I noticed in the Paleolithic Infographic that oily fish, walnuts and flaxseed oil are listed as good O3 sources right under the ideal ratio of O6:O3 being 1:1 to 4:1. Yet the ratio for walnuts exceeds 4. Not by a lot, but it's about 4.5:1. It seems those O6's sneak in with other foods and when one is deliberately trying to increase their O3 intake those foods should reduce the ratio. What say you?
My understanding has been that nuts are not particularly good foods when it comes to balancing your PUFA intake, for exactly the reasons you cite. I haven't actually thought about it in a long time because it seemed like one of those settled questions that is obvious once you've been down the rabbit hole long enough; most paleo bloggers have commented on it (or at least that's what I would have said prior to reading this question).
So I would say, good catch. I've never read the infographic carefully and this seems like a worthy fix to make.
Not all of the omega6 in walnuts will be as bioavalable as if you were using walnut oil. The fiber content of the whole nut and whether or not you are eating them raw are also confounding factors as to the bioavailability of the omega 6. If you enjoy walnuts, enjoy them freshly cracked and raw. If you have a sluggish thyroid, best to enjoy them in moderation and dry roasted if you tend to eat lots of them as raw walnuts are a goitregen --ymmv.
If you want omega 3 -- ditch the nuts and eat sardines or oily fish as overweights, diabetics, hypothyroids do not convert the ALA well as per Beth's excellent answer. IMO, this whole omega-6 to omega-3 ratio business has gone way too far down the road of pure speculation. I see omega 6 becoming a scapegoat just as carbs were demonized (fear of whole grains, tubors etc) and then fructose (fear of figs, pears, watermelon, etc).
Since an oz of walnuts provides ~2.5 g of omega 3s, it makes sense to list it as a source. As far as the ratio goes, I believe the idea is to have an overall diet ratio of 1:1 to 4:1, not that all individual foods eaten need to be that ratio. And what ultimately seems to be important is keeping omega 6 to under 4% of your dietary calories. Stephan Guyenet has a great post talking about Bill Lands' work on this.
Some in paleo space give nuts a pass because the omega 6s in them are not really on a par with those from refined veggie oils. Mark Sisson talks about this over on MDA:
When we strip a nut of everything but the liquid fat, we’re asking for trouble, but if we eat the whole nut, the fat remains protected by the natural antioxidants, at least to a point (eating burnt, damaged, or rancid nuts isn’t the same as eating raw or soaked nuts). In other words, extracting, refining, and isolating a highly unstable Omega-6 fatty acid in oil form is entirely different than eating the odd handful of pistachios every other day or so. If you roast your nuts to the point of burning, then, yeah, you’re probably eating damaged fats, and that could be a problem. But eating a quarter cup of nuts every few days isn’t going to hurt you – even if they’re high-O6 walnuts (the horror!). Even if the Omega-6 fat in nuts is bad, the positives of the nut seem to weigh more heavily.
Lots of good minerals in nuts! That said, the omega 3 in walnuts is ALA and there is some question about our efficiency at converting ALA to the forms we need (EPA & DHA). Seth Roberts discounts this, but then, he gets his ALA from flax seed which has a great ratio of 6:3 (nearly 1:4).
I think what matters most isn't the omega 6/3 ratio of each specific food, although that's a factor, but the omega 6/3 ratio of your overall diet. If you don't eat any processed foods and eat lots of fish and seafood and don't eat vast amounts of nuts, especially the ones higher in omega 6s, then you don't have to worry about how much walnuts you eat. It's best to eat foods that have DHA and EPA like fish since those are the omega 3s that our brain uses directly, unlike ALA, which needs to be converted. As noted in another answer, there's some debate about the efficiency of this conversion and so far the science shows that it's not very efficient. "Using deuterated ALA in controlled human trials coupled with GLC-mass spec analysis of newly formed DHA in human trials, conversion efficiencies ranging from 0 to 8% on average have been reported. Furthermore, a recent study has shown that the consumption of several grams of ALA per day failed to increase the low levels of DHA in human breast milk" http://www.dhaomega3.org/Overview/Differentiation-of-ALA-plant-sources-from-DHA-%2B-EPA-marine-sources-as-Dietary-Omega-3-Fatty-Acids-for-Human-Health. The omega 6/3 ratio of each food, to me, isn't as important as my overall 6/3 ratio because I can eat some foods that have a high omega 6/3 ratio while eating some that have a lower one, as long as the total balance per day is about 1-3:1. However, we do have to pay attention to the individual omega 6/3 ratio of foods we eat a lot of. Take beef for example. One study showed that, "Cattle fed grain for 120 days (40 fewer days than typical for feedlot cattle) had Omega-6 to Omega-3 ratios of 11 to one. Forage-fed (alfalfa hay) cattle had Omega-6 to Omega-3 ratios of 3 to one." We probably shouldn't be relying on beef for our omega 3s in terms of overall amount (Grass fed beef: 25mg omega-3/ounce; Grain fed beef: 15mg omega-3/ounce), but if you eat a lot of it, I think there will be significant negative cumulative effects of beef that has a high omega 6/3 ratio vs beef with a low one (grass fed) http://texasgrassfedbeef.com/omega_3_fatty_acids.htm. Eggs are much more important in terms of total omega 3 amounts (they have a lot more than beef), therefore the kind of eggs you buy (from grass fed, free-range chickens vs grain-fed, caged ones) will determine what omega 6/3 ratio they have. I read that each grass fed egg has 225mg of omega 3s. Also, one study showed "The Greek egg had a Omega-6 to Omega-3 ratio of 1.3 to one whereas the “supermarket egg” had a ratio of 19.4 to one." This is because the greek chickens were fed on grass high in omega 3s whereas the standard eggs were from grain fed chickens. We can't just focus on isolated nutrients and then view all foods in terms of how much they have of those nutrients. Rather, we have to look at the whole food, because real food is the sum of its parts, like nuts having antioxidants (vitamin E) to balance out some of the inflammation their omega 6s cause. To answer your question directly, I don't believe walnuts are a good source of omega 3s and you shouldn't be relying on them for that, but I think eating moderate amounts of them on a regular basis is just fine as part of a balanced diet.
Prevent overeating on nuts by buying them in shell form. Shell each one, and you'll find that nuts, all of a sudden, are fairly hard to eat (at least 20 at a time). Otherwise, some walnuts, or any nut, here n' there, is okay.
jemiedany Very good article about walnuts, I enjoyed reading. When searching earlier I also found an interesting guide that answered the question are walnuts good for you. I am going to start eating these every day now.
Well that's not good to hear. I just bought some raw walnuts I think for O3 because I read that it was a good source (and Vitamin E). What am I gonna do with all these nuts? I don't particularly care for the flavor either. They were pretty expensive too. I guess I gotta suck it up and eat them til they are gone. Interesting about the grass fed eggs too. How does that work for chicken? I wasn't sure if they are supposed to eat grass or corn or what. I never see grass fed chicken in Whole foods. I have been buying pasture raised eggs and spending way too much on them might I add, because I thought they were the cream of the crop. So these grass fed eggs are superior to those? Not sure where I'd find them anyway.