Mayo Clinic finds green tea extract fights leukemia
In an article appearing online on May 26, 2009 in the Journal of Clinical Oncology, Mayo Clinic researchers report positive effects for a green tea compound known as epigallocatechin gallate (EGCG) in a phase I trial involving patients with early stage chronic lymphocytic leukemia (CLL). Chronic lymphocytic leukemia, the most common subtype of leukemia in the United States, is a cancer of the blood and bone marrow that is characterized by abnormal proliferation of white blood cells known as lymphocytes. Half of the patients with early stage CLL have an aggressive form of the disease which increases the risk of early mortality.
Acting on preliminary findings that included a significant effect of EGCG against leukemia cells in cell cultures as well as in some CLL patients who used over the counter green tea supplements, Mayo Clinic hematologist Tait Shanafelt, MD and colleagues administered 8 doses varying from 400 to 2000 milligrams twice per day of an extract containing EGCG as its active ingredient to 33 CLL patients.
A third of the patients treated with EGCG experienced a reduction in lymphocyte count of at least 20 percent following treatment. "We found not only that patients tolerated the green tea extract at very high doses, but that many of them saw regression to some degree of their chronic lymphocytic leukemia," Dr Shanafelt stated. "The majority of individuals who entered the study with enlarged lymph nodes saw a 50 percent or greater decline in their lymph node size."
Possible mechanisms attributed to green tea include antiangiogenic properties, cell-cycle arrest, modification of DNA damage, and reductions in level of antiapoptotic proteins. The researchers hope that EGCG can stabilize chronic lymphocytic leukemia or improve the effectiveness of other treatments. A second phase of clinical testing has already enrolled a similar number of patients as participated in the preliminary trial, who will receive 2000 milligrams of the green tea extract.
Risk factors for leukemia include advanced age, poor nutrition, previous chemotherapy and radiation treatment for other cancers, and smoking. Medical treatment for leukemia primarily revolves around chemotherapy and radiation therapy. Nutritional supplements help support the healthy function of the immune system, and in particular, the white blood cells in leukemia patients. In addition, some nutritional supplements are able to kill leukemia cells. Key examples include vitamin A, genistein from soy extract, and curcumin from turmeric.
Leukemia can be classified into four major types based on whether the disease is acute or chronic and according to the type of white blood cell affected:
Acute myelogenous leukemia (AML)
Chronic myelogenous leukemia (CML)
Acute lymphocytic leukemia (ALL)
Chronic lymphocytic leukemia (CLL)
Myelogenous leukemia involves myeloid cells, granulocytes (neutrophils, basophils, and eosinophils) and monocytes (macrophages). Lymphocytic leukemia involves T and B cells (lymphocytes).
Epigallocatechin gallate (EGCG) in green tea blocks the production of vascular endothelial growth factor (VEGF), considered essential for leukemia growth and spread (Lee YK et al 2004). EGCG may be particularly useful in CLL, a leukemia type that relies heavily on VEGF for its survival. EGCG significantly increased the rate of cell death in 8 out of 10 CLL samples (Lee YK et al 2004). Green tea blocks the proliferation of lymphocytes from adult T cell leukemia patients (Li HC et al 2000). Theaflavins found in black tea have also been shown to be as potent as EGCG from green tea in blocking proliferation of leukemia cell lines (Lung HL et al 2004).
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Scientists have identified specific extracts from cruciferous vegetables (broccoli, cauliflower, Brussels sprouts, etc.) that modulate hormones in a way to help maintain healthy cell division. For instance, animal studies have shown that the cruciferous vegetable extract indole-3-carbinol (I3C) modulates estrogen hormones by favorably changing the ratio of protective 2-hydroxyestrone versus the damaging 16-hydroxyestrone. Indole-3-carbinol also induces phase I and II detoxifying enzymes that can help neutralize estrogen metabolites and xenobiotic estrogen-like environmental chemicals. Human studies support the beneficial role of I3C in positively altering estrogen metabolism. Di-indolyl-methane (DIM), a phytonutrient found in cruciferous vegetables, has been shown in animal studies to help maintain normal levels of a potentially damaging estrogen called 4-hydroxyestrone.
The term “vitamin E” refers to a family of eight related, lipid-soluble, antioxidant compounds widely found in plants. The tocopherol and tocotrienol subfamilies are each composed of alpha, beta, gamma, and delta fractions having unique biological effects. Different ratios of these compounds are found in anatomically different parts of a plant. For example, the green parts of a plant contain mostly alpha-tocopherol and the seed germ and bran contain mostly tocotrienols. Along with other nutrients, tocopherols and tocotrienols are concentrated in the bran layers of the rye grain, and are only present at low levels in the flour endosperm. Tocopherols are also present in algae, mint teas, and other food stuff.
New studies continue to elucidate the unique benefits of individual members of the vitamin E family. For these and other reasons, the original definition of vitamin E has been enhanced to include all eight family members and the related compounds that convert to them in the body.