EFA stands for essential fatty acid, and an EFA supplement provides omega-3 and omega-6 fats that your body cannot produce on its own. Humans lack the enzymes needed to build these two specific fats from scratch, so they must come from food or supplements. The two true essential fatty acids are linoleic acid (an omega-6) and alpha-linolenic acid, or ALA (an omega-3), though most EFA supplements also contain their longer-chain derivatives like EPA, DHA, and GLA.
Why These Fats Are “Essential”
Your body can manufacture most of the fats it needs from other nutrients, but it physically cannot create linoleic acid or ALA. These two fatty acids serve as starting materials that your cells convert into longer, more specialized fats. ALA gets converted into EPA and DHA (the omega-3s found in fish), while linoleic acid gets converted into GLA and arachidonic acid (omega-6 derivatives). The catch is that this conversion process is inefficient, which is why many supplements skip ahead and deliver EPA and DHA directly.
What EFAs Do in Your Body
Essential fatty acids are structural building blocks of every cell membrane in your body. They influence how fluid and permeable your cell walls are, which in turn affects how well receptors, channels, and signaling molecules function. About 20% of the brain’s dry weight is polyunsaturated fat, and one in every three fatty acids in the nervous system is a PUFA. DHA is especially concentrated in the brain and retina, where it supports neurotransmitter release and the formation of synapses.
Beyond structure, EFAs are the raw material your body uses to produce signaling molecules that regulate inflammation, blood clotting, and immune responses. Omega-3s generally produce anti-inflammatory signals, while omega-6s tend to produce pro-inflammatory ones. Both responses are necessary, but the balance between them matters.
Common Forms of EFA Supplements
EFA supplements come in several forms, each with a different fatty acid profile:
- Fish oil is the most widely used source, providing EPA and DHA directly. A large review of 23 studies involving nearly 44,000 participants found that EPA and DHA supplementation reduces triglyceride levels by about 15%.
- Krill oil delivers EPA and DHA in a phospholipid form rather than a triglyceride form, which some evidence suggests may absorb slightly differently.
- Algal oil is a plant-based source of DHA (and sometimes EPA), making it the primary option for vegetarians and vegans.
- Evening primrose oil, borage seed oil, and black currant seed oil are rich in GLA, an omega-6 derivative. These are often marketed specifically as “EFA supplements” and are popular for skin and hormonal support.
- Flaxseed oil is high in ALA but provides no preformed EPA or DHA, so its benefits depend on your body’s limited conversion ability.
The Omega-6 to Omega-3 Ratio Problem
Both omega-3 and omega-6 fats are essential, but the modern Western diet delivers them in a lopsided ratio. Up until about 100 years ago, the typical ratio of omega-6 to omega-3 was roughly 4:1. Today, it’s closer to 20:1 in favor of omega-6, driven largely by the widespread use of industrial seed oils in processed food. At the same time, intake of the marine omega-3s EPA and DHA has dropped to around 100 to 200 milligrams per day, compared to estimates of 660 to 14,250 milligrams daily during the Paleolithic era.
This imbalance creates a pro-inflammatory state in the body. The overconsumption of omega-6 linoleic acid, combined with a shortage of omega-3s, has paralleled the rise in autoimmune conditions, allergies, asthma, and other chronic inflammatory diseases. For most people, the practical takeaway is that EFA supplementation typically means adding more omega-3s, since omega-6 intake is already more than sufficient.
How Much You Need
The National Institutes of Health sets adequate intake levels for omega-3s as ALA: 1.6 grams per day for adult men and 1.1 grams per day for adult women. During pregnancy, the recommendation rises to 1.4 grams, and during breastfeeding, 1.3 grams. No official intake recommendations exist for EPA and DHA specifically, though many health organizations suggest 250 to 500 milligrams of combined EPA and DHA daily for general health.
Children need less: 0.5 grams of total omega-3s for infants, scaling up to 0.9 to 1.2 grams of ALA by age 9 to 13.
Brain and Eye Health
DHA plays an outsized role in the central nervous system. It’s the most abundant polyunsaturated fat in the brain, where it maintains membrane fluidity and supports the formation of synapses, the connections between neurons. A deficiency in omega-3s reduces synaptic density in the hippocampus (a memory-critical area) by 30%, cuts glucose uptake into neurons by 30%, and slashes dopamine release by 90%.
In the eyes, DHA is critical for retinal function. Infants who receive adequate DHA develop better visual acuity, and consuming ALA alone does not provide the same benefits because the conversion to DHA is too slow and incomplete. This is why DHA-fortified formulas and prenatal supplements have become standard.
Signs of Deficiency
True EFA deficiency is uncommon in people eating a varied diet, but it does occur, particularly in those with fat malabsorption conditions, extremely restrictive diets, or prolonged low-fat intake. The hallmark signs involve the skin and eyes: dry, scaly skin, poor wound healing, and impaired vision. Cognitive symptoms can include difficulty concentrating and mood changes. In infants and children, insufficient DHA can impair learning ability and alter behavior.
Safety Considerations
EFA supplements, particularly fish oil, are generally well tolerated at standard doses. The most common side effects are fishy aftertaste, mild nausea, and digestive discomfort. However, omega-3 fatty acids inhibit platelet aggregation, meaning they reduce your blood’s ability to clot. This becomes a serious concern if you’re taking blood-thinning medications like warfarin, where the combination can make it difficult to control bleeding. Case reports describe patients on both fish oil and warfarin whose clotting could not be corrected after injury.
If you take anticoagulant or antiplatelet medications, or if you have a scheduled surgery, the interaction between omega-3 supplements and blood clotting is worth discussing with your prescriber before starting or continuing supplementation.