Dr. Kumar’s Take:
In this important study, researchers found that the amount of linoleic acid (LA)—a type of omega-6 fat found in seed oils—has more than doubled in the body fat of Americans since 1959. This sharp increase mirrors our rising intake of seed oils like soybean oil. Because LA affects inflammation, metabolism, and hormone signaling, this shift may help explain why chronic health conditions like obesity and diabetes have become more common during the same period.
Key Takeaways:
✔ Adipose (body) fat linoleic acid levels rose 136% from 1959 to 2008.
✔ This rise strongly correlates with increased consumption of seed oils, especially soybean oil.
✔ LA plays a role in inflammation, metabolism, and heart health—and is the most oxidized fat in LDL.
Actionable Tip:
Minimize high-LA seed oils like soybean, corn, cottonseed, and sunflower oil. Choose fats with lower omega-6 content like olive oil, avocado oil, or grass-fed animal fats.
Brief Summary:
This study reviewed 37 published datasets on the amount of linoleic acid (LA) in human body fat collected in the U.S. over the last 50+ years. It found a large, steady increase—going from about 9.1% of body fat in 1959 to 21.5% in 2008. This rise mirrors our increased use of seed oils rich in LA, especially soybean oil. Because LA influences inflammation and disease risk, this dietary change could be impacting public health.
Study Design:
The researchers performed a systematic review of 37 studies that measured the amount of LA in subcutaneous fat (usually from the buttocks or abdomen) in U.S. adults between 1959 and 2008. They compared these trends with government data on national seed oil consumption (called “food disappearance data”).
- Only studies on healthy adults eating typical American diets were included.
- They excluded data from diseased or obese subjects and fat depots other than subcutaneous tissue.
- Linear regression was used to analyze trends in fat composition over time and its relationship with dietary LA.
Related Studies and Research
Soybean Oil and the Omega Balance Shift – Tracks the industrial rise of soybean oil and omega-6 dominance in the food supply.
Railway Workers, Diet, and Heart Disease in India – Highlights contrasting cardiovascular outcomes in populations exposed to seed oils.
Omega-6 Linoleic Acid and Heart Disease Risk – Explores how oxidized LA products contribute to vascular damage.
Linoleic Acid and Obesity: A Review – Reviews associations between adipose LA and fat gain mechanisms.
Health Risks of Linoleic Acid – Synthesizes research on systemic effects of chronic linoleic acid accumulation.
LDL Cholesterol and Heart Disease: A Review – Contextualizes how seed oil–rich LDL may be more prone to oxidation and plaque formation.
Mediterranean Diet and Heart Disease – Connects ancestral diets low in seed oils with favorable cardiovascular outcomes.
Why This Matters
Linoleic acid isn’t just a neutral fat—it plays active roles in:
- Inflammation (through oxidation and conversion to arachidonic acid)
- Metabolism and fat storage (via PPARs)
- LDL oxidation (oxidized LA in LDL is linked to heart disease)
- Possibly chronic pain, diabetes, obesity, and autoimmune conditions
The U.S. population now has more than twice as much LA in their fat stores compared to 60 years ago, which may affect how our bodies respond to stress, store fat, and regulate inflammation.
Frequently Asked Questions
Why did linoleic acid in our diets increase so much?
Mainly due to the rise of industrial seed oils like soybean, corn, safflower, and sunflower oil, which are high in LA. These oils became widespread in processed foods starting in the mid-20th century.
Is linoleic acid bad for you?
Not necessarily in small amounts. But at high levels, it’s more prone to oxidation, which can trigger inflammation and damage cells. The body also stores excess LA in fat, where it can stay for years.
Can we reduce LA in our bodies?
Yes, but slowly. LA has a half-life of 1.9 years in body fat, meaning it takes several years of dietary change to significantly reduce levels.
What are better alternatives to seed oils?
Oils lower in LA include olive oil, avocado oil, coconut oil, and grass-fed butter or ghee. Animal fats from grass-fed sources also have better omega-3:omega-6 ratios.
Conclusion
This study shows a striking shift in the fatty acid makeup of American bodies. Over 50 years, we’ve doubled the amount of linoleic acid in our fat stores—likely due to changes in our diet. Because LA plays a role in inflammation and metabolism, this trend could have wide-reaching health implications.
Future research should look at whether reducing LA intake can help prevent or reverse chronic diseases.