The nutritional benefits of sea greens have long been recognised: pound for pound, seaweed contains more iron than sirloin steak, more calcium than cheese, and more fibre than prunes.
With an unusually high proportion of protein – as much as 48 per cent in some varieties – seaweed is also richer in essential vitamins and micronutrients than any other food group. A prime source of bodybuilding minerals such as iodine and potassium, it is also the only plant source of vitamin B12, which is necessary for the production of red blood cells, and which is often lacking in meat-free diets.
According to recent research, seaweed – which is part of the algae family – also contains a host of bioactive substances proven to lower cholesterol, reduce blood pressure, promote healthy digestion and even tackle the free radicals that can cause cancer. Some studies suggest that seaweed might also aid weight loss.
The brackish fingers that get washed up on the beach contain more sand than a seafront sandwich, which is why seaweed-hunters cut theirs fresh, from the submerged rocks on which it grows, rather than collect the scrags along the shoreline. Among seaweed's greatest consumers are the Japanese, who eat so much of it – more than 4kg per head a year – that certain varieties, such as wakame (kelp) and kombu (sugar kelp), are known globally by their Japanese names.
Scientists have long believed that iodine-rich algaes such as seaweed play a role in reducing the incidence of cancer among Japanese women. Preliminary research published by the American Association for Cancer Research in March found seaweed extracts can also inhibit the growth of cancer cells that lead to lymphoma.
Seaweed extracts are already used to combat obesity, notably in diet pills and appetite suppressants such as Appesat. Researchers at the University of Newcastle have found that alginates – seaweed fibres – can also significantly reduce the body's absorption of fat. Some claim that this opens a new front in the war on weight problems and related issues, including diabetes and heart disease. Additionally, as the metabolism is stimulated by iodine, seaweed might be a useful for people with underactive thyroids.
Dr Iain Brownlee, research associate in human nutrition at Newcastle, said: "We've found that by adding these natural fibres to food products, up to 75 per cent of the fat we consume could simply pass through the body – so in theory it could be used to fight obesity. Alginates could be used in place of the fat that gives food its flavour. In tests, people have actually preferred bread with small levels of alginate in it – so it's not something you have to force yourself to eat."
Despite being a saltwater foodstuff, seaweeds don't taste particularly fishy, but instead enhance existing flavours. The NHS is investigating whether adding it to meals can help elderly patients recover their appetites, following an Age Concern-funded initiative involving researchers from Reading University and Michelin-starred chef Heston Blumenthal. Dr Lisa Methven, lead researcher on the project, explained: "As people get older their taste buds fade. Sense of smell is also depleted. Flavour can be enhanced by use of monosodium glutamate, but our approach is to find a natural source for improved flavour."
Blumenthal has long been a fan of seaweeds, using several varieties (particularly kombu) at his Fat Duck restaurant to add taste and flavour to meat dishes. "Seaweed is full of properties that boost what the Japanese call umami, the fifth taste, commonly referred to as "savouriness"," he says. "It brings out the meatiness in a dish as well as adding an exciting and unexpected burst of flavour."
So why don't we cook with seaweed more? It's a bountiful, natural resource, growing freely on rocks around our coastline. As a foodstuff, it's easier to prepare than most Sunday lunch veg – a quick rinse with a kettle of boiling water is often all that's needed to turn a brown clump into a plate of sprightly greens. It can also be baked dry on a high heat then crumbled to thicken broths, or be eaten as delicate crisps. Yet seaweed is mostly overlooked by the British. Why? Because it's not something you can buy on your big weekly shop at the supermarket.
Dried seaweed is available in oriental groceries and health food shops. But outside Wales, where seaweed is used traditionally to make laver bread, it's almost impossible to buy fresh in the UK.
Iain McKellar runs www.JustSeaweed.com Britain's only fresh seaweed store, selling rock-grown algaes cut from the waters off the Isle of Bute. Ever since seaweed's fat-busting properties were revealed, he has struggled to keep up with demand.
"Once you get over that squeamishness, seaweed makes a tasty meal, and one that's full of goodness. It's a very versatile ingredient, too. One of my customers chucks it into his bolognese sauces so his kids get their nutrients but are none the wiser."
Supermarket chain Waitrose is trialling seaweed on its fresh-produce aisles, after promising sales of another seashore plant, samphire. Until then, however, would-be seaweed enthusiasts are best foraging for their own. And what are bank holidays for if not a quick trip to the seaside?
Unlike mushroom-picking, which can have unpleasant, even fatal, consequences if you confuse a death cap with a chanterelle, you'll come to no harm with seaweed. "Although not all species taste nice, none is poisonous," says Craig Evans, creator of the Dolmor seaweed spa product range (dolmorspa.co.uk), and an enthusiast who took me foraging along Newgale Beach on the Pembrokeshire coast.
"There's a wealth of sea vegetables to be found around Britain. It's just a case of knowing what to look for," says Evans. All you need is a knife, a swimming costume and, for the deeper-water varieties that grow on submerged rocks, a snorkel.
With the tide out along the two-mile-long sandy beach, we head first for a cluster of rock pools. This Blue Flag beach has more varieties than anywhere else in Wales, thanks to the meeting of warm waters from the south and cold currents from the north. Evans tells me we'll easily see a dozen species before the tide rolls back in.
Highest up the beach we find thin, black, delicate, plasticy films of seaweed covering rocks. This is laver, one of the most nutritious species, which the Welsh have cooked for centuries. After several hours on the boil, it turns into a purée. Rolled in oatmeal and fried for breakfast, the resulting laver bread tastes delicately of olives.
Next we find sea lettuce, with pale, fragile leaves which I nibble on raw. It's tender, with a peppery flavour and great in salads, or as a garnish, and is tasty deep-fried for a few seconds, too. In the same pool, we pick some reddish-coloured dulse, which is chewy, with a strong marine taste – you only need a little, pan-fried with sesame oil to add colour and a savoury bite to potatoes.
The long, light green-coloured swathes of kombu that we find in pools on the lower shore are delicious toasted, says Evans. "When it's dried and sprinkled on food, it tastes just like smoky bacon."
Seaweed that tastes like bacon? Now that's got to be worth a try…
Seaweeds to forage for around Britain
Pelvetia (channel wrack)
• Leafy, fronded algae that holds its finger shape when "cooked" – to prepare, simply rinse through with boiling water and serve as an alternative to cabbage.
Broad kelp
• A thick and meaty variety that looks like pasta ribbons and requires soaking to reduce its salt content, and a thorough boiling to make it edible. Great as a stand-alone side vegetable, chopped into chunks in soups, or baked in a very hot oven into delicious crispy strips.
Purple laver
• With a distinctive flavour like olives and oysters, this smooth and fine variety boils down to a dark green pulp – perfect for making into laver bread, the traditional Welsh dish.
Sea lettuce
• Bright green algae found in rock pools. With a strong flavour similar to sorrel, it can be added to salads, or pressed and dried into crispy green sheets used to wrap Japanese nori rolls.
Cordia filia (sea spaghetti)
• Grows in billowing strands in deep waters, so you'll need more than a snorkel to harvest your own. When boiled, it has a crispy bite and the texture of beansprouts. It's green, slimy and something few of us would consider putting in our mouths. But, following a string of recent scientific studies into the benefits of seaweed, it could soon be replacing superfood side-dishes such as kale and broccoli on the nation's dining tables.