People who know good nutrition probably also know a diet rich in omega-3 fatty acids promotes cardiovascular health and brain function. They might even know that seaweed (better known as sea vegetables) is a nutrient-dense food that can be a source of omega-3 fatty acids and other marine nutrients. Indeed, some internet articles claim that seaweed is a good or even rich source of omega-3s. Are sea vegetables really a rich source of omega-3s? How much do they contain? Are some sea vegetables better sources than others? Read on to learn more (and click on the blue links for additional information).
Essential Facts About Essential Fats
Dietary fat can be a murky topic, especially when scientific jargon such as “polyunsaturated,” “trans fats,” “partially hydrogenated,” and other technical terms gets used. Not so long ago, it seemed like a simple topic: fat was bad and a low-fat diet was healthy. We now know this understanding was too simple. Fat is as essential to human health as is protein, minerals, carbohydrates, and vitamins, but some types of fat are more essential than others. The issue is not necessarily one of how much fat is too much, but rather what kind of fat to consume and what kind to avoid.
The internet has a wealth of accessible, easy-to-understand information on the topic of dietary fat. So rather than devote several paragraphs, we will pare it down to six bullet points. With that done we can then move on to the role sea vegetables play in a healthy fat diet.
Six Fat Bullets
- People require dietary fat (also known as lipids or fatty acids) for energy, cell growth, and nutrient absorption; for brain function and eye health; to control cholesterol and blood pressure; and to regulate or produce certain hormones.
- The four major dietary fatty acids in order of least to most healthy are trans fats, saturated fats, monounsaturated fats, and polyunsaturated fats (sometimes called PUFAs). They all contain nine calories per gram, but their molecular structures and physiological effects differ.
- Trans fats naturally occur at low levels in meat, but most are created by an industrial process known as hydrogenation where hydrogen is added to vegetable oils to make them more solid and thus more useful in processed food such as baked goods. These products are often labelled as containing “partially hydrogenated oils,” and they should be avoided. Trans fats are used in margarine, which ironically was once considered a healthy alternative to butter before scientists learned more about the adverse health effects of hydrogenated oils.
- Saturated fats are typically solid at room temperature, in part because their carbon-chain bonds are “saturated” with hydrogen atoms. Saturated fats are found in dairy foods, meat, and oils from coconuts, palm fruits, or palm kernels. The role of saturated fat in heart disease and stroke is still under debate, but the American Heart Association recommends getting no more than 5% to 6% of your calories from saturated fats because they elevate cholesterol levels. Although the body needs cholesterol to build cells and manufacture vitamins and hormones, our livers synthesize what we need, and dietary saturated fat is thought to elevate levels of “bad” low density lipoprotein (LDL) cholesterol.
- Monounsaturated fats have only one unsaturated double-carbon bond in their molecules. They are typically liquid at room temperature but become solid when chilled. Monounsaturated fats are considered healthy because they may reduce inflammation, improve insulin response, and lower the risk of heart disease and stroke by reducing LDL cholesterol and increasing “good” high density lipoprotein (HDL) cholesterol. Olive oil, nut oils, and avocados contain monounsaturated fats, and the cells of your body also manufacture them.
- Polyunsaturated fatty acids (PUFAs) have more than one unsaturated double-carbon bond. Like monounsaturated fats they are liquid at room temperature and harden at colder temperatures. Plant-based oils typically contain varying proportions of both monounsaturated and polyunsaturated fats, with soybean oil, corn oil, and sunflower oil being high in polyunsaturated fats. Oils from seeds and nuts also contain them, as does most seafood. Polyunsaturated fats come in various forms, some of which the body requires but has limited capacity to manufacture itself. These essential fatty acids must be obtained in our diets. Two of the most important PUFAs are the omega-6 and omega-3 fatty acids found in sea vegetables and other seafood.
Fatty acids are often identified using a numbering scheme based on the number of carbon atoms they contain, number of double bonds, and double bond location. This diagram shows oleic acid, a monounsaturated fatty acid found in avocados and canola oil. Sourced from Course Hero.
PUFAs: A Question of Balance
The ratio of certain polyunsaturated fats in the diet is thought to play a role in everything from cardiovascular health to Alzheimer’s disease. For some time, a popular media narrative has been that a high ratio of omega-6 PUFAs relative to omega-3 PUFAs can cause poor health outcomes. According to this narrative, excessive intake of omega-6 PUFAs, such as those found in soybean or other vegetable oils, causes inflammation and other health problems. Omega-3 PUFAs, on the other hand, are anti-inflammatory. However, studies indicate that the real culprit isn’t so much an excess of omega-6, but rather a deficiency of omega-3 PUFAs in our modern diets. In other words, the ratio may be less important than the total amount of omega-3s we get on a daily basis.
Omega-6 fatty acids are found in leafy greens, vegetable oils, and nuts and seeds. The most common form, linoleic acid (not to be confused with alpha-linolenic acid (ALA), which is an omega-3), is linked to health benefits such as lower rates of heart disease and possibly reducing cholesterol. Omega-6 fatty acids are also said to promote inflammation because the body converts linoleic acid into arachidonic acid (ARA), which in turn can be converted into pro-inflammatory eicosanoids. However, this may be an overly simplistic view. Some eicosanoids are anti-inflammatory and our bodies also convert linoleic acid into gamma-linolenic acid (GLA), a compound that may fight inflammation. This conversion is thought to depend on having adequate stores of magnesium, zinc, and vitamins C, B3, and B6, highlighting the importance of a balanced diet. Omega-6 fatty acids are relatively abundant in the average American diet, whereas omega-3 fatty acids are not. This imbalance is cited as a reason for many Americans’ poor health compared to other countries where citizens consume more seafood and omega-3s.
Research links high omega-3 intake with heart, eye, and immune health, lower inflammation, increased bone density, and longevity. The evidence showing that high omega-3 blood levels improve cardiovascular health is especially strong. Omega-3 PUFAs are also thought to play key roles in brain development and mental health. In this regard, it is significant that PUFA’s, predominately arachidonic acid (ARA) and docosahexaenoic acid (DHA), make up almost 20% of total brain weight and 80% of total membrane phospholipids. Studies suggest that having adequate or high levels of omega-3 PUFAs may improve cognition and mood, and maybe even slow the progression of Alzheimer’s disease.
Seafood is one of the best sources of omega-3 PUFAs, but modern Western diets are characterized by being high in processed foods and low in seafood consumption. This means they contain high amounts of Omega-6 fatty acids and are deficient in omega-3s compared with the traditional diet on which humans evolved. This results in an out-of-whack ratio of omega-6 to omega-3 fatty acids. A good ratio is considered to be about 4:1 or less, but Americans tend to consume about 10 or even 20 times more omega-6 than omega-3. Japanese people who eat processed foods but also typically include a lot of fish in their diet have a ratio of about 4:1. This is thought to be one of several contributing causes as to why Japan has lower rates of coronary disease and cancer compared to the United States.
The three main omega-3 fatty acids essential for human health are α-linoleic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA is mostly found in terrestrial plant-based foods, while EPA and DHA are primarily found in marine algae, shellfish, and finfish, especially fatty fish such as salmon, herrings, anchovies, and cod. The body converts ALA into EPA and DHA, but ALA is poorly absorbed and the conversion process is not very efficient. Moreover, EPA and DHA are extremely bioavailable.
How much Omega-3 should I get?
It has been understood since the 1990’s that omega-3 fatty acids are good for health. In 1994 the UK Committee on Medical Aspects of Food Policy recommended a daily intake of 0.2 g (200 mg). This advice was revised in 2004 to recommend that people consume 1-4 portions of marine fish per week, which translates into 0.4 g to 0.9 g of omega-3 per day. The World Health Organization recommends 200-500 mg per day for Adequate Intake. Pregnant and lactating people are especially advised to ensure adequate omega-3 intake because of its important role in fetal and infant brain development. People with a history of heart disease, depression, or experiencing cognitive decline may benefit from consuming more than 500 mg; some studies have seen encouraging results with up to 6 g per day.
Based on current evidence, daily intake of 1-2 grams (1,000-2,000 mg) of omega-3 seems advisable and safe for most people. At minimum, people should probably consume about 250 mg per day. However, a major dietary survey of the American population found that average adult intake was only about 52-54 mg per 1,000 calories. Even with a 3,000-calorie diet this falls short of recommendations! Since vegetarians and vegans do not consume finfish and shellfish, and because most plant-based foods are poor sources of EPA and DHA, vegetarians and vegans are especially at risk for insufficient omega-3 intake.
The same survey found that only about 0.8% of the population uses omega-3 supplements. A variety of supplements based on fish or algal oils that deliver anywhere from 200 mg to 3 grams of omega-3 are available. However, supplements should be just one aspect of a holistic nutritional approach for optimum health, and some people may find them cost prohibitive. A recent publication by the National Institutes of Health (NIH) concluded that whether omega-3 supplements are beneficial to health remains uncertain. Other studies have found that supplements may contain less omega-3 than what they claim. Including seafood (especially fish) in the diet is equally if not more effective than taking supplements. In their small way, sea vegetables can also contribute to omega-3 intake.
Sea Vegetables and Omega-3s
Fish and shellfish, like humans, get most of their omega-3 fatty acids from their diet, with microalgae being the ultimate source at the bottom of the food chain. Microalgae, also known as phytoplankton, are microscopic single-cell organisms that use photosynthesis to convert carbon dioxide, water, and other molecules into biomass and nutrients, including omega-3 fatty acids. There are thousands of species of microalgae, and depending on species, their lipid content can range from 2% to 80% on a dry weight basis (DWB). Microalgae are consumed by shellfish or by krill and other plankton, which in turn get eaten by finfish, thus transferring life-essential omega-3s up the food chain. Some popular omega-3 supplements, including those used to boost milk DHA levels, are based on microalgal oils grown using controlled industrial processes.
Macroalgae also synthesize omega-3 fatty acids, but they have a much lower total lipid content than microalgae. Though some sea vegetables may contain up to 12% fat DWB, most have only about 2-4%. This means a typical 3-8 gram serving of sea vegetables might contain only between 60-320 mg total fat. Omega-3 as a percentage of total seaweed lipid content ranges between 5% or less to as high as 50%, depending on species, season, and locale. At the most, this means an 8-gram serving containing 4% fat, 50% of which is omega-3, might contain 160 mg of omega-3. However, 8 grams is a large serving and 4% fat with 50% omega-3 is an optimistic scenario. One study concluded that on average, 130 to 160 grams of dulse would have to be consumed every day to provide 250 mg of EPA. For this reason, scientists advise that one should not rely on sea vegetables alone for omega-3.
So why then do some web sites and nutritional experts say that low-fat sea vegetables are a good sources of omega-3s? This statement may be accurate in the sense that most of the fat found in sea vegetables is the good kind our bodies need. However, the FDA has strict rules about when terms such as “good source” or “high in” can be used on food labels, and we at Maine Coast Sea Vegetables are careful about making such claims. A "good source" claim may be made only when a food contains 10-19% of the RDI or DRV (Daily Reference Value; shown on the label as the % Daily Value (%DV)). The FDA has not established a Daily Value for omega-3s, and "high" or "good source" claims may not be made for nutrients lacking an established FDA daily value.
Which Sea Vegetables Contain the Most Omega-3?
Even though sea vegetables are a low-fat food, they can still help boost our intake of omega-3s and other essential nutrients. With that in mind, are some sea vegetables higher in omega-3 than others?
Quite a number of research articles have been published in the past 20 years reporting the lipid composition of various seaweed species. Most of them find that popular sea vegetables such as kombu, wakame, laver, and dulse have fat contents ranging between 1.5-4%, which qualifies them as low-fat foods. Many of these same studies also find that most sea vegetables are relatively rich in omega-3 PUFAs as a percentage of their total fat. EPA omega-3 is usually the dominant PUFA, especially in red algae such as dulse and laver, while DHA omega-3 is rarely detected in most species. A study comparing nine species of North Atlantic red algae from Denmark found that although dulse only contained about 1.2% fat, 41.7% of the total fat was EPA omega-3, the highest of the nine species.
Brown sea vegetables are sometimes found to contain more lipids than red sea vegetables, but with a lower EPA omega-3 content. Rockweed (Ascophyllum nodosum) and bladderwrack (Fucus vesiculosus) were reported to contain 3.62% and 3.75% lipid, respectively, with about 43-48% of that being made up of PUFAs. Less than 9% of the PUFAs were EPA omega-3 and no DHA omega-3 was detected in these species. The most commonly distributed fatty acid in brown algae was found to be arachidonic acid (ARA).Green sea vegetables such as sea lettuce (Ulva sp.) have lipid profiles more closely resembling those of land plants, with linoleic acid and alpha-linolenic acid (ALA) being among the dominant PUFAs. Palmitic acid is also a dominant fatty acid in Ulva. Palmitic acid is a major lipid component of human breast milk and our bodies require it, but in adults it can raise low-density lipoprotein (LDL) and cholesterol.
Colder temperatures tend to increase the fat content of sea lettuce and many other sea vegetables as well, with a corresponding increase in PUFAs. A study comparing lipid profiles between 15 species of tropical and temperate seaweeds found that more northern species had a higher proportion of omega-3 PUFAs. All of the sea vegetables sold by MCSV are harvested from cold northern waters and most are harvested in the spring, when lipid content is still relatively high, and into the summer, when lipid content diminishes.
Which Sea Vegetables have the Best PUFA Ratio?
As discussed earlier, many scientists and media accounts state that the optimum ratio of omega-6 to omega-3 is 4:1 or less. Most sea vegetables perform very well in this regard. A study that examined fatty acid contents and profiles of 16 macroalgae collected from the Irish coast found that most had an omega-6/omega-3 ratio close to 1. The ratio in brown species ranged from 0.6 to 2.8, and dulse had the lowest ratio of the red species, at 0.04. Other studies support these findings. For example, a study done on laver (Porphyra) from Maine found P. amplissima had an omega-6/omega-3 ratio of 1:3 and the ratio in P. umbilicalis was 1:2. A study conducted in Norway on dulse, sugar kelp, and Alaria found that all three had low omega-6/omega-3 ratios, but dulse was the lowest due to the high percentage of EPA it contained.
Sea Vegetables for Health
By now, it should be apparent that sea vegetables are low in fat but that the lipids they do contain are mostly the kinds that promote heart and brain health. Moreover, they all have favorable omega-6/omega-3 ratios. Recommending one sea vegetable as a better lipid source over another is probably not advisable without accounting for the other nutritional and health benefits they offer. For example, those who want to boost their iodine intake as well as improve their lipid intake might want to consider a brown species over a red species, because even though dulse may have a somewhat better lipid profile than Alaria, it contains less iodine. For some, the opposite scenario might be more important.
Regardless of species, ease of use and flavor will play big roles in determining whether one wants to eat it every day. One tried and true approach is to combine a milled form with a whole leaf form. Milled sea vegetables, whether they be dulse flakes, rockweed granules, or bladderwrack powder, are easy to use as a seasoning or nutrition booster in just about any dish. They can be added by the teaspoon or tablespoon to smoothies, cooked cereal, broths, or whatever else it is you like to eat every day. Most of our species are available in pure milled forms in quantities ranging from sample size to 10 lbs. Sea Seasonings are convenient shaker blends for everyday use as a salt replacement or flavor enhancer for everything from scrambled eggs to popcorn and soup to roasted nuts.
Most of our species are also available year-round as whole leaf. Some, such as dulse, are great right out of the bag, while others, such as sugar kelp or Alaria, are equally good in broths or various recipes. Our website has a range of recipes that should please just about anyone, and several good sea vegetable cookbooks have been recently published, in addition to our timeless classic, Sea Vegetable Celebration.
For maximum benefit, we suggest consuming 3-7 gram per day using combinations that include a brown, red, or green species. One such combination is to use kelp granules as an all-purpose seasoning and smoked dulse leaf for snacking and in recipes, but other combinations are certainly possible. The important thing for optimum nutrition is to find a combination of species, or even just a single species, that you can easily enjoy every day!