Often referred to as the “kale of the ocean,” seaweed is more than just a sea vegetable—it’s a nutritional powerhouse. In fact, seaweed, which boasts a variety of health benefits, is loaded with a wide range of wonderful nutrients, ranging from fiber and vitamins to minerals, antioxidants, and iodine. And, while often touted as a superfood, thanks to its amazing health benefits (more on that below), it’s worth noting that, as with many things in life, consuming too much of a good thing can have negative consequences. How much is too much? What are the nutritional benefits of seaweed? What should you be on the lookout for when purchasing seaweed? Let’s dive in.
What is Seaweed?
In essence, “seaweed” (more formally known as macroalgae) is the umbrella term for countless marine plants and algae that flourish in our vast oceans and rivers, lakes, and other aquatic ecosystems.
There are thousands of different varieties of algae. Scientists have identified over 10,000 distinct seaweed species, though estimates suggest that the total number of species could be much higher.
These species are typically classified into four primary groups based on their pigmentation and other characteristics: green algae (Chlorophyta), brown algae (Phaeophyceae), red algae (Rhodophyta), and Blue-green algae. Each group contains a multitude of species with their unique features and habitats.
While this is a relatively new delicacy in American cuisine, cultures in Asia, Britain, and the Caribbean have been savoring these marine delicacies for thousands of years. And they were undoubtedly onto something. Bursting with minerals, vitamins, fiber, antioxidants, and a substantial amount of iodine, these marine vegetables (yes, we can refer to them as vegetables in the culinary context) offer a variety of health benefits.
Common Edible Seaweeds
If you’ve eaten Japanese, Korean, or Chinese cuisine at some point in your life, you’ve most likely encountered one or more of these types of sea vegetables.
Here’s a quick overview of some of the most common edible seaweeds:
- Wakame (Brown Algae): A staple in many Asian cuisines, wakame is often the star ingredient in seaweed salads and miso soup. Its tender texture and subtly sweet taste make it a favorite among many.
- Kombu (Brown Algae): Related to wakame, kombu is a form of kelp known for its robust flavor. It serves as the backbone in crafting the umami-rich Japanese broth, dashi. Kombu is not just flavorful but also a rich source of minerals.
- Nori (Red Algae): Arguably the most well-known seaweed, nori’s dried sheets are the outer wrap that holds sushi rolls together. Its crisp texture and unique taste are most likely what comes to mind when you think of sushi.
- Spirulina/Chlorella (Blue-green Algae): Touted as “superfoods” by many, these freshwater algae are typically processed into powders or capsules. Packed with protein, vitamins, and other nutrients, they’re popular additions to smoothies and health supplements.
Seaweed and Iodine
Seaweed stands out as a stellar natural source of iodine. But what exactly is iodine, and why is it vital for our health?
Unpacking Iodine’s Importance
Iodine is a trace mineral indispensable for the human body, specifically playing a pivotal role in supporting thyroid health. Quick side note: the thyroid, a tiny yet crucial gland, is located in the lower front part of your neck. It oversees regulating numerous body processes, from our metabolism and energy production to influencing our mood.
Note: Trace minerals, as the name suggests, are essential minerals that our bodies need in minimal amounts, but their role is paramount for overall health.
The average adult’s recommended daily intake (RDI) for iodine stands at 150 mcg per day for most adults, which small quantities of seaweed can easily cover. However, it’s worth noting that pregnant and nursing women have higher iodine requirements to support their health and their baby’s development.
Variability in Iodine Content
The iodine content in seaweed isn’t fixed; it can fluctuate significantly across different varieties of seaweed. According to the Linus Pauling Institute, some varieties of algae can pack a whopping 4,500 micrograms of iodine per quarter ounce of dried seaweed. To put it into perspective, just a quarter teaspoon of kelp can deliver an astounding 2,000 percent of the average adult’s RDI for iodine.
So, remember that while seaweed is an excellent source of iodine, it’s important to enjoy it in moderation. You want to snag all those good nutrients without overdoing it. A little goes a long way!
Note on Balancing Iodine Intake
Excessive iodine can cause health issues such as thyroid cancer and hyperthyroidism, a condition in which the thyroid produces too many hormones. Conversely, insufficient iodine intake can lead to symptoms like weight changes and fatigue and, over time, result in conditions like goiter (an enlarged thyroid gland).
Always consult a medical professional regarding iodine intake, particularly if you have existing thyroid conditions.
Seaweed’s Dietary Fiber
Like most leafy greens, seaweed is very high in fiber, especially soluble fiber. This type of dietary fiber dissolves in water, forming a gel-like material in the digestive system, which helps lower cholesterol and blood sugar levels, supports gut health, and assists in weight management by making you feel fuller for longer. On the other hand, insoluble fiber, which is present in fruit skins, whole wheat products, nuts, and seeds, does not dissolve in water but aids in digestion and regular bowel movements.
Dulse, a type of seaweed, boasts over 5 grams of predominantly soluble fiber per 3.5 oz serving. While kombu offers more than 6 grams, most of which is soluble. Note: According to the Mayo Clinic, women should aim for 21 to 25 grams of fiber daily, while men should target 30 to 38 grams. These recommendations are based on a 2,000-calorie diet and can vary based on age, gender, and caloric needs.
What sets seaweed apart from most plant-based greens, though, isn’t just its fiber content but the nature of that fiber. Seaweeds are rich in distinctive long-chain carbohydrates, known as polysaccharides, such as agar and carrageenans. These polysaccharides are not only good sources of dietary fiber but can also function as prebiotics. This means they support the growth and activity of beneficial bacteria in the large intestine, positively influencing gut microbiota and overall digestive health.
While probiotics are the good bacteria in our gut, prebiotics are their food source. Typically, they are fibers and certain sugars that we don’t digest or absorb but that the bacteria in our intestines feed on, which in turn supports a balanced and healthy gut environment.
In a nutshell, while the fiber content in seaweed supports digestive health much like other plant-based greens, its distinctive composition plays a crucial role in nurturing a healthy gut microbiota.
Seaweed’s Vitamin and Mineral Richness
There’s no doubt that adding a bit of seaweed to your diet not only adds delicious flavor to your meals, but it’s also a simple way of boosting your intake of vitamins and minerals.
Seaweed is an excellent source of several key vitamins, such as vitamins A, C, D, E, and K, and an array of B vitamins.
Beyond its vitamin content, this marine vegetable offers an abundance of minerals, including calcium, magnesium, potassium, copper, and iron.
Additionally, seaweed is celebrated for its diverse range of phytonutrients, especially flavonoids and carotenoids. These potent antioxidants are known for their ability to protect our cells from the harmful impact of free radicals, contributing significantly to our overall health and well-being.
Flavonoids and Carotenoids Benefits
Both flavonoids and carotenoids are phytonutrients, aka “plant chemicals,” that can be found in the cell walls of various plants. Because of their antioxidant and anti-inflammatory behaviors, it’s believed that diets rich in flavonoid/carotenoid-containing foods can aid in the prevention of certain types of cancers and cardiovascular diseases.
Fun fact: Flavonoids and carotenoids create the bright colors of fruits and vegetables. Carotenoids, specifically, give the orange hue to foods such as squash, carrots, grapefruits, oranges, and apricots.
The Potential Risks of Seaweed Consumption
Seaweed’s nutritional richness partly stems from its impressive capacity to absorb sunlight and retain oceanic minerals effectively. However, this same trait can be a double-edged sword, as it may also lead to the accumulation of potentially harmful substances found in the water, including toxins like arsenic, lead, and cadmium. This absorption typically occurs when seaweed grows in contaminated waters, often resulting from industrial pollution or poor sewage systems.
For instance, hijiki seaweed, common in Japanese dishes, has been found to contain some of the highest levels of arsenic among seaweed.
Experts generally agree that when enjoying seaweed, moderation is key. The recommendation is to indulge in this tasty sea vegetable no more than three times a week. Additionally, varying the types of seaweed and brands you consume can be beneficial.
Seaweed Brand Recommendations
Many seaweed harvesting companies in the U.S. are committed to ensuring the safety of their products. Regular testing for contaminants is a common practice, which includes checking for arsenic, heavy metals, bacteria, polychlorinated biphenyls (PCBs, industrial chemicals), pesticides, and radiation. Two such companies you might consider checking out are Rising Tide Sea Vegetables and Maine Coast Sea Vegetables. However, you should always verify the safety and testing practices of any seaweed product before consumption.
Seaweed is a nutritious and flavorful addition to your diet but it’s important to enjoy it in moderation. As with any food, balance is key. Incorporate seaweed for its unique health benefits, but remember to maintain a varied and balanced diet. Eat well, but eat wisely!
A simple (and delicious) way to add more seaweed to your diet? Check out my Healing Seaweed Soup!