The Critical Differences Between Omega-3 Fats From Plants and Marine Animals

Story at-a-glance -

  • Omega-3 from plant sources do not provide the same benefits as that from marine animals, as the omega-3 found in plants can’t be converted by your body into the omega-3 you find in marine oils
  • ALA is a precursor to EPA and DHA. However the conversion rate is extremely small, so you cannot eat enough plant-based omega-3 to achieve healthy levels of EPA and DHA
  • Short-chain fatty acids like ALA are a source of energy, while the long-chain fatty acids DHA and EPA are structural elements that actually make up your cells

By Dr. Mercola

Omega-3 fats are essential polyunsaturated fatty acids (PUFAs) your body needs for digestion, muscle activity, blood clotting, visual acuity, memory and much more. They're particularly important for proper cell division and function of cell receptors.

These fats, although originally synthesized by microorganisms in the oceans, are ideally obtained from the consumption of small fish that are free of toxins.

Most omega-3s are considered "essential fats" as your body cannot make them. You have to get them from your diet. However, there's plenty of confusion when it comes to which omega-3 fats are required for optimal health.

Can you substitute marine animal-based omega-3 for plant-based omega-3? And is there really a difference between the omega-3 you get from fish, versus that from krill? In this interview, Nils Hoem, Ph.D., a Norwegian scientist specializing in omega-3 phospholipids, answers these and other crucial questions.

The 2 Sources of Omega-3

You can obtain omega-3 fats from both plants and marine animals like fish and krill. However, it's really important to realize that these sources provide DIFFERENT TYPES of omega-3, and they are NOT interchangeable.

If for whatever reason you choose to avoid all animal-based foods, you simply cannot substitute with plant-based omega-3 and think you've covered all your omega-3 needs.

Both plant- and animal-based omega-3 have their first double-bond in the third position — hence the name "omega-3." However, the length of the carbon chain of each omega-3 fat makes a significant difference when it comes to bioavailability and biological effect.

  • Marine animal-based omega-3 (fatty fish, fish oil and krill oil) primarily contain docosahexaenoic acid (DHA), a long-chained PUFA consisting of 22 carbons and eicosapentaenoic acid (EPA), which has 20 carbons.
  • Plant-based omega-3 (found in flaxseed, flaxseed oil, chia seeds, walnuts and leafy greens, for example) contain alpha-linolenic acid (ALA), a shorter-chained PUFA consisting of 18 carbons. They are completely devoid of DHA and EPA.

Why You Cannot Substitute Animal-Based Omega-3 With Plant-Based Omega-3

ALA is a precursor to EPA and DHA. However, an enzyme is required to convert the shorter 18 carbon ALA into long-chained omega-3. In most people, this enzyme doesn't work very well and hence the conversion rate is exceptionally small.

Typically, less than 1 percent of the ALA is converted to EPA. Some studies have found the conversion rate to be as 0.1 to 0.5 percent.1 Your conversion is also dependent on having adequate levels of other vitamins and minerals.

So, while a tiny amount of the ALA you consume can be converted by your body into long-chain omega-3, it's a highly inefficient strategy and nowhere near as helpful as supplying "straight" DHA and EPA from marine sources. It pays to beware of misleading and confusing advertising here. As noted by Hoem:

"Chemically you could name any fatty acid that has its first level bond in the third position an omega-3 fatty acid. Increasingly we see different players trying to use the label 'omega-3' as a general label for healthy or a general label for having biological effects in line with EPA and DHA.

That's simply not the case. It's a kind of mislabeling. [Ed. Note: Omega-3 eggs are an example, as the hens were not actually fed marine animal-based omega-3.]

We should be distinct in saying marine omega-3s, or we should say long-chain omega-3s; that's correct. But the 18-carbon-chain omega-3s, they do not have documentation about biological effects. In fact, meta-studies ... come out with them being neither bad nor good.

We turn a very small amount of them into long-chain omega-3 fatty acids, but it really doesn't help as much. There may be genetic differences as told by a professor from Japan ...

But all in all, you cannot [attach] the same type of biological and health effects on the shorter-chain omega-3s as you can with EPA and DHA.

In Norway, for example ... we had a big headline in our main newspaper telling us that reindeer meat contains as much omega-3s as cod, which is technically correct, but it really confuses people.".

Additionally it is important to know that you should NEVER take flax oil or use ground flax seed unless it is freshly ground because the highly perishable ALA will be oxidized. If you have any throw it away immediately. I take one tablespoon of organic flax seeds a day but they are soaked overnight and blended into my smoothie.

How Different Lipids Affect Your Health

The short-chain or plant-based ALA does not provide the same health benefits as EPA and DHA. And there's no evidence to show it can significantly be converted by your body into the longer-chain EPA and DHA fats.

But there's even more compelling evidence that you cannot replace animal-based omega-3 with plant sources. Hoem's research shows that after eating a meal of salmon or taking krill or fish oil, the fatty acid level in your plasma (blood) will remain elevated for more than three days afterward.

"Your body works on its distribution, redistribution and re-redistribution for three days. That's hardly consistent with being food," he says.

On the other hand, the short-chain omega-3s (ALA) are rapidly absorbed, peaking a couple of hours after ingestion. Within 10 hours, they're gone. This suggests your body is using long- and short-chain lipids (fats) very differently.

According to Hoem, the short-chain fatty acids are simply food — they're a source of energy — while the long-chain fatty acids, those with 20 and more carbons, especially EPA and DHA, are structural elements that actually make up your cells. This is a MAJOR difference between plant- and animal-based sources.

EPA and DHA have many biological effects, most notably anti-inflammatory activity and communication within the cell and between cells.

Another tell-tale sign suggesting the importance of EPA and DHA is their half-life, which may be as long as 60 days for DHA. Your body tends to accumulate and hold on to it and not want to let it go.

EPA is used up much faster, in about 80 hours, in part because it's a smaller molecule, but also because it behaves differently from DHA.

According to Hoem, EPA is "the mother" of docosapentaenoic acid (DPA), a third member of the long-chained omega family that has gained a lot of interest lately. The main difference is your body makes DPA. When you eat EPA, a proportion of it becomes DPA.

EPA and DHA Are Crucial for Health

DHA is especially important, as it is a component of every cell in your body, and it's particularly crucial for your brain. More than 90 percent of the omega-3 fat found in brain tissue is DHA, and the development of a normal brain in a fetus is dependent on the availability of DHA. All other omega-3 fats are found only in trace amounts in your brain, including ALA, regardless of how much ALA you consume.2

There are actually specific transporters for long-chained omega-3s in your blood-brain barrier, the placenta (in pregnant women), and likely also in your liver, which transport these molecules in a very precise way into the cell membranes where they belong. No such transporters exist for the short-chained omega-3s.

So please, don't make the mistake of confusing plant-based (short-chained) and animal-based (long-chained) omega-3, as doing so could have severe health consequences. You absolutely need animal-based omega-3 (DHA and EPA), and you simply cannot obtain the same benefits from plant-based sources.

I'm not vilifying plant-based omega-3 fats. You do need ALA; you just don't need an excess of it. And don't think you convert that ALA to EPA and DHA, because you just can't. That said, ALA is a very healthy fat that serves its own useful purpose.

Identifying Healthy Sources of Animal-Based Omega-3 Fat

The next practical question becomes: how do we identify healthy sources of marine-based omega-3? Healthy, meaning, uncontaminated by toxins and structurally intact with a high rate of absorption. Those are three big issues. If you make a mistake on one of them, you're not going to be as successful in integrating these important molecules into your cell membranes.

Omega-3 fat bound to ethyl esters — a synthetic form of marine omega-3 fat used in some pharmaceutical-grade omega-3 supplements — appears to have a particularly poor absorption rate. According to Hoem:

"If you have it together with a decent meal, ethyl esters will be taken up. But I have seen experiments done where the ethyl esters simply pass through without being absorbed whatsoever."

This synthetic form of marine omega-3 fat is a fatty acid that has been sliced off from its triglyceride source, and then ethylated with ethanol. The rationale for doing this is to have a safe way of purifying it to meet pharmaceutical standards. This way it can also be standardized and highly concentrated. One of the general principles for healthy eating is that the less refinement a food goes through, the better and this certainly appears to be true in the case of omega-3 supplements.

"I would maintain that the best way of getting your marine omega-3s would be to eat safe, fresh fish. Whenever I'm asked, that is my standard answer," Hoem says. "I lectured in physiology for almost 20 years. I told my students about how fats are being taken up. They get down into your gut.

There are lipases in your gut that will decompose them and they will be re-synthesized in the erythrocyte. They will be taken up and they will be re-synthesized. They will be made into other microns (small emulsions). Then they will flow through your lymph ... Now, while that is mostly right for the triglycerides, I never even considered what happens with phospholipids.

With phospholipids, we've become aware of that it isn't exactly like that. In phospholipids, at least part of the omega-3s is taken up as lysophosphatidates. They are water-soluble enough to be taken directly up into the blood. They're then passed into the liver and are redistributed before they are sent into systemic circulation.

That explains part of why it takes so long to redistribute those fatty acids. I think we've been grossly underestimating how complicated this is. We've been underestimating the very fundamental problem our bodies have with regards to the uptake of fat. Fats are not water-soluble. Our bodies have to go through very radical techniques to emulsify these fats after transporting [them] into different parts of our body."

Lipid Groups

The two largest groups of lipids (fats) are both called glycerol lipids, as the steroid hormone to which you add your fatty acids is glycerol, a trivalent alcohol. Three fatty acids can be added to this little glycerol molecule. This turns it into a triglyceride, which you find in both fish and vegetable oil. This type of fat is an excellent energy source, although high fasting triglyceride levels in your blood is also a marker or risk factor for heart disease.

The other lipid molecule also starts out with glycerol. To this you add two fatty acids, but instead of a third fatty acid, either a phosphate or a choline is added. This seemingly small difference renders this lipid into something "quite beautiful," to quote Hoem.

"If you take this molecule into water, it spontaneously forms membranes or sheets. This molecule really is the molecule that forms the sheets that every cell in our body is made of. If I were to select a molecule of life, it would not be DNA; it would be phospholipids. Phospholipids make us. It's impossible to think of life without this membrane ... Everything that makes up a cell can be made from these membranes.

[So] we have two glycerol lipids. One of them is not water-soluble at all. It will not form any sheet because it's completely hydrophobic and is basically used for energy. Then the other type makes us. We're made of it."

Krill Oil Has a Unique Fat Profile

Indeed, fats are a complicated business, and minor differences can have a big impact. For example, there are two key differences between the phosphatidylcholine found in krill and that found in soybeans and sunflowers. Hoem explains:

"Krill is quite unique with respect to the fact that almost all of its phospholipid is phosphatidylcholine (PC). There is a little bit of phosphatidylethanolamine, but otherwise there are two other types — phosphatidylserine (PS) and phosphatidylinositol (PI) — that you really don't find in krill at all.

For example, in lecithin from soybeans, you will find pretty much equal amounts of the four different types. The other difference is the fatty acid composition. Krill has very specific fatty acid composition. Almost every PC molecule has one EPA or DHA. In the other possible position, you will find either oleic acid or palmitic acid ... That describes the phosphatidylcholine you find in krill oil, which is pretty unique."

So krill oil contains all three types of fat: saturated, monounsaturated and polyunsaturated. However, it bears noting that this only applies to Antarctic krill (Euphausia superba). Krill is found in oceans around the globe, but only krill from the cold waters of the Antarctic will contain this unique lipid profile — likely because it allows the krill to survive the cold.

How Krill Oil Is Extracted

Krill are plankton that feed on algae. However, it must be below freezing in order for them to be able to digest it. In your stomach, it's 98.6 degrees F (37 degrees C), and your lipases are really active at that temperature. If you dropped the temperature down to freezing, your lipases wouldn't work.

But krill lipases are able to digest at really low temperatures. This means that if you leave a bucket of krill in a frozen state, it will still decompose. To inactivate the enzymes you have to heat them. This is done right on the krill boats, immediately after harvest. The krill is heated for a very brief period of time to inactivate the enzymes and kill off bacteria. After that the krill are dried to remove the water.

"That's the product that we bring onshore and from which we extract lipids," Hoem says. "We learned how to do that in a very gentle way. You keep a blanket of water vapor on top to displace air as we go.

When I entered Aker Biomarine, I thought ... we could do it the same way as we do with fish oils. No way ... With fish oil, you can use quite harsh extraction techniques ... None of that can be done with krill oil. You would completely ruin your phospholipids.

We use only ethanol and water. That's the magic medium by which you can extract both triglycerides and phospholipids. We manage to take out quantitatively the lipids out of the krill meat. Of course, when that has been done, you have to remove some of what you do not want ...

We have a separation technique, again, using only water and ethanol, that takes out all polar constituents like salts, trimethylamine oxide and so forth. Remove that and you're left with a lipid that is clean, but in many respects extracted almost like virgin olive oil. It's very gentle."

Not all companies use these gentle methods however. Some will use more dangerous solvents like hexane. Aker Biomarine uses no toxic solvents at all, and that's a really important consideration when choosing a krill oil product.

Hoem also provides details on the harvesting and sustainability standards for krill oil. Overall, it's a far more sustainable source than fish. If this is a concern for you, please listen to the full interview, or read through my previous article, "Why Krill is your Best and Most Sustainable Source of Omega-3 Fat."

Phospholipids Make Krill Oil a Superior Source of Omega-3 Fat

Total Video Length: 05:40

Just as there are two different types of omega-3 sources, plants and marine animals, there are two primary types of marine animal-based omega-3 supplements: fish oil and krill oil. While both are marine animals, krill oil is everything that fish oil is and more. As Hoem says, "Fish oil has its place, but krill oil is a much more complete lipid package. It's a more complete nutrient."

Both fish and krill oil contain EPA and DHA. However, there are important differences between these two marine sources. One of the most important differences is the fact that krill oil is bound to phospholipids.

Fatty acids are water soluble, but they cannot be transported in their free form in your blood — they require "packaging" into lipoprotein vehicles. Most fatty acids are typically bound to esters, which do not travel efficiently in your bloodstream. As indicated earlier, krill oil is an exception in this regard.

Fish oil is bound to triglycerides and methyl esters: which must be broken down in your gut to its base fatty acids of DHA and EPA. About 80 to 85 percent is simply eliminated in your intestine.

Krill oil is bound to triglycerides and phospholipids: which allows the omega-3 fats to travel efficiently into your hepatic system; hence they're more bioavailable. Your body can readily absorb it. Studies have shown that krill oil may be 48 times more potent than fish oil.

This means you need far less of it than fish oil, as confirmed by a 2011 study published in the journal Lipids.3 Researchers gave subjects less than 63 percent as much krill-based EPA/DHA as the fish oil group, yet both groups showed equivalent blood levels, meaning the krill was more potent.

Phospholipids are also a principal compound in high-density lipoproteins (HDL), which you want more of, and by allowing your cells to maintain structural integrity, phospholipids help your cells function properly. (You can learn more about this in the video above.)

Krill oil also has natural astaxanthin: This is important as the omega-3 fats in marine oils are polyunsaturated meaning that they are highly susceptible to oxidation and going rancid. Astaxanthin is a potent antioxidant that protects these perishable fats and is not naturally present in fish oil.

Tests reveal that krill oil remains undamaged after being exposed to a steady flow of oxygen for 190 hours. Fish oil goes rancid after a single hour. That makes krill oil nearly 200 times more resistant to oxidative damage compared to fish oil.

Other Advantages of Krill Oil Over Fish Oil

Research also shows krill oil has a number of other advantages over fish oil, including the following:

Contains phosphatidylcholine: when you consume fish oil, your liver has to attach it to phosphatidylcholine in order for it to be utilized by your body. Krill oil already contains phosphatidylcholine, which is another reason for its superior bioavailability. Phosphatidylcholine is composed partly of choline, the precursor for the vital neurotransmitter acetylcholine, which sends nerve signals to your brain, and for trimethylglycine, which protects your liver.

Choline is important to brain development, learning and memory. In fact, choline plays a vital role in fetal and infant brain development and is particularly important if you are pregnant or nursing. According to Hoem, krill oil is about 90 percent phosphatidylcholine, so it's an excellent source of this important phospholipid.

"Remember, we're talking about a basic building block," he says. "You need it for your membranes. You need it as a methyl donor in a number of fundamental and biochemical transformations. It's a basic building block for your body ...

If you take choline chloride, for example, most of that is not taken up at all. It actually ends up as food for bacteria, which makes it into trimethylamine, which is taken up and then excreted as trimethylamine oxide. The phosphatidylcholine form is taken up [well] because it's not being broken down. We know now that a substantial part of it is taken up directly and delivered to the liver."

The importance of choline has been known for a long time. This is one of the reasons why decades ago many health food enthusiasts were recommending lecithin as a source of phosphatidylcholine. Again, the primary difference between soybean or sunflower lecithin and the phosphatidylcholine you get from krill is the fatty acids.

Rather than getting an omega-6 based fat, which most get too much of already from their diet, you're getting long-chain fatty acids, EPA and DHA, omega-3s.

Superior metabolic influence: researchers have found that krill oil is vastly superior to fish oil when it comes to having a beneficial influence on your genetic expression and metabolism. Genes have "switches" that can be flipped on and off, which control virtually every biochemical process in your body, and nutrients like omega-3 fats control those switches.

Fatty acids help to direct metabolic processes such as glucose production, lipid synthesis, cellular energy, oxidation and dozens of others. We now know that various types and sources of omega-3 fat affect liver tissue differently, which is what a 2011 study4 in Frontiers in Genetics was designed to examine.

It compared the livers of mice fed krill oil to those fed fish oil by looking at the gene expression triggered by each. Although both fish oil and krill oil contain omega-3s, they differ greatly in how they affect the genes controlling your metabolism. Krill oil:

Enhances glucose metabolism in your liver, whereas fish oil does not

Promotes lipid metabolism; fish oil does not

Helps regulate the mitochondrial respiratory chain; fish oil does not

Decreases cholesterol synthesis, whereas fish oil increases it

So, krill oil will help lower your triglyceride and cholesterol levels and increase your energy production, whereas fish oil does neither. Last year, an Italian study5,6 confirmed that krill oil helps improve lipid and glucose metabolism and mitochondrial function, which may help protect against hepatic steatosis (fatty liver disease) caused by an unhealthy diet (such as diets high in unhealthy fats).

By stimulating certain mitochondrial metabolic pathways, including fatty acid oxidation, respiratory chain complexes and the Krebs cycle, krill oil helps restore healthy mitochondrial energy metabolism.

Contaminant-free: fish are very prone to mercury and other heavy metal contamination, courtesy of widespread water pollution. Antarctic krill is not prone to this contamination. Not only are they harvested from cleaner waters, but since krill is at the bottom of the food chain, it feeds on phytoplankton and not over other contaminated fish.

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The Importance of Maintaining a Healthy Omega-3 to Omega-6 Balance

As you increase your intake of animal-based omega-3 fats, the EPA and DHA content in your red blood cells increase. As your omega-3 ratio increases in the cell, it "pushes out" omega-6 at a ratio of about 1 to 1. While you need some omega-6 fats, most people get FAR too much of it in their diet these days. Consumption of soybean oil (which is almost exclusively omega-6) rose 1,000-fold between 1900 and 2000.

Modern processing and refinement add to the problem as it damages the omega-6 fats, not to mention most soybeans are genetically engineered and heavily treated with Roundup. In my view, it's reasonable to assume this massive increase in damaged omega-6 oils has significantly contributed to our current epidemics of diabetes, heart disease, cancer and neurodegenerative diseases.

"I think only recently have we started to realize that we need a balance between these two [omega-3 and omega-6]," Hoem says. "Of course, you need inflammation, but when inflammation overshoots or it becomes too keen, then it may do more harm than good ... You need your omega-3s in the right proportion to modify or modulate inflammatory response.

By now we also know that the omega-3s have important actions downstream. You have the inflammation started, for example, by arachidonic acid. To start it all, what our bodies need to do at the same time is to limit excessive inflammation with the proper fats."

The Omega-3 Index — An Important Health Test

In terms of how much omega-3 fat you need, there's been a lack of reliable ways of measuring them. Hoem cites a recent paper that looked at omega-3 intakes on a global scale, identifying countries with high and low intakes.

"It really puts a lot of numbers behind things that we need to know with regards to the global consumption," he says. "They also compared different ways of measuring omega-3s — in your blood, plasma and erythrocyte.

They consistently found that the best way of doing it, the way that correlates best with tissue levels on your whole body level, is the omega-3 index [which measures the omega-3 in your red blood cells or erythrocyte]. Doing that, you will know [whether you're getting enough]. Your index ideally should be above eight.

In experimental animals, I've seen levels up to 20. I've heard that dolphins have levels way above 20. They're really loaded with omega-3. Their diet will secure that. They're pretty intelligent animals too. Their brains will be well supplied. I think the best way ... is to have people measure their levels. They would have to adjust their dosage until they reach [the optimal] level."

I believe the omega-3 index test can be an enormously important health screen, and it's commercially available. As with vitamin D, getting your level tested is really the best way to customize your dosage to ensure sufficiency, because requirements for omega-3 will vary depending on your lifestyle; your intake of fatty fish, for example, and your level of physical activity.

Athletes tend to burn off their omega-3 quite rapidly, as the DHA gets burned as fuel rather than being used as a structural component of their cell membranes. Hence they will need higher dosages. Interestingly, when this index is done on vegans, the results are typically half of what is found in those who are eating some marine fats.7

Speculative Suggestions That May Improve Omega-3 Uptake

While speculative, I also believe it may be advantageous to take your DHA/EPA with some form of short-chained fat like MCT oil or coconut oil, which is a medium-chain triglyceride that burns quickly. It's possible this fat could be used to discourage your body from burning up the omega-3 fat, which is more important for maintaining structural integrity. Hoem weighs in on this hypothesis saying:

"That's an interesting speculation. I think you're onto exactly why the uptake of long-chain omega-3s is so slow. I think they're so slow to get below the radar, not to be eaten. They kind of hide themselves. Yes, that might be one strategy; take them together with other fats ... I would [also] probably advise athletes to take their krill oil in the afternoon after they've had their exercise ... "

Dosage Recommendations

According to Hoem, fatty fish is your best source of long-chained omega-3 fats. However, remember that all fish do NOT contain these fats. Tilapia, for example, contains no EPA or DHA. Ideally, the fish needs to be harvested from cold water, as this is what triggers the production of these fats in the fish.

"There are particular types of fish that are fatty and fish that live in cold waters. You need to inform yourself with regards if your particular type of fish contains enough of the long-chain omega-3s or not. But I would guess in a fatty fish, typically I would say two to three servings a week would be enough.

With regards to krill oil, again depending on who you are and what you do, I certainly would not recommend less than 1 gram. I take 2 grams a day. By that I am well supplemented. I'm between eight and 10 in my omega-3 index. Also, I would say ... I wouldn't be afraid of taking too much. I hardly think, within the normal ranges we're seeing, that we would be able to do that. I have still not yet seen an overdose of fish."

Setting the Record Straight on Plant- and Marine-Based Omega-3s

To recap, it's really important to realize that you cannot trade animal-based omega-3 for plant-based omega-3. Even if you take large amounts of plant-based omega-3, it simply will not provide you with the raw materials you need for a healthy body and brain.

This strategy doesn't work because your body cannot convert enough ALA into DHA and EPA. Unfortunately, there are a lot of people who believe that. Even many health professionals have fallen for this misconception. If you're in this camp, I strongly urge you to reconsider.

"I think it is pretty clear. All research point in that direction," Hoem says. So please remember, while plant-based omega-3s are quite healthy, and you do need them, without marine based omega-3s you're unlikely to achieve optimal health. If you're an unwavering vegetarian and refuse to eat either fish or krill, you could potentially obtain some EPA and DHA from eating algae, although there are open questions about algae as a clean, healthy source.

"I think you're still left with some lipid extract from algae. I do not know much about it," Hoem says. "I know that the products used for baby formula is technically speaking very high-quality with respect to control of the extraction and, for example, any residual solvents.

But you're simply left with that. I would still maintain that the best way of doing it would be to eat some sort of seafood. I don't know if any larger algae from marine sources would ever be available. And there would always be concerns with algae from marine sources as they may contain natural toxins."