Conflicting information regarding ALA conversion rates

In the following article: Why Vegetarians and Vegans Should Supplement with DHA, under the ‘Sex’ section, it says that:

One study showed that women converted 21 percent of ALA to EPA and 9 percent to DHA, whereas men converted 8 percent of ALA to EPA and 0 percent for DHA.

This references the following article: Eicosapentaenoic and docosapentaenoic acids are the principal products of alpha-linolenic acid metabolism in young men*.

In the following article from Huel: Guide to EPA and DHA in Huel, under the ‘Conversion Rates’ section, it says that:

One [study] looked at ALA metabolism in males and indicated that approximately 8% of dietary ALA is converted to EPA and 4% is converted to DHA.

This references the same article as the first.

So my question is why do these two statements conflict when they are using the same source? My knowledge of nutrition is not good enough to read the source article and find the reason for myself, so ideally it would be good to hear from someone who can read the source article and point out where this discrepancy is coming from.

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@Dan_Huel or @JamesCollier - could you answer that?

Interesting. The study on women seems to say 21.1% EPA and 9.2% DHA. On men, 7.9% EPA and 0% DHA.

The study itself says that non-0% values of ALA to DHA conversion have been measured in other studies, and that one theory is that the conversion to DHA conversion only occurs when needed.

At a guess, Huel’s article doesn’t only use this study and is basing the 4% on other studies, perhaps the ones mentioned in this one (e.g. Vermont et al 1999, 2000.)

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Hi guys

Thanks for picking up on this @bdax; I’ve had to use my brain more than I’m used to on a Monday morning!

I originally wrote our article, I think, about 3 years ago, and, on reflection, I don’t think that section is worded correctly and referenced well enough and we will update asap.

In the meantime, to provide confidence, these references indicate adequate conversion to DHA:

And in a study comparing blood EPA and DHA levels in non-fish-eaters (who had a 57-80% lower omega-3 intake) with fish eaters, both groups had similar circulating levels of both fatty acids, suggesting that there are different conversion rates with people with different dietary habits.

I hope this provides sufficient confidence while we update the article. Any other queries, please let us know.


Thanks for the replies. It will be good to see the adjusted conversion rate for males when you’re done @JamesCollier :+1:

Any updates on this? I notice that the article has still not been updated

It’s on our list to be updated Tom, the content team are a bit snowed under at the moment!

Here’s some of the updated text with references:

Some papers have cited that human conversion of ALA into EPA ranges from 8% to 20% and conversion of ALA to DHA ranges from 1% to 9%[11]. One study indicated that ALA conversion is about 6% for EPA and 3.8% for DHA[15]; another report stated 5-10% and 2-5% respectively [16]. The factors mentioned above are the reason for these huge variations of rates.

  1. Linus Pauling Institute. Oregon State University. Essential Fatty Acids. [Available from:].
  2. Gerster H. Can adults adequately convert alpha-linolenic acid (18:3n-3) to eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3)? Int J Vitam Nutr Res. 1998; 68(3):159-73.
  3. Davis BC, et al. Achieving optimal essential fatty acid status in vegetarians: current knowledge and practical implications. The American journal of clinical nutrition. 2003; 78(3 Suppl):640s-6s.

Interesting, and the numbers you cite are not obtained from averaging the male and female results? Because of course if it’s 8% for women, and 0% for men, then that averages out to 4% for ‘humans’. I’m waiting to see the article updated as I’m keen to see what the average is for men specifically, and if this can reasonably ever be 0% as is suggested by your current source.

If it turns out that ALA is not a valid source of Omega-3 for males, then perhaps Huel should consider switching to a water-soluble DHA powder, obtained from algae?

It should also be noted that if you supplement with EPA/DHA, or eat foods that already contain EPA/DHA, then the conversion of ALA to EPA/DHA is drastically reduced.