Preliminary research in animals found that the citrus flavonoid tangeretin, found primarily in the peel of citrus fruits, interferes with the ability of tamoxifen to inhibit tumor growth. Although the evidence is far from conclusive, people taking tamoxifen should probably avoid citrus bioflavonoid supplements, as well as beverages and foods to which citrus peel oils have been added.

Preliminary research in animals found that the citrus flavonoid tangeretin (found primarily in the peel of citrus fruits) interferes with the ability of tamoxifen to inhibit tumor growth. Although the evidence is far from conclusive, people taking tamoxifen should probably avoid citrus bioflavonoid supplements, as well as beverages and foods to which citrus peel oils have been added.

Studies have shown that grapefruit juice significantly increases estradiol levels in the blood. One of the flavonoids found in grapefruit juice is quercetin. In a test tube study, quercetin was found to change estrogen metabolism in human liver cells in a way that increases estradiol levels and reduces other forms of estrogen. This effect is likely to increase estrogen activity in the body. However, the levels of quercetin used to alter estrogen metabolism in the test tube were much higher than levels found in the body after supplementing with quercetin.

There is evidence from test tube studies that another flavonoid in grapefruit juice, naringenin, also has estrogenic activity. It has yet to be shown that dietary or supplemental levels of quercetin (or naringenin) could create a significant problem.

Preliminary research in animals found that the citrus flavonoid tangeretin (found primarily in the peel of citrus fruits) interferes with the ability of tamoxifen to inhibit tumor growth. Although the evidence is far from conclusive, people taking tamoxifen should probably avoid citrus bioflavonoid supplements, as well as beverages and foods to which citrus peel oils have been added.

Quercetin is a flavonoid found in grapefruit juice, tea, onions, and other foods; it is also available as a nutritional supplement. Quercetin has been shown in test tube studies to inhibit enzymes responsible for breaking down felodipine into an inactive form. This interaction may result in increased blood levels of felodipine that could lead to unwanted side effects. Until more is known about this interaction, patients taking felodipine should avoid supplementing with quercetin.

Preliminary research in animals found that the citrus flavonoid tangeretin (found primarily in the peel of citrus fruits) interferes with the ability of tamoxifen to inhibit tumor growth. Although the evidence is far from conclusive, people taking tamoxifen should probably avoid citrus bioflavonoid supplements, as well as beverages and foods to which citrus peel oils have been added.

Preliminary research in animals found that the citrus flavonoid tangeretin (found primarily in the peel of citrus fruits) interferes with the ability of tamoxifen to inhibit tumor growth. Although the evidence is far from conclusive, people taking tamoxifen should probably avoid citrus bioflavonoid supplements, as well as beverages and foods to which citrus peel oils have been added.

Preliminary research in animals found that the citrus flavonoid tangeretin (found primarily in the peel of citrus fruits) interferes with the ability of tamoxifen to inhibit tumor growth. Although the evidence is far from conclusive, people taking tamoxifen should probably avoid citrus bioflavonoid supplements, as well as beverages and foods to which citrus peel oils have been added.

Preliminary research in animals found that the citrus flavonoid tangeretin (found primarily in the peel of citrus fruits) interferes with the ability of tamoxifen to inhibit tumor growth. Although the evidence is far from conclusive, people taking tamoxifen should probably avoid citrus bioflavonoid supplements, as well as beverages and foods to which citrus peel oils have been added.

Preliminary research in animals found that the citrus flavonoid tangeretin (found primarily in the peel of citrus fruits) interferes with the ability of tamoxifen to inhibit tumor growth. Although the evidence is far from conclusive, people taking tamoxifen should probably avoid citrus bioflavonoid supplements, as well as beverages and foods to which citrus peel oils have been added.

Preliminary research in animals found that the citrus flavonoid tangeretin (found primarily in the peel of citrus fruits) interferes with the ability of tamoxifen to inhibit tumor growth. Although the evidence is far from conclusive, people taking tamoxifen should probably avoid citrus bioflavonoid supplements, as well as beverages and foods to which citrus peel oils have been added.

Preliminary research in animals found that the citrus flavonoid tangeretin (found primarily in the peel of citrus fruits) interferes with the ability of tamoxifen to inhibit tumor growth. Although the evidence is far from conclusive, people taking tamoxifen should probably avoid citrus bioflavonoid supplements, as well as beverages and foods to which citrus peel oils have been added.

Preliminary research in animals found that the citrus flavonoid tangeretin (found primarily in the peel of citrus fruits) interferes with the ability of tamoxifen to inhibit tumor growth. Although the evidence is far from conclusive, people taking tamoxifen should probably avoid citrus bioflavonoid supplements, as well as beverages and foods to which citrus peel oils have been added.