Omega-3 fats are widely praised in both conventional and holistic nutrition for their many roles in supporting brain, vision, cardiovascular health and more. Not to mention how they contribute to optimal fertility (in men and women), overall health during pregnancy, as well as fetal brain and vision development.

But did you know that not all omega-3 fats are created equal?

That’s right, much like folate, the term “omega-3 fats” is an umbrella term that describes numerous subtypes — and not all types of omega-3 fats have the same benefits.

After reading this article, you’ll understand more about the different subtypes of omega-3 fats, where we find them in food, and why you can’t rely on plants for all of your omegas.

Omega-3 Fats: Why you can’t rely on plants for all of your omegas

DHA and omega-3 are not interchangeable terms 

Let’s start with the basics. Omega-3 fats are considered “essential” because our bodies cannot manufacture these fats from other raw materials.

There are several types of omega-3 fats. 

• Plants contain mainly ALA (alpha-linolenic acid). 
• Animal foods contain mainly DHA and EPA (docosahexaenoic acid and eicosapentaenoic acid). 

The most widely praised omega-3 fat is DHA, a specific subtype that has an incredible body of research supporting its benefits. 

With regards to the childbearing years, DHA is essential for egg and sperm quality, for the proper development of the brain and eyes (which is why intake is so important during pregnancy), and for lactation (DHA helps replenish mom’s depleted stores and also transfers via breast milk for baby’s continued neurocognitive development). It remains a key brain-supportive nutrient through childhood and the entire lifespan, not only for cognition, but for emotional and mental health.

Some nutrition resources use the term omega-3 fat and DHA interchangeably, however, it is important to separate the two since not all omega-3 have the same functions and benefits as DHA.

I remember being particularly appalled when a major prenatal education organization distributed pamphlets at a conference I spoke at (circa 2011), which stated that walnuts, chia seeds, and flaxseeds are a source of DHA. This is factually incorrect; as plant foods, they contain ALA, not DHA.

Where do you find DHA in food?

DHA is most concentrated in fish and seafood. Individuals who do not regularly consume ~12 oz of seafood per week are unlikely to consume enough DHA

In fact, 95% of childbearing-age women don’t consume enough DHA, primarily due to low intake of fish and seafood (only about 3 oz per week). Average DHA intake in women — from food and supplements combined — is only 62 mg/day, a far cry from the recommended minimum of 250 mg or more (and let me stress, 250 mg is a minimum).

While some foods — other than seafood — contain DHA, their concentrations are much lower, making sufficient intake of this important omega-3 fat difficult if your diet doesn’t contain any seafood. Cold water, fatty fish — particularly the skin or eggs (roe) — are the richest sources of all.

Land animals contain a bit of DHA, especially if they’re grass-fed and free roaming (such as eggs from pasture-raised chickens and meat from grass-fed cows), but they have nowhere close to the concentrations in seafood. See below for some comparison images showing what portion size of various foods is equivalent to some of the best sources of DHA — namely, Alaskan sockeye salmon and fish eggs.

At minimum, you should aim to consume 250 mg of DHA per day for you and your baby (though higher amounts have been shown to be beneficial in some research and there’s still active debate about how much DHA is optimal). Nonetheless, 250 mg is widely acknowledged to be the minimum target.

Best food sources of DHA (how the DHA content compares between different foods)

Sockeye salmon with the skin on contains 1,400 mg of DHA per 3 oz, while fish eggs (roe) contains 1900 mg per 1 oz.

The image below shows how the DHA content compares between these two foods and other dietary sources of DHA, including herring, sardines, oysters, pasture-raised eggs (or omega-3 eggs), and grass-fed beef.

As you can see, while seafood is more concentrated in DHA, it can take a fairly large portion of eggs or grass-fed beef to obtain equivalent amounts. These images also show that some types of seafood are more concentrated in DHA than others.

But can I get DHA from plants since our bodies can convert some into DHA?

Plant foods contain omega-3 in a form called ALA (alpha-linolenic acid), but they do not contain DHA.

Our bodies can convert very small amounts into DHA, but this conversion is, at best, only 3.8%.

Plus, if your diet is high in omega-6 fats (which happen to be concentrated in seeds, nuts, and vegetable oils), this conversion rate drops to 1.9%. 

So let’s calculate this out for one of the top sources of plant-based omega-3: flaxseeds.

Flaxseeds have about 1600 mg of ALA in one tablespoon. When you calculate the theoretical conversion, this equates to only 30-60 mg of DHA.

If you’re trying to match the amount of DHA you obtain from 3 oz of salmon (1,400 mg), you’d need to consume 23 to 47 tablespoons of flaxseeds. That’s 1.4 to 2.9 CUPS of flaxseeds.

We ran the numbers for other plant-sources of omega-3s and it’s equally dismal. See the graphic below for more!

As you can see from the conversion chart, it takes an unreasonably large quantity of even the richest plant sources of omega-3 to theoretically obtain the same quantities of DHA that you get from salmon. 

This is something prenatal education materials are often lacking correct information on, especially when it comes to vegetarian sources often touted for their omega-3 benefits such as flaxseed, chia, hemp, and walnuts. 

These materials should be clarifying what type of omega-3 that these plant sources contain! But I digress… Details are not everyone’s strong suit.

How can vegetarians get enough DHA?

The ONLY plant-based source of DHA is algae-based DHA supplements. All other plant sources of omega-3 are only in the form of ALA.

If you’re thinking you can just gather and eat any type of algae to get your DHA, beware. 

Algae-based DHA supplements are derived from specific varieties, grown in controlled conditions to maximize DHA production, and then the DHA is extracted from the algae and packaged into supplements. 

While algae-based DHA supplements can be a reliable source, eating algae isn’t. For vegetarians who do not consume eggs, an algae-based DHA supplement is the only reliable source of DHA.

If this were true, wouldn’t vegetarians be deficient in DHA?

Yes, it is true — and yes, this is the case.

A review of the research on vegetarian diets and DHA status found that the “proportions of DHA in plasma, blood cells, breast milk, and tissues are substantially lower in vegans and vegetarians compared with omnivores.” 

This is not surprising now that you understand the food sources of DHA and the dismal conversion rate of plant-sourced omega-3 (ALA) to DHA in humans.

In studies where they have supplemented breastfeeding moms with flaxseed oil in an attempt to increase the DHA concentration in breast milk, the studies have failed. Our bodies don’t have the capability to convert enough ALA into DHA to meet the high demands for DHA, especially during pregnancy and breastfeeding. No matter how much flaxseed oil you give a nursing mom, her milk does not become enriched in DHA. In contrast, studies using fish oil show a substantial increase in DHA concentrations in breast milk following maternal supplementation.

This means that vegetarians need to be especially diligent about supplementing with an algae-based DHA, particularly during their childbearing years!

In addition, vegetarian diets (even more so vegan diets) result in an unfavorably high ratio of omega-6 to omega-3 fats, which can further compromise DHA status since omega-3 and 6 fats share some of the same receptor sites.

The truth about different types of omega-3 fats

So the next time you’re looking at that package of hemp or chia seeds with their bold omega-3 claims — just know that this should not count towards your daily DHA quota. I’ve got no problem with either of these foods (for what it’s worth, I discuss the benefits of chia seeds in some of my books!), they simply aren’t a source of DHA.

To be crystal clear… You must consume a source of DHA to get enough from fish/seafood or one (or more) of the following sources: fish oil, krill oil, cod liver oil, or algae-based DHA supplements.

Not a seafood fan? Well, even if you eat eggs and grass-fed beef every day, you probably are going to want a supplement. I link to some options for supplemental omega-3 on my Fullscript (including algae-based DHA). I’m also a big fan of FullWell’s fish oil for its sustainable sourcing, low oxidation levels, and stringent quality control (my link saves you 20% on first time orders).

Want to learn more about the benefits of DHA? I cover the many benefits of its roles in supporting a healthy pregnancy and fetal brain development in Real Food for Pregnancy. And if you’re curious about the role of DHA in male and female fertility, see Real Food for Fertility.

Worried about consuming fish due to fears over mercury exposure? Or are you wondering if you can eat “too much” of a good thing? See my article about consuming fish during pregnancy for some fascinating research on fish consumption, cognitive development, mercury exposure and more.

Summary

• There are different subtypes of omega-3 fats — ALA, DHA, and EPA — and their functions in the body differ
• Plants are a source of ALA, not DHA or EPA
• While our bodies can convert small amounts of ALA to DHA, the conversion rate is insufficient. This means that plant sources alone cannot provide us with enough converted DHA
• If you do not consume animal-sources of omega-3s, an algae-based DHA supplement is a requirement if you want to avoid a deficiency

Let me know in the comments if you found this article helpful!

Until next time,

Lily

PS – If you found this article interesting and are wondering whether there are other nutrients on a plant-based, vegetarian, or vegan diet that may be difficult to get enough of, make sure you pick up a copy of Real Food for Fertility. Chapter 5 is devoted to discussing the complex nutritional considerations on these eating patterns. It has, so far, been the chapter that I have received the most positive feedback on — even from women who continue to choose a vegetarian diet after reading it. Keep an open mind and give it a read. I truly want the best for your fertility, your pregnancy, and your future child. I mean it.

If you’d like a sneak peek of the book, head over to realfoodforfertility.com to download the first chapter for free.

 

References

• Burns-Whitmore, Bonny, et al. “Alpha-linolenic and linoleic fatty acids in the vegan diet: do they require dietary reference intake/adequate intake special consideration?.” Nutrients 11.10 (2019): 2365.
• Gerster, H. “Can adults adequately convert alpha-linolenic acid (18: 3n-3) to eicosapentaenoic acid (20: 5n-3) and docosahexaenoic acid (22: 6n-3)?” International Journal for Vitamin and Nutrition Research. 68(3) (1997): 159–173.
• Sanders, T.A.B. “DHA status of vegetarians.” Prostaglandins, Leukotrienes and Essential Fatty Acids 81(2) (2009): 137–141.
• Francois, Cindy A., et al. “Supplementing lactating women with flaxseed oil does not increase docosahexaenoic acid in their milk.” The American journal of clinical nutrition 77.1 (2003): 226-233.
• Ureta-Velasco, Noelia, et al. “Human milk composition and nutritional status of omnivore human milk donors compared with vegetarian/vegan lactating mothers.” Nutrients 15.8 (2023): 1855.