There is currently considerable debate in both the scientific world and the public as to which types of oils are better for long-term health and for helping in maintaining a healthy weight. Saturated fatty acids (SFAs) were deemed unhealthy due to studies in the 1950s and 1960s that showed an increased risk of cardiovascular disease with high saturated fat diets. Since then the war on saturated fat had begun. National nutritional recommendations encouraged people to reduce fat from meat and dairy products and to increase the intake of polyunsaturated fatty acids (PUFAs) found in plant oils (1,2). These guidelines are still in effect today (3).
In recent years, however, there has been a shift in the dialogue surrounding which dietary fats are the most harmful, with some studies suggesting a reconsideration of nutritional guidelines (4,5). In particular, there is a growing body of evidence that suggests that saturated fat from sources such as coconut and palm oil, which are rich in medium chain triglycerides (MCTs), may actually be beneficial for the prevention and treatment of Metabolic Syndrome (6,7,8).
Today I wanted to share with you the results of a 2015 study that found that soybean oil is more obesogenic (related to metabolic changes that lead to obesity) and more diabetogenic (leading to diabetes) than the saturated coconut oil (9). This is an alarming find, as soybean oil is commonly used in large amounts in western diets.
It has been estimated that soybean oil represents half of all the edible vegetable oil and one-third of all fats and seed oils produced in the US (10). For many it is the oil of choice for home cooking, while it is also used heavily in processed foods, margarines, salad dressings and snack foods. It is also the oil of choice for many restaurants and fast food establishments (11).
The study compared the metabolic effects and liver morphology changes induced by a diet high in soybean vs coconut oil. All diets had the same calories. This was a study carried out in mice as the desired strict nutritional intake cannot be achieved in humans.
Alarming results on weight and other metabolic parameters
The group of mice receiving the high soybean oil diet showed increased weight gain and had a striking accumulation of fat on the liver. They also developed diabetes, glucose intolerance and insulin resistance. These effects are of great importance considering the high prevalence of these risky metabolic conditions in western countries.
Another striking finding was that in the mice fed the high soybean oil diet, a significant number of genes that associated with cancer became dysregulated. More specifically, a number of cancer promoting genes were upregulated and a number of cancer suppressing genes were suppressed, indicating an increased risk of cancer.
On the contrary, coconut oil, rich in medium chain triglycerides (MCTs), was shown in the study to be anti-obesogenic, anti-inflammatory and insulin sensitizing.
Take home message
Olive oil and coconut oil are the oils we recommend for use in cooking and baking.
You can reduce your intake of soybean oil by avoiding processed foods and choosing simple healthy snacks such as fruits, nuts, homemade granola bars with lots of seeds, dried fruits, yogurt with honey etc.
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Deol, Poonamjot, et al. "Soybean oil is more obesogenic and diabetogenic than coconut oil and fructose in mouse: potential role for the liver."PloS one10.7 (2015): e0132672.
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