Seed oils have officially joined the list of buzzwords people like to throw around in the world of nutrition. Some argue they contribute to inflammation and should be avoided like the plague, while others insist there’s not enough scientific evidence to support those concerns. If you google “are seed oils bad for you”, you’ll find a lot of conflicting opinions, most of which downplay potential risks and suggest that seed oils are safe.
But, a lot of the research defending seed oils comes from institutions with a clear interest in keeping them in the American diet.
Take the American Heart Association for example; they’ve long supported the diet-heart hypothesis, which recommends swapping out saturated fats for polyunsaturated fats (aka seed oils). So it’s no surprise that they continue to publish content in favor of seed oils that aligns with that belief.
This article published by the American Heart Association specifically pretty much includes all of the common “pro seed-oil” arguments:
Summary of arguments by Dr. Christopher Gardner:
Omega-6 (seed oils) are polyunsaturated fats that lower LDL cholesterol and reduce heart disease risk. They may be pro-inflammatory, but the inflammation hasn’t been shown to be harmful.
People shouldn’t worry about how oils are processed. Seed oils help people eat more vegetables, which outweighs any potential harm.
Butter or lard is a worse alternative. Studies show replacing saturated fats with unsaturated ones lowers heart disease risk.
Polyunsaturated fats (PUFAs) play key roles in human health. They contribute to cardiovascular function, brain performance, and skin and hair vitality. However, not all PUFAs behave the same in the body.¹
PUFAs are classified based on the number of double bonds in their fatty acid chains:
Saturated fats have no double bonds.
Monounsaturated fats have one double bond.
Polyunsaturated fats have two or more double bonds.
Two essential types (meaning our bodies cannot synthesize them, so we must obtain them through our diet) of polyunsaturated fats are:
Omega-6 fatty acids, such as linoleic acid (LA), found in seed oils like sunflower, safflower, soybean, and grapeseed oil.
Omega-3 fatty acids, such as alpha-linolenic acid (ALA), found in flaxseeds, chia seeds, walnuts, and hemp seeds.²
Once consumed, these fatty acids are metabolized through specific biochemical pathways that produce a variety of prostaglandins and leukotrienes, key signaling molecules involved in inflammation and immunity.³
Omega-6 fatty acids (seed oils) follow a metabolic pathway that can produce both beneficial and harmful outcomes:
LA → gamma-linolenic acid (GLA) → dihomo-gamma-linolenic acid (DGLA) → series 1 prostaglandins (anti-inflammatory and vasodilatory).
In excess, LA is diverted to another pathway: LA → arachidonic acid (AA) → series 2 prostaglandins and leukotrienes, which are pro-inflammatory.⁴
This shift toward arachidonic acid-derived compounds becomes problematic in diets where seed oil consumption is disproportionately high. When intake of linoleic acid far exceeds the body’s need, the conversion prioritizes arachidonic acid and its inflammatory derivatives, overwhelming the beneficial anti-inflammatory prostaglandins.5
Contrary to Dr. Gardner’s argument, the inflammatory potential of omega-6s has been shown to be harmful in the context of modern consumption patterns. Chronic overconsumption promotes a biochemical environment linked to atherosclerosis, arterial stiffness, insulin resistance, and other inflammatory conditions.6
Omega-3 fatty acids counterbalance this by converting into EPA and DHA; long-chain fatty acids that produce series 3 prostaglandins and resolvins, compounds known for their anti-inflammatory and neuroprotective properties.7
However, plant-based omega-3s come mostly in the form of ALA, which has a low conversion rate to DHA and EPA, less than 10% in most people.8 This makes it difficult to achieve balance without including pre-formed EPA and DHA from sources like:
Fatty fish (salmon, sardines, mackerel, trout)
Shellfish (oysters, mussels, crabs)
Grass-fed red meat (in smaller amounts)
It’s also important to note that farming practices affect nutrient content:
Farm-raised fish and conventionally raised cattle often contain fewer omega-3s as opposed to wild or grass-fed due to poor-quality diets and industrial farming methods.9
These animals are frequently exposed to hormones, antibiotics, and unnatural feed, which further degrades the nutritional profile of the meat.
For example, grass-fed cows consume ALA-rich grasses, enabling them to convert and store DHA and EPA in their fat tissue. Grain-fed cows do not, resulting in meat that’s significantly lower in omega-3s.10
Thus, while omega-6 fatty acids are essential, the balance between omega-6 and omega-3 intake determines whether these fats support health or contribute to disease. A proper ratio closer to 1:1 or 2:1 is required to maintain homeostasis, yet most Western diets exceed a 15:1 ratio in favor of omega-6.11
One of the biggest problems with seed oils is their industrial extraction process.
PUFAs are highly sensitive to heat, light, and air. During typical commercial oil production, where profit usually comes before principles, they’re exposed to all three. This makes for a cheap product that’s able to be mass produced, but also accelerates oxidation and creates free radicals: unstable molecules that damage cells and promote inflammation.12
Most commercial seed oils are:
Heated to high temperatures
Exposed to oxygen and light
Processed with chemical solvents (such as hexane)
Resulting in oils that are already oxidized before they reach your plate. The body, in turn, must expend antioxidant resources to neutralize these damaged fats, which can increase oxidative stress.13
Arguing that seed oils help people consume more vegetables (e.g., stir-frying or salad dressings), and thus the benefits outweigh any potential harm, does not reflect the widespread nature of the issue. These oils are found in nearly every packaged food, restaurant meal, and takeout container.
They are not simply occasional cooking aids, they dominate the food supply.14
Cold-pressed oils, like extra virgin olive oil, avoid high-heat and solvent-based processing, preserving nutrients and minimizing oxidation. This makes them a safer choice for everyday consumption that doesn’t involve high-heat cooking.15
We must challenge the belief that consumption of saturated fats are to blame for heart disease.
In reality, inflammation plays a more central role in cardiovascular disease.16
Saturated fats, especially from whole, unprocessed sources like butter, ghee, coconut oil, and tallow, don’t increase heart disease risk or affect cholesterol levels when consumed in moderation as part of a nutrient-dense diet.17
Inflammation causes the liver to send LDL cholesterol to damaged tissues as part of the healing response. Elevated cholesterol is often a symptom of systemic inflammation, not its root cause.
Seed oils may not be beneficial for health, but that doesn’t mean consuming them is going to be life-threatening or that abstinence is the most important pillar in health. The reality is in this modern world seed oils are extremely prevalent, so chances are the stress caused by striving for total elimination would be more detrimental for your health than the seed oils themselves.
So instead, all we can do is focus on educating ourselves and making strategic choices for our health when possible.
For instance:
Cook at home more often.
Use traditional fats like olive oil (cold-pressed, extra virgin), coconut oil, ghee, beef tallow, and butter.
Shop the perimeter of the grocery store: fresh produce, meats, dairy, and eggs.
Read labels: Avoid buying processed foods when the ingredients list canola, safflower, sunflower, soybean, or corn oil.
Make your own snacks when possible
Eat wild-caught fatty fish 2–3 times a week.
If you don’t eat fish, take a high-quality omega-3 supplement with 250–500 mg of EPA and DHA (sourced from wild-caught fish, tested for heavy metals).
The goal isn’t perfection, it’s continuing to make informed decisions that support long-term health.
Sources :
