Omega-3 Side Effects: Myths, Facts, and How to Choose

From supporting a healthy inflammatory response to blood vessel health, eye health, and brain health, omega-3 has become an essential supplement for people today.

It’s no exaggeration to say we live in a time when taking omega-3 has become a must.

Many people take omega-3 for their health, but few realize that omega-3 is a nutrient that’s especially prone to going rancid.

Rancid oil, simply put, is oil that has gone bad. It’s a lot like eating food fried in oxidized oil.

That’s why, when it comes to omega-3 side effects, rancidity matters: taking rancid omega-3 can do more harm than good.

Rancidity isn’t the only concern.

Add the worry that heavy metals can build up, and it’s only natural for consumers to feel uneasy.

Amid these concerns, it’s easy to see why “plant-based omega-3” catches people’s attention. When it’s said to be free from both rancidity and heavy metals, it’s hard not to be tempted.

So, is plant-based omega-3 really better than animal-based omega-3?

I often see people choose an omega-3 based only on marketing claims that it’s “safe,” without any real criteria.

Faced with hundreds of omega-3 products on the market, you’ve probably felt lost about which one to choose.

To help with that, today I’ve put together an “Omega-3 Buying Guide.”

Rather than simply listing popular products, I’ll compare the labels of products on the market and explain in detail why a particular omega-3 is good and what criteria you should use to choose one.

If you’ve been choosing your omega-3 because “it was cheap” or “it was said to be safe,” I hope this post helps you make a smarter choice and steer clear of omega-3 side effects.

The idea is that DHA makes up a much larger share of the omega-3 in our bodies, and since this DHA gets converted into EPA, plant-based omega-3 is enough on its own.

Add the claim that it also carries less risk of heavy metals, radioactive contamination, microplastics, and endocrine disruptors, and it’s only natural for consumers to be tempted.

Because it’s plant-based, it feels safer somehow, and since DHA supposedly converts into EPA on its own, it feels like there’s no need to bother with animal-based omega-3.

But is that really true? And if it does convert, how much actually gets converted?

According to research, when DHA is consumed through food, less than 1.4% of it is converted into EPA, and one study found that up to 12% was converted when people took high doses of DHA supplements over a long period.

In other words, even if DHA is metabolized into EPA, only a small amount gets converted, somewhere between 1.4% and 12% at most.

Applied to actual intake, this means that if you take 500 mg of DHA, the EPA your body makes is only about 7 mg, or 60 mg at most.

That’s a tiny amount, isn’t it?

In fact, research suggests that the claim plant-based omega-3 companies make, that “DHA is converted into EPA in the body,” doesn’t hold up.

Taking DHA alone does raise EPA levels in the body, but the main reason EPA levels go up isn’t that DHA is converted into EPA; it’s that having plenty of DHA in your body slows down the rate at which EPA is metabolized (used up).

Generally, what we call omega-3 means “oils that contain EPA and DHA.”

It’s important to get both in a balanced way.

Even among plant-based omega-3s with relatively high EPA content, the ratio is around DHA:EPA = 5:2, so the share of EPA is still low, which leaves them lacking in terms of balance.

Animal-based omega-3 already contains a balance of DHA and EPA, so is there really any reason to choose this kind of plant-based omega-3?

Q&A (2) Is Animal-Based Omega-3 Safe When It Comes to Heavy Metals?

When it comes to animal-based omega-3, the issue that always comes up is heavy metals.

The key term in any discussion of omega-3 and heavy metals is the food chain. The higher a fish sits on the food chain, the greater the risk that heavy metals can build up.

The bigger the fish that prey on small fish like anchovies, the more heavy metals like mercury and cadmium inevitably build up in their bodies over time.

So it’s certainly true that animal-based omega-3 is more likely than plant-based omega-3 to contain heavy metals.

Worried About Heavy Metals? Here's My Take.

As a pharmacist, I'd say heavy metal concerns in omega-3 are largely a story from the '80s and '90s.

GOED, the global omega-3 industry organization, holds its member companies to strict heavy metal limits. If a company is a GOED member, oil that exceeds those limits can't make it into their products.

On top of that, refining technology has come a long way. Whether fish-based or plant-based, today's omega-3 oils contain only trace amounts of heavy metals, if any.

Ingredient suppliers’ own certificates of analysis list every heavy metal tested, and the levels are far lower than the limits, often just a few hundredths to a few thousandths of them, so they’re hardly a concern.

Many people really don’t like the idea of anything known to be harmful being in their supplements, even in tiny amounts.

Pregnant women in particular often steer clear of supplements associated with words like heavy metals, microplastics, or synthetic additives, and that’s completely understandable.

Amid these concerns, one ingredient that’s been getting attention lately is “spirulina.”

Spirulina is a microalga that grows in clean environments, and it’s rich in protein and a variety of antioxidant compounds.

What stands out most is its potential to bind heavy metals like lead, mercury, and cadmium, which researchers have been studying.

Spirulina is rich in a blue pigment protein called “phycocyanin,” and many of the benefits associated with spirulina are credited to “phycocyanin.”

Phycocyanin has been studied for its ability to bind heavy metals such as cadmium, mercury, lead, and aluminum, and to support the body’s natural defenses against compounds like pesticides and hydrocarbons.

Phycocyanin has a unique structure that allows it to bind with positive ions, and in lab studies it has been shown to bind heavy metals like silver (Ag+).

The image above shows experimental data that tested how strongly heavy metals bind to phycocyanin.

When phycocyanin is made fluorescent and then reacted with heavy metals, the fluorescence disappears, which shows that the two substances actually bound together.

Thanks to these properties, products that keep the benefits of animal-based omega-3 while adding spirulina, which offers heavy metal binding and antioxidant functions, have recently been launched, giving consumers another option when it comes to omega-3 quality.

2. How to Choose the Right Omega-3

Tip 1) A Trusted Ingredient Supplier

Omega-3 is a supplement where the ingredient supplier matters more than with almost any other supplement.

That’s because absorption, purity, bioavailability, and how easy it is to take (fishy taste) can differ like night and day depending on which ingredient is used and what form it comes in.

Because omega-3 is sensitive to rancidity and heavy metals, it’s no exaggeration to say that the “ingredient,” the foundation of the product, determines its quality.

So when you choose a product, you should first check whether it uses an ingredient from a trusted supplier with a proven production and quality control system.

Well-known ingredient suppliers include Polaris (France), KD Pharma (Germany), AlaskOmega (USA), and GC Rieber (Norway), companies with a strong reputation in the omega-3 ingredient market.

These suppliers each have their own extraction methods built on long traditions and research, and they’re widely recognized for purity and safety.

All of them are GOED members, and their ingredients are IFOS certified.

IFOS and GOED are international bodies focused on omega-3 quality; GOED sets strict quality standards, and IFOS tests omega-3 products for endocrine disruptors, oxidation levels, and heavy metals, with strictly managed threshold values.

Standards and testing like these help confirm that an omega-3 meets safety benchmarks for heavy metals, oxidation, and other impurities, and they can serve as one indicator of trust when choosing a high-quality omega-3.

 Tip 2) Omega-3 Form

Absorption varies from product to product, and that difference starts with the form of omega-3.

Depending on how it’s refined, omega-3 is classified by its molecular structure into TG, EE, and rTG forms.

The TG form is the natural state found in fish oil, with three fatty acids attached to a glycerol backbone, and only one of them is omega-3 (a polyunsaturated fatty acid).

Its structure is stable and it absorbs well, but since polyunsaturated fatty acids make up only one-third of it, its purity is low.

The second-generation EE form went through a chemical process to raise purity. It has a higher omega-3 content than the TG form, but its downside is that it’s absorbed relatively less well.

Most omega-3 products today are the third-generation rTG form. It has a structure similar to the natural TG form, with three polyunsaturated fatty acids attached to a single glycerol, so it’s high in both purity and absorption and also has excellent bioavailability.

So when you buy omega-3, some products state “rTG” right in the product name.

Even if a product is simply labeled “omega-3,” you can check the Supplement Facts panel or the ingredient list to see whether it’s the rTG or EE form.

If you look at omega-3 products, you’ll see labels like “1 capsule = XX mg.” This refers to the weight of the entire capsule.

What matters in omega-3 content is the combined amount of EPA and DHA, the active ingredients behind its many benefits.

So when choosing a product, it’s important to check the combined amount of EPA and DHA, not the weight of the capsule.

In fact, when you look at the combined EPA and DHA shown on the Supplement Facts panel, it often differs from the total capsule amount.

That difference comes from saturated fat and other components, and you can think of it this way: the closer the combined EPA and DHA is to the total amount, the less unnecessary fat there is and the higher the product’s purity.

For example, if a 1,400 mg capsule contains 1,120 mg of EPA + DHA, the purity is 80%.

The remaining 280 mg is made up of saturated fat and other components.

In other words, the higher the purity, the more of omega-3’s active components you can take in from the same size capsule.

So it’s important to check purity this way and choose a product that is at least 80%.

Purity Matters. So Does the Dose.

Purity isn't the only thing I look at. The amount matters just as much, because the level of support you can expect from omega-3 depends on how much you're actually getting.

For general adult health, the usual target is roughly 250 to 500 mg of combined EPA and DHA per day. Yet according to the latest Dietary Guidelines for Americans, the average American gets only about 110 mg a day. And to see the benefits shown in the chart above, you need even more.

That's why I recommend 900 mg of combined EPA and DHA per serving. It goes well beyond that baseline, supporting heart, brain, and eye health* all at once.

A product with less than 500 mg of EPA and DHA may be cheaper, but it doesn't even reach the starting point shown in the chart.

To sum up, when choosing an omega-3, check two things rather than the capsule’s size:

① How much the combined EPA and DHA comes to

② What percentage of the capsule’s total weight that amount represents (purity)

 Tip 4) Individual Packaging

It’s easy to overlook, but packaging also has a big impact on how fresh your omega-3 stays.

Large-size omega-3 in bottles, which are common on the market, are exposed to air again and again every time you open the lid.

This speeds up the rate of oxidation.

In contrast, individually sealed blister-pack products keep each omega-3 capsule sealed on its own, so they hold up well against outside factors like temperature, air, humidity, and light. This minimizes oxidation and keeps the ingredients fresh for longer.

Of course, bottled omega-3 products made with excellent ingredients and manufacturing processes can still maintain a certain level of quality, but it’s worth keeping in mind that the packaging itself is less favorable for preserving freshness.

What Makes Aqua Glow Omega-3 Different?

There are so many omega-3 products on the market that tout similar ingredients and formulas, so it’s no surprise that many people struggle to decide which one to choose.

For everyday consumers in particular, checking and comparing everything from ingredient quality to manufacturing methods, purity, and safety is never easy.

So YoungLong asked a question:

Could we make a product that keeps the strengths of traditional omega-3 while directly addressing the concerns consumers have?

That question led to YoungLong Aqua Glow Omega-3.

One of the biggest concerns people have when choosing an omega-3 is heavy metals and oxidation.

In the end, an omega-3's quality comes down to where the ingredient is sourced and how stable it is against oxidation.

YoungLong designed Aqua Glow with both in mind, from ingredient selection to the manufacturing process and supporting ingredients.

We started with the ingredient. We chose rTG omega-3 from Polaris, a trusted supplier in France, and tested it for heavy metals to verify its quality and safety.

The ingredient is produced with low-temperature supercritical CO₂ extraction to reduce the oxidation that heat can cause during manufacturing.

On top of that, we added vitamin E, which helps keep the oil stable against oxidation, and blue spirulina, known for its antioxidant compounds.

We didn’t compromise on potency or purity, either. Out of 1,400 mg of total fish oil per 2 softgels, the combined EPA and DHA is 1,120 mg, making it a high-purity omega-3 with an 80% EPA+DHA concentration.

Since omega-3 is something you take every day, it's worth looking beyond the amount alone to what ingredient was used, how it was made, and how its quality is managed.

YoungLong Aqua Glow Omega-3 was made with care at every step.

[1] U.S. Department of Agriculture & U.S. Department of Health and Human Services (2015). 2015–2020 Dietary Guidelines for Americans, 8th Edition.

[2] Zhang, Z., Fulgoni, V. L., Kris-Etherton, P. M., & Mitmesser, S. H. (2018). Dietary Intakes of EPA and DHA Omega-3 Fatty Acids among US Childbearing-Age and Pregnant Women: An Analysis of NHANES 2001–2014. Nutrients, 10(4), 416.

[3] Seafood Nutrition Partnership (2018). Seafood Recommendations from the Dietary Guidelines.

[4] Metherel, A. H., Irfan, M., Klingel, S. L., Mutch, D. M., & Bazinet, R. P. (2019). Compound-specific isotope analysis reveals no retroconversion of DHA to EPA but substantial conversion of EPA to DHA following supplementation: a randomized control trial. The American Journal of Clinical Nutrition, 110(4), 823–831.

[5] Arterburn, L. M., Hall, E. B., & Oken, H. (2006). Distribution, interconversion, and dose response of n-3 fatty acids in humans. The American Journal of Clinical Nutrition, 83(6 Suppl), 1467S–1476S.

*This content has not been evaluated by the U.S. Food and Drug Administration (FDA). This product is not intended to diagnose, treat, cure, or prevent any disease.