Soy lecithin, which comes from soybean oil, makes foods creamier. It's also an inexpensive ingredient in cooking oils, where UC Riverside researchers say that's where we get most of it.
"It's been a huge increase and that increase happened primarily over the 1960s and the 1970s," said toxicologist Frances Sladek.
Sladek says that tofu, soy milk and other soy proteins are fine. The concern is the linoleic acid found in soybean oil. Our bodies need 1-2% daily, but many Americans take in 8-10%.
"And that's what the problem is," remarked Sladek. "It's really an issue of the amount of soybean oil and hence the amount of linoleic acid that we are taking in."
In animal studies, microbiology researcher Sonia Deol found excessive linoleic acid to be associated with irritable bowel diseases and a leaky gut.
"In our study, what we have found is that linoleic acid is able to increase the susceptibility to colitis, which is basically an inflamed colon," said Deol. "Linoleic acid decreases the expression of a protein that is very important in maintaining the integrity of the intestinal barrier."
Researchers also found that linoleic acid decreases the good bacteria in the gut microbiome and increases the bad. Though these studies were done in animals, researchers see a strong human connection.
"This bad bacteria that we found when we fed the mice the soybean oil diet, that was the same type of bacteria that came from human IBD patients," said Sladek.
Sladek recommends a few tips to help avoid too much linoleic acid intake. First, read the packaging.
"You want to read those labels and avoid the ones that have soybean oil. Again, it's not gonna have a lot but it's all gonna add up," said Sladek.
Additionally, avoiding processed and fried foods can help reduce linoleic acid. At home, olive, avocado or coconut oil serve as healthier alternatives to soybean oil.
It is also important to remember that farm-fed animals and fish are usually given soy byproducts.
Overall, Sladek says that a greater attention to what we consume can greatly benefit us: "We need an additional awareness of just what we're eating."