Concerns with Polyunsaturated Vegetable Oils – Part 1

INTRODUCTION: Both the US and Canadian Dietary Guidelines encourage us to limit saturated fat in order to reduce the risk of heart disease and to eat unsaturated fat, including polyunsaturated vegetable oils instead but what are these fats, where do they come from and what role might these play in development of obesity, Type 2 Diabetes, non-alcoholic fatty liver disease and even cancer?  This article is part 3 in the series titled Bad Fats and Enduring Beliefs.


Polyunsaturated vegetable oils” is really a misnomer, as neither soybeans nor rapeseed / Canola are “vegetables”.  More accurately these should be called “industrial seed oils“, as they are seed crops that have been deliberately engineered for food use.  These are created oil products which are quite unlike natural oils that can be easily expressed from nuts, seeds and fruit using a millstone, as has been done since the Bronze Age [1].

Image result for ancient olive press
Ancient olive oil press

If you simply press olives, almonds, sesame or poppy seeds between your fingers you will be able to express a little bit of their oil on your fingers.

Not so with soybeans!

You can squeeze a soybean as hard as you like and for as long as you like and you are not going to get any oil out of it!

The first attempt at trying to express oil from soybeans occurred in the United States, a few years after the creation of Crisco® shortening in 1911.  For 3 long years (1922 – 1925) scientists tried over and over again to extract oil from soybeans  imported from Manchuria using hydraulic presses,  and time and time again they failed. Finally, in 1925 scientists turned to the use of chemical solvents  to get oil from soybeans and solvent extraction of soybean oil has been used ever since.

Trans Fats and Industrially Produced Shortening

In days gone by, deep-fat frying in restaurants (e.g. for French fries) was done in beef tallow, sometimes in lard. Pastry crusts were made with lard or butter, and baked goods such as cakes and brioches were usually made with butter – that is until 1911 when Crisco® shortening was invented. When it was noticed that hardened cottonseed oil used in the soap-making industry had an appearance like lard, scientists decided to further process it to remove the strong odor inherent with cottonseed oil, and market it to housewives as the ‘modern’ way to bake.

Beginning in the 1950s, trans fats (which occurs naturally in very small quantities) were industrially produced from other industrial seed oils such as soybean oil for use in other natural fat substitutes, including  margarine, fat for commercial baked goods and fat for deep-fat frying in the fast food industry [2]. Unfortunately, it was only in the late 1990s and early 2000s that it became widely-accepted by the scientific community that eating foods made with trans fats or fried in trans fats raised LDL-cholesterol while lowering protective HDL cholesterol, and also raised triglycerides; promoting systemic inflammation and contributing to the development of heart disease. 

How ironic that the fats that were created to replace naturally-occurring saturated fats ended up being so detrimental to health!

After trans fats were discontinued due to their adverse health effects, industrial seed oils such as soybean oil and canola oil became the number one and number two oils of the food industry. These unsaturated (liquid) industrial seed oils have replaced saturated (solid) trans fat industrial oils in our food supply, however there is considerable evidence emerging which should cause us to question whether these fats are any safer (more on that below).

The Created Market for Industrial Seed Oils

The market for industrial trans fats and liquid industrial seed oils was itself created based a belief that ‘dietary saturated fat led to heart disease’.  Much  of what we have come to believe about this originated with a pathologist named Ancel Keys who proposed his ‘diet-heart hypothesis‘ in the 1950s.

Physiologist Dr. Ancel Keys.

In 1967, Keys published his “Seven Country  Study” that reported that populations that consumed large amounts of saturated fats in meat and dairy had high levels of heart disease but when data from 22 countries that was available since 1957 was plotted, it was a great deal more scattered, indicating a much weaker association than Keys’ Seven Country  Study data indicated.

In August of 1967, just as Ancel Keys published his study, Stare, Hegsted and McGandy, 3 Harvard researchers paid by the sugar industry published their reviews in the New England Journal of Medicine which vindicated sugar as a contributor of heart disease and laid the blame on dietary fat and in particular, saturated fat and dietary cholesterol (previous article on that topic here). Sponsorship of this research by the sugar industry certainly casts a dark shadow over their findings.

These 3 researchers insisted in their conclusion that there was a link between dietary cholesterol and heart disease and that there was “major evidence” which suggested that there was “only one avenue for diet to contribute to hardening of the arteries and the development of heart disease”,  but as covered in the previous article, it is known that a year after their publications (1968), the report of the Diet-Heart Review Panel of the National Heart Institute made the recommendation that a major study be conducted to determine whether changes in dietary fat intake prevented heart disease because such a study had not yet been done.

Just 10 years after the sugar industry paid Stare, Hegsted and McGandy to write their reviewsHegsted was directly involved with developing and editing the 1977 US Dietary Guidelines which recommended that Americans decrease intake of saturated fat and cholesterol and increase dietary carbohydrate – entrenching the belief that saturated fat caused heart disease into American public health policy. That same year (1977), based on the same body of literature, Canada adopted very similar dietary guidelines around saturated fat…and the rest is history.


Public Health Policy Based Rooted in a Belief

For the last forty years Americans and Canadians have shunned natural fats such as butter, cream and lard in place of man-made margarine, non-dairy creamer and Crisco® – all in the enduring belief that ‘saturated fat is “bad” and leads to heart disease’.  Given that published reports vilifying saturated fat were funded by the sugar industry and that Ancel Keys study left out 2/3 of the nutrition and health data available at the time, it has become evident that public health policy was founded on what is now questionable data.

In addition, more and more current peer-reviewed published studies are concluding that saturated fat is not associated with an increased risk of developing cardiovascular disease.

If saturated fat is not associated with increased risk of heart disease then should we be eating industrial seed oils that were created and marketed as a replacement for them?

Creation of Industrial Seed Oils

Inexpensive soybean oil has been the leading oil used in food production in the United States since 1945 [3]. It was previously made into a hard fat through hydrogenation and sold to consumers as trans-fat based shortening and margarine and came into wide-spread use as both synthetic hard fat and as a food-based oil product in the late-1960s.

In Canada, soybean oil is just behind canola oil in terms of the most used, and canola is another industrial seed oil that was created by science. In 1978 rapeseed, a prairie weed was specially bred in Canada to produce a novel plant that was lower in erucic acid (a toxin found in rapeseed) and this new plant was named “canola” (‘Canadian Oil‘).

A 2015 study on Canadian vegetable oil purchased and eaten in Canada found that in 2013, 42% was canola oil (a Canadian bio-engineered industrial seed oil) and 20% was soybean oil, an industrially-engineered seed oil developed in the US [4]. Keep in mind this figure excludes food products available in Canada that are manufactured in the US, which uses predominantly soybean oil.

Soybean Oil is a Modern, Industrial Product

According to an article titled “Soybeans Are Ancient; Oil Is Not” published in the Wall Street Journal in 2011 [5], soybeans as the basis for tofu and soy sauce is an ancient food in China, but soybean oil was virtually unknown until global food oil shortages during World War I created an interest to extract the fatty part of the soybean for oil. Soybean oil is a modern creation.

How is oil made from seeds such as soybean and canola?

“Soybeans are first crushed into crude oil and then refined to remove impurities like free fatty acids. Over days, the crude is “neutralized” of acidity with phosphoric acid, “winterized” through filters that remove wax, bleached at high heat to lighten the color and finally vacuum “deodorized” to eliminate impurities.” [5]

Related image
soybean extraction plant

The extraction of soybean oil involves the industrial processing of soybeans with solvents at very high heats over an extended length of time in order to have the soybean give up its small amount of oil.

Solvent extraction of canola oil occurs in a similar method, beginning with an hour or more ‘wash’ of the rapeseed with a hexane solvent, then a sodium hydroxide wash. Bleach is then used to lighten the cloudy color of the processed oil and then it is steamed injected at high temperatures to
remove the bitter smell.

Yummy! Now this oil is ready to sell to the public to cook with and eat!

Should we even be eating these industrial seed oils?

Are they any safer than trans fats that were approved for consumption for 50 years and later found to contribute to heart disease?

Part 2 of this article will continue in Concerns with Polyunsaturated Vegetable Oils – Part 2.


References

  1. Alfred Thomas (2002). “Fats and Fatty Oils”. Ullmann’s Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH.
  2. “Tentative Determination Regarding Partially Hydrogenated Oils”. Federal Register. 8 November 2013. 2013-26854, Vol. 78, No. 217.
  3. Dutton, HJ. Journal of the American Oil Chemists Society, Vol. 58, No.3 Pages: 234-236 (1981),  https://pubag.nal.usda.gov/pubag/downloadPDF.xhtml?id=26520&content=PDF
  4. Schaer, L., Grainews, Canola gets competition from soybeans, Feb 01, 2016, https://www.grainews.ca/2016/02/01/canola-gets-competition-from-soy/
  5. Wall Street Journal, “Soybeans Are Ancient; Oil Is Not“, 2011, https://blogs.wsj.com/chinarealtime/2011/01/03/soybeans-are-ancient-oil-is-not/

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