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Dear Mark: Nuts and Omega-6s

Nuts have gotten a surprising amount of flack as of late. Many nuts have a fairly high PUFA content, and most of that PUFA is Omega-6, which is the bad one. It’s easily oxidized, highly unstable for cooking, usually rancid on the shelf, and, thanks to government farm subsidies and public hysteria over animal fat [7], it’s in absolutely everything nowadays. We Primal types generally avoid it for good reason, and that tends to influence how we react to the O6 content of nuts [8]. Last week I received this email from a reader:

Dear Mark,

I’m a little confused. I get the animal fat, the meat, the veggies, and the lowish sugar fruit recommendations, but what about nuts? I love nuts, don’t get me wrong… I’m just a bit paranoid about the Omega 6 content. You recommend nuts in the book. If you (and pretty much all other Primal bloggers) tell us to avoid Omega 6 fats, should we still be eating them?  I’m having trouble reconciling the two bits of advice and there seem to be mixed messages out there. Thanks.

Is there a place for nuts in the Primal Blueprint diet [9]? Let’s take a closer look.

Omega-6 Content Various Nuts (1/4 cup)

Walnuts – 9.5 g

Almonds – 4.36 g

Cashews – 2.6 g

Macadamias – 0.5 g

Brazil nuts – 7.2 g

Hazelnuts – 2.7 g

Pistachio – 4.1 g

Pine nuts – 11.6 g

Pecans – 5.8 g

The basic takeaway is that quite a few nuts are fairly O6-intensive (with several, like macadamia nuts, being extremely low). A diet high in these nuts, then, would presumably skew the vaunted tissue O6-O3 [10] ratio toward pro-inflammatory bodily processes… right? I mean, if you were to eat food fried in high-O6 vegetable oil at some restaurant, that would be pro-inflammatory. If you were to eat cheap Chinese food stir-fried in cheap, high-O6 soybean oil [11] every day for lunch, you’d expect a good amount of oxidized LDL at your next lipid test [12]. And if you were to supplement your diet with a few daily tablespoons of unheated corn oil, there would be markedly negative effects (besides gagging and/or vomiting) on your body. How are nuts any different?

For one, nuts aren’t just “bags of linoleic acid” (as Stephan Guyenet [13] recently pointed out in a comment board I’ve misplaced). Isolating Omega-6 fatty acids and then exposing them to air or heat is bad dietary policy. I don’t care where it is – in your body, in your cupboard, or in the skillet. But nuts are much more than linoleic acid. In fact, a nut is a pretty complete nutritional source. After all, it’s the seed of a tree, a sort of arboreal egg. Contained within is everything that tree needs to start growing from scratch – fats [14], carbohydrates [15], even protein [16], plus natural antioxidants like Vitamin E and plenty of minerals. We have to remember that antioxidants in foods exist, first and foremost, to protect the food from damage. That linoleic acid in the walnut isn’t meant for you to consume (we’ve adapted to it, not the other way around); it’s there to provide energy for the budding tree. A damaged, oxidized fat is no good to any tree, and Vitamin E helps prevent oxidation. 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 [17]). 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. Whole nut intake seems to reduce markers of systemic inflammation [18], and inflammation is linked with a wide range of ailments and afflictions (obesity, insulin resistance, heart disease, excess cortisol, etc.). The study’s (PDF [19]) authors hesitate to isolate and praise a single component of the nut, referring to them as “complex food matrices containing diverse nutrients and other chemical constituents.” I think that’s an accurate appraisal of the humble, irreducible nut.

What’s the Downside?

Problems arise with steady year-round access to foods whose historical availability was seasonal and intermittent [20]. If you were a hunter-gatherer, you probably weren’t gathering bushels of nuts on a daily basis – at least, you weren’t finding enough nuts in the wild to eat eight ounces a day. Nuts should never comprise the bulk of your diet, anyway. A quarter cup as a snack every now and then isn’t going to kill you. It’s not even going to compromise your progress. I mean, they’re nuts. They aren’t meals, and they’re not meant to be. They’re snacks, basic supplements to an already nutritious diet replete in animal fat, protein, and vegetables. And in a high Omega-3 diet like the Primal Blueprint [21] they definitely have a place.

Just make sure you treat your nuts as delicious snacks, rather than staple cornerstones of a meal. Don’t burn your nuts, and don’t cook with the oil. The safest bet is to buy them raw and soak [17] or roast them yourself. That way, you control the heat and you can mediate the oxidation.

Overanalyzing your food intake is a good way to stress yourself out and make every little dietary choice an internal struggle. Avoid falling into this trap [22]. Be vigilant of your food choices, but pick your battles wisely. Making sure you ask the waiter to cook your omelet in butter rather than vegetable oil is worth the trouble; stressing over the Omega-6 content of the twenty walnuts in front of you is decidedly not.

This is a fairly contentious topic in the community, with a ton of bloggers weighing in. Richard Nikoley (last I heard) opts for the harvest-and-gorge nut consumption style, going regular periods of time where he eats none at all. He’ll avoid buying any “for 2-3 store visits in a row.” Remember, Grok [23] didn’t have around the clock access to nuts.

Stephan Guyenet and Don Matesz go back and forth in the comments section of Don’s recent post on walnuts [24], in which Don offers very sound evidence in favor of walnut consumption. Definitely check it out.

My general take, as I see it, is that nuts shouldn’t make up the bulk of your caloric intake. It’s not that Omega-6s are inherently dangerous, especially bound up in whole food, nut form; nuts may even be beneficial to heart health, probably by decreasing systemic inflammation. It’s that they’re often too available, too plentiful, and way too easy to consume in excess. What drew our ancestors to nuts – the caloric density and the fat content – is what makes them “dangerous” to modern man. Most seeds, including grains, were passed over because the labor involved in their gathering and their refining was prohibitive with inadequate payoff. Nuts are meaty, though, and they’re dense and (somewhat) filling. It makes sense that we easily snack on them all day, because our ancestors probably gorged themselves on nuts when they were available. We should eat them, too, but it’s important to stick to reasonable, evolutionarily realistic amounts.

Care to weigh in with your thoughts on nuts? I know a lot of forum members have reservations about them, so I’d love to hear in the comments section.