I wrote about linoleic acid, which is the primary component of vegetable oils, and its role in heart disease here about one month ago. Linoleic acid is classified as an omega-6 fat/oil. But it turns out that it damages our health in many more ways and is most likely much worse than the processed carbohydrates and saturated fat in our diets. The appearance of heart attacks in the early 1900s has also coincided with steep rises in type 2 diabetes, cancer, obesity, macular degeneration, and Alzheimer's; traditionally, processed carbohydrates and saturated fats get most of the blame. Before the early 1900s, most of these conditions were rare. As we will see, processed carbs were already a big part of our diets, but vegetable oils, also called industrial seed oils, were introduced right when we started our trend towards all of these terrible conditions.

 Here are some other trends

Heart disease has risen from 12.5% in 1900 to 32% in 2010.

Cancer deaths had gone from .8 % in 1811 to over 30% in 2010.

Type 2 diabetes has gone up 2500% in the last 80 years.

Obesity rates have gone from 1.2% in the 1900s to 40% today.

50 cases of macular degeneration were documented in 1930; now, there are 196 million cases. 1

Grains

Grains, which are processed carbohydrates, have provided the most calories to our diets during the 20th century, so the correlation makes sense. Sugar is a significant contributor to our total calorie intake as well. 2 

Animal Fats

On the other hand, Saturated animal fats have gone down, but somehow, they are still blamed for our poor health. 3 As you can see in the graph below, our consumption of animal foods has remained steady except for chicken.

Chickening Out

Chicken consumption alone accounts for increased animal-based food consumption, and chicken does not contain significant amounts of saturated fat, but it does have significant amounts of linoleic acid. The higher amounts found in chicken today are due to factory farming. Notice How poultry consumption, which is mostly chicken, has risen on the graph above. It is the red line on the top graph.

Vegetable Oils Are The Major Dietary Change

Despite our increased reliance on chicken as a dominant linoleic acid source, seed oils, also called vegetable oils, contribute much more. Seed oils are canola, corn, soy, sunflower, safflower, cottonseed, rapeseed, sesame seed oils, etc. Some products made from vegetable oils are Crisco and shortening. Click Here for a comprehensive list of vegetable oils. NOTE that there are some oils made from vegetables that are safe. These include avocado, olive, and coconut. These oils are not made from the seed, but rather the fleshy part of the plant’s fruit, and confusingly they are not designated as vegetable oils. As you can see from the graph below, we have decreased our animal fats intake but vastly increased our margarine and vegetable oils intake in the twentieth century. Also, note how margarine is being replaced by vegetable oil. The graph has it labeled in red as shortening. Keep in mind that the only sources of linoleic acids in the 19th century were from unprocessed foods, The technology to produce them had not been developed yet, and our intake was minimal and consistent with our ancestral levels.

Carbs Are Actually Lower Now

As we have been adding vegetable oils, we have decreased our carbohydrates, except for sugar and refined starch, which has increased significantly less than the seed oils. The graph below shows this trend. Notice the lower trends below, total carbs are diminishing steadily, and fats are rising. 

 Notice on the graph above how fat consumption has gone up about 20% while carbs have dropped about the same amount, but obesity is still on the rise. The graph below shows this trend.

A quick look at the type of fats tells the story; vegetable oils have gone way up.

Carbs Have Changed

The kind of carbohydrates has also been changing. The graph below shows how we have switched to sugars and processed carbs, away from whole food sources (starch on the graph) of carbohydrates. 

Carbs Are Not Innocent, But Soybean Takes The Cake

You know my stance against processed carbs. They are vastly contributing to our obesity and diabetes. But the century-long trends seem to correspond more to vegetable oils and linoleic acid. As you can see from the data below, soy is the king of seed oils. Notice the falling grain level during the century.  

Soybean Oil

The incidence of obesity in the U.S. has increased from 15% to 35% in the last 40 years and is expected to rise to 42% by 2030. Paralleling this increase in obesity is the greater than 1000 fold increase in consumption of soybean oil, which is 50-60% linoleic acid. Our intake has increased 136% over the last half-century alone, and studies show how it accumulates in our fat cells. Other sources say that our energy intake from linoleic acid has increased from 2% to over 7% per day.  

Vegetable Oils In China

The change in the health of the Chinese is much more recent and shows the same trend as the U.S. Thirty years ago, rates of overweight and obesity were meager compared with the rest of the world; today, nearly half the Chinese population is overweight. Edible oil nearly tripled in China as the total daily energy from carbohydrates decreased 18%. 4 If carbs are to blame for Americans, they don’t seem to be in China.  Below is a study of three diets fed to Chinese subjects. All three groups ate the same amount of calories. The fats were soybean oil. The Carbs were white rice and wheat. The highest body weight and waist circumference were found in the low carb high soybean oil diet (HF-LC on the graph), and the best results were from the low soybean oil high carb group LF-HC on the graph). Incidentally, the MF-MC diet on the graph represents moderate amounts of fat and carbs. 5

Linoleic Acid Is Needed, But Only In Small Doses

The correlation of linoleic acid to our ever diminishing health is solid, and researchers have determined that linoleic acid appears to be toxic when intake exceeds 1 to 2% of total energy intake. 6 The content of linoleic acid in our cells was already at toxic levels in 1960, but it rose from around 6% in 1960 to 18% in 1986. 7  The mechanisms of how excess linoleic acid causes health problems are a bit complex. I covered them a few years ago in this post if you are curious. 

What you can do today

You absolutely should throw away any cooking oils that are made from seeds. On the other hand, avocado, coconut, and olive oil are excellent. Animal fats are also acceptable, but avoid chicken fat and lard from industrially raised animals, as they accumulate unnaturally high levels of linoleic acid. Believe it or not, most of our linoleic acid comes from prepared and restaurant foods. Take a look at the ingredients below to understand how vegetable oils sneak into our diets. The bottom line is the same as I always say: avoid processed foods. Period. Notice the common foods below all contain linoleic acid. I could easily find hundreds of other examples. You should always read food labels, but please avoid processed foods as much as possible, especially those with seed oils.