Linoleic Acid in Soy Strongly Linked to Obesity Epidemic

A recent study has found that Big Ag’s reliance on soybeans for cheap oil and animal feed has caused us to consume way too much linoleic acid, a type of omega-6 fat that is linked to obesity.

| August/September 2015

Seldom does a story stand so starkly illuminated, boldly outlined by the lines of a graph. The focal point is a period in the mid-1960s, when forces aligned to launch the current obesity epidemic and a host of health problems in the United States. As you’ll see, it was a perfect storm.

The data for this graph comes from an ambitious 2011 study called Changes in consumption of omega-3 and omega-6 fatty acids in the United States during the 20th century, which was published in the American Journal of Clinical Nutrition. Researchers posed a question fundamental to understanding modern health concerns, including diabetes, heart disease, obesity and mental health: How does our collective diet today differ from the common diet 100 years ago? The study examined consumption of 373 foods, but then went deeper by looking at how the composition of those foods varied over time, from 1909 to 1999. This latter detail — for example, how a modern chicken breast is different from its 1909 counterpart — turned out to be critical. Specifically, researchers examined fat consumption — not just fat in general, but the quantities of particular fats.

An Era of Cheap Vegetable Oil

Despite what you may have heard, per capita fat consumption hasn’t increased substantially in the United States throughout the past century. Per capita carbohydrate consumption has increased, however, causing low-carb advocates to cite this factor alone as the cause of the obesity epidemic. The data from the fat study doesn’t contradict this hypothesis, but certainly refines the picture to pin at least some blame on the dramatic increase in our consumption of soybean oil, thanks to industrial agriculture’s concentration on this single crop.

Myriad food sources provide dietary fats, from lard and butter — the mainstays of the Edwardian-era kitchen, when the study’s data stream began — to margarine, canola oil, flaxseed oil and olive oil. Starting in the mid-’60s, what stands out — indeed, leaps off the graph — is the thousand-fold increase in per capita consumption of soybean oil (see graph). No other food in the study comes even close to matching that explosion.

Partly this is because of the ubiquitous vegetable oils, made mostly from soy, that now lurk on grocery shelves and in processed foods. But it’s also related to the way animals are raised. Today’s industrially raised livestock, poultry and farmed fish are almost universally fed soybean meal and oil. Their feed’s components are then found in the meat, milk and eggs sold to consumers. This study and others like it are explicit about this: Consumers get much of the soy in their diets secondhand from eating industrial meat, eggs and dairy products, as well as farmed fish.

Linoleic Acid: Omega-6 Overload

Why is this a problem? Soybean oil is very high in linoleic acid, an essential omega-6 fatty acid that is linked to obesity. Because we now consume a thousand times more soybean oil than we did a few decades ago, this means we’re getting a much higher amount of linoleic acid. A diet that has a high omega-6 to omega-3 fatty acid ratio is linked to inflammation, but the evidence on obesity connects specifically to linoleic acid.

8/10/2015 9:55:09 AM

How does one effectively counteract the presence of linoleic acid for omega six other than being consciously aware of all food additives on a daily basis that contains soy and soy related products? Can the use of high omega-3 content supplements such as fish oil or flaxseed be used to reduce the presence of linoleic acid in our diet?

8/6/2015 1:07:46 PM

I enjoyed the print article enough to share, but cannot seem to access the concluding paragraph. What happened?

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