What are the adverse effects of consuming seed oils?

From the Guidelines

Consuming high amounts of seed oils, particularly those rich in omega-6 polyunsaturated fatty acids like linoleic acid, may promote inflammation and increase the risk of chronic diseases such as heart disease, obesity, and metabolic disorders, as suggested by recent studies 1.

Key Points to Consider

• Seed oils like soybean, corn, canola, and sunflower oils contain high amounts of omega-6 polyunsaturated fatty acids, which may promote inflammation when consumed in large quantities relative to omega-3 fatty acids.
• Some studies have linked high consumption of these oils to increased oxidative stress, inflammation, and potentially higher risks of chronic diseases 1.
• The concern centers around the processing methods that may create harmful compounds and the dramatic increase in consumption of these oils in modern diets.
• However, it's essential to note that not all research shows negative effects, and moderate consumption within a balanced diet may not pose significant health risks.
• For those concerned, alternatives include olive oil, avocado oil, coconut oil, and butter in moderation, with an emphasis on cold-pressed, unrefined options that typically contain fewer potentially harmful compounds than highly processed versions 1.

Mechanisms and Associations

• The mechanisms by which seed oils may exert harmful effects include the promotion of lipid peroxidation, the formation of harmful aldehydes, and the initiation or augmentation of diseases such as cancer, inflammation, asthma, type 2 diabetes, atherosclerosis, and endothelial dysfunction 1.
• Associations have been found between high intake of omega-6 fatty acids and increased cancer risks, as well as between high intake of saturated fats and increased risk of cardiovascular disease, although the evidence is not conclusive and may depend on the specific type of fat and the overall dietary pattern 1.

Dietary Recommendations

• Given the potential harmful effects of seed oils, it is recommended to consume them in moderation and to prioritize alternative sources of fat, such as olive oil, avocado oil, coconut oil, and butter, as part of a balanced diet.
• The quality of oils is crucial, with cold-pressed, unrefined options being preferable to highly processed versions.
• A holistic approach to dietary policy, focusing on the overall dietary pattern rather than individual nutrients, may be more effective in promoting health and preventing disease 1.

From the Research

Adverse Effects of Consuming Seed Oils

• High intake of omega-6 fatty acids, commonly found in seed oils, has been linked to an increased risk of breast cancer 2
• A high omega-6 to omega-3 fatty acid ratio, often resulting from excessive seed oil consumption, can lead to chronic low-grade inflammation, predisposing individuals to autoimmune diseases, asthma, and allergies 3
• Some seed oils, such as peanut oil and corn oil, may be contaminated with mycotoxins like aflatoxins and zearalenone, which can pose health risks including immunotoxicity, reproductive toxicity, and liver cancer 4
• Regular consumption of seed oils high in omega-6 fatty acids may not be the optimal strategy for preventing cardiovascular disease and cancers, as it can lead to a pro-inflammatory state 2, 3

Health Risks Associated with Seed Oil Consumption

• Children may be at a higher risk of adverse health effects from seed oil consumption due to their higher exposure to mycotoxins like aflatoxins 4
• The health risks posed by mycotoxins in seed oils are non-negligible and long-term surveillance is necessary to mitigate these risks 4
• A diet high in seed oils and low in omega-3 fatty acids may contribute to an increased risk of cardiovascular disease and other health problems 2, 3

Dietary Recommendations

• The American Heart Association recommends using liquid plant oils, such as those found in seed oils, in place of tropical oils and partially hydrogenated fats, but also emphasizes the importance of a balanced dietary pattern 5
• A healthy dietary pattern should include a variety of fruits, vegetables, whole grains, and healthy sources of protein, with minimal intake of added sugars, salt, and ultra-processed foods 5