Thanks for this post, it was very useful. However, I have some issues with the article you used to support your claims about conversion rates for alpha-linoleic acid (ALA) to EPA and DHA. Given its quality, I don’t think the conclusion that “the vegan-hostile health gurus happen to be right this time” is warranted.
Firstly, take this paragraph near the beginning of the article:
However, research clearly indicates that the conversion of ALA to EPA and DHA is extremely limited. Less than 5% of ALA gets converted to EPA, and less than 0.5% (one-half of one percent) of ALA is converted to DHA.
There is no study cited for this this.
Also, not long after:
Studies have shown that ALA supplements (like flax oil) are unable to raise plasma DHA levels in vegans, despite low DHA levels at baseline. (ref)
It simply says ‘(ref)’ in brackets, but the reference is nowhere to be found.
I just did some preliminary research on these conversions, and it seems like the evidence is quite mixed. I believe I found the study that the author of that article was looking at[1], but I also found multiple other studies ([2], [3] and [4][2]) which suggest the rates are considerably higher, and in fact high enough for only 1 or 2 grams of ALA to provide enough EPA and DHA.[3]
In summary, I don’t think it’s at all clear that vegetarians or vegans don’t get enough EPA, DHA or DPA, although it is still possible.
Based on a lot of research, the Australian National Health and Medical Research Council recommends 160 mg per day of combined DHA, EPA and DPA, for adult males, and 90 mg for adult females (source). The said maximum amount would require 3.2 grams of alpha-linoleic acid at a 5% conversion rate, and 1.6 grams at a 10% conversion rate.
In fact arguably even the rate mentioned in the original article is sufficient, since overall it is >5% (and that’s without DPA). The low amount of DHA is somewhat concerning, but there is generally no specific stipulation for a DHA requirement, and it seems this is partially because there is interconversion between the three fatty acids, e.g. from EPA to DHA.
Thanks for this post, it was very useful. However, I have some issues with the article you used to support your claims about conversion rates for alpha-linoleic acid (ALA) to EPA and DHA. Given its quality, I don’t think the conclusion that “the vegan-hostile health gurus happen to be right this time” is warranted.
Firstly, take this paragraph near the beginning of the article:
There is no study cited for this this.
Also, not long after:
It simply says ‘(ref)’ in brackets, but the reference is nowhere to be found.
I just did some preliminary research on these conversions, and it seems like the evidence is quite mixed. I believe I found the study that the author of that article was looking at[1], but I also found multiple other studies ([2], [3] and [4][2]) which suggest the rates are considerably higher, and in fact high enough for only 1 or 2 grams of ALA to provide enough EPA and DHA.[3]
In summary, I don’t think it’s at all clear that vegetarians or vegans don’t get enough EPA, DHA or DPA, although it is still possible.
Which supports the first, but not the second quoted claim.
This study indicates 5% conversion of ALA to DHA, especially after an extended period of time, which is interesting.
Based on a lot of research, the Australian National Health and Medical Research Council recommends 160 mg per day of combined DHA, EPA and DPA, for adult males, and 90 mg for adult females (source). The said maximum amount would require 3.2 grams of alpha-linoleic acid at a 5% conversion rate, and 1.6 grams at a 10% conversion rate.
In fact arguably even the rate mentioned in the original article is sufficient, since overall it is >5% (and that’s without DPA). The low amount of DHA is somewhat concerning, but there is generally no specific stipulation for a DHA requirement, and it seems this is partially because there is interconversion between the three fatty acids, e.g. from EPA to DHA.