soybean oil
Brittany Hambleton
Brittany Hambleton
February 1, 2024 ·  5 min read

America’s most widely consumed cooking oil may cause genetic changes in the brain, according to animal studies

Soybean oil is the most widely consumed edible oil in the United States. In 2019, Americans consumed about 10.66 million metric tonnes of soybean oil, which equates to almost 67 percent of all edible oils consumed that year. Soybean oil consumption was more than four times that of canola oil, and seven times that of palm oil [1].

The food industry in the U.S. uses the oil to fry food, in large-scale bakeries, in salad dressings, and in margarine. You can find it on grocery store shelves in bottles as pure vegetable oil [2].

It appears that our diets tend to contain high amounts of soybean oil, and while most things in moderation should be ok, there is some concern. New research has revealed that soybean oil, at least in higher quantities, may be having a more negative impact on our health than we thought.

Soybean Oil and Our Brains

A recent animal study from the University of California Riverside has found that not only could soybean oil lead to obesity and diabetes, but it could also impact neurological conditions like autism, Alzheimer’s disease, anxiety, and depression [3].

The team that carried out this study previously found in 2015 that soybean oil induces obesity, diabetes, insulin resistance, and fatty liver in mice. They then found in a separate study in 2017 that if the oil was modified to be low in linoleic acid (an omega-6 fatty acid), the effect on obesity and diabetes was lowered [3].

The latest study compared mice that were fed three different kinds of diets: one high in soybean oil, one high in the oil but modified to be low in linoleic acid, and one high in coconut oil. They found that, regardless of whether or not the oil was low in linoleic acid, the effect on the brain was the same [3].

The Hypothalamus

The reason behind this has to do with a small region of your brain called the hypothalamus. Margarita Curras-Collazo, a UCR associate professor of neuroscience and lead author on the study, explained that this small region located at the base of your brain has several important roles.

“The hypothalamus regulates body weight via your metabolism, maintains body temperature, is critical for reproduction and physical growth as well as your response to stress,” she said [3].

The researchers found that soybean oil has pronounced effects on the hypothalamus. They also found that there were a number of genes found in the mice who were fed soybean oil that was not functioning properly, notably the gene that is responsible for producing oxytocin, aka the “love” hormone.

The team discovered approximately one hundred other genes that were also affected by soybean oil, and believe that this could have important consequences for brain function and neurological diseases [3].

There are a number of reasons why soybean oil has become the king of oils. Soybeans are some of the most commonly cultivated and utilized plants, so they are widely available [4].

The food industry likes to work with soy oil because it doesn’t have much taste, and will instead enhance and support the natural flavors of prepared foods. It also blends very easily when compared with other vegetable oils, making it a popular choice for the general food industry [4].

It has a high smoke point and is inexpensive, making it an ideal choice for cooking processes that require large amounts of oil, such as in deep-frying [5].

A Healthy Appearance

In the 1990s, research came out suggesting that diets high in saturated fat and cholesterol were associated with negative health outcomes like high blood pressure. For that reason, many health professionals began recommending that people attempt to lower their intake of saturated fat by replacing animal fat with vegetable oil, such as soybean oil [6].

The oil contains primarily polyunsaturated fat, which provides essential fatty acids to your diet that your body can’t create itself, such as omega-3 and omega-6 fatty acids, as well as vitamin E [7]. However, the omega 6:3 ratio is not ideal, as you’ll read below.

The polyunsaturated fat in soybean oil contains plant sterols, which lower overall cholesterol levels by decreasing cholesterol absorption in the stomach [8].

The Issue: We’re Consuming Too Much

In the frenzy of trying to remove saturated fats from our diets, it appears we have now swung too far in the opposite direction. Registered dietitian Natalie Rizzo explains that there is a downside to consuming too many polyunsaturated fats.

“It should be noted that soybean oil is higher in omega-6 than many other plant oils, and too much omega-6 may cause inflammation,” says Rizzo [9].

She recommends consuming the oil in moderation to avoid the negative side effects of inflammation [9].

So Is it Good or Bad?

The world of nutrition is still somewhat divided as to whether or not the oil is good or bad. The issue is that while there have been a few studies now showing that soybean oil consumption contributes to obesity, diabetes, and now possible neurological conditions, all of these studies have been conducted on animals, most commonly mice. 

Studies on mice don’t always translate directly to humans. Furthermore, the recent research connecting soybean oil to brain health was done only on male mice. Oxytocin is very important to maternal health since it promotes mother-child bonding, so more studies need to be conducted on female mice to see if there is a difference in their reaction [10].

Frances Sladek, a UCR toxicologist and professor of cell biology, is not suggesting that soybean oil should be removed completely from your diet, but that it might not be as good for you as once thought, and decreasing your intake of the oil is a wise choice.

“The dogma is that saturated fat is bad and unsaturated fat is good. Soybean oil is a polyunsaturated fat, but the idea that it’s good for you is just not proven,” he said [10].

He suggests switching some of your soybean oil for other oils, such as coconut oil.

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