Flaxseed oil is a rich plant source of ALA, but the body converts only a small share of ALA into DHA, and in adults the share appears to be very small. Algae oil supplies DHA directly, so it fills a different role. The two oils are not interchangeable, though they can sit side by side. This article explains how the omega-3s differ, what the conversion research shows, and how to choose between them.
ALA, EPA, and DHA: How the Three Omega-3s Differ
The NIH Office of Dietary Supplements names three main omega-3 fatty acids: ALA, EPA, and DHA. ALA comes from plant foods such as flaxseed, chia seeds, walnuts, and soybean and canola oils. NIH lists daily ALA amounts of 1.6 grams for men and 1.1 grams for women.
EPA and DHA come from different places. A published review of microalgae oil notes that these fats originate with algae in aquatic ecosystems, and fish accumulate them through the food chain. Algae oil taps that original source directly.
How Little ALA Converts to DHA
Your body can turn ALA into EPA and then DHA, but NIH says this happens only in very small amounts. Because of that, NIH describes getting EPA and DHA from foods or supplements as the practical way to raise their levels.
Researchers describe the same limit. A 2016 review in Progress in Lipid Research says humans have limited capacity to convert ALA to EPA and DHA. A 2009 review of ALA supplementation reports that tracer studies suggest conversion to DHA of about 1 percent in infants and considerably lower in adults.
Why Conversion Stays Low
One reason is a bottleneck in the biology. A 2010 cardiovascular review reports that in supplementation trials ALA raised blood ALA and EPA but not DHA, and it identifies the enzyme delta-6-desaturase as the rate-limiting step. The supplement database Examine adds that ALA and omega-6 linoleic acid compete for the same enzymes, and it estimates conversion at under 8 percent for EPA and under 4 percent for DHA.
Who Might Convert More
Conversion is not identical for everyone. The 2016 review notes differences between men and women, and Examine reports that premenopausal women convert at higher rates, which it links to estrogen. Even so, the reviews describe conversion as limited across most people, so it is a weak basis for planning your DHA intake.
What Flaxseed Oil Does Well
None of this makes flaxseed oil a poor choice. It is one of the plant oils NIH lists as an ALA source, and ALA is an essential fat that your body cannot make. If you want more ALA in your diet, flaxseed oil is a reasonable way to add it.
Experts also disagree about how much a plant-based eater needs beyond ALA. In a Harvard Nutrition Source Q&A, Dr. Sacks says he does not advocate omega-3 supplements for vegans who get enough ALA from plant foods and is unsure they need an algal DHA supplement. The same page suggests a 500 mg daily omega-3 supplement for people who do not eat fish, so it is worth weighing both views with a healthcare provider.
Algae Oil Delivers Preformed DHA
Algae oil skips the conversion step. A 2013 randomized pilot in the Proceedings of the Nutrition Society gave 31 adults either algal oil or fish oil providing 600 mg of DHA per day for two weeks. Blood DHA rose in every group, and vegetarians and vegans reached levels similar to omnivores.
Treat that as early evidence. The study was small, open-label, and short, and the authors noted that the two oils were not shown to be bioequivalent. It does fit the broader finding that preformed DHA raises blood DHA, which ALA supplementation generally does not.
Choosing Between Flaxseed Oil and Algae Oil
Pick based on your goal. If you want ALA, flaxseed oil and other plant sources work. If you want DHA or EPA, look for a product that lists them, and read the label for milligrams of DHA and EPA per serving rather than total oil.
Safety basics apply to both. NIH says side effects of omega-3 supplements are usually mild and can include an unpleasant taste, heartburn, and stomach discomfort. The FDA recommends no more than 5 grams per day of EPA and DHA combined from supplements, and NIH warns that high doses may cause bleeding problems when combined with anticoagulants such as warfarin. Ask a healthcare provider before starting a supplement, especially if you take medication.
Frequently Asked Questions About Algae Oil and Flaxseed Oil
Short answers to common questions about ALA, DHA, and plant-based omega-3s.
Can the Body Make DHA From Flaxseed Oil?
Slightly. Research shows conversion from ALA to DHA is limited, and in adults it appears to be very low, so flaxseed oil should not be counted on as a DHA source.
Is Flaxseed Oil Still Worth Using?
Yes, as a source of ALA. NIH lists flaxseed oil among the plant sources of this essential fat.
Do Vegans Need Algae Oil?
Experts differ. Some say enough plant ALA may be adequate, while others point to algae oil as a direct source of DHA for people who eat no fish. A healthcare provider can help you decide.
Can You Take Algae Oil and Flaxseed Oil Together?
They supply different omega-3s, so many people use both. NIH advises talking with a provider about possible medication interactions before taking omega-3 supplements.
