“Some scientists believe that certain vegetable oils, such as soybean oil, promote inflammation due to their very high omega-6 fatty acid content,” says Healthline.com.
What’s behind the popular claim that omega-6 fats cause inflammation?
One source of the claim: omega-6 fats like linoleic acid can be converted to arachidonic acid in the body.
“And arachidonic acid can get converted to prostaglandins, which can set off inflammatory responses,” notes Frank Sacks, professor of cardiovascular disease prevention at the Harvard T.H. Chan School of Public Health.
But hardly any linoleic acid actually gets converted to arachidonic.
“Although the pathway is there, it’s not active unless there’s a deficiency of omega-6 fats,” says Sacks.
And the body keeps a tight control on arachidonic acid levels.
“When you eat omega-6s, you’ll see an increase in linoleic acid, but you won’t see an increase in arachidonic acid or prostaglandins,” notes Sacks.
That may explain why studies find no increase in inflammatory markers when people are given foods rich in omega-6s.
And when researchers tracked roughly 69,000 people from 30 studies, those with the highest blood levels of linoleic acid had a lower risk of cardiovascular disease. (The analysis was partly funded by mayo and margarine maker Unilever. Both foods are rich in omega-6 fats.)
What’s more, when people were randomly assigned to eat more omega-6 fats instead of saturated fats, they had a lower risk of heart disease.
“There is no good clinical research that shows adverse effects for omega-6 fats,” says Sacks. “In fact, studies actually show beneficial effects.”
The bottom line
Researchers still don’t know which foods cause inflammation, but there’s no good evidence that omega-6 fats are to blame.
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