PLEASE NOTE: The information in this blog is for educational purposes only. It is not a substitute for professional medical advice. Consult your healthcare provider if you’re seeking medical advice, diagnoses, or treatment.
To put it simply, Americans are sick!
An estimated 60% of adults in the US have at least one chronic disease like diabetes or obesity (1). 40% have two or more.
While many chronic diseases are preventable, they account for about 70% of the deaths globally and about 75% of total healthcare spending in the US (2).
What has gone so wrong? Unfortunately, there are many things!
While the typical diet and lifestyle have changed dramatically, seed oil consumption is one of the most dramatic changes to the human diet.
Take soybean oil (a popular seed oil) as an example. Between 1909 and 1999, the estimated soybean oil consumption in the US increased by over 1000% (3).
This article will explore the connection between seed oils and chronic diseases like cardiovascular disease and obesity.
The Many Origins of Chronic Disease
Chronic diseases are impacted by various factors like diet, activity level, genetics, weight, age, and tobacco or alcohol usage (4). Other lifestyle factors like pollution, stress, and inadequate sleep also play a role (5).
These diseases are rising exponentially throughout the globe (6).
How are seed oils and chronic disease related? Let’s find out!
What Are Seed Oils?
As a quick primer, vegetable oils are derived from nuts, legumes, oilseeds, or fruits (7). Seed oils are a type of vegetable oil that comes from the seeds of crops and contain high levels of linoleic acid, an omega-6 polyunsaturated fatty acid (PUFA).
Emerging evidence shows that seed oils and chronic diseases are intertwined.
Seed Oils and Chronic Diseases: What’s the Connection?
While linoleic acid is needed by the human body in small amounts, the excessive quantities found in seed oils can contribute to the most common chronic diseases like obesity, cardiovascular disease, and diabetes (8, 9).
Obesity
Out of all developed countries, the US has the highest obesity rate and consumption of seed oils per person (10). Over 66% of adults in the United States are overweight or obese, with a body mass index greater than 30 (11).
Being overweight or obese plays a role in the development of numerous other chronic diseases like diabetes, hypertension, and arthritis (12). Emerging evidence shows that seed oils’ polyunsaturated fatty acids (PUFAs) contribute to the obesity epidemic (13).
Both human and rodent studies have shown that high-fat, omega-6-rich diets can increase the risk of diabetes and obesity (14). Research from 2015 on mice found that a diet high in soybean oil led to diabetes and obesity (15).
The concentration of linoleic acid in adipose tissue (body fat) reflects dietary habits (16). One study found that linoleic acid in body fat increased by 136% from 1959 to 2008 (17).
While obesity is complex and seems to be exploding due to physical inactivity, seed oil consumption appears to be a major dietary factor (18), along with increased intake of refined sugars and ultra-processed foods (19).
Cardiovascular Disease
Cardiovascular disease (stroke, coronary heart disease (CHD), and other diseases), which was once rare in the 1800s, is now a leading cause of death globally (20, 21).
Diet plays a role in the development of stroke and other forms of cardiovascular disease (22).
While saturated fats (primarily from animal foods) get most of the attention, recent evidence has shown that they have no effect on heart attacks, strokes, total mortality, or major cardiovascular outcomes (23).
Meanwhile, seed oil consumption is likely a key dietary culprit for coronary heart disease (24). A balanced ratio of omega-6 and omega-3 appears to be important for preventing CHD (25). Levels of linoleic acid in body fat are positively associated with coronary artery disease (26).
It’s generally agreed upon that linoleic acid slows the development of atherosclerosis (plaque buildup in the arteries), but this is now being questioned (27).
For decades, people have been advised to reduce their saturated fat consumption and opt for fats like seed oils to lower the risk of cardiovascular disease. Yet, human studies have shown that seed oil consumption does not decrease the risk of death from cardiovascular disease or rates of atherosclerosis!
A study from 2016 noted that “no randomized controlled trial has shown that replacement of saturated fat with linoleic acid significantly reduces coronary heart disease events or deaths” (28).
It’s also been found that the proposed benefits of linoleic acid against coronary heart disease are clouded by the respective intakes of omega-6s and omega-3s (29). This means that the benefits of linoleic acid may be overestimated or actually from omega-3 consumption. Some interventions consisting specifically of omega-6 led to an increased risk of CHD (30).
Cancer
The ratio of omega-6 to omega-3 consumption by humans was around 4:1 (or less) until about 100 years ago (31).
This ratio now appears to be anywhere from 15-20:1 (32,33) or up to 50:1 (34) and may play a role in the development of cancer (35, 36).
One experiment aimed to test the hypothesis that an increased intake of linoleic acid would reduce the risk of heart disease; instead, the high-linoleic acid group had greater levels of cancer and cancer mortality (37).
Animal studies have also connected cancer incidence to seed oil consumption of around 4-10% of energy intake (38). The Western world consumes an estimated 8-10% of its total energy from vegetable oils (39).
Autoimmune Disease
Overconsumption of linoleic acid (primarily from seed oils) and inadequate omega-3 consumption may make the body prone to an autoimmune-prone state (40). A lower omega-6 to omega-3 ratio appears to reduce inflammation and autoimmune reactions (41).
Diabetes
The US alone experiences an estimated 1.7 million new cases of diabetes yearly (42).
Soybean oil is linked to both diabetes and obesity (43). A study on mice compared a diet of PUFA-rich soybean oil to saturated fat-rich coconut oil. The soybean oil led to the dysregulation of genes, diabetes, and obesity!
The Emerging Connection Between Seed Oils and Chronic Disease
The connection between seed oils and chronic disease is complex, but a clear relationship is materializing.
Seed oils are highly processed, rich in linoleic acid, and implicated in obesity, cardiovascular disease, and more. Yet, they’re used in the majority of restaurants and processed foods.
Chronic diseases are a significant cause of death, disability, and reduced quality of life worldwide. They often involve a complex interaction between genetics, environment, diet, and other lifestyle habits.
While saturated fat from animal foods often takes the blame for a wide variety of these health challenges, evidence continues to emerge that seed oil consumption is a contributing factor to chronic diseases!
Subscribe to future articles like this: