Myth or Truth: Are Seed Oils Really Unhealthy?

Zoe Science and Nutrition published recently a Podcast with Professor Sarah Berry called “Seed oils are not ‘evil’, they could lower your risk of disease”.

Sarah Berry is a professor in the Department of Nutrition Sciences at King’s College London and has researched the impact of different oils and fats on cardiovascular diseases risk factors.

I will discuss here the key takeaways of this podcast as well as additional information missing from the discussion so that YOU can make the best decision for your health when consuming seed oils.

Lipids are one of the major macronutrients necessary for the growth and functional maintenance of organisms. Excessive intake of ‘unhealthy’ fats such as certain saturated fats and trans-fats, usually leads to the occurrence of disease like obesity, hypertension, cardiovascular and cancer.

What are seed oils and where are they found?

Seed oils are oils extracted from a seed such as corn, sunflower, safflower, rapeseed, sesame seed oils, corn seed oil. The largest contributor of fat in our diets is palm oil (which is not from a seed), followed by rapeseed oil in the UK and NZ and soybean oil in the US. Seed oils can be categorised as monounsaturated and polyunsaturated fats.

What are monounsaturated and the polyunsaturated fats, where can we find them, and why they are labelled as ‘healthy fats’?

Monounsaturated fats are liquid at room temperature and turn cloudy when kept in the refrigerator. People following traditional Mediterranean diets, rich in foods containing monounsaturated fats, have a lower risk of cardiovascular disease which gives rise to the popularity of this way of eating.

Primary sources: Olive oil, avocados, nuts and seeds such as almonds, hazelnuts, pecans, pumpkin and sesame seeds.

Polyunsaturated fats are liquid at both cold and room temperatures. This family of fats includes the omega-3 and omega-6 groups of fatty acids, which your body can’t make. Hence the term essential fatty acids; it is essential to obtain them in your diet for optimal health.

Primary sources: Nuts, seeds and seed oils, olive oil, flax seed oil, hemp seed oil and oily fish.

Why are seed oils being labelled as unhealthy on social medias and what does the science says?

MYTH: Seed oils are rich in Omega-6 and low in Omega-3 and therefore pro-inflammatory

• Seed oils contained a high ratio of Omega-6 to Omega-3.

• However, Omega-6 fatty acids (a polyunsaturated fatty acid) is an essential fatty acid: it needs to be present in our diet for optimal health.

• Omega-6 fatty acids include Linoleic Acid ‘LA’ (plant oils, nuts and seed oils) and Arachidonic Acid ’AA’ (grain-fed meat and dairy).

• Omega-3 fatty acids include Alpha Linolenic Acid ‘ALA’ (flaxseeds, hempseeds, walnuts, pumpkin seeds) and Eicosapentaenoic Acid ‘EPA’ and Docosahexaenoic Acid ‘DHA’ (oily fish, algae).

  • Omega-6 LA converts to Gamma Linolenic Acid ‘GLA’ and haș anti-inflammatory properties in the body especially in Rheumatoid arthritis, ADHD and Eczema.

  • On the other hand, omega-6 AA is inflammatory BUT essential as inflammation is a key part of the immune system’s response to injury and infection.

  • With Omega-3s, both ALA and EPA/DHA present anti-inflammatory, neurological and cardiovascular health benefits but there is much research into the benefits of EPA and DHA as opposed to ALA.

  • A diet rich in omega-6 AA leads to more inflammation. But equally, a high consumption of EPA and DHA from omega-3 can result in immune-suppression. Hence, it is all about balance of omega-3 and omega-6 consumption.

• Seed oils are therefore not always pro-inflammatory and can benefits our overall health if consumed in moderation and from non ultra processed sources. Indeed, 60% of the seed oils we consume today are coming from highly processed foods (biscuits, chips, cakes, etc.) which is detrimental to our health.

• A typical western diet is abundant in Omega-6 from AA and LA and Low in Omega-3, therefore pro-inflammatory (see point #2 below). The standard American diet has 14 to 25 times more omega-6 fatty acids than omega-3 fatty acids, with the majority of omega-6 intake coming from LA.

• That is why it is important to focus on our Omega-3 fatty acids consumption and to reduce our consumption of highly processed foods for optimal health.

• The European Food Safety Authority recommends a daily intake of 250mg EPA/DHA (Omega-3) per day which corresponds to a palm size portion of fatty fish 3x/week (sardine, salmon, anchoivies, mackerel, herring).

TRUTH: Polyunsaturated fats (e.g. vegetable oils, seed oils, olive oil) oxidise when heated and produce free radicals that damage cells.

• Excess omega-6 consumption from LA leads to cellular tissue damage, because this highly fragile Polyunsaturated fats is easily altered through oxidation.

• During metabolic processes (e.g., energy production or utilization), the LA become vulnerable to damage by oxygen, heat, and pressure. When they become damaged or oxidized, they are converted into harmful metabolites (e.g., OXLAMs and OXAAMs). It is these metabolites, and not the Polyunsaturated fats themselves, that are responsible for their profoundly negative impact on health.

How to safely consume polyunsaturated oils from seeds and plants?

• Polyunsaturated oils should only be used in their raw, cold-pressed form for pouring over cooked or raw foods or using in dressings.

• Store in dark-coloured bottles in the fridge or freezer as they can go rancid quickly and can be oxidised simply through direct light exposure.

• As a general rule it is best to purchase polyunsaturated fats with a pressing date as well as a use-by date.

• Prefer coconut oil, butter and ghee for cooking as they contain saturated fats that can tolerate being heated.

What matters is getting sufficient amount of EPA and DHA from the diet (omega-3).

• Include good sources of ALA in the daily diet, such as flaxseed and hempseed.

• Support ALA conversion into EPA and then DHA through increasing dietary intake of enzyme co-factors (zinc, magnesium and B6). Vitamin C also plays a role.

• Moderate the use of oils rich in omega-6 fatty acids, and avoid processed foods rich in these oils.

• Consider fish or algae EPA / DHA supplements.

See my recent post of good fats for some ideas on how to easily incorporate them in your diet!