Sunflower (Helianthus annuus) oil ranks fourth in world vegetable oil production, after palm oil, soybean oil and canola oil. Sunflower oil (i.e., sunflower seed oil) is an abundant dietary source of unsaturated fat, primarily the polyunsaturated omega-6 fatty acid, linoleic acid. It is also a good source of vitamin E. Unlike olive oil, canola oil or walnut oil, sunflower oil has not been found to be associated with health benefits such as reducing cardiovascular risk factors. Nor has it been associated with any reductions in cancer risk in population studies. Sunflower seeds have been shown to have antioxidant activities and are a very good source of vitamin E and several B-vitamins.
Breast cancer-related effects of eating sunflower oil
The relationships between oil and fat consumption and breast cancer are complex and appear to depend on the specific attributes of the oil or fat in question. It was originally thought that consumption of fat promoted breast cancer, regardless of the source of the fat. The focus then shifted to saturated versus unsaturated fat, with further refinements concerning monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs). More recently, the emphasis has shifted to the balance between omega-6 and omega-3 fatty acids in the diet. The reason for these changes in emphasis is that none of the theories were found to hold consistently in population studies. While the theory that cancer is caused in part by an excess of omega-6 fatty acids in the Western diet appears to be valid, it is not a global explanation for the relationship between oils and fats and breast cancer. For example, it does not explain the fact that olive oil, which does not have a high omega-3 content, is protective against breast cancer.
In the case of sunflower oil, there is evidence from experiments using either carcinogen-induced or transplanted animal mammary tumor models, as well as in vitro studies, which demonstrates that linoleic acid, the primary fatty acid in sunflower oil, promotes mammary tumor development.
One study found 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 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 sunflower oil would tend to increase the ratio for most women because of its high omega-6 content.
It has been demonstrated that consumption of either olive oil or eicosapentaenoic acid (found in fish oil) improves absorption and metabolism of beta-carotene in food compared with linoleic acid. This could be important for reducing breast cancer risk since dietary carotenoids have been found to be associated with lower risk of breast cancer.
Sunflower seeds are a dietary source of cadmium and copper
Of the products typically consumed as snack foods, pistachio and sunflower kernel were found to be richest in phytosterols, according to one study. Sunflower seeds are also a good dietary source of the lignan enterolactone.
However, sunflower seeds and kernels can contain high levels of the carcinogenic heavy metal cadmium, since sunflower plants have a tendency to accumulate cadmium. Sunflower seeds grown for consumption as seeds are known as confectionary sunflower seeds. U.S. confectionary sunflower seeds are grown primarily in North and South Dakota, a region with relatively high cadmium levels in the soil. Stricter European rules on cadmium in sunflower imports from the U.S. have caused confectionary sunflower seeds grown in U.S. soils with lower levels of cadmium to be diverted to the European market. Efforts have been under way for several years to breed sunflower hybrids that will take up less cadmium, however it is not clear to what extent U.S. consumers are benefiting from such efforts.
In addition, sunflower seeds also contains relatively high levels of copper, which has been shown to increase angiogenesis and metastasis of breast cancer, especialy in women with inflammatory breast cancer (IBC) or triple negative (ER-/PR-/HER2-) disease.
Below are links to recent studies concerning this food. For a more complete list, including less recent studies, please click on sunflower oil.