Kaempferol is a flavonol found primarily in plant-based foods such as kale, broccoli, chives, dill, saffron, and turnip greens. Flavonols (including quercetin and fisetin, as well as kaempferol) are a class of flavonoids, pigments found in a wide variety of plants. Several population studies have reported that diets high in flavonols are associated with reduced risk of breast cancer. A 2013 meta-analysis of previous studies reported that women with high flavonol intake had a 12% lower risk of breast cancer than those with low intake. Now a new study has reported that kaempferol's chemopreventive effects in hormone receptor positive (ER+/PR+) breast cancer cells are due in part to inhibition of glucose uptake.

Flavonoid types

Flavonoids are pigments found in a wide variety of plants. Flavonoids can subdivided into six major groups: flavones, flavonols, anthocyanins, isoflavones, flavan-3-ols, and flavanones. There are thousands of flavonoids in total. Below are the most abundant and well studied flavonoids with respect to breast cancer risk:

Flavones and anthocyanins are found in a variety of plant-based foods. Soy foods are the primary dietary source of isoflavones, green and black tea are the main source of flavan-3-ols, and citrus fruit are the main source of flavanones. Stilbenes such as resveratrol (red grapes) and curcuminoid such as curcumin (turmeric) are two important types of non-flavonoid phytochemicals with anti-cancer properties.

Kaempferol helps protect heart from Adriamycin chemotherapy

Kaempferol has been shown to reduce the cardiotoxic effects of Adriamycin (doxorubicin) chemotherapy in rats. The usefulness of Adriamycin is limited by its cardiotoxicity, which can lead to heart failure in susceptible breast cancer patients. Some compounds that decrease side effects do so at the cost of potentially reducing the effectiveness of treatment. Not so for kaempferol, which appears to use a mitochondrion-dependent pathway to inhibit the Adriamycin-induced cardiotoxicity. It has been demonstrated that the cytotoxicity of doxorubicin against cancer cells is not reduced by exposure of the cells to kaempferol.

Note that while black tea and green tea dietary sources of kaempferol, they might reduce the effectiveness of Adriamycin and other anthracycline chemotherapy through their caffeine content.

Latest research finds kaempferol reduces ER+/PR+ breast cancer glucose uptake

The study referenced at the beginning of this news story was designed to investigate the effects of five polyphenols (myricetin, chrysin, genistein, resveratrol, kaempferol, and xanthohumol) on the uptake of glucose by hormone receptor positive breast cancer cells. In the absence of any of the polyphenols, uptake of 3H-deoxy-D-glucose ("glucose") by ER+/PR+ MCF-7 breast cancer cells was time-dependent, capable of being saturated so that no more could be absorbed (saturable), and inhibited by cytochalasin B plus phloridzin.

Myricetin, chrysin, genistein, resveratrol, kaempferol, and xanthohumol (at concentrations of 10-100 ÁM) all were found to inhibit glucose uptake in the short-term (26 minutes). Kaempferol was the most potent short-term glucose uptake inhibitor. Kaempferol (30 ÁM) was also able to inhibit glucose uptake (associated with a 40% decrease in GLUT1 mRNA levels) in the long-term (defined as 24 hours). At 100 ÁM, kaempferol demonstrated antiproliferative and cytotoxic properties similar to those caused by low extracellular glucose conditions and reversible by high extracellular glucose conditions. In addition, exposure of MCF-7 cells to kaempferol (30 ÁM) caused higher extracellular lactate levels over time as a result of inhibition of cellular lactate uptake. The authors conclude that kaempferol potently inhibits glucose uptake by ER+/PR+ breast cancer cells, apparently by decreasing GLUT1-mediated glucose uptake. The authors further comment that the antiproliferative and cytotoxic effect of kaempferol in these cells appears to be dependent on this effect.