Thursday, April 08, 2010

How Does A Vegan Get Omega-3?

Melinda asked this question in a prior post.

A good way, vegan or not, to get more relative omega-3 (that is, to get a higher omega-3:omega-6 ratio) is to decrease omega-6 intake. You don't even have to take a pill.

You can take all the omega-3 you want, in pill or food, but if you're not also decreasing omega-6 you're not benefitting from it as much as you could. When omega-3 is high relative to omega-6, different amounts of compounds get made downstream, like the longer chain EPA and DHA.

Vegetable oils are high in omega-6, as are the nuts and seeds they are made from. Oils from grains like corn, rice, and soybean are also high in omega-6. Not adding oil to food is a great way to reduce omega-6. Whole grains, however, like corn or rice are low in fat and so provide little omega-6 per serving.


Spreadsheet (This shows the ratios)

Above is a chart I made that shows omega-6 in some foods. Note that greens (romaine, broccoli, kale, spinach) generally have more omega-3 than omega-6 and so are excellent ways to improve your ratio. Walnuts on the other hand have more omega-6 than omega-3 and so are not a good way to improve your ratio. Although flax is high in omega-3, eating lots of it isn't a good idea. See below.

Both omega-3 and omega-6 are polyunsaturated fats. If you choose to take extra omega-3, in pill or food, instead of or in addition to decreasing omega-6, know that you are intaking more polyunsaturated fat. Fats that are not saturated have many highly-reactive double bonds and oxidize quickly, especially when they hit the acids in your stomach. Oxidized fats, and their metabolites, have been shown to increase risk for atherosclerosis and some cancers.
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15 comments:

Dr. Mel said...

Thanks Bix, this is very helpful! As I'm vegetarian, not vegan, what about butter as an option for cooking recipes that call for some fat?
Why is it that people are always saying that nuts like walnuts, almonds, pine nuts, are good for the heart? It's so complicated to know what to do!
Two easy ways I use to cook greens w/o fat is 1) chop and cook them in with cooking rice or quinoa or millet, etc. (adding greens at appropriate time to produce desired texture), and 2) do the same thing by adding raw greens to whole grain pasta. (Oh, but I just noticed that rice has the wrong ratio, too, and presumably other grains are in that category--I guess I'll just have to eat nothing! Aargh.) I cannot eat "stand-alone" greens, just hate them. Frustrating!
The olive oil comes up in making

Bix said...

You're welcome, Melinda. Great ideas... to add greens to grains while cooking. I'll try that with spinach & rice tomorrow. I've been experimenting with soaking rice before cooking it. It's great -tastier, faster cooking, and easier to digest!

Yes, eating the nut or grain is different from eating its oil, as eating an apple is different from drinking its juice. They're all fine foods. It just depends on what outcome you want.

Dr. Mel said...

I meant to finish that comment on olive oil, which is a necessary component in pesto sauces, which can be made w/ lots of heavy-duty greens (bitter greens, chard, kale, dandelion greens, etc.) I've just done a search on ND for high in O-3 and low in O-6. Haven't had time to peruse it thoroughly, but among grains, the best is (it figures) tapioca. Uck. And under nuts, it's "chestnuts, japanese, boiled and steamed--
Total Omega-3 fatty acids: 5mg Total Omega-6 fatty acids: 45mg

Let's see, outcomes.... death by O-6's? Death by calcium loss? Death by plaque in arteries? So many outcomes, so little time (!).

caulfieldkid said...

One word Bix: beans :)

shaun

Chris D said...

There's another problem vegeterians and non-meat eaters have to address.

Conversion of short chain w-3 and w-6 fatty acids has been shown to be poor in tracer biomarker studies. Women are better than men, but still only convert at most 10-20% to EPA & DHA, i think it's higher for AA but can't recall.

So you'll have to eat more w-3's than your equivalent seafood/grass fed eating counterpart.

Dr. Mel said...

@caulfieldkid--yeah! Beans are good in O-3/O-6 proportions, and I love 'em.
@ChrisD--I'm not a nutritionist--could you explain the conversion stuff in lay terms? Also what you mean by "grass fed eating counterpart"? Thanks!

Chris D said...

@Mel

Polunsatures are enlongated by the body (carbons added) before they're used in various roles as prostanoids etc.

This chart shows a rough overview

This elongation process isn't that efficient, the body seems to prefer to simply metabolize some of the short chain fatty acids you ingest as energy.

It's also less efficient in men.

RB said...

Don't worry about the particulars. From a practical standpoint, just eat more beans & greens and less meat.

Bix said...

The point about conversion is a good one. Many things affect it. One thing, as Chris said, is how much substrate or raw material is available.

As I noted in my 2nd par., the conversion or elongation of omega-3 and omega-6 is dependant upon the ratio, how much of each is present in cell membranes, since N3 and N6 compete for elongation enzymes.

You can more efficiently convert vegetable omega-3 (mostly short chain) to longer chain EPA, DPA and DHA if there is less omega-6 present.

The following analogy is not entirely accurate, but it's one way I think about it:

Say I have a high omega-6:omega-3 ratio, 50 or 100 to 1...
I'll have 50 or 100 omega-6s floating around all vying for a spot on one enzyme, but only 1 omega-3. You can imagine the omega-3 isn't going to fill that spot very often.
Now, say I have a 1 to 1 ratio. Omega-3 has a better chance of contacting the enzyme and getting converted.

But conversion is complex. There are feedback mechanisms, initiation and resolution compounds that are in turn controlled by stimulus and feedback. I don't understand it all that well, but I enjoy the science.

When it comes to application however, I liked what RB said. Pollan's "Eat food." is also good. Coincidentally I wrote a post about this this morning.

Chris D said...

@Bix

Sex of the individual is probably a significant factor, I haven't reviewed more than 5-6 papers on the subject, but it seems clear that women are better at elongation to EPA & DHA as compared to men (25-50% better I would guestimate from what i've read)

Also, always an interesting line of thought, is there an example of a hunter gatherer society that is relatively vegeterian and derives a large amount of omega-3 fats from primarily plant based sources?

Would be interesting to see what their habits are.

Was also interesting to see Stephen at wholehealthsource comment the brazilian hunter gatherers who eat lots of mononogo nuts have relatively poor hunter gatherer health on don's primal wisdom blog.

Bix said...

Chris,

I didn't know about the gender differences. I could believe it, seeing DHA's use in fetal brain development.

I don't know. Orangutan?

Anrosh said...

i think Tamarind is another source of omega-6.

Chris D said...

Well pregnant women's diet in traditional cultures is a different but interesting topic.

I've read from a few sources that in hunter-gatherer tribes, men are given prime access to the kill of the hunt, relegating women to "more" gathered foods.

My conjecture is that women who were more efficient at elongating the short chain w-3 fatty acids they ingested had a reproductive advange, to explain the apparent sexual dimorphism.

This is a pretty interesting paper on male firefighters. In a nutshell 0.6-1.2 g/day of fish oil was equivelent to 2.4-3.6 g/d of flax oil.
Assessment was "erythrocyte total phospholipid ALA, EPA, and docosapentaenoic acid (22:5n-3) fatty acid content, etc."
http://www.ajcn.org/cgi/content/abstract/88/3/801

Bix said...

Chris, that was a good study, appreciate it. Nice to see that flax, or plant-based sources get incorporated in amounts not too dissimilar from longer-chain animal sources.

I enjoyed Richard Wrangham's take on historical gender roles regarding food ... in his book Catching Fire. By historical I mean over a million years ago:

http://en.wikipedia.org/wiki/Catching_Fire:_How_Cooking_Made_Us_Human

(Sorry for the delay, I've added house painting to the agenda and it's taking me away from the computer.)

Chris D said...

@Bix

They get incorporated at similar rates as short chain 18:3 n-3 (table 3) where 2.4g flax oil/day > 0.6g fish oil/day.

But as elongation occurs to EPA, DPA & DHA, 0.6 g fish oil/day is comparable or outperforms 2.4 g and 3.6 g flax oil/day. Particularly in DHA where it's around ~.8 higher starting at week 2.

0.6 g fish oil/day also lowers all omega-6 fatty acids similiarly to 3.6 g flax oil/day.

This makes flax out to be roughly 1/6 as efficient as fish oil, at least in men as this study had 3 female participants out of 62 firefighters.