Seed Oils - the Truth

What are seed oils?

The term ‘seed oils’ refers to plant/vegetable oils that are derived from the seeds of the plant. Examples of these oils include:

• cottonseed

• sunflower

• safflower

• canola

• and grape seed.

Generally, this term is also used to refer to vegetable oils such as soy, corn, rice bran, sometimes peanut, and possibly others which don’t actually come from seeds.

These can be contrasted with plant/vegetable oils that are derived from fruit including olive, coconut, avocado, and palm.

The controversy

Recently, seed oils have been referred to as:

• toxic

• bad for health

• the root cause of increased rates of certain diseases

• a large source of free radicals in the body

• a source of the bad omega-6s

• poisonous

• produced in a toxic way

• and the list goes on.

Are they really bad? Not necessarily, let’s break this down by looking at each crime of which they’ve been accused.

The truth, should you choose to accept it

Toxic, produced in a toxic way & poisonous

Vegetable oils first came into use 1000’s of years ago. In those days people learned that oil could be extruded from the plants by heating the plant products in the sun, over a fire, or in an oven. In Mexico and North America, peanuts and sunflower seeds were roasted, ground into a paste, and then boiled until the oil rose to the top and could be skimmed off.

Over the years better ways to extract and refine oils were invented and improved using a variety of different pressors and expeller systems, however these were time consuming and inefficient with only about 10% of the available oil being obtained.

As technology improved, the production of vegetable oils became more efficient as it was discovered solvents could be used to extract the oils with all but 2-5% of the oil being extracted, therefore decreasing waste.

Today, vegetable oils may be produced either via chemical or mechanical means. There are a variety of different ways this can happen and getting into each step is out of the scope of this article. One thing to mention however is that simply squeezing the oil from the fruit or seed of a plant is only an option in a few oils produced. Even in mechanical processing, high heat and pressure processing may be used. Cold pressing is probably one of the most minimal ways to produce oil, however this technique is not suitable for most oils because it may leave trace elements in the oil that produce a bad odor and taste. Most of the oils available in supermarkets require additional processing to be at the standard consumers expect. Additionally, most people favor olive and avocado oils as a healthy, and this is certainly true. However, olive and avocado oils may be produced by mechanical or chemical means (using organic solvents), which is something not everyone may know.

Most consumers do not like the idea of solvents being used to extract oils, even though they may not know what solvents actually are. Let’s break those down briefly. Solvents are chemical compounds that are used in a variety of different industries to dissolve, suspend, or extract other materials, without changing the chemical nature of the material or the solvent. There are many solvents used across different industries. A few examples include hexane, acetone, methanol. Industries that use solvents include construction, printing, paint manufacturing, textiles, pharmaceuticals, food, footwear manufacturing, and dry cleaning to name a few. Solvents are widely used across many industries to manufacture products people use daily. Back to vegetable oil production.

Following the use of the solvents to extract the oil, the entire product goes through what’s called a refining, bleaching, and deodorizing process to remove any unwanted components of the oils that have come through the processing from the fruit/seed/nut, remove any remnants of solvents used for extraction, eliminate color pigments that are not necessary, and remove free fatty acids and volatile compounds that could contribute to odor and rancidity.

When it comes to food oils, manufacturers are required to test their oils before they reach consumers. Each test must be printed on a Certificate of Analysis (CoA) that accompanies the oil through their life and beyond. CoAs are not usually available to consumers. Testing requirements include consistency, flavor and odor, inclusion of foreign material, chemical constituents of the oils including free fatty acids, peroxide value (a measure of oxidation), color, stability of oil at high temperatures, linolenic acid content, iodine value, heavy metals (arsenic and lead), and they must determine that if solvents are used in the processing of the oils that any remaining solvent is below appropriate detectable levels. If an oil does not meet these parameters it is not allowed on the market. Now, is it possible that products get to market that do not meet industry standards? Of course. Manufacturers are expected to self-regulate which is why it’s incredibly important to choose vegetable oils from a reputable source.

Bottom line, most vegetable oils that are used today are produced via processing as described above. Does this make them toxic, poisonous, or produced in a toxic way? The short answer is no. If you are a consumer sho does not want an oil produced in that way, look for oils that are 100% cold-pressed. Be advised, these are usually higher in price.

Bad for health & the root cause of increased rates of certain diseases

It is no secret that rates of disease have increased over the years. It's natural to want answers as to why, and who or what is to blame. Has disease increased because of the types and amounts of food people eat, busier lives that lead to inactivity, an increase in stress and anxiety, exposure to more chemicals in foods and the environment, is disease more easily diagnosed these days, is it because of seed oils, or something else entirely? Humans seem programmed to want an answer and to point to one thing that is to blame. Is it seed oils alone? The likely answer is that it's a combination of several factors that are contributing to an increased rate of disease and lower life expectancy.

The truth is that the rate of processed food consumption has increased. Processed foods came about due to the need for improved food availability, safety, shelf-life, transportability, and digestibility. There is a large population to feed and processed foods, for better or worse, help to do that. Processed and ultra-processed foods often contain ingredients from additives rather than whole foods. They usually have a higher fat content, more saturated fat, added sugars, high salt, low fiber, and a low number of vitamins. Research has correlated the shift towards a high consumption of processed foods with an increase in chronic disease and a higher consumption of processed foods being associated with a higher rate of death.

Vegetable oils are often a large component of processed foods (including fried foods) because they help to enhance the flavor, add texture, support stability, add nutritional content, or they are a preferred and more affordable oil with which to cook in bulk. Because consumption of processed foods has increased, naturally the consumption of vegetable oils has increased. Does this make the vegetable oils or seed oils bad for health or the root cause of increased disease? Not necessarily because they're only one component of a processed food. Continue reading to learn more.

A source of the bad omega-6s

Omega-6 fats are a type of polyunsaturated fat. Another type of polyunsaturated fat are omega-3 fatty acids. Omega-3 fatty acids have gotten a lot of positive press and have been shown through research to support heart health, decrease cholesterol, and contribute to the health of the brain, gut, and skin.

Omega-6s have gotten more negative press, however these fats are actually beneficial. Omega-6s are required for infant growth and development, they lower LDL and help to boost HDL cholesterol, and they may help to keep blood sugar in check. Omega-6s get a bad rep however because a common omega-6, linolenic acid, can be converted into arachidonic acid (ARA), which is a building block for molecules that may promote inflammation. The body can also convert ARA into molecules that may fight inflammation and prevent blood clots.

Recently, the American Heart Association convened a scientific panel of nine independent scientists who concluded that omega-6s are beneficial for the heart and blood circulation. They found that very little linolenic acid is actually converted into arachidonic acid, even when linolenic acid is abundant in the diet. It was concluded that eating omega-6 fat could actually down-regulate markers or inflammation or leave them completely unchanged. Interestingly, a meta-analysis of 6 randomized controlled trails found that replacing saturated fats with omega-6 fatty acids reduced the risk of heart attacks and coronary events by 24%. Another meta-analysis found that replacing saturated fats with polyunsaturated fats (omega-6 and omega-3) reduced rates of heart disease more than replacing them with monounsaturated fats and carbohydrates.

Sources of omega-6 fats include safflower, sunflower, corn, and soybean oils, walnuts, and pumpkin seeds. Many people tend to eat more omega-6 than omega-3, and while a low amount of omega-3 is not ideal for general health, bringing the two into better balance is a good idea. A general guideline for doing this is to add more omega-3s to the diet and cut back on the amount of ultra-processed foods consumed. (See the Omega-3 article in the Lunch Lady files to learn more).

They’re a large source of free radicals

Free radicals are formed in the body through a variety of methods. They are generated by the body as a natural byproduct of turning food into energy, they are formed after exercising, from exposure to cigarette smoke, air pollution, and sunlight. They come in many different shapes and sizes and share one thing in common: an insatiable appetite for stealing electrons from nearby substances. When this happens, the electron can radically alter the loser’s structure or function. For example, it can cause a LDL particle to get trapped in an artery wall. At very high levels, free radicals are capable of damaging cells, genetic material, and leading to chronic disease.

As already mentioned, oils must be tested for PV (peroxide value) prior to being packaged and sold. PV is a measure of oxidation. Exposure to oxygen (oxidation) contributes to degradation of oils, otherwise known as rancidity. It occurs when oxygen is absorbed from the environment, if moisture in the environment interacts with the oil, when exposed to increased temperatures, light, water, trace minerals, or simply over time. This process, no matter how it occurs, may produce free radicals within the oil. Ingestion of rancid lipid products has been linked to the development or exacerbation of several diseases including cancers, heart disease, kidney disease, and neurodegeneration.

Bottom line is that any oil can be at risk for becoming rancid and therefore being a source of free radicals, even those that are cold-pressed. A good rule of thumb is to limit exposure to oils that have been tremendously heated (decrease consumption of fried foods), avoid ordering items at restaurants that are cooked in a batch deep fryer, cap oil immediately after using it, keep it away from light, throw it away when it is old, do not use it if it smells "off", and buy oils from reputable companies and brands. And know, that even the purest of oils will degrade over time.

Bottom line

In June of 2022, scientists at Harvard wrote an article to debunk the claims related to seed oils and their associated health risks, suggesting that the saturated fat, refined carbohydrates, sodium, sugar, and overall lack of nutrition in processed foods is to blame for the ill effects attributed to seed oils, rather than the seed oils themselves.

So, are seed oils bad? Not necessarily. Should people be monitoring how much of them are consumed? It’s definitely a good idea, along with decreasing consumption of ultra-processed foods, considering making food from scratch, food prepping, and eating more whole foods, including fresh fruits, vegetables and whole grains.

References

Blanco-Rojo, R., Sandoval-Insausti, H., Lopez-Garcia, E., Banegas, J. R., Rodriguez-Artalejo, F., Guallar-Castillon, P. (2019). Consumption of Ultra-Processed Foods and Mortality: A National Prospective Cohort in Spain. Mayo Clinic Proceedings, (94)11, P2178-2188. Retrieved from https://www.mayoclinicproceedings.org/article/S0025-6196(19)30418-5/fulltext

Encyclopedia.com. (n.d.) Cooking Oil. Retrieved from https://www.encyclopedia.com/manufacturing/news-wires-white-papers-and-books/cooking-oil

Harvard Health Publishing, Harvard Medical School. (2019, August 20). No need to avoid healthy omega-6 fats. Retrieved from https://www.health.harvard.edu/newsletter_article/no-need-to-avoid-healthy-omega-6-fats

Harvard T.H. Chan School of Public Health. (n.d.). Antioxidants. Retrieved from https://www.hsph.harvard.edu/nutritionsource/antioxidants/

Harvard T.H. Chan School of Public Health. (2022). Scientists debunk claims of seed oils health risks. Retrieved from https://www.hsph.harvard.edu/news/hsph-in-the-news/scientists-debunk-seed-oil-health-risks/

Koon, R. (2009, August 4). Understanding rancidity of nutritional lipids. Natural Products Insider. Retrieved from https://www.naturalproductsinsider.com/regulatory/understanding-rancidity-nutritional-lipids

U.S. Department of Agriculture. (2021, April 14). Commercial Item Description: Salad Oils, Vegetable. A-A-20091E. Retrieved from https://www.ams.usda.gov/sites/default/files/media/AA20091E_Salad_Oils%2C_Vegetable.pdf