to try. Some will be ready to eat, others may need soaking. Even the more mainstream supermarkets are now stocking some types of seaweed – nori for sushi for example.

A large proportion of seaweeds on the market are imported, so look out for suppliers from the British Isles, where it can be hand collected. 

Recipe suggestions

Fancy rolling your own sushi? Our step-by-step video guide will show you how, then put your new skills to use in some of our recipes:

Simple sushi
Salmon & cucumber sushi rolls
Smoked salmon & avocado sushi
Japanese-style bento box
Baked new potato pebbles & seaweed mayonnaise
Miso soup

Now, discover the health benefits of more of your favourite (and soon-to-be favourite) foods.

Have you experienced the health benefits of seaweed first-hand? Do you regularly use it in your cooking at home? Share your tips and experiences below in the comments…

This article was last reviewed on 27th September 2017 by nutritional therapist Kerry Torrens.

A registered Nutritional Therapist, Kerry Torrens is a contributing author to a number of nutritional and cookery publications including BBC Good Food. Kerry is a member of the The Royal Society of Medicine, Complementary and Natural Healthcare Council (CNHC), British Association for Applied Nutrition and Nutritional Therapy (BANT).

Jo Lewin is a registered nutritionist (RNutr) with the Association for Nutrition with a specialism in public health. Follow her on Twitter @nutri_jo.


All health content on is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. If you have any concerns about your general health, you should contact  your local health care provider. See our website terms and conditions for more information.