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Coconut Oil Less Fattening Than Soy

Study: PUFA-Rich Soy Oil Promotes Obesity and Fatty Liver

PUFA-Rich Soy Oil More Fattening than Mostly Saturated Coconut Oil

“Everyone is consuming a lot of soy oil even if we don’t know it” ~Frances Sladek

Big food manufacturers love soy oil. They put it in millions of products, yet most Americans have no idea they’re eating it. In 2011, an article revealed that consumption of soy oil has increased 1000 fold over the past century, leading some to suggest that this change represents the largest, most rapid diet shift in all human history and to speculate it may play a special role in the obesity epidemic. Currently, the thinking is obesity causes fatty liver. But this research certain fatty acids themselves can cause fatty liver.

Soy Oil Calories More Fattening than Coconut Oil Calories

When a UC Riverside professor Frances Sladek read about the dramatic rise in soy oil consumption, she decided to investigate whether soy could possibly play a role in the dramatic rise in obesity we’ve seen over the time period since soy oil consumption has skyrocketted.

To better understand how soy impacts obesity, she formulated four special chows for her study mice to eat. The most interesting of the four was designed to effectively mimic the diet consumed by average Americans, composed of 40% fat (by caloric composition) and with a good portion of that fat coming from soy oil, while the carb came either from starch or fructose. She then fed each type of chow to different groups of mice for several months, and collected data on how each formulation affected the development of obesity.

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The study results were published recently in the influential PLoS journal (Public Library of Science), and the title says it all: “Soybean Oil Is More Obesogenic and Diabetogenic than Coconut Oil and Fructose in Mouse.”

soy oil more fattening than coconut
Animals fed 3 different types of pelleted formulas but the same number of calories gained weight at different rates.

The Fatty Acids Matter More Than the Total Fat

Above I’ve posted the most important figure 1 from the study. This figure graphs out the weight gain in mice eating three different formulas: 40% calories from fat mostly soy-oil based (orange line), 40% calories from fat mostly coconut-oil based (blue line), and standard high-carb rat chow with roughly 5% fat (grey line).

It’s important to know that all three mice were eating the same amount of total calories. The orange line shows that the mice eating the soy-oil formula (orange line) gained weight faster than those on the coconut formula (blue line). The mice eating standard chow gained less than both of these high-fat groups.

Before we go running off and concluding that low-fat, high-carb diets are the answer again, let’s remember that these are mice in cages eating pellets. This does not mean low-fat, high-carb diets are the answer for humans eating real food.

The important part of the study is not the difference between high and low-fat diets. It’s the differences in the kind of fat fed to the two different high-fat groups. Soy oil made the mice about 25% fatter than coconut oil, even though the groups of mice ate the same total calories. In other words, soy oil is more fattening than coconut oil.

During an interview, the authors summarize: “The mice fed the soybean oil diet became much more obese, diabetic and insulin resistant than the mice fed the coconut oil diet even though they had similar food intake.”

Soy Oil Promotes Higher Blood Sugar than Fructose

Fructose has been vilified as a major contributor to the epidemic not just of obesity but also diabetes. And while the high consumption of fructose is certainly an issue, a bigger issue may be the high consumption of soy.

The UC Riverside group also performed a test called a glucose tolerance test. This test measures how high blood sugar goes after eating carbs.  The higher blood sugar goes, the more the animal is glucose intolerant. Insulin resistance is another word for glucose intolerance. In humans, we know insulin resistance is the beginning of diabetes. It also puts people at a high risk of heart attack, stroke, cancer and much more.

Their research shows fructose and soy oil both make mice fat, but soy causes more severe insulin resistance than fructose.

The orange line in graph A shows that the rats on the soy oil diet were more glucose intolerant than rats on the other diets. Graph B shows that they were also more insulin resistant.
The orange line in graph A shows that the rats on the soy oil diet were more glucose intolerant than rats on the other diets. Graph B shows that they were also more insulin resistant.

Soy Oil Found To Cause Liver Damage, Possibly Fatty Liver

The authors were surprised at what they found when they examined the liver closely. Unexpectedly, the mice eating soy oil had larger livers with more cellular ballooning than the mice eating soy oil plus fructose!

In an interview (link below), the authors explain “[The mice] also had large lipid droplets in their liver and ballooning, a sign of liver injury.” Ballooning leads to fatty liver.

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Rats eating soy oil without fructose have worse fatty liver than rats eating soy oil with fructose.
Rats eating soy oil without fructose (orange line) have worse fatty liver than rats eating soy oil with fructose (red line).

Biochemical Explanation: Oxidative Stress

Personally, I’ve been avoiding soy oil and other vegetable oils (The Hateful8) since 2002, when I learned my medical education had seriously misinformed me on the topic of fats. It is scientifically gratifying to see soy oil pinpointed as a cause of fatty liver and insulin resistance. It shows–once again–that biochemistry makes pretty accurate predictions.

I started advising my patients with fatty liver to avoid soy and other vegetable oils years ago. When they do, their labs improve. One patient with advanced, fibrotic form fatty liver was told to get on the transplant list. After avoiding seed oils for two years, blood tests and ultrasound show that his liver is fully recovered.

The biochemistry that predicts soy oil would be unhealthy has to do with oxidation. Soy contains a lot of polyunsaturated fatty acids (PUFAs), and PUFAs react easily with oxygen. On the other hand, Coconut oil contains almost no PUFA. Coconut oil is high in saturated fat, and saturated fat protects your cells against oxidative stress.

Factory refining damages the PUFAs in seed oil, and destroys the antioxidants. Factory refining also destroys vitamins and generates trans fats that do not need to be listed on the label. Trans fats can promote fatty liver, too. But the real danger to your liver comes from the PUFAs.

Polyunsaturated Fatty Acids Omega-3 and -6 Promote Oxidative Stress

Since I originally posted this, another important research article shows that PUFAs damage the liver during the liver’s attempt to metabolize them. The mechanism of damage is oxidation.

Oxidative stress is a biochemical process that leads to a cellular response called inflammation. Liver inflammation promotes insulin resistance. Insulin resistance, in turn, tells your body to quickly convert sugar in your diet into fat. This is my explanation for how our Western diet makes us fat. (If you’re interested in this topic you’ll get a lot out of my book, The FatBurn Fix..

Bottom line? All fat has lots of calories. But this study suggests fats that high-PUFA seed oils make us store fat faster than saturated fat-rich coconut oil. And it’s very likely that saturated fat rich animal fats would have the same effects.

Sources:

PLOS Article: Soybean Oil Is More Obesogenic and Diabetogenic than Coconut Oil and Fructose in Mouse: Potential Role for the Liver

Q & A With Soybean Oil Researchers: UC Riverside’s Frances Sladek and Poonamjot Deol explain research in which they compared a genetically modified soybean oil to conventional soybean oil

Bad sources:  Walter Willet, from the Harvard School of Public Health prefers soy over coconut

With over two decades of clinical experience and expertise in genetic and biochemical research, Dr. Cate can help you to reverse metabolic disease and reshape your body.

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