What we think of as the health benefits of green tea today are not the result of controlled clinical studies, but only hints of positive effects that emerged from epidemiological literature from the late 1980s onward. These studies attempt to associate dietary and other factors with health outcomes. Results in epidemiology–the study of the incidence of disease in populations–are complicated by numerous factors that could account for either an increase or decrease of disease in a certain population. Such factors include lifestyle habits, differences in home and work environments, alcohol consumption, smoking, diet, and climate. Many epidemiological studies have shown that a diet rich in foods such as vegetables, fruits, legumes, grains, and green tea, and dietary supplements such as vitamins C and E, beta-carotene, and selenium can reduce the risk of cancer. This has encouraged researchers to try to identify chemicals in foods that help to protect against DNA damage. Many of these substances block specific carcinogen pathways.
Epidemiological, laboratory cell cultures, and animal studies have shown that green tea or its polyphenols may protect against many types of cancer. Epidemiological studies often point the way to new research. For example, prostate cancer affects as many as one out of eleven American men. It is the second-leading cause of cancer deaths among men in the United States, and is one of the most invasive forms of cancer. Epidemiological observations show that tea-consuming populations have much lower rates of prostate cancer than non-tea drinkers. The prostate cancer rate among green-tea drinking Chinese men is the lowest in the world. Of course, other risk factors such as smoking may also contribute to higher cancer rates.
In one study on green tea, researchers at the Korea Research Institute of Chemical Technology examined the effect of green tea (and coffee) on men who smoke cigarettes using a measure for a blood compound that indicates a greater predisposition to cancer development. The scientists divided fifty-two clinically healthy men into four different groups. One group was made up of non-smokers, the second group contained smokers, the third group included smokers who drank green tea, and the fourth group was made up of smokers who drank coffee. In the last two groups, the men averaged ten cigarettes a day and two to three cups of their chosen beverage.
The men were monitored for six months. Researchers found that the smokers who drank green tea had levels of the target compound similar to that of nonsmokers. Those who smoked and drank coffee did not have significantly different levels of the marker compound than smokers who did not drink stimulant beverages. This study implies that consuming green tea could help protect smokers from cancers. Of course, so could quitting smoking!
Green and black tea contain different types of flavonoids and antioxidants that may prevent certain forms of cancer (including lung, stomach, esophagus, duodenum, pancreas, liver, breast, colon, and skin cancers in laboratory animals) and reducing the risk of cardiovascular disease. A recent epidemiological study of 8,552 residents in Saitama Prefecture, Japan, evaluated green tea for the prevention of cancer and cardiovascular disease. Analysis of the data showed that there was a relative decrease in the cancer risk of people who consumed more than ten cups a day, compared with individuals who consumed only three cups daily. A Japanese “cup” of tea is probably equivalent to about 4 fluid ounces (or about half of a standard 8-oz. cup). The average decrease in cancer risk was about 60 percent. This study also showed that drinking green tea produced a significant delay in the onset of cancers. A relative decreased risk of death in cardiovascular disease of about 58 percent was also observed.
Despite the fact that much of the evidence on green tea comes from epidemiological studies, and that blinded, controlled, randomized clinical studies are few and far between, the evidence for the health benefits of green tea heavily tips in favor of positive effects. It appears that consuming an average of four standard cups of green tea daily can produce positive benefits for helping to prevent some cancers and improving cardiovascular function. Besides, the caffeine helps to keep you awake.
What about additives to tea such as sugar, milk, or a squeeze of lemon juice? One recent study looked at the effects of milk and lemon on antioxidant activity when added to tea. The Indian researchers found that adding lemon to a cup of tea increased the antioxidant potential of the tea. Milk had no additional benefits. Some studies suggest that the addition of milk to tea does not affect the bloodstream’s uptake of beneficial compounds in tea, but other studies suggest that milk proteins inhibit the absorption of polyphenols in tea. More research will reveal the truth.
Vitex for PMS
Vitex agnus-castus, commonly known as chaste tree or vitex, is a shrub in the verbena family native to western Asia and southwestern Europe. Vitex has been used for menstrual difficulties for at least 2,500 years. In the past fifty years, research has focused on the use of vitex for premenstrual syndrome (PMS) and menstrual difficulties such as overly frequent menstruation or excessive bleeding. Clinical trials to date have primarily involved a tincture of berries and have confirmed the value of the tincture in treating symptoms associated with PMS. German health authorities allow vitex preparations for menstrual problems. Vitex preparations are frequently used in the treatment of PMS, heavy periods, too-frequent periods, acyclic bleeding, suppressed menses, and other conditions. Vitex is an excellent example of an herbal medicine that serves as a low-priced tool in European gynecological practice, rather than an “alternative” treatment.
Most of the research on the herb has been conducted in Germany. Recently, a major clinical study on vitex extract was published in the British Medical Journal. The study was conducted by researchers at the Institute for Health Care and Science in Huttenberg, Germany. The randomized, double-blind, placebo- controlled study included 178 women with PMS. At the end of the three-month trial, 170 women were evaluated, including eighty-six in the treatment group and eighty-four in the placebo group. The average age of the women was thirty-six years. Their average length between menstrual cycles was twenty-eight days, and the average duration of their periods was four and a half days. Women received either tablets containing a dry extract of vitex fruits or a placebo once a day. The product used contained 20 mg of an extract, prepared in 60 percent ethanol (alcohol). The extract was then dried and standardized to contain casticin, a component of the fruits. Women self-assessed symptoms such as irritability, mood alteration, anger, headache, and other menstrual symptoms such as a feeling of fullness or bloating and breast fullness.
Volunteers also received a complete medical examination by the participating physicians along with various laboratory tests. After three months, more than half of the women in the treatment group had a 54 percent or greater improvement in symptoms, while only 24 percent of the women in the placebo group reported improvements. Side effects were few and mild in nature: gastrointestinal upset, intermenstrual bleeding, rash, and acne. One woman in the placebo group withdrew due to pregnancy. The authors concluded that vitex extract is a safe and effective treatment for PMS, as assessed both by the women and the attending physicians. (1)
Will the real ginseng please stand up?
Ginseng is generally defined to mean American ginseng (Panax quinquefolius) and Asian ginseng (Panax ginseng), which includes both Panax ginseng of Korean and Chinese origin, and white (dried) or red (steamed) ginseng. Another herb sometimes classified as a type of ginseng is “eleuthero,” so-called Siberian ginseng (Eleutherococcus senticosus). Over the years, some in the herbal community have questioned this practice, leading one herb company official to ask, “Can you call something ginseng that is harvested with a chainsaw?”
In 1992, the American Herbal Products Association published the first edition of Herbs of Commerce, which listed more than 600 plant species then sold as herbs in the American market. The recently published, revised edition of Herbs of Commerce (American Herbal Products Association, 2000) includes more than 1,600 plant species sold as dietary supplements. The work includes a listing of species in trade with the plants’ scientific names (and synonyms) along with a “standard” or preferred common name for use in the herb trade. The original version of Herbs of Commerce is listed in the regulations under the Dietary Supplement Health and Education Act of 1994 (DSHEA) as the source for the common and usual names of botanical ingredients in dietary supplements. The second edition of Herbs of Commerce is listed in the Act as the information source to determine whether or not an ingredient is grandfathered under DSHEA and does not require safety testing to be submitted to the FDA as a new food ingredient prior to marketing.
In the first and second editions of Herbs of Commerce, “eleuthero” is listed as the standard English name for Eleutherococcus senticosus, so-called Siberian ginseng. Herbal products generally fall under the regulatory umbrella of the Food and Drug Administration, but related advertising and trade practices may also come under the scrutiny of the Federal Trade Commission. So while you may be familiar with Eleutherococcus senticosus under the name Siberian ginseng, chances are you will have to look for it under the product name eleuthero in the future. (2)
All names, aside, consumers should understand that the name ginseng should apply only to species in the genus Panax, because studies on American and Asian ginseng products do not apply to eleuthero. Recently, researchers published a comprehensive review evaluating the scientific evidence for ginseng (Panax). They analyzed ginseng’s potential to enhance physical performance and relieve fatigue. They indicated that the research does not resolve questions regarding “sourcing” of ginseng products. Furthermore, problems such as inadequate sample size, lack of double-blinding, controls, and placebo comparisons in many studies further complicate the analysis of the research. In the future, basic fundamental design considerations with more human studies are needed to determine ginseng’s real value. (3)
(1) Schellenberg, R. “Treatment for the premenstrual syndrome with agnus castus fruit extract: prospective, randomised, placebo-controlled study.” British Medical Journal 2001, 322:134-137.
(2) Foster, S., Ed. Herbs of Commerce. Austin, Texas: American Herbal Products Association, 1992.
McGuffin, M., et al. Herbs of Commerce 2nd ed. Silver Spring, Maryland: American Herbal Products Association, 2000.
(3) Bahrke, M. S., and W. P. Morgan. “Evaluation of the ergogenic properties of ginseng: an update.” Sports Medicine 2000, 29(2):113-133.
Abdulla, M., and Gruber, P. “Role of diet modification in cancer prevention.” Biofactors 2000, 12(1-4): 45-51.
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Lee, I. P., et al. “Chemopreventive effect of green tea (Camellia sinensis) against cigarette smoke-induced mutations (SCE) in humans.” Journal of Cellular Biochemistry Supplement 1997, 27(2): 68-75.
Nakachi, K., et al. “Preventive effects of drinking green tea on cancer and cardiovascular disease: epidemiological evidence for multiple targeting prevention.” Biofactors 2000, 13(1-4): 49-54.
Shim, J. S., et al. “Chemopreventive effect of green tea (Camellia sinensis) among cigarette smokers.” Cancer Epidemiology, Biomarkers and Prevention 1995, 4(4): 387-391.
Tewari, S., et al. “Comparative study of antioxidant potential of tea with and without additives.” Indian Journal of Physiology and Pharmacology 2000, 44(2): 215-219.