by Marion Nestle
Jun 19 2007

Flaxseed Omega-3 Fats

A reader in California writes: Hello, I am reading your book, what to eat, overall I am very much enjoying it, but I have noted a few things that I have to disagree with you on. One in particular regards Flaxseeds as a source for Omega-3 fatty acids…I am well aware that Flaxseeds are a great source of Omega-3 fatty acids, but they also have a very dense husk. My understanding is that if you eat the Flaxseeds in their whole form your digestive system is not able to breakdown the outer casing of the seeds and allow for the absorption of the fatty acids contained inside…You seem to believe that you can absorb the fatty acids in flaxseeds while they are in their whole form and I would love to hear back from you about the basis for your opinion.

My response: The writer is referring to a comment in What to Eat about a cereal said to contain 2,000 milligrams of omega-3 fatty acids per 2-ounce serving. The question is whether any of that is usable. I would assume that the seeds have been broken during processing so that some of their fats can be absorbed, but I am unfamiliar with research on this question. Readers: do you know anything about this? If so, please post.

  • Susie Cahill

    Dr Bob Arnot, in his Breast Cancer Prevention Diet book, recommends grinding your own linseeds to avoid oxidation. and keeping them for 3 days only in the fridge to avoid oxidation. Dr Arnot goes on tho say ” Linseeds contain a desirable weak estrogen and omega-3 fatty acids and reseach is being done at the University of Toronto by Dr Lillian Thompson on ground, brown linseeds and breast cancer prevention. Linseed is a richest known plant source of omega-3 and the richest sourse of weak oestrogens. Studies also show linseeds could limit the oestrogen in fat cells, limit the booster effect and extend the menstral cycle as well as increasing the number of oestrogen carriers having an oestrogen blocker effect. Since the oestrogen blocker is created by the bowel after digesting the linseed, only linseed, not oil, provides the proper oestrogen-blocking effect. It is important that the seeds be ground – grinding breaks the seed’s hard outer coat so that the human enzymes have a better access to the benificial elements inside the seed” Arnot and Thompson recommend 25g per day. I highly recommend Dr Bob Arnots book, ISBN 0733610684. Info on Lillian Thompson’s work with linseeds can be easily Googled.

    Susie Cahill

  • Jim Morris

    I have heard and read that Chia seeds, (Salvia hispanica, a plant of the genus Salvia in the Mint family) are very high in omega-3s and very nutritious in several other ways. They were highly prized by the Aztecs and have been touted as a little-known “superfood”. Have you any knowledge about them or the accuracy of this?

  • Anna

    Purslane is another plant source of omega-3 fatty acids. It is a common garden weed, yet the greens are delicious as a salad component or slightly sauteed. Culinary varieties of seeds for growing the plant can be ordered. The only source I know of is Seeds of Change, but I am sure it is available elsewhere.

    However, I would not rely solely on plant sources of omega-3s. Other animals are far better converters to omega-3s, which is why some animal foods are such rich sources of preformed Vit A and omega-3s. Even grass-fed meats (not grain-fed) are better sources than plants because of all the chlorophyl they consume (like plankton and krill). The omega-3s in fatty cold water fish come from the plankton and krill they eat.

    Plant sources of beta-carotene and omega-3s are inefficient sources because the body needs to convert the precursers to Vit A and omega-3 form.

    My understanding is that not everyone is efficient at converting the oils in flaxseed into omega-3 fatty acids (flax does not contain omega-3s in complete form, they need ot be converted), similar to those with hypothyroidism not being efficient converters of beta-carotene to Vitamin A in the body (therefore needing formed Vitamin A food sources from animal sources).

  • kombucha99

    Re Jim’s comment.

    If you’re going with plant sources of omega-3 fatty acids, then chia seeds are better than flax. They not only contain a better balance of essential fats (omega-3 and omega-6), they’re also high in antioxidants that protect these fats, even after grinding (e.g., in a blender or coffee grinder).

    Apparently, the Aztecs were able to store chia flour for long periods without significant oxidation, whereas flax lacks the antioxidants so abundant in chia. I’m not suggesting you store ground chia unrefrigerated or indefinitely. But chia’s antioxidants protect both its freshness and protect you from free radicals.

    You can find organic chia in many health food stores and now online from several suppliers including:

    While chia does not need to be ground before eating, I would recommend either chewing it well or grinding it. Some people have an easier time fully breaking chia down, and grinding ensures better digestion and assimilation of the essential fats.

  • Eddie Vos

    Flax oil is 55% omega-3, 18 carbons long, and a small tea spoon, or 2 table spoons canola [10% omega-3] or about 2 tablespoons of GROUND flax [= lin] seed would give anyone the about 2 grams of PLANT based omega-3’s ISSFAL suggest and the trial suggest is very heart healthy. In India, the poor man’s mustardseed oil, like any ‘brassica family seed’, also has 10% omega-3.

    We slowly convert a small amount of this 18 carbon omega-3 into EPA, the 20 carbon long omega-3, but NEVER into DHA, the 22 carbon omega-3. The latter 2 are only found in fish oil [any kind] and one fish oil pill [1 gram] get you about the amount most recommend as heart healthy, and more. There is not enough ‘fatty fish’ for all in the ocean so fish oil pills are the only sustainable and responsible source I’m afraid.

    Chia is similar to flax but more omega-6 in it is no health benefit, so I’d go with flax, that is plain old linseed, and that is more widely available and dirt cheap.

    Finally, if some of the not ground flax seeds wind up on your toilet paper, you can plant it; trust me!

    Section 1 of has all the links and references to the omega-3 picture.

  • Jimmy Wear

    Eddie is so wrong to include all Chia, Mila has the perfect ratio of 3 omega 3’s to 1 part omega 6’s. Mila is FDA approved as a whole raw food and is micro sliced where you get 3000 mg of Omega 3’s per serving. Mila is the number one source of Omega 3’s in the world, thanks to 20 years of research, planting and harvesting by the rediscorver of the seed, Dr. Wayne Coates. You see Mila is a proprietory selection of Salvia hispanics L. Take a look at Dr. Coates video at
    God Bless

  • Manwith Lethervest

    Mila and Chia are not genetically different. There are no proven traits that claim so. Even the genetically modified seeds or cultivar are unpatentable because there are no obvious trait difference. kinda like bumble bees, very close in genes. Also, chia and mila are grown in mexico, so if your pretty much getting the same thing. same conditions, same seed. get it from a reputable processing plant, like maybe from the healthfood store and you’ll save, lots of money!

  • Michael

    To actually answer the question: “Yes, the omega-3 fatty acids in flaxseed are absorbed if they are first ground/milled.”

    * * *

    … 30 g of seed or 6 g of ALA in the oil were baked into muffins for delivery over a 3 month test period in healthy male and female subjects.

    RESULTS: Flaxseed ingestion over a 1 month period resulted in significant (P = 0.005) increases in plasma ALA levels in the flaxseed oil and the milled flaxseed supplemented groups. The former group had significantly (P = 0.004) higher ALA levels than the milled flaxseed group. The subjects supplemented with whole flaxseed did not achieve a significant (P > 0.05) increase in plasma ALA levels. An additional two months of flaxseed ingestion did not achieve significantly higher levels of plasma ALA in any of the groups. However, no significant increase was detected in plasma eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) levels in any of the flax-fed groups. There were no changes in plasma cholesterol or triglycerides or in platelet aggregation at any time point in any of the groups. Subjects in all of the groups exhibited some symptoms of gastro-intestinal discomfort during the early stages of the study but these disappeared in the oil and milled seed groups. However, compliance was a problem in the whole flaxseed group.

    PMID: 18689552
    * * * *
    There was no control over the rest of the subjects’ diets, so they may have been consuming too much omega-6 to see the increase in plasma EPA usually seen in such studies.