U.S. researchers reviewed 15 studies and said they could find no evidence that a diet high in linoleic acid (omega‑6) had any links to inflammation in the body. “Our evidence does suggest that you can achieve a heart-healthy diet by using soybean, canola, corn and sunflower oils instead of animal-based fats when cooking,” they noted in their review that was published in the Journal of the Academy of Food and Nutrition (formerly known as the Journal of the American Dietetic Association).
Canola oil was included in the list of recommended vegetable oils even though it is not such a rich source of omega‑6 compared to other vegetable oils, with 20 percent of fatty acids being from linoleic acid, compared to 60 percent in corn oil.
Olive oil was not mentioned anywhere in the study.
Olive oil is in fact, low in linoleic acid with an average of 10 percent of fats coming from this particular fatty acid. For this reason it is recommended for cooking since it helps keep a balanced ratio of the two fatty acids: omega‑6 and omega‑3.
Most researchers agree that there are too much omega‑6 fatty acids in western diets and not enough omega‑3 fatty acids. Omega‑6 and Omega‑3 are both essential fatty acids, which means that our body needs to get them through our diet. Both fatty acids have beneficial qualities, though they need to be somewhat in balance in our diet.
Currently in most western diets the amount of omega‑6 fatty acids is 15 to 50 times higher than omega‑3. This is problematic as omega‑6 fatty acids compete for some of the same enzymes as omega‑3, and interfere with the health benefits of the omega‑3 fatty acids.
The high intake of omega‑6 fatty acids in the diet appears to come mainly from the consumption of processed foods, which contain several types of vegetable oils high in omega‑6 fatty acids such as linoleic acid. Omega‑6 has been associated with inflammation in some studies but not in others.
Apart from a potential conflict of interest in the study, the reality is that western diets contain too many omega‑6 fatty acids and to suggest using vegetable oils such as soybean and corn oil that are also rich in omega‑6 fatty acids would be compounding the problem.
A high ratio of omega‑6 to omega‑3 fatty acids has been associated with increased risk of prostate and breast cancer, increased risk of Alzheimer’s and depressive symptoms as well as problems with reproduction.
The Mediterranean diet is an example of a diet that has a healthier ratio of omega‑6 to omega‑3 fatty acids, most likely due its use of fresh food (very low intake of processed food products), olive oil as the main source of fat (low in linoleic acid), and high intake of fatty fish rich in omega‑3 such as sardines and anchovies.