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Seed Oils: Latest Evidence and Ongoing Controversy


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What it is:

Currently, there is widespread discussion on whether oils or fats are best for frequent human consumption and if they increase inflammation or disease risk. Nutrition is a highly complex science, and therefore, its nuances can be confusing when crammed into social media snippets or clickbait articles.


At its core, it is not the seed oils themselves but the fact that they are prevalent in ultra-processed, fried foods. Replacing the oil with fats does not matter in the grand scheme of things if you’re eating copious amounts of fried food. When any oil or fat is highly modified, processed, and chemically altered, it can become an issue. The seed oil vs. butter/tallow discussion ultimately comes down to the quality of the ingredients and their utilization.


The most basic action items to ensure healthy eating patterns:

1. Eat whole food items (nuts, seeds, extra virgin oils, grass-fed butter).

2. Avoid fried or heavily processed items.


Seed oils, such as canola, sunflower, soybean, corn, safflower, and grapeseed, contain varying degrees of beneficial monounsaturated and polyunsaturated fatty acids, including omega-3s and omega-6s. When consumed in moderation, they are part of a healthy eating pattern.



What the research says:

Seed oils are widely used as cooking oils, ingredients in processed foods, and for frying foods. The distinction between the seed oil and the methods used for frying/processing needs to be clarified.


Repeatedly processing and reheating oil leads to a cascade effect. This specifically refers to the continuous reheating of oils, such as those used for frying, in restaurants, where the accumulation of harmful chemicals can become a concern. It's important to note that this issue is not limited to seed oils; any type of fat can experience this effect over time.


One suggestion is that beef tallow is better for deep frying foods due to its high smoke point and rich flavor. However, it has a high saturated fat content and will have the same outcome of detrimental oxidation if overheated (frying) or consumed consistently (e.g. fried foods). There is strong evidence that high amounts of saturated fats are detrimental to heart health. For example, one study showed that replacing butter with plant oils reduced mortality risk.


Olive oil should be consumed frequently, but other items such as coconut oil or beef tallow can be part of a healthy eating pattern when consumed in moderation. But do not consume them under the pretense that it is a healthy alternative to other fats or oils, as they both contain high levels of saturated fat.


Highly processed foods are rarely healthier than their whole food counterparts. For example, when you remove the fiber from fruits and are left with just the juice, you alter the food, making it less nutritionally valuable. In some cases, this can be detrimental, as the whole food, which is beneficial in its natural state, now lacks balance. Similarly, seeds, which contain naturally beneficial oils, can also become harmful when they are overly processed.


Refined and processed oils are created to increase their smoke point and stability, which allows for a longer shelf life. However, when cooking with any oil or fat, it’s crucial not to let it smoke, as this can produce harmful compounds and diminish the nutritional value. This is one reason refined oils became popular; the refining process enhances the oil's smoke point and stability by extracting impurities. While refined oils tend to have a longer shelf life, there are trade-offs for this extended durability. Therefore, the fresher and less processed the oil is, the better it is for your health. Always aim to prevent your oil or fat from smoking.


Seed oil fears are linked to a few misunderstood components. The idea that seed oils in small amounts cause inflammation and related diseases (e.g., obesity, heart disease, diabetes, cancer, and other metabolic diseases) is not backed by scientific evidence. And although anything in excess is detrimental, seed oils have recently been shown to provide beneficial biomarkers. Specifically, linoleic acid, the primary omega-6 fatty acid in seed oils, correlates with lower markers of inflammation and improved cardiovascular and metabolic health.


Therefore, the facts we know for sure regarding the complex science of nutrition are that consuming a variety of whole, high-quality foods is best. And avoiding fried or ultra-processed foods will benefit your health.



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