Corn oil has a relatively high omega-6 fatty acid content, in the form of linoleic acid. Linoleic acid is converted into arachidonic acid in the body. Increasing consumption of corn oil has been shown in animal studies to be associated with higher risks of cancer of the stomach, prostate, pancreas, liver and lung. Exposure to cooking oil fumes, including corn oil fumes, has been shown to increase the risk of lung cancer.
One study published in 2008 attributed the documented increase in the incidence of esophageal cancer in the U.S. to increasing carbohydrate consumption, including corn. On the other hand, cornmeal appears to be protective against colon cancer, possibly due to its dietary fiber content.
Various studies of non-U.S. populations have found that consumption of corn contaminated with fusarium fungi accounts for high levels of esophageal cancer in parts of Iran, Brazil, South Africa, and China. Fusarium fungi produce fumonisins that reduce to compounds that synthesize carcinogenic nitrosamines. Fumonisins have been found to survive most types of baking and frying. Both fumonisin and aflatoxin (also found in corn) levels are regulated by the Food and Drug Administration in corn meant for human consumption and animal feed.
Breast cancer-related effects of consuming corn oil
Numerous studies have shown that a diet high in corn oil stimulates the formation of breast tumors in laboratory rats. Several experiments also have shown that offspring of rat mothers fed high corn oil diets are more likely to develop mammary tumors than offspring of mothers fed canola oil diets. The explanations given for these findings are related to corn oil's relatively high level of omega-6 fatty acids.
One study reported that women with a specific genotype (ALOX5AP −4900 A>G polymorphism) who consumed a significant amount of linoleic acid in their diets had an increased risk of breast cancer. Another study found increased breast cancer risk among women cooking primarily with high linoleic acid vegetable or corn oil compared to women using olive or canola oil.
Women with breast cancer have been found to have higher levels of omega-6 in their breast tissue than similar women without breast cancer. Several studies have found that lower dietary omega-6/omega-3 ratios are associated with reduced risk of breast cancer. Consuming corn oil would tend to increase the ratio for most women because of its high omega-6 content.
Corn and corn products
There is little available information concerning the relationship between the consumption of fresh corn, cornmeal, cornstarch and grits and breast cancer risk. Sweet corn is a source of melatonin. Melatonin protects against breast cancer in several ways, including by reducing aromatase activity within the breast, thereby reducing estrogen production. Sweet corn and field corn (used to make corn tortillas, corn chips) contain some lutein and zeaxanthin, which may have chemopreventive properties.
Corn and foods made from corn have a high glycemic index. Cornmeal, cornstarch and grits do not appear to promote breast cancer directly. However, one study found a link between increased starch intake after a diagnosis of early-stage breast cancer and a greater risk of recurrence.
Below are links to recent studies concerning this food. For a more complete list of studies, please click on corn oil.