If you’ve heard that vegetable oils or “industrial seed oils” will compromise your health, you’re not alone. This belief has been circulating among the natural health space for at least a decade. I once subscribed to this idea, but have become familiar with more recent research and wanted to share it here.

To be clear, vegetable or “industrial seed oils” include the following oils

• Corn
• Cottonseed
• Canola
• Peanut
• Safflower
• Soybean
• Sunflower

Current research has studied vegetable oils’ effects on human subjects– rather than effects on animals or lab experiments of past studies. Current research has also been able to take away confounding variables like trans fats, which skewed data in older studies. With the help of Dr. Sarah Ballantyne, I’d like to bring your attention to the current high quality research that focuses on health outcomes data so we can be sure that these oils aren’t putting our health in jeopardy.

Primary Concerns

Primary concerns with vegetable/seed oils frequently include:

1. They are high in linoleic acids (an omega 6 polyunsaturated fat) which, when metabolized, convert into pro-inflammatory compounds
2. Polyunsaturated fats, like those found in vegetable oils, are unstable at higher heat. These fats are more easily oxidized than saturated fats. Oxidized oils can cause cellular damage and increase the risk of cardiovascular disease
3. The chemical solvents used in extraction are still present in the oil

Current Linoleic Acid Outcomes Data

These arguments are not entirely without merit, but consider: relying on lab experiments alone produced confounding variables which have since been recognized. It’s important to base recommendations on outcome data that show what actually happens when consuming these oils, versus what is projected to happen.  Current high quality literature supports the consumption of linoleic acid, as it’s been linked to:

• Reduced risked of  all-cause mortality
• Reduced risk of death from cardiovascular disease
• Reduced death from cancer
• Reduced risk of diabetes
• Reduced risk of stroke
• Reduced risk of coronary heart disease events

The above findings have come from current systematic reviews or meta analysis papers. These types of studies are of the highest confidence, meaning they synthesize all available evidence on a specific research topic. Basing conclusions off these types of studies are preferred vs. using a single study, because it shows that the outcomes are reproducible.

Dr. Sara Balentyne’s review on vegetable oils is excellent for sourcing the individual research papers used to arrive at the conclusions above. She also covers the details of studies done in the 60’s and 70’s, showing negative health impacts with increased seed oil consumption. One study ending in 1973 used safflower oil as its source of linoleic acid. The results were worrying- but upon further investigation, the oil was given both in liquid and soft margarine form (trans fat!). This confounding variable wasn’t taken into consideration at the time. We now know that trans fats are indeed harmful, which would explain the results of the study.

Linoleic acid has historically been used for its cholesterol lowering effects (which are well studied) but a new concern arose that linoleic acid could potentially increase inflammatory factors.  Linoleic acid can potentially be converted into arachidonic acid (AA), which at high levels have been associated with inflammatory conditions and cancer.

 Current Arachadonic Acid Outcomes Data

A number of studies have connected linoleic acid with detrimental effects on certain inflammatory pathways.  Again, however, those studies were lab studies. While it’s true that high levels of AA can produce molecules that have been linked to cancer and inflammatory conditions, the amount that converts from eating vegetable oils isn’t enough to show any measurable negative health impact. The studies that have been done in humans show an overwhelmingly positive or neutral effect on inflammation. Here are some examples from high quality research papers:

• A 2011 systematic review of clinical trials found no impact of linoleic acid intake on arachidonic acid levels in the body, even when linoleic acid intake was decreased by as much as 90% or increased by as much as 600%.
• A randomized controlled trial from 2023 likewise found that among overweight or obese women, lowering linoleic acid intake had no independent effects on plasma arachidonic acid levels.
• a 2017 cross-sectional study found that higher intakes of polyunsaturated fat-rich cooking oils had no association with plasma arachidonic acid levels (red meat intake, however, did).

Interestingly, AA hasn’t even been consistently linked to pro-inflammatory effects or adverse health outcomes. There are a number of quality studies that actually appear to lead to the opposite conclusion.  There are both pro and anti inflammatory mediators produced by AA, which could explain this phenomenon. Basically, the effect on inflammation from increased AA isn’t guaranteed in either direction.

Putting It All Together

What matters most is not a hypothesis about any certain pathway or mechanism of action, but what the actual health outcomes are when linoleic acid consumption is tested in humans. If you need more convincing that vegetable oils won’t ruin your health, I recommend reading Dr. Sara Balentyne’s review on vegetable oils. I hope this information allows you to make food choices more freely and without fear. With this being said, I still recommend using olive oil as the main cooking oil. It does have extensive research showing a wide variety of health benefits. Avocado, canola and coconut oils also have a net positive effect on various health markers.

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