Linoleic acid competes with alpha-linolenic acid, an omega-3 fatty acid, for enzymes that convert simple polyunsaturated fatty acids into more complex ones. Since complex omega-3 fatty acids such as EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are associated with heart disease prevention, reduced inflammation, and other health benefits, some authorities have argued that the high amounts of linoleic acid in the typical Western diet are detrimental to health because they can reduce the body’s production of EPA and DHA.⁶ While most controlled research suggests that dietary linoleic acid has some influence on the production of EPA in the body,^{7, 8, 9} conversion of alpha-linolenic acid into more complex omega-3 fatty acids is limited for other reasons,^{10, 11, 12} so that achieving adequate levels of EPA and DHA depends mostly on consuming oily fish and fish oils, which are good sources of these complex omega-3 fatty acids.¹³ Furthermore, higher dietary intake or high body levels of omega-6 fatty acids, most of which is linoleic acid, has been associated with reduced coronary heart disease risk in numerous preliminary studies, and with no effect on other diseases such as stroke or cancer.¹⁴

A diet high in polyunsaturated fats such as the omega-6 fatty acids increases vitamin E requirements. Based on available evidence, at least 0.6 mg (0.9 IU) of vitamin E is needed for every gram of polyunsaturated fat consumed.¹⁵