DHA and Non-Fish-Eating Cultures

I just got back from AR2011 where someone asked me why vegans would need to take DHA if there are cultures that have lived without eating fish. I told him I don’t know the details about the health or DHA levels of such cultures.

What we do know is that vegans tend to have very low blood levels of DHA, even if they supplement with ALA. I pointed out that blood levels of DHA do not necessarily mean that vegans have unhealthfully low levels of DHA in other tissues, such as the brain, but until we know more, most vegans should take a moderate DHA supplement just to be safe.

One thing that could explain any phenomena of ancient cultures not eating fish, yet having adequate DHA status, is that our ratio of omega-6 to omega-3 is much higher today. This higher ratio hampers conversion of ALA to DHA; people in ancient cultures were probably able to convert ALA to DHA more efficiently.

People who can get their omega-6 to omega-3 ratio down to 4:1 or less, might be able to convert DHA efficiently. But I would recommend doing this without raising ALA intake much higher than 1.5 g per day (a level that has been associated with damage to the eyes). In today’s world, getting the ratio down to this level without adding large amounts of ALA to the diet would likely mean a very low fat diet which would be difficult to maintain for many people.

11 Responses to “DHA and Non-Fish-Eating Cultures”

  1. e Says:

    A question re ALA and DHA/EPA after reading ch 5 in Vegan For Life. If I do take a DHA/EPA supplement 2-3 times a week, does that lower/raise the needed ALA intake or is that constant?

  2. Jack Norris RD Says:

    e,

    Taking DHA does not change the recommendations we give for ALA on p. 55.

    Jack

  3. Sharky Says:

    Jack,

    I’m still a bit fuzzy on the ALA recommendation. On veganhealth.org, under “Summary of Omega-3 Benefits and Concerns” adding .5g ALA is recommended if supplementing with DHA. The book suggests 1.5 g/day.

    I’ve been grinding 1 tbsp of flaxseed and throwing it in with my steel-cut oats. And I usually take 200mg DHA. Also, should I be concerned about cooking the flax meal?

  4. Jack Norris RD Says:

    Sharky,

    It’s a good question and one that Ginny and I struggled with. My advice on VeganHealth.org assumes that your average vegetarian is going to be getting at least 1 g of ALA from foods they throughout the day (it is found in very small amounts in many plant foods; for example see Table 11 here: veganhealth.org/articles/omega3), whereas in the book we did not assume this. I’d be happy if this was more clear on VeganHealth.org, but I’m not really sure there is a good spot to interject it (where it would cause more clarity than confusion). If you have a suggestion, I’m all ears.

  5. Sharky Says:

    Jack,

    My concern is with the possible harmful effects of excessive overall consumption of ALA. In addition to ground flaxseed, I consume walnuts, chia seed, and edamame in small amounts but regularly. The website does mention the possibility of omega-3 consumption leading to bleeding (I problem I’ve had, due to low platelet count), but in reading about the need for dietary ALA I too easily think “more” rather than “not too much.” That’s one reader’s response. Thanks for working to make all this info so readily available.

  6. Betty Says:

    Why are vegetarians fixated on taking DHA supplements to the (apparent) exclusion of EPA? I found my answer on (gulp!) Barry Sears blog. Barry Sears is the founder of the Zone diet, which right now is neither here nor there.

    I am sorry about the reference to killed animals, but here is one paragraph from his article:

    “So why isn’t there as much EPA in the brain compared to DHA? The reason is simple. EPA enters the brain just as quickly as DHA, but it is rapidly oxidized, whereas DHA is sent off to long-term storage in neural tissue (5-7). The lifetime of DHA in the human brain is measured in years, whereas the lifetime of the EPA is measured in days. So obviously when you kill an animal and look at the brain, you are not going to find very much EPA.”

    As I understand things, the relationship between DHA and EPA is like the one between Vitamin A and Vitamin D. One element could be described as yin and the other as yang,i.e., structural and functional. They support each other.

    I should think that a person could be deficient in EPA only.

    http://www.zonediet.com/blog/2011/05/the-fallacy-of-using-dha-alone-for-brain-trauma/

  7. Jack Norris RD Says:

    Betty,

    The reason I’m more concerned about vegetarians supplementing with DHA than EPA is that the body more readily converts ALA into EPA than into DHA.

  8. Betty Says:

    Would you say that conversion of anything into anything else (that’s necessary for health) is dependent largely on the health of the liver? I would. Who has a healthy liver these days? From our first glub of formula to countless vaccine poisons to antibiotics and/or over-the-counter drugs, by the time you are in your 20s I’d opine that nothing works in your body as it should. That is why supplements were developed.

  9. Jack Norris RD Says:

    Betty,

    > Would you say that conversion of anything into anything else (that’s necessary for health) is dependent largely on the health of the liver?

    I probably wouldn’t make that claim given that there are multitudes of chemicals being converted outside of the liver.

  10. Betty Says:

    I’m not finished yet! I am still interested in the topic of DHA/EPA supplementation. Here is what I found on nomeatathlete.com

    “DHA is great for brain health, but can actually raise bad cholesterol.”

  11. Jack Norris RD Says:

    Betty,

    It would help if you provided direct links to what people are saying. I’m happy to try to answer nutrition questions, but I don’t have time to hunt down where someone has said something counter to current thinking on a subject. I’m not really too interested in responding if they haven’t even cited research to back themselves up – I’m not going to go looking for research to back them up.

    In this case, I have not seen evidence that DHA increased LDL cholesterol, in fact, most of the research tends to point in the other direct (as far as what I’ve seen). But, that said, all fat, protein, and carbs will increase LDL cholesterol if you eat enough of them. In other words, if someone takes their normal amount of calories and adds significant amounts of DHA on top of what they are already eating, then I would imagine their LDL would indeed go up. But I don’t know if that is what nomeatathlete.com means.

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