Seed Oils, Harmful or Healthy? What is the Real Story? An Introduction to the Evidence.
- Alastair Hunt
- May 3
- 4 min read
Updated: 4 days ago
Part 1 of the Seed Oils Series
Seed oils have become one of the most divisive topics in modern nutrition, certainly online. The vast majority of nutritional scientists and the medical community view them as health-promoting essentials, others see them as toxic triggers for obesity, heart disease and chronic inflammation. As usual, the reality is more complex - and more interesting - than social media headlines suggest.
Seed oils, including sunflower, canola (rapeseed), soybean, corn and safflower oils, are extracted from plant seeds. They are rich in polyunsaturated fatty acids (PUFAs) and monounsaturated fats (MUFAs), both of which are central to current dietary advice aimed at reducing cardiovascular risk. National dietary guidelines, including those from the UK’s NHS, the American Heart Association and the European Society of Cardiology, generally recommend replacing saturated fats with unsaturated fats - an advice pattern rooted in decades of epidemiological and interventional research.
However, critics of seed oils raise concerns about their heavy presence in processed foods, their omega-6 fatty acid content relative to omega-3s, and the methods used to extract and refine them. These concerns deserve a fair hearing - but they must also be weighed against the broader body of high-quality human research.
A key principle in interpreting nutrition science is prioritising human evidence, particularly large cohort studies, randomised controlled trials and meta-analyses (studies that combine the results of multiple studies). While animal studies and in vitro biochemical experiments provide valuable early signals, their findings often do not translate neatly to real-world health outcomes in humans.
It is worth remembering that nutritional advice around fat evolved substantially over the last 50 years. Early guidelines in the 1970s focused mainly on reducing total fat intake. However, by the 1990s and 2000s, emphasis shifted towards the quality of fats - encouraging more unsaturated fat consumption rather than blanket fat restriction. This shift was based on mounting evidence that monounsaturated and polyunsaturated fats improve blood lipid profiles and reduce the risk of cardiovascular disease compared to saturated fats or refined carbohydrates.
In this series, we will explore the main questions around seed oils:
Part 2: Do they cause weight gain or obesity?
(Go direct to Part 2)
Part 3: Do they drive systemic inflammation?
(Go direct to Part 3)
Part 4: Are industrial processing and cooking methods damaging to health?
(Go direct to Part 4)
Part 5: How do seed oils compare to saturated fats for heart health?
(Go direct to Part 5)
Part 6: What role does omega-6 to omega-3 balance play in chronic disease?
(Go direct to Part 6)
Each article will take a clear, evidence-led approach, drawing on human studies wherever possible. Please note that the information we provide here does not replace personalised medical advice. Always consult your doctor, dietitian or medical professional before making significant changes to your diet, particularly if you have pre-existing conditions, are managing a chronic illness or are pregnant.
Seed oils are a complex topic - but with a careful look at the evidence, we can cut through confusion and find practical, real-world answers.
Next, Part 2: Do Seed Oils Make You Fat? Separating Fact from Fiction
Final Thoughts
While seed oils can be a divisive issue online, we are relatively agnostic when it come to diet and eating patterns. If you enjoy cooking with olive oil, a dab of butter, avocado oil or (as a treat) duck fat, we do too. In the same regard, we are not concerned about a splash of canola in our stir fry and we try to avoid ultra-processed foods as part of our daily eating.
Changing health for the better is about progress, not perfection, and even small changes can make a meaningful difference over time. For most people, improving health is about finding motivation and prioritising self-care - with an ultimate goal of taking action. If you want to take effective and targeted steps that fit into your unique lifestyle and circumstances, The Whole Health Practice is here to help.
Whether your interest is healthspan and longevity, to beat chronic illness or to enhance your mental health and well-being, our consultations and programs deliver results that are tailored to your needs.
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Stay Healthy,
Alastair
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Note
This series of artciles is a reworking of our original article and overview of seed oils:
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