Seed oils: are they safe to eat?
Seed oils, including rapeseed, soybean, and sunflower oils, have recently faced scrutiny regarding their impact on health. Claims linking them to inflammation, cardiovascular issues, and chronic diseases have sparked concerns. In this blog post, we'll unravel the science behind seed oils to answer the question: Can you eat seed oils without compromising your health?
Understanding omega-6 fatty acids
The crux of the fear surrounding seed oils lies in their high omega-6 content. Omega-6 fatty acids, such as linoleic acid, are polyunsaturated fats with a structure similar to omega-3s. Both omega-3 and 6 have a double bond in their chemical structure. In omega-3s, the double bond is three carbon atoms from the end of the molecule. In contrast, in omega-6, the last double bond is six carbons from the end.
Linoleic acid
One of the most common types of omega-6 is linoleic acid. This is converted into arachidonic acid in our bodies after eating. It is arachidonic acid that has been thought to be linked to inflammation. This can be useful -arachidonic acid is used in wound healing and localised inflammation is an important part of this process. However, can we extrapolate these pathways of wound healing into wider markers of inflammation?
The complexity of omega-6 and inflammation:
Both linoleic acid and arachidonic acid have been linked to both pro- and anti-inflammatory pathways. A review revealed that individuals with the highest levels of linoleic acid had the lowest inflammation levels (1).
The evidence for linoleic acid causing inflammation appears to be less robust in human studies. The evidence for linoleic acid and inflammation appears to exist primarily in in vitro studies, and not in actual human studies (2). This is a common challenge of nutrition studies, as it can be tricky to capture the complexities of someone’s diet over an extended period of time.
Omega-6 ratios:
Concerns also revolve around the omega-3 to omega-6 ratio, with suggestions of an optimal ratio between 1/1 and 1/4, whereas a typical western diet may have a 1/15 ratio. A lower ratio is thought to reduce the risk of a range of chronic diseases (3). However, it seems that the ratio may not be as relevant as first thought, based on an aggregate review of other trials (4).
A multi-year cohort study (a study that follows a group of people over an extended period of time) involving 854 participants found that high levels of both omega-3 and omega-6 were associated with the lowest inflammation levels, challenging the idea that omega-6 is inherently detrimental (5) or that it blocks the benefit of omega-3s.
Seed oils in ultra-processed foods:
Correlations between increased seed oil consumption and rising obesity and type 2 diabetes rates do exist. You may have seen a chart showing similarities between increases in seed oil consumption and type 2 diabetes. However, correlation does not imply causation.
Seed oils can be found in some ultra processed foods. These foods are more likely to be higher in calories, salt, sugar and saturated fats that less processed counterparts. Eating a diet high in ultra processed foods may lead to less positive health outcomes, but not because of seed oils.
While seed oils are found in some ultra-processed foods, it's the overall quality of the diet, not just the presence of seed oils, that impacts health outcomes.
The bottom line:
Limiting foods with added seed oils may not cause harm, but it's crucial to consider the overall dietary context. Swapping seed oils for alternatives like butter or other animal fats may not be more health-promoting due to saturated fat content.
If opting for a reduced seed oil approach, consider unsaturated alternatives like olive oil. Remember that it is the bigger picture of your overall diet, not the individual ingredients that make the difference.
The narrative around seed oils is more complex than initial fears suggest. While mindful choices can contribute to a balanced diet, demonizing specific ingredients oversimplifies the intricate relationship between nutrition and health. Remember, it's the comprehensive picture of your diet that truly makes a difference.
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References:
- Fritsche, K.L., 2008. Prostaglandins, Leukotrienes and Essential Fatty Acids
- Choque, B., Catheline, D., Rioux, V. and Legrand, P., 2014. Biochimie,
- Simopoulos, A.P., 2002. Biomedicine & pharmacotherapy,
- Harris, W.S., 2006. Current atherosclerosis reports,
- Pischon, T., Hankinson, S.E., Hotamisligil, G.S., Rifai, N., Willett, W.C. and Rimm, E.B., 2003. Circulation,
