There have been quite a few claims lately on the internet (though all look deceptively similar), that vegetable oils in general are bad for your health and that one should prefer oils which are not extracted from seeds, like coconut and olive oil.

Usually, in these claims there is no differentiation between oils - All are equally branded as "unnatural" and therefore bad. In addition, it is claimed that they are responsible for cardiovascular and other diseases.

I am wondering if these claims are correct and whether all vegetable oils can be shown to be collectively problematic to human health, when consumed in regular, day-to-day amounts.

Are vegetable oils (such as canola, corn, sunflower, etc.) linked to health problems?

  • 1
    This question would be greatly improved by focusing on an individual claim that you've heard and asking us if it's true. There is a lot of distracting content in this question that takes focus away from a single claim that we could verify/falsify/examine.
    – user5582
    Apr 19 '14 at 20:49
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    There are too many claims here. We can't hope to answer "which is healthiest" when there are so many factors. (i.e. What if one is correlated with a terminal cancer, one is causally associated with a milder cancer, one increases the risk of heart-disease, one increases (bad) cholesterol - which is assocated with heart disease, one reduces bio-diversity (through farming practive), one has the highest carbon footprint, one involves GMO, and one is the least organic? Which is "healthiest"?)
    – Oddthinking
    Apr 19 '14 at 22:55
  • @Oddthinking Thank you for your contribution. I tried to make my question a bit more specific. The problem I am having is precisely that: There are too many claims in the world of nutrition. When I am asking about "healthiest", I do mean healthy for the consuming individual. organic/non-organic and GMO vs nonGMO has, to my knowledge, not been shown to have anything to do with health and more with ideology. Reducing bio-diversity is also not a health but an environmental problem, as does having a high carbon footprint. I hope the question is now improved a bit. Apr 20 '14 at 7:38
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    Isn't a coconut a seed?
    – Flimzy
    Apr 21 '14 at 17:08
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    Castor oil may not be too healthy in certain formulations.
    – Ken Y-N
    Apr 22 '14 at 2:19

One major concern is the fatty-acid content of these oils.

The major point of contention is about unsaturated fatty acids.

An unsaturated fatty acid is a molecule with "free slots" to bind other molecules (mono-unsaturated as only one slot, poly-unsaturated can have many). So unlike saturated fatty acids which are stable, unsaturated fatty acid are prone to induce many chemical reactions in the body, some of them being necessary to proper function, some of them being bad for health (inflammatory reaction causing degenerative conditions such as cancers).

If you ingest far more unsaturated fatty acids than are necessary for the good reactions, the remaining will still be there and will be available for unwanted reactions.

These fatty acids are necessary in small amount (they are even labeled "essential" as the human body cannot produce them by itself) but too much of it is toxic. As always in toxicology, that's the dose that makes it toxic.

Many vegetable oils tends to have high concentrations of poly-unsaturated fatty acids, but there are exceptions (coconut and palm are mainly saturated, olive is mainly mono-unsaturated).

With these concentrations, it's easy to reach toxic levels.

Some nutrition books in the ancestral/paleo movement touch this subject. For example:

  • Perfect Health Diet (Paul Jaminet and Shou-Ching Shih Jaminet)
  • Deep Nutrition (Catherine Shanahan)

Vegetable oils tend to be higher in omega-6 fatty acids, contributing to the unhealthy, skewed omega-6 to omega-3 ratio of the typical Western Diet, as described in this paper

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