Modern Diet Myth No. 3: Seed oils cause heart disease

There are lots of oils derived from seeds – sunflower, canola, soybean, cottonseed, sesame, flax, grape seed, peanut and safflower to name a few. The first thing that strikes you about these oils is not how similar they are but how different. Traditional sunflower oil is high in polyunsaturated fats, whereas canola has more monounsaturated fats, plus some omega 3. Flaxseed oil has lots of omega 3 and so on.

About the only thing that all these seed oils have in common is that they are relatively low in saturated fat, which is considered to be a good thing by every reputable nutrition and heart health authority in the world.

Of course, things are very different in the curious world of celebrity-driven nutrition advice where for some reason saturated fat is seen as desirable and coconut oil, one of the most saturated of all oils, is promoted a healthy choice.

What’s the problem with seed oils?

Supposedly the biggest threat that seed oils pose to heart health is inflammation caused by omega 6 polyunsaturated fats. This is a myth, but it is repeated so often that I will happily address it in depth in another post in this series.

It should be remembered that polyunsaturated fat is the only type of fat that is actually essential for human nutrition. Mother Nature would certainly have made a mess of things if the only essential fats in our diet also caused heart disease.

Some critics say we just eat too much polyunsaturated fat. But the amount of polyunsaturated fats in the Australian diet has been falling for 30 years and is now just 4% of daily calories, right at the bottom end of the recommended intake range of 4-10%.

None of the arguments against seed oils stands up to any scrutiny. Critics of seed oils tend not to dwell on the fact that polyunsaturated fats lower the level of cholesterol in the blood, which lowers heart disease risk. Or that saturated fat raises blood cholesterol, which increases heart disease risk. Instead, they argue that the whole cholesterol story is wrong, ignoring the last 60 years of research in the process.

Image: source

A natural experiment

So, nutrition experts say eat more seed oils and less saturated fat to promote heart health while the celebrity chefs and book sellers say the exact opposite. Who’s right?

It wasn’t too long ago that a whole country put the idea to the test. During the 1990s a natural experiment occurred in Poland. Following major political changes some government subsidies were removed raising the prices on saturated animal fats; less expensive seed oils like canola and soybean oils flooded into Poland. But was this sudden rush of seed oils bad news for heart health?

On the contrary, between 1990 and 2002 rates of heart disease in Poland fell by about 40% in both men and women, a remarkable change in such a short period.

Maybe nutrition experts know what they are talking about after all.


26 thoughts on “Modern Diet Myth No. 3: Seed oils cause heart disease

  1. Dear Bill….THANK YOU once again for your brilliant research and wise words of wisdom. What would we do without you? …Pamela

  2. Thank you Bill. I’ve often wondered what these chefs & book sellers mean by “inflammation” and look forward to your discussion on this topic in the future. Meanwhile, I will happily continue to use my seed oils in my cooking &, dare I say, I will use them to dress the salads I make that include legumes.

  3. You keep echoing old ideas on LDL, did you know that 75% of CVD patients admitied to hospital had lot to normal LDL? It sort of makes a mockery of the “low LDL is good” theory. I am linking to an article on the study. “Almost 75 percent of heart attack patients fell within recommended targets for LDL cholesterol, demonstrating that the current guidelines”

    And what is laughable is the Dr’s want to recommend even lower levels which are know to be dangerous. “How low can we go? Low cholesterol is associated with accidents, depression, and cancer? Is that what we have to look forward to? Wouldn’t it make more sense to conclude that elevated cholesterol is not the cause of heart attacks, the cholesterol hypothesis is wrong, and the National Cholesterol Education Program should vote itself out of business? ”

    We know that won’t happen there is too much money to be made from drugs.

    • Rob, our discussions would be easier if you had a better grasp of the scientific literature. Whether or not lowering cholesterol with statins drugs lowers heart disease risk has been tested in many scientific experiments. Last time I looked there were no fewer than 24 published meta-analyses of these experiments and ALL of them concluded that lowering cholesterol with statins lowers heart disease risk. Denying the facts is just silly.
      Read these studies, then come back to me. Regards, Bill

      • There is NO interdependent article that shows that Bill, not a one. All are funded and the original data is kept closed. Not to mention there are no randomized control trials anywhere.
        I am sorry you can’t grasp simple concepts like the fact that 75% of people with low or normal cholesterol were admitted with CVD. Hardly a stellar endorsement for promoting lower cholesterol. You might try reading the studies rather than what big pharma tells you.
        I did find it interesting that you were unable to produce a single independent study to back your claim.

      • A Meta-analysis Bill? And you are worried that I don’t have a grasp on Scientific literature? You do no a meta-anaysis can not prove causation? Just because results show a correlation, there is no proof of an underlying causality. You need actual random controlled studies to do that.

        • I’m sorry Rob. You are very confused about some of the basics of assessing scientific literature.
          A meta-analysis of RANDOMISED CONTROLLED TRIALS is exactly the way you prove causation.
          In epidemiology, correlations don’t necessarily mean causation, but a randomised controlled trial is not epidemiology. Regards, Bill

    • Hi Rob,

      The 75% figure was based on an LDL target of <130mg/dL. Only 17.6% had LDL <70mg/dL, which appears to be the physiologically "normal" amount (given that this is the LDL cholesterol concentration seen in healthy hunter-gatherers, newborn humans, and wild non-human primates).

      Also, a mendelian randomization study found that although low LDL cholesterol was associated with cancer risk, genetically lower LDL cholesterol was not. This suggests that low LDL per se doesn't cause cancer.

    • Jenny, do you REALLY think omega 6 affects the risk for cancer, diabetes and Alzheimer’s?
      Originally I thought that I would have 10 myths in this ‘myth series’ of posts. I think I’d better make it 20. Regards, Bill

        • Jenny, if you have really been studying this topic for 20 years how did you manage to adopt a position different to that of every cancer authority in the world?
          Can you name one authoritative cancer organisation that recommends limiting omega 6 polyunsaturated fat intake to lower breast cancer risk? World Cancer Research Fund? No. World Health Organisation? No. Cancer Australia? No.
          Please read this paper – a pooled analysis of cohort studies – it’s the definitive epidemiological study. It finds no link between polyunsaturated fat intake and breast cancer risk.

          Regards, Bill

          • Bill I am concerned that you are suggesting I read research from 2001 (which I had already read years ago) when so much research has been done subsequently! I am somewhat sceptical about the recommendations of WHO and WCRF! And downright contemptuous of the recommendations Cancer Australia (have been doing the opposite to their fat and carb and sun recommendations at the instruction of my gp and endo to address a hormonal imbalance and bone issue). I think you will find that the more research is recognising the dangerous role of omega 6 (and sugar) in cancer development.

          • Hello Jenny. Healthy scepticism is a good thing but when your point of view ends up different to that of learned bodies whose job it is to review science and make recommendations you need to think again. My question was: Can you name one authoritative cancer organisation that recommends limiting omega 6 polyunsaturated fat intake to lower breast cancer risk? Regards, Bill

          • Hi Bill, I wish I could be as trusting as you! But when I did that and followed standard recommendations I just got sicker and sicker! I’m afraid that my head is well and truly out of the sand now and there is no going back!

          • We mustn’t confuse the concepts of individual health and population health. There are lots of instances where a food may be dangerous for an individual (allergy) yet desirable for the broader population. Nuts is a good example. Regards, Bill

          • I agree Bill and am not confused what I am concerned about is the number of people suffering unnecessarily because of the lack of acknowledgement, lack of understanding and lack of availability of affordable testing for coeliac disease, non-coeliac gluten sensitivity and other common issues which have been exacerbated by the nature of common processed food and the genetic changes in many agricultural products especially wheat and soy.

    Joseph Hibbeln, a researcher at the National Institute of Health (NIH) who has published several papers on n-3 and n-6 intakes, didn’t mince words when he commented on the rising intake of n-6 in a recent paper:

    The increases in world LA consumption over the past century may be considered a very large uncontrolled experiment that may have contributed to increased societal burdens of aggression, depression and cardiovascular mortality.

    • Jenny, you need to realise is that there are people who are employed to discredit omega 6. You don’t have to think too hard to work out who is the funding body driving it along.
      I have heard Jo Hibbeln speak at conferences. People of his ilk sound very convincing we they demonise omega 6 until they get challenged by someone who knows what they are talking about, at which time they gently backpedal. It’s a game. Are we playing it now? Regards, Bill

      • Conspiracy! Oh my!!! Bill I’ve been researching this stuff for 20 years, I have a science degree (including some human physiology and biochemistry). I used to think what you seem to promote and now think differently. I’m not playing any games I’m just so thankful that now I am well.

  5. This article is a bit dangerous. Its not about omega 6 alone. Its the inherent instability of these oils:

    Incidence of cancer in men on a diet high in polyunsaturated fat. Pearce ML, Dayton S. PMID: 4100347;

    Cancer Res. 1994 Dec 15;54(24):6441-5.
    Unsaturated fatty acids are required for continuous proliferation of transformed androgen-dependent cells by fibroblast growth factor family proteins.

    Lipids. 1987 Jun;22(6):445-54.
    Effects of fatty acids on gap junctional communication: possible role in tumor promotion by dietary fat.

    • Hello Ed. No diet-cancer authority in the world recommends limiting seed oils or unsaturated fats to prevent cancer. Regards, Bill

  6. Ravnskov, U., DiNicolantonio, J. J., Harcombe, Z., Kummerow, F. a., Okuyama, H., & Worm, N. (2014). The questionable benefits of exchanging saturated fat with polyunsaturated fat. Mayo Clinic Proceedings. Mayo Foundation for Medical Education and Research. doi:10.1016/j.mayocp.2013.11.006

    • Hello Edward. I’m very familiar with Dr Ravnskov’s views. The thing is, none of the world’s leading heart health agencies agrees with him. Regards, Bill

  7. Hmm, in Poland did the “large increase in consumption of non-hydrogenated rapeseed and soya bean oil” partially replace a large consumption of sunflower oil, therefore changing the makeup of the vegetable oil category ? This merits a closer look – “Surprisingly, during the 1990′s CHD mortality substantially decreased in some Eastern European countries but not in others. Our data show that countries which experienced an increase in ALA consumption also experienced a substantial decline in CHD mortality.”

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