The close cousin of โartery-clogging saturated fatโ is โheart-healthy canola oilโ โ which should be your first clue that maybe all those suspiciously cheap bottles of golden liquid arenโt so great for you after all. And indeed, one of the central tenets of Paleo has always been that seed and vegetable oils โ soy, canola, peanut, and the rest of the crew โ are major contributors to modern disease.
But how, and why? Itโs not just because theyโre โunnaturalโ (that word is almost meaningless anyway); itโs because theyโre very high in polyunsaturated fat (PUFA), specifically the Omega-6 type.
PUFA is such a big Paleo issue that itโs already been covered in several places, notably here. But one other aspect deserves a look: the line that just wonโt die about polyunsaturated fat being โgood for your heart.โ So hereโs a quick review of what PUFA actually is and why it can be a problem, and then a hard look at whether or not it really benefits heart health. (If you already know basically what PUFA is, feel free to skip to here.)
What Is PUFA?
Without getting into all the molecular details, PUFA is a type of fat thatโs chemically unstable. In other words, it easily goes rancid when itโs exposed to heat (deep-frying, grilling, etc.) or light (sitting in a clear bottle on the shelf in the grocery store). There are two major types of PUFA:
- Omega-6 PUFA, found abundantly in nuts, seeds, soy, and oils made from them (including โvegetable oilโ).
- Omega-3 PUFA, found abundantly in fish and seafood, with smaller amounts in fat from grass-fed animals.
We can also get the precursors for Omega-3s from plant sources (like flax seeds), but human bodies just arenโt very efficient at converting those precursors into Omega-3s themselves, so itโs better to get the Omega-3s directly.
Whatโs Wrong with PUFA?
In a nutshell: too much Omega-6!
The problem isnโt that Omega-6 fats are โbadโ in the abstract. We actually need them: if we donโt get them, weโll die. But we donโt need a lot of them.
As far as we can tell, the ratio of Omega-6 to Omega-3 in ancestral diets was something between 1:1 and 4:1. But in modern diets, itโs around 10:1, thanks to the amazing amount of vegetable oils we eat.
This imbalanced ratio of Omega-6 to Omega-3 fats is a problem because itโs inflammatory. The inflammation from excessive Omega-6 exacerbates all other kinds of inflammatory health problems, including familiar faces like obesity, diabetes, autoimmune diseases, depression, and heart disease. Itโs not that PUFA overload really causes any one particular disease; itโs that it gives all kinds of other diseases a nudge in the wrong direction.
But if Omega-6 fats are so inflammatory and unhealthy, then why do they get such a good reputation as โheart-healthy?โ As it turns out, theyโve really been piggybacking on the Omega-3s!
Does PUFA Improve Heart Health?
This is the idea behind that โheart-healthy canola oilโ line, but actually itโs much more complicated. This study gives a good summary:
โโฆa recent meta-analysis found that interventions [replacing saturated fat with] mixed ฯ3 and ฯ6 PUFAs resulted in a significant (22%) decrease in CAD events compared with control diets with fewer PUFAs. However, interventions that used ฯ6 polyunsaturated oils with no ฯ3 PUFAs showed โผ16% more cardiovascular events compared with the control dietsโฆโ
In plain English: adding Omega-3s and Omega-6s is beneficial. Adding only Omega-6s is harmful. And thatโs not surprising at all when you think about what it actually means in terms of ratios.
In the modern American diet, adding any amount of Omega-3 would probably improve the ratio of Omega-3 to Omega-6. For example, using the numbers from this paper and assuming a 2,000 calorie diet:
| Omega-6 content | Omega-3 content | O6:O3 ratio | |
| Estimated Paleolithic/hunter-gatherer diet | Between 1:1 and 4:1 | ||
| Current US diet | 16 grams/day | 1.6 grams/day | 10:1 |
| Add 1 gram of Omega-6 and 1 gram of Omega-3 | 17 grams/day | 2.6 grams/day | 6.5:1 |
In other words, these studies donโt show that eating more PUFA is good for you. They really show that improving the ratio of Omega-6 to Omega-3 fats is good for you. The American diet is so astonishingly deficient in Omega-3 fats that people still benefit from adding them even when they come along with Omega-6s. But that doesnโt mean the Omega-6s are healthy!
PUFA By the Numbers
The next big question, of course, is โwhat does this actually mean in real food?โ Nobody eats grams of PUFA; people eat fish, or almonds, or tofu. And unless you really love doing nutritional math, you probably want to know what a healthy fat intake is in the real world.
Unfortunately, easy numbers are hard to come by. Itโs not quite clear exactly what the ideal ratio of Omega-6 to Omega-3 is, much less how to get it. And all of us have better things to do than obsessively tally up our almond intake. But here are some general guidelines:
- Avoid soy, โvegetable oil,โ peanut oil, corn oil, canola oil, and other highly concentrated sources of Omega-6 fats, especially if theyโve been deep-fried or otherwise exposed to extreme heat.
- Eat nuts and seeds in small amounts, not as staple foods.
- Eat plenty of fish and seafood โ approximately 1 pound of fish per week is a good goal.
- Do not just add more Omega-3s onto a diet rich in Omega-6s to โbalance it out.โ This doesnโt work. You cannot โeraseโ the effects of a bunch of tofu by slugging down a shot of fish oil. Instead of adding more Omega-3s, lower Omega-6s.
- Keep it proportional. Most foods that contain fat contain a little Omega-6, but thereโs no call to go crazy over olive oil and avocados. Before you avoid a food for fear of Omega-6 fats, look up exactly how much it contains: you might be surprised at how little it actually is.
Summing it Up
Canola oil is not a health food โ especially not for your heart. The line that โPUFA lowers cholesterol/reduces the risk of heart diseaseโ is true only if โPUFAโ includes Omega-3 and Omega-6 fats: Omega-6s on their own are likely to make the problem worse.
For overall health, a good general plan is to keep overall PUFA intake low, especially the Omega-6s. Ditch the seed and vegetable oils and all the soy products, and keep nuts and seeds to small amounts. Make sure youโre getting enough Omega-3s by eating plenty of fish and other seafood, but donโt try to โmake up forโ too much Omega-6 by piling on more Omega-3s: it doesnโt work that way!
Most importantly, donโt stress out over otherwise nutritious foods just because they have some Omega-6. As long as youโre avoiding the biggies (seed oils and soy) youโll probably be just fine. Enjoy plenty of Paleo-friendly fats like olive oil, coconut oil, and animal fat, and try to have some kind of seafood at least once a week: your Omegas will take care of themselves.
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