Why is fish always credited as a good source of Omega 3 fats when walnuts and flaxseed have plenty also?-- Diane Grant
Tucson, AZ
Although we often refer to "Omega 3 fats" as one general category, there are three different types of Omega-3 fatty acids: Alpha-Linolenic Acid (ALA), EicosoPentaenoic Acid (EPA), and DocosaHexaenoic Acid (DHA).
ALA is found exclusively in vegetable sources, including walnuts and flaxseeds.
You might have heard some people talk about the Omega-3's in dark, leafy green vegetables.
However, they are so low in fat to begin with that, although nutritious in many ways, I don't consider them to be a good source of Omega-3 fatty acids.
EPA and DHA are found in large quantities in cold water fish. Grass-fed beef will contain a little, as well.
One concern with getting Omega-3's solely from vegetable sources is that some people are unable to convert ALA to EPA and DHA.
Even if you are able to convert ALA to EPA and DHA, 10 grams of ALA are needed to make 600 milligrams of EPA and 400 of DHA.
Considering that current recommendations call for 1 gram of EPA and another of DHA, that's a lot of ALA to consume -- and convert!
And while ALA is indeed good for us, there is, as always, too much of a good thing. Several recent studies have linked very high intakes of ALA among men with a higher risk of prostate cancer.
It's also important to realize that as good for us as Omega 3 fats are, they do not work alone. Vitamin C, zinc, and magnesium are involved in the conversion of ALA to EPA and DHA.
If you are not consuming enough of those nutrients, your conversion will happen at an even slower rate.
Walnuts and flaxseed are nutritious and have their share of health benefits. However, for optimal Omega-3 fat consumption, it is highly recommended to include sources of EPA and DHA in your diet.
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2 comments:
Hi Andy!
I think you made a typo here - 10 grams of ALA needed for a conversion to 600 MILLIgrams of DHA and 400 MILLIgrams of EPA? Otherwise, 600 grams from 10 grams doesn't really make sense. :)
I have been looking at the articles you've tagged with flaxseed and it looks like you wholeheartedly encourage the addition of ground flaxseed meal to foods. However, I wonder if doing this is ultimately beneficial - as you point out, men at risk for prostate cancer should watch their consumption of ALA. Additionally, omega-3 or not, adding fat to foods will increase the calories... for those watching their weight, is this really a smart decision?
On the other hand, as a vegan, I can attest to difficulty getting nutrients like vitamin b12. Do you think that, for vegans, the addition of flax meal is a good idea (even with a diet that incorporates a lot of nuts [in particular, walnuts] and -for cooking- canola oil)?
Thank you so much! You have an excellent blog.
Christine
Christine,
Thank you for pointing out that typo.
I am my own editor, and doing so on a computer monitor can lead to some things being overlooked!
I will answer your question in a separate post.
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