Soybean oil is a bigger cause of obesity than fructose

I’ve already mentioned that high-fructose corn syrup is a major contributor to the rise of obesity, diabetes, and other chronic illnesses, but a recent study is also highlighting how another big ingredient in processed food, soybean oil, also contributes to obesity and a host of other problems. Soybean oil is a cheap, home-grown source of oil that is primarily used in fast food, processed foods, salad dressings, and by many restaurants, so naturally, Americans consume a pretty large amount of it on a regular basis.

What the study found

This mouse study tested four different diets that all contained 40 percent fat to represent the amount found in a typical American’s diet. One group was fed primarily coconut oil (a saturated fat), the other group was fed half soybean oil (a polyunsaturated fat) and half coconut oil to represent the typical fat content Americans get from vegetable oils in processed foods, and the final two groups had the same fat ratios but added in the typical percentage of fructose that Americans consume. All four diets were adjusted to make sure they were calorically equal.

The researchers assumed the fructose would be the most detrimental factor, so they were surprised to discover that soybean oil caused far more harm, such as:

• Increased weight gain (25 percent higher than coconut oil, 9 percent higher than fructose)
• Larger fat deposits
• Increased amounts of fat in the liver which leads to fatty liver disease
• Hepatocyte (liver cell) ballooning which is a sign of liver damage in addition to the fat deposits
• Insulin resistance which led to diabetes by the end of the study
• Altered expression of genes in the liver that helped metabolize foreign compounds which could effect the way the body handles drugs and environmental pollutants

Why it’s an unhealthy fat

We’ve been told for decades that plant fats are good for us and animal fats are bad. I’ve also written about saturated and unsaturated fat many times in the past, and while I’ve stated that saturated fat doesn’t cause heart disease or other illnesses like we previously thought, it is harder to mobilize from fat cells than unsaturated fats. That’s why I too have recommended a higher percentage of unsaturated fats versus saturated fats in our diets. So if unsaturated fats are the better option, then why is soybean oil so bad for us?

The problem is that soybean oil contains a small amount of alpha-linolenic acid, a healthy omega-3 fatty acid. While this sounds like it should be a good thing, the reason we don’t get enough omega-3 in our diets is because this type of fat tends to degrade too quickly to be used in processed foods. This means the processed food industry had to figure out how to make use of a cheap source of oil from soybeans and still extend shelf life. The answer they came up with was hydrogenation. By boiling hydrogen through the oil at high pressure, it stabilized the fats so they could last longer on store shelves, but it also turned partially-hydrogenated soybean oil into a trans fat. Since the FDA recently declared trans fats are not generally recognized as safe, companies like Monsanto had to come up with an alternative to hydrogenation.

The easiest solution they came up with was to reduce the amount of omega-3s and raise the amount of omega-9s (a non-essential fatty acid also found in healthy oils like olive oil and canola oil) in their new soybean oil they call Vistive. This stabilized it’s shelf-life and possibly improved it’s health profile, but it’s too early to tell. Judging by the fatty acid profile listed in the current study, they used conventional soybean oil rather than Vistive. It’s too early for me to pass judgment, but my initial reaction is that reducing the amount of omega-3s we get is the last thing we need. We get far too many omega-6 fatty acids in our diet. While they are also essential, it’s best when consumed in a 1 to 1 ratio with omega-3 fatty acids. Currently Americans are at roughly 15 to 1, so reducing omega-3s even more just worsens the ratio.

Best oil for home cooking

This study and others support the idea that coconut oil is a healthy alternative to “vegetable oil” (the generic term for soybean oil). Canola oil has a healthier fat profile as well and olive oil is another excellent choice due to it’s polyphenol content. Once again, the main advice I want to reiterate is avoid processed foods as much as possible and you’ll be just fine.