The World of Aquatic Foods: A Treasure Trove of Nutrition Worth Exploring
By Sharon Palmer, MSFS, RDN
Today’s Dietitian
Vol. 25 No. 5 P. 22
Data support their nutrition, health, and sustainability benefits, so RDs can encourage clients to include more of them in their diets.
Bright green wakame seaweed mixed into a flavorful salad, and hearty mussels simmered in olive oil and garlic piled over pasta. These are but two examples of the delicious, nutritious cultural ways people have been celebrating aquatic foods—foods derived from aquatic animals, plants, or algae—over the centuries. Today, these foods from the sea, which include sea vegetables and bivalves, such as clams, mussels, oysters, and scallops, are experiencing a renaissance due to their nutritional value and sustainability.
Chefs, farmers, food producers, dietitians, and sustainability experts are excited about the potential of aquatic foods to provide a steady source of human nutrition with a smaller environmental footprint. Familiarizing your community with how to prepare and consume blue foods can reap multiple rewards.
Aquatic foods have a rich history in human diets. While many people often have visions of “luxury foods” when they think of raw oyster bars at restaurants and scallops prepared in the classic French recipe Coquilles St-Jacques, aquatic foods have offered everyday sustenance throughout the ages across many culinary traditions, including East and Southeast Asian, Hispanic, Caribbean, European, and Native American. A simple meal in Nordic countries is smoked oysters (canned) served atop dark rye bread; in Puerto Rico, you’ll find the flavorful sopa di pesacado prepared with mussels; and in Japan, sheets of nori seaweed encase sushi rolls. It’s no wonder that diets in countries bordering the sea have found a wealth of uses and recipes relying on sea vegetables and bivalves. After all, these blue foods were plentiful and easy to harvest and provided important nutrients in traditional diets. Today, sea vegetables and bivalves may be lesser known to many cultures in the United States, but they’re climbing the ladder to “superfood” status, due to their ripe possibilities, from rich flavors in culinary applications to sustainable sources of nutrients in a world looking for more climate-friendly food options.
What Are Aquatic Foods?
Aquatic foods are collectively called “blue foods” by leading reports, such as the Blue Foods Assessment, which is a joint initiative of the Stockholm Resilience Centre at Stockholm University, the Center for Ocean Solutions, the Center on Food Security and the Environment at Stanford University, and the global nonprofit EAT. Blue Foods Assessment provides an evidence-based research foundation in the field of aquatic foods, acknowledging the essential role these foods play in shifting towards more healthful, equitable, sustainable food systems.
Both wild and cultivated, aquatic foods contribute to the production of nutrients for billions of people every day, and the demand is increasing with our rising global population. Across the world, wild ocean stocks are becoming depleted, whether from overharvesting or changing environmental conditions. Thus, aquaculture has emerged as an important alternative to ensure an ample food supply of foods from the sea.1 Today, aquaculture supplies more fish (including bivalves) and seaweed for human consumption than capture fisheries and wild harvesting.2
The species diversity of aquatic foods is vast. Within the context of nutrition education on aquatic foods, the nonprofit organization Food + Planet focuses on some of the most commonly available aquatic foods in the United States, including sea vegetables (eg, dulse, hijiki, kelp, kombu, and nori) and bivalves (eg, clams, mussels, oysters, and scallops).
Sustainability of Aquatic Foods
One of the chief attributes of consuming more aquatic foods is their sustainability benefits, which occur on many levels. Indeed, blue foods are so green for the environment that they can create a sustainable swap on the plate for land-based animal proteins, such as meat and poultry, which have significantly higher carbon emissions, rates of eutrophication, and land use than bivalves and sea vegetables.3
First, bivalves contribute to food security by providing relatively low-cost, accessible, high-quality calories and protein, with high efficiency production methods and low costs.4 The bivalve farming industry is widely considered a sustainable aquacultural model because bivalves feed on plankton species, organic detritus, and bacteria, which decreases their dependence on external inputs such as feed.5 Because they’re filter feeders, bivalves absorb and neutralize excess carbon, nitrogen, and phosphorus from agricultural runoff in waterways, helping filter waters and fight ocean acidification and climate change. A single mussel can filter about two liters of water per day, according to Stanford University’s Stanford Woods Institute for the Environment.6 And that’s not all. Bivalves usually are grown without fossil fuel–based agricultural inputs, like pesticides or fertilizers, and they require no land to produce high-quality food, which is important because half of the planet’s livable land is used for agriculture.7
Similar to bivalves, sea vegetables require no land for cultivation and usually are grown without the use of pesticides or fertilizers. Notably, sea vegetables have the ability to sequester carbon; they’re 20 times more effective at carbon sequestration than land-based plants.8 According to Oceana, the largest international advocacy organization focused on ocean conservation, sea vegetables can sequester around 173 million metric tons of carbon each year, about as much as the annual emissions of the state of New York.9 In addition, sea vegetables provide marine ecosystem support, as they contribute to increased fish habitat, marine biodiversity, and ocean restoration.10
Deeper Dive Into Sea Vegetables
“Sea vegetables, which are packed with dozens of minerals and vitamins, are grown sustainably and used across cultures—eaten on their own or added to dishes to create umami-packed flavor,” says Sherene Chou, MS, RD, a culinary dietitian focused on culture and sustainability, and cofounder of Food + Planet.
Also called seaweeds, sea greens, or sea plants, sea vegetables are a vast group of edible marine algae and plants that grow in or near the ocean, rivers, and lakes. There are more than 10,000 types of seaweeds in US waterways, though just a handful of edible varieties make it to Americans’ plates. Sea vegetables traditionally have been hand-picked, but today 96% are cultivated. In the United States, those locations include New England, Alaska, Washington, and California.
Archaeological evidence shows that sea vegetables have been used in food and medicine for millennia. Today, they’re enjoyed as popular foods in Japan, Korea, China, Polynesia, Scotland, and Iceland. In fact, sea vegetables are part of the “Blue Zone” Okinawan and Mediterranean diet patterns, which are associated with health and longevity. Growing abundantly along coasts in Japan, umibudo (known as sea grapes) is an important ingredient in the Okinawan diet. Sea vegetables often take on the role of dark green leafy vegetables in many traditional diets. Asian countries, including Korea, Japan, and parts of China, consume the greatest proportion of the seaweeds harvested each year for human consumption.11
Some clients already may enjoy sea vegetables as familiar ingredients on their plates, while others may consider them new foods to be discovered. Dietitians can assess their clients’ knowledge of sea vegetables as they encourage this nutritious food. Sea vegetables increasingly are gaining attention due to their perception as an environmentally friendly option that’s also low in calories and rich in nutrients absorbed from seawater, such as iodine, iron, and vitamin A. Seaweed species range in nutrient diversity and also can contain a wide variety of phytonutrients, antioxidants, and essential fatty acids.11 For example, they contain 23 essential nutrients, including vitamin A, folate, omega-3 fats (DHA/EPA), iron, and magnesium.12 Sea vegetables also contain the following nutrients and properties that may be beneficial to health:
• iodine that helps support thyroid function and metabolism;13
• bioactive compounds, including porphyrin and fucoidan, that have potential cancer-fighting, antioxidant, and antiviral properties;14
• astaxanthin, a carotenoid pigment, that may help protect against cancer and support skin and heart health;14
• gut-friendly prebiotics that may help increase the population of friendly bacteria; 15 and
• low-to-moderate sodium levels, along with a good source of glutamic acid for umami, making them an ideal salt substitute.
While many cultures have long enjoyed sea vegetables as part of a healthful diet pattern, they can be very rich in iodine, which can be a concern for clients. On one hand, sea vegetables can help address a low intake of iodine, considering many people in the United States are not meeting their iodine needs. On the other hand, high iodine levels may be an issue, especially for those with thyroid disorders. When working with clients, compare their intake of iodine with the daily requirement of 150 mcg/day for adults (higher during pregnancy and lactation). If high iodine intake is a concern, read labels, switch varieties (species vary in iodine content due to environmental and genetic factors), and aim for moderate consumption.16 Recommend 3 to 7 g dried (about 1 tsp) or 9 to 21 g (about 1 T) of fresh (or rehydrated) sea vegetables as a side dish, condiment, or ingredient about one to two times per week.
And while increasing evidence suggests that sea vegetables may have health benefits, several questions need to be further explored, including their seasonal and geographical variations in composition and bioavailability of their bioactive compounds.17 Two large Japanese cohort studies reported the association of seaweed intake with reduced risk of CVD. However, the evidence for the effect of seaweeds on cancer is limited and inconsistent.18 A recent meta-analysis found that brown seaweeds show potential for preventing and managing type 2 diabetes, as seaweeds positively affect plasma glucose homeostasis.19 Overall, we need large-scale, well-designed, randomized controlled trials to fully describe the impacts of seaweeds on human health, including the responsible mechanisms.11
Opening Up to Bivalves
“Beyond being a highly sustainable protein choice, bivalves are chock full of essential minerals, vitamins, and omega-3 fats—offering a convenient way for people to get seafood on their plates a couple of times per week for optimal health,” says Kate Geagan, MS, RD, sustainable nutrition expert and strategic advisor and cofounder of Food + Planet. “It’s no wonder that bivalves are at the foundation of many of the world’s healthiest traditional diet patterns, such as Okinawan and Mediterranean diets.”
Clams, mussels, oysters, and scallops are bivalve mollusks (class bivalvia, phylum mollusca), characterized by having a shell made up of two hinged valves connected by a ligament. Bivalves are a type of shellfish, but they’re different from crustaceans, which have exoskeletons, segmented bodies, and jointed appendages.
Bivalves have been hand-harvested for millennia, thus, becoming an important source of nutrition for coastal communities around the world. Today, the aquaculture of bivalves is considered a sustainable, resource-efficient method of increasing seafood production while bringing health benefits to populations and economic benefits to coastal communities. With more than 20,000 species of bivalves, they come in an array of colors, shapes, and sizes, stretching across many cultures and food traditions; from local mussels featured in the Spanish dish Mejillónes de Galicia to green-lipped mussels found only in New Zealand, which are a staple in Indigenous Maori diets.
In some cultures, bivalves are staple foods, such as Thailand’s clams in coconut curry broth, while other cultures enjoy them for special meals, such as a New England clambake. Consumers’ knowledge of how to choose and prepare bivalves is shaped by cultural and demographic factors, as well as proximity to coastal areas. Bivalves are a powerhouse of good nutrition. Recommend a 3-oz cooked serving size of bivalves at least twice per week as part of the Dietary Guidelines for Americans’ recommendations for seafood intake. Here’s a look at some of their nutritional attributes:
• Packed with protein, cooked clams, mussels, and scallops contain 15 to 20 g per 3-oz serving.
• They’re an excellent source of omega-3 fats, with mussels containing more than 700 mg of DHA and EPA per serving.
• They provide a micronutrient boost of vitamin B12 and other essential minerals, including zinc, choline, and selenium. Mussels and oysters contain more iron than red meat.20
Safety of Aquatic Foods
Like other fish and seafood, bivalves are susceptible to environmental contaminant accumulation in their soft edible tissues and need to be closely monitored for the presence of toxic constituents such as heavy metals and microplastics.21,22 The source of bivalves is an important consideration when determining the level of possible contaminants. Seaweeds are subject to similar heavy metal and microplastic contamination risks, which are most often observed in perennial species.23 Regarding food safety outbreaks from bacterial contamination, bivalves produced in the United States are heavily monitored at harvest based on water quality standards determined by the FDA. All imported seafood (including bivalves) is required to be FDA approved. Unlike most other food industries, bivalve suppliers and retailers maintain a routine tracking system with geotagging of locations and harvest dates for tracing and preventing outbreaks.24 As it pertains to food allergies, not all people with shellfish allergies have bivalve allergies, which is much less common.
Quality Evaluation Programs
Several organizations offer guidance on choosing safe, healthful, sustainable aquatic foods, including the following:
• Natural Resources Defense Council Smart Seafood Buying Guide puts clams, mussels, oysters, and scallops on their list of seafood choices with the least amount of mercury.
• Environmental Working Group considers mussels a “Best Bet” and oysters as a “Good Choice,” factoring in issues like low mercury, high omega-3s, and high sustainability.
• Monterey Bay Aquarium’s Seafood Watch ranks bivalves and sea vegetables as a “Best Choice” for sustainability and health.
• Aquaculture Stewardship Council certification verifies safe, sustainable practices are upheld for bivalve and sea vegetable cultivation.
• Marine Stewardship Council certification signifies practices have been followed to ensure safe, sustainable production of bivalves and sea vegetables.
Putting It Into Practice
Data collected in a 2022 Food for Climate League and Food + Planet survey found that clear, simple messages around health, wellness, and sustainability work best when it comes to educating the public on the consumption of aquatic foods. Dietitians should educate clients on the benefits of aquatic foods, as well as how to include them in familiar formats. RDs can host a blue foods cooking demo in their hospitals, clinics, or communities and provide information in newsletters, blogs, or social media. Receive more resources and recipes on aquatic foods by visiting eataquaticfoods.org.
— Sharon Palmer, MSFS, RDN, is cofounder of Food + Planet, and author of the upcoming book The Plant-Powered Plan to Beat Diabetes.
References
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