Seaweeds are versatile “sea vegetables” and “sea herbs” that can inspire play and creativity in the herbal kitchen or serve as the base for numerous holistic health protocols in your home, apothecary, or in a clinical setting. There are many ways to incorporate seaweeds into these realms—integrating them as foods in daily life or preparing extracts that highlight specific phytochemicals for use in herbal-medicine preparations. This article provides a foundational overview of best practices for working with seaweeds across the extraction categories familiar to herbalists—teas, decoctions, tinctures, oils, and vinegars—and offers guidance for crafting preparations that honor their unique healing gifts while supporting a range of therapeutic applications.
(If you’d like a broader overview of seaweeds as food and medicine—including iodine nuance, polysaccharide actions, and species selection—you may also enjoy my earlier overview essay Seaweeds in the Herbal Kitchen.)
Food as Medicine: Eating Seaweeds as a Foundational Practice in Marine Herbalism
Seaweeds are one of our greatest food-based medicines; in fact, they could be considered one of our lesser-known “superfoods.” They contain a wide range of nutrients and phytochemicals—often in significantly higher concentrations than most land-based foods. The following simple guidelines offer a clear framework for incorporating seaweeds safely and effectively into your daily diet.
Eat small amounts of seaweed daily.
As a food-based medicine, eating seaweeds is the best way to use them for general nutritive and health-supportive purposes—they don’t require complicated extraction techniques for you to receive their benefits. Using them in a water-based or rehydrated form allows access to most of their nutrients and medicinal compounds. And because these nutrients are so concentrated, you only need small amounts—eating a little every day is one of the best ways to build a relationship with seaweeds and steadily replenish the body with their dense and diverse nutrients.1 Small amounts daily can also help folks who are new to eating seaweeds cultivate specific seaweed-digesting gut bacteria that support digestion and absorption of seaweed constituents.
What is a small daily amount? The generally recommended dosage for adults (approx. 175 lbs) is 3–5 g dry weight (DW) daily or 1–1.5 oz per week—a standard established by my mentor, Ryan Drum, and confirmed in various other international resources about seaweed intake. About 5 g equals roughly 1 teaspoon of powdered seaweed, depending on the fineness of the powder (see image below). The average intake of seaweeds globally ranges from 2.6–8.5 g/day DW and is higher in Asian countries that have a culinary tradition steeped in seaweed use. While most sources recommend the lower end of this typical consumption range, some experts have observed notable benefits from the higher end (8.5g/day DW).
Eating small amounts daily also generally keeps consumption within safe limits for contaminants as established by international food safety organizations. Seaweed contamination and nutrient levels vary widely by growing conditions, location, and species. Contamination and consumption safety are also complex and highly contextual topics: just because a contaminant is present in the water does not mean the seaweed will absorb it—and just because a contaminant is present in the seaweed does not mean it is bioavailable to the human body. This topic is explored in more detail in my ongoing Seaweed Detox series. Regardless, generally speaking, 3–5 g daily is a good balance nutrient-wise for most people and low-risk with regard to safety concerns. A lower, more cautious dosage of 3–7 g once or twice per week is recommended by some researchers for certain health conditions or low-iodine or other therapeutic diets (Vogliano et al., 2024).
With these standards in mind, I also want to emphasize that optimal seaweed consumption amounts are highly individual. Some of the reasons for this include:
The iodine threshold varies significantly from person to person and some people may respond to iodine differently due to gut health or nutrient status.
Everyone is unique in their health and lifestyle picture, in the foods that they eat on a daily basis, and in herb and nutrient needs.
There are also several situations where seaweeds may best be used in limited amounts or not at all (see Storage, Stability, and Safety section).
Eat the seaweed rainbow (reds, greens, and browns).
Since nutrient and phytochemical profiles of seaweeds are highly variable—perhaps more so than land plants—depending on season and growing conditions, among other factors, mixing and matching seaweeds is one of the best ways to get a more balanced complex of nutrients and bioactive compounds into your diet. Because seaweeds from each class tend to have similar nutrient and phytochemical profiles, mixing from the three main classes—red (e.g., Irish Moss/Chondrus crispus, Dulse/Palmaria palmata), green (Sea Lettuce/Ulva spp.), and brown (kelps such as Nereocystis luetkeana and Laminaria/Saccharina spp.; Bladderwrack/Fucus spp.)—ensures a diversity of nutrients and phytochemicals.
Recommendations for proportions from each seaweed class are variable. While Ryan Drum has recommended eating brown to red seaweeds in a ratio of 2:1 because of the generally higher mineral profile of brown seaweeds, other folks recommend eating brown seaweeds such as kelp, kombu, and bladderwrack only 1-2 times a week. Certainly this lower brown seaweed consumption rate may be more appropriate for some folks if the seaweeds are uncooked and there is concern about too much iodine consumption. There are few green seaweeds commonly available or used in food-based preparations—the main one is Sea Lettuce (Ulva spp.), a lower iodine-containing seaweed with a mild flavor that is good for daily use.
Eat a variety of seaweed species.
Varying the species you eat within each class is also a way to diversify the nutritional compounds you are getting from seaweeds. Despite similarities in nutrient and phytochemical content amongst seaweeds of the same class, each species tends to accumulate more of certain minerals and less of others and has its own unique polysaccharide profile and content (more on seaweed polysaccharides in a moment). For instance, Bullwhip Kelp (Nereocystis luetkeana) is especially high in minerals (up to 40% dry weight), particularly potassium and magnesium salts, compared to other brown seaweeds, and kombu (Laminaria/Saccharina spp.) has a significantly higher iodine content (up to 5000 µg/g) compared to other brown seaweeds such as Wakame (Alaria spp./Undaria pinnatifida) (295 µg/g).
Eat cooked and uncooked seaweeds.
Varying your use of cooked and uncooked seaweeds as an integrated part of your diet helps to provide a balance of seaweed nutrients and phytochemicals, which can be are more or less available, depending on the type of preparation. Soaking and discarding soak water—or cooking and allowing steam to evaporate—can significantly reduce the iodine content of seaweeds if that’s a concern. Cooking or decocting seaweeds in water can also enhance bioavailability of certain nutrients such as minerals, polysaccharides, amino acids, and some vitamins (Mabeau & Fleurence, 1993; Holdt & Kraan, 2011) while uncooked (but usually dried) or gently rehydrated seaweeds retain the more heat-sensitive compounds such as essential fatty acids and vitamins (such as Vitamin C), carotenoids, and polyphenols.