Seaweed: The Ancient Superfood Making Waves Down Under
Once relegated to the slippery, slimy shores and rocky outcrops, seaweed is emerging from obscurity to claim its rightful place as a nutritional powerhouse. Far from being just an unglamorous marine garnish, this humble macroalgae is packed with an impressive array of vitamins, minerals, and fibre, offering a potent boost to our health. For Australians, with our extensive coastline, the opportunity to embrace this ancient food is closer than ever.
A Culinary Journey Through Time
Humans have a long and storied history with seaweed, with archaeological evidence pointing to coastal communities harvesting it for sustenance over 10,000 years ago. Long before the advent of supplements and biohacking trends, our ancestors relied on the readily available bounty of their local environments. For those living by the sea, seaweed provided an immediate source of vital minerals, iodine, fibre, and trace nutrients that are often difficult to obtain elsewhere.
While East Asian cuisines are perhaps most famously associated with seaweed delicacies – think Japanese kombu in dashi stock, nori for sushi, and wakame in soups and salads, or Korean miyeok-guk (seaweed soup) traditionally consumed after childbirth – its culinary roots run deep across the globe. In Europe, dulse has been a staple in Ireland and Scotland, often enjoyed dried or fried. Icelanders incorporate carrageen moss into desserts, and in Wales, laverbread, made from laver seaweed, has graced tables since at least the 17th century, traditionally served with oats and bacon for an earthy, savoury flavour.
Today, chefs, nutritionists, and sustainability advocates are championing seaweed, rediscovering its immense benefits and versatility. It’s a case of ancient wisdom being repackaged for a modern, health-conscious generation – a testament to an ingredient that was both convenient and effective for our forebears.
Unpacking the Nutritional Goldmine
Despite its impressive health credentials, seaweed often remains shrouded in myth. To clear the air, we delve into what makes this marine wonder so special.
Fibre: The Gut’s Best Friend
Yes, seaweed is exceptionally rich in both soluble and insoluble fibre, crucial for maintaining digestive regularity. Amanda Swiminer, a marine biologist and kelp harvester from Victoria, B.C., explains that fibre constitutes the largest component of seaweed’s biomass. “Some of these fibres, like fucoidan,” she notes, “have been shown to have disease-preventing properties in peer-reviewed in-vitro and in-vivo studies.” Fucoidan has been linked to immune system boosts, reduced inflammation, lower blood pressure, and even fat loss, according to a 2020 study.
A Comprehensive Nutrient Profile
Seaweed is remarkably low in fat, typically ranging from just 0.1 to 3 per cent of its dry weight, and is also low in calories, with specific amounts varying by species. Ms. Swiminer highlights the vast diversity of macroalgae, with an estimated 12,000 species, most of which are marine.
While all seaweeds are nutrient-dense, different varieties offer unique benefits:
- Nori: Stands out for its high protein content, comprising approximately 45 per cent of its dry weight. It also contains porphyran, a soluble fibre with demonstrated anti-tumour properties.
- Kelp varieties (including wakame and kombu): Are the richest sources of iodine.
- Sea lettuce: Is the highest in iron.
- Winged kelp and wakame: Are exceptionally high in calcium.
“Your best bet is to eat seaweed from all three groups – greens, reds, and browns,” advises Ms. Swiminer. “Think of them like your different coloured vegetables: different colours will have different nutritional properties.”
Vitamins, Minerals, and Essential Fatty Acids
Seaweeds are arguably the most concentrated source of minerals on the planet. Most edible varieties contain a broad spectrum of vitamins, including A, B-complex, C, D, E, and K, and are all excellent sources of calcium. They also provide essential fatty acids, including rare omega-3s, which are typically associated with cold-water fish. In fact, the original source of these omega-3s in fish is algae, and edible seaweeds often boast a near 1:1 ratio of omega-3 to omega-6 fatty acids, considered optimal for human health.
Furthermore, seaweeds are a significant source of prebiotics, which nourish the beneficial bacteria in our gut microbiome, aiding digestion and nutrient absorption. Ms. Swiminer points out that seaweeds store minerals in chelated and colloidal forms, making them highly bioavailable for human absorption. “They are a rich source of both macro-essential minerals and rare trace minerals,” she says, adding that they often contain these minerals in ratios beneficial to humans, citing the sodium/potassium ratio in kelp as being similar to human blood.
Protein content varies by species, with nori leading the pack at around 45 per cent of dry weight, and bull kelp and winged kelp offering about 25 per cent.
The Crucial Role of Iodine
The rich iodine content of seaweed is particularly noteworthy. Registered nutritionist Lily Soutter, BSc MSc, points to research by the British Thyroid Association, which found that a staggering 70 per cent of young women in the UK are iodine deficient. This deficiency can lead to thyroid dysfunction, manifesting as weight gain, dry skin, hair loss, fatigue, and depression, along with a sensitivity to cold.
Iodine is a vital mineral for thyroid health, essential for producing thyroid hormones. These hormones are critical for maintaining healthy cells and regulating our metabolic rate – the speed at which our body converts food into energy. Adequate iodine levels are especially crucial during pregnancy, as even mild deficiency can negatively impact a baby’s brain development, cognition, and future academic performance.
Who Needs to Be Cautious?
While generally safe in moderation, individuals with pre-existing medical conditions, particularly thyroid issues, should approach seaweed consumption with care.
“Anyone with thyroid issues needs to tread carefully and see how their body responds when introducing seaweed into their diet, due to its rich iodine content,” advises Ms. Soutter.
Signs of Iodine Deficiency Include:
- Constant fatigue
- Muscle weakness
- Difficulty concentrating
- Unexplained weight gain
- Depression
- Puffy face
- Hair loss
- Dry skin
- Constipation
- Slow heartbeat
- Enlarged thyroid (goitre)
For individuals with hyperthyroidism, excessive iodine from seaweed could exacerbate their condition. Similarly, those taking synthetic thyroid medication like levothyroxine should be aware that seaweed, especially kelp, can potentially affect its potency.
Conversely, people with an underactive thyroid (hypothyroidism) who are not on medication might benefit from incorporating iodine-rich seaweed or supplements, but should consult their GP first. Ms. Soutter suggests starting with seaweeds lower in iodine, such as nori or dulse, and monitoring thyroid levels closely with a physician.
How Much is Enough?
Due to its nutrient density and concentration when dried, small portions of seaweed can deliver significant benefits. Consuming just 3 to 5 grams per day can provide notable nutritional advantages. “Obtaining the health benefits from seaweeds is about consistency,” emphasises Ms. Swiminer. “Eating a little most days is more effective than eating a large amount once in a while.”
Supplementation: Proceed with Caution
The market is flooded with seaweed-based supplements, but caution is advised. While mild iodine deficiency can lead to sluggishness, depression, and weight issues, excessive intake can also cause thyroid problems. The NHS classifies over 500-600 micrograms of iodine per day as excessive, which can paradoxically lead to symptoms similar to deficiency, including goitre.
The NHS specifically warns against kelp-based supplements, as a single serving can contain over 2,000 micrograms of iodine, far exceeding the safe upper limit of 150 micrograms.
Maximising Benefits: Food Pairings and Preparation
Drawing inspiration from cultures where seaweed is a dietary staple, like Japan where it comprises about 30 per cent of the traditional diet, offers insights into optimal consumption. Ms. Swiminer notes that many Japanese dishes enhance seaweed’s benefits while mitigating potential downsides. For instance, dashi, made by boiling kombu, significantly reduces the seaweed’s iodine content. Miso soup is another excellent example; the probiotics in fermented miso aid digestion, allowing for better absorption of seaweed’s abundant nutrients.
Addressing Microplastic Concerns
Sadly, microplastics are a pervasive issue in our oceans, affecting all levels of the food chain, including seaweeds. While scientific research in this area is less extensive than for fish, Ms. Swiminer offers reassurance. “Current studies show that microplastics cling to the outside of seaweed and that washing seaweed can be very effective in removing microplastics,” she states. Research also indicates that the location of growth matters, with seaweeds from wave-exposed areas and further from contaminated zones showing less microplastic contamination.
As we increasingly look towards sustainable and nutrient-rich food sources, seaweed stands out as an ancient, versatile, and highly beneficial ingredient, readily available along Australia’s vast coastline. By understanding its nutritional profile and consuming it wisely, we can harness the power of this remarkable marine superfood.
