Do Vegetable Oils Raise Heart Disease Risk?

Chart showing relation between tissue levels of omega-6 fatty acids and death from coronary heart disease

In several recent articles, we’ve seen that vegetable oils, better known as industrial seed oils, are implicated in a number of diseases, including heart disease. In this article, we’ll take a closer look at the relation between vegetable oils and heart disease.

Association between seed oil consumption and heart disease

The levels of omega-3 fatty acids, the kind most abundant in fish and fish oil, strongly and negatively correlate to heart disease rates, both on a population basis, and in individuals.

Since omega-6 fatty acids, in which seed oils are abundant, and omega-3 fatty acids compete for absorption into body tissues, it follows that a higher level of omega-6 in tissues correlates to higher heart disease rates, and indeed they do. See chart below. (Source.)

There’s a strong, straight-line relation between tissue levels of omega-6 fatty acids and death from coronary heart disease.

Clinical trials

Associations are one thing, but can’t show causation. Maybe the association between omega-6 fats in the body and coronary heart disease is just a coincidence. To show causation, you need stronger evidence.

The American Heart Association wants us to consume more vegetable oils in place of saturated fat to reduce the incidence of heart disease. Surely they have some evidence.

A recent meta-analysis of trials that involved greater consumption of seed oils found that in those trials that also managed to raise tissue omega-3 levels, there was benefit, but in trials that raised omega-6 levels, there was no benefit, but a greater risk of death from heart disease.

A reanalysis of the Sydney Diet Heart Study found an increased death rate in the intervention group, who

received instructions to increase their PUFA [polyunsaturated fatty acid] intake to about 15% of food energy, and to reduce their intake of SFA [saturated fatty acid] and dietary cholesterol to less than 10% of food energy and 300 mg per day, respectively. To achieve these targets, intervention participants were provided with liquid safflower oil and safflower oil polyunsaturated margarine (“Miracle” brand, Marrickville Margarine). Liquid safflower oil was substituted for animal fats, common margarines and shortenings in cooking oils, salad dressings, baked goods, and other products, and was also taken as a supplement. Safflower oil polyunsaturated margarine was used in place of butter and common margarines. Safflower oil is a concentrated source of n-6 LA (table 1) and contains no other reported PUFAs. Therefore, the intervention oil selectively increased n-6 LA without a concurrent increase in n-3 PUFAs; this LA selective PUFA intervention will be referred to as the LA intervention.

Hard to imagine such a high intake of an unnatural food for humans as safflower oil at 15% of calories could help things, and it didn’t.

The intervention group had higher death rates from all causes, cardiovascular disease, and coronary heart disease. All-cause death risk was 1.62 times higher in the polyunsaturated group compared to controls, and results were similar for CVD and CHD. The charts below, from the article, show cumulative death rates in the intervention group that consumed more safflower oil, versus the control group that didn’t.

Similar results were found in a reanalysis of the Minnesota Coronary Experiment, which used corn oil, and in which the intervention group  had “a 22% higher risk of death for each 30 mg/dL (0.78 mmol/L) reduction in serum cholesterol.”

Omega-6 fatty acids from seed oils could increase heart disease risk by a number of mechanisms: increasing platelet aggregation (and thus increasing blood clotting tendency), increasing oxidation of LDL, and increasing the generation of inflammatory cytokines and prostaglandins.

How to decrease consumption of omega-6 fats

Given all of the above, it would be prudent to avoid the consumption of excess omega-6 fatty acids. The most obvious way is to avoid the consumption of seed (vegetable) oils.

However, lots of foods are either made with seed oils or are naturally high in omega-6 fats.

In a study of different foods and the balance between omega-6 and omega-3 fats, the ten food items with the most negative Omega 3-6 score were:

  • soybean oil,-50;
  • mayonnaise, -46;
  • tub margarine, -39;
  • microwave popcorn,-37;
  • “Italian” salad dressing, -35;
  • potato chips, -29;
  • stick margarine, -28;
  • vegetable shortening, -28;
  • peanut butter, -24;
  • tortilla chip snacks, -24.

That’s basically a list of common junk food items. If you do nothing else but avoid those, you’d be avoiding huge sources of excess omega-6 fats.

Eat whole, unprocessed food – but you knew that already.

PS: Check out my Supplements Buying Guide for Men.

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  1. Steve says:

    Another legendary series destroying mainstream medical doctrine and the moneyed interests. This certainly proves that the medical mainstream is incompetent or practicing scientific misconduct.

  2. al becker says:

    Thanks. Very convenient to have a list of what to avoid.

  3. paul rivas md says:

    Very nice job. A real eye-opener P.D. I knew it was bad, but honestly didn’t know it was that bad! The AHA should be ashamed of themselves for continuing to propagate the myth. I guess you only need to follow the money trail. They get tons of money from food companies as I’m sure you know.

  4. Bill says:

    Ahhhh PD….. Thanks for this list & article. It’s a looong time since I ate any ‘Miracle’ or Marrickville margarine. I always instinctively avoid that crap here in Oz.

    There was a period when that company marketed a blend of olive & safflower margarine as more healthy here. It became very popular and may still be. Certainly I fell or that bs for years before discovering the joys of butter again..

    But I have always been a ‘chipaholic’ and no doubt I should have stopped eating chips ( crisps ) decades ago. instead of a year or two ago…

    Again thanks PD.

  5. TeeDee says:

    The one thing on the list I’ve had trouble giving up is the mayonnaise that I use on occasion for chicken or seafood salad. I double up on fish oil after I have some mayo and I’m hoping it will balance it out somewhat :/

    • Bill says:

      TeeDee, make your own mayo mate. Dead simple !
      But use olive oil instead of the industrial crap in commercial mayo.

      • TeeDee says:

        I have made my own with bacon fat, melted butter and liquid coconut oil (olive oil gives it a bitter, unpleasant taste, but maybe that’s just me). The problem is it has to be eaten within 5 days, apparently and I hate to waste. I may have to just bite the bullet and make as needed and be sure to use it all up. Not sure how that’s going to work, though. Thanks for your reply–take care.

  6. JohnD says:

    Per Wiki, safflower oil uses, there are two types of Safflower oil sold, The first is predominately monounsaturated fat, this being used for food products. The second predominately omega 6 PUFA, which is used in paints. The quoted study appears to be evaluating the health effects of consuming the Omega 6 oil that is currently used primarily in paints.

    • P. D. Mangan says:

      John: I looked at the Wiki article, and at the table in the paper, and it appears you’re correct. Of course, from the viewpoint of those who designed the Sydney trial, they wanted as much PUFA as possible, so for them, the safflower oil with high omega-6 was a feature, not a bug.

      What the safflower oil one now buys at the supermarket contains, I don’t know.

    • TeeDee says:

      Good to know, John; thanks!

  7. Benji says:

    Any thoughts on nuts? One cup of almonds is about 18 grams of omega 6, which is about the same as 2.5 tablespoons of corn oil.

    • P. D. Mangan says:

      Good question. I rarely eat nuts for exactly that reason. Almonds aren’t even the worst offenders (and one cup is a lot anyway). Walnuts are loaded with omega-6. Besides that, I don’t believe that ounce for ounce, nuts offer superior nutrition. Protein levels aren’t good, and they’re very high in calories. I’d just prefer to eat meat and eggs, and if I need a snack, have a piece of cheese or a bit of plain, whole-milk yogurt.

      I’ve also cut way back on chicken because that’s also loaded with omega-6. I eat more beef now, pork as well – beef is superior to pork in fatty acid profile though.

  8. Gil says:

    So peanuts are junk food? I love peanuts. I was hoping peanuts were more of a wash.

  9. oil boy says:

    Mangan has really uncovered something in his latest line of articles dealing with oils.

    What I’ve noticed in the above chart: mayo, chips, and some other things (peanut butter, wow, sad…just sad…maybe cashew butter or almond butter?)…is the recombination of soybean oil and other crap into the foods that make them bad in the first place.

    You can find avocado oil mayo instead of the common stuff in the store which are almost all made with soybean oil.

    Utz’s old school chips are cooked in lard, and better grocery stores have chips that are cooked in coconut or avocado oil.

    One big surprise to me is that Bugles, of all things, seem to be healthy as they are cooked in coconut oil and use corn, not flour.

    I think the next book for mangan should be something on this subject…or I may steal this idea for an e-book.

    • P. D. Mangan says:

      Thanks, yes a good topic for a book. I don’t know how much the dangers of veg oils are unknown. I think I overlooked them myself until recently, and they could be a major factor behind the rise of coronary heart disease in the 20th C. That and smoking.

    • TeeDee says:

      Unfortunately, there seems to be more ingredients in the Canadian version of bugles (not that I’d eat them anyway as they contain sugar): › … › Chips & Snacks › Chips & Salty Snacks › Chips
      Rating: 5 – ‎5 reviews – ‎$2.25Degermed Yellow Corn Meal, Coconut Oil (Contains Bht, Citric Acid), Sugar, Salt, Baking Soda, Monoglycerides, High Monounsaturated Canola Oil (Contains Citric Acid), Rice Bran Oil (Contains Bht). May Contain Milk And Wheat Ingredients.

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