context: var s_context; s_context= s_context || {}; s_context['wb.modimp'] = 'vidfloat'; if(webmd.useragent && webmd.useragent.ua.type === 'desktop'){ webmd.ads2.disable Initial Load(); webmd.ads2.disable Ads Init = true; $(function() { webmd.p.pim.increment(); $('.responsive-video-container').insert After('.module-social-share-container'); require(['video2/1/responsive-player/video-loader'], function(video Loader) { video Loader.init({ autoplay: webmd.useragent.ua.type === 'desktop' && ! !s_sensitive, chron ID: $('article embeded_module[type=video][align=top]:eq(0)').attr('chronic_id'), continuous Play: true, cp Options: { flyout: true }, display Ads: true, mode: 'in-article', sticky: true }) }); }); } else { $(function(){ $('.responsive-video-container').remove(); }); } Black tea is made from the leaves of a bush called Camellia sinensis. A process called oxidation turns the leaves from green to a dark brownish-black color. Oxidation means the leaves are exposed to moist, oxygen-rich air. Tea manufacturers can control the amount of oxidation. Black tea is a fully oxidized tea. Green tea comes from the same plant, but is not oxidized. Many people drink black tea for alertness and energy. There is good scientific evidence to show this works. Black tea contains caffeine. It also contains a little bit of a stimulating substance called theophylline. Both can speed up your heart rate and make you feel more alert. Black tea is also full of healthy substances called polyphenols. Polyphenols are antioxidants that can help protect your cells from DNA damage. Some scientists think that specific antioxidants in tea, including polyphenols and catechins, may help prevent some types of cancer. For example, some research shows that women who regularly drink black tea have a much lower risk of ovarian cancer than women who do not. But more research is needed. So far, research has shown that black tea does not lower the risk of breast, stomach, or colorectal cancer. Increasing evidence hints that the antioxidants in black tea may reduce atherosclerosis (clogged arteries), especially in women. It may also help lower the risk of heart attack and cardiovascular disease. Regularly drinking black tea may also lower your risk for these conditions: Diabetes High cholesterol Kidney stones Parkinson's disease But more research about black tea's effect on these conditions is needed to be sure. Early evidence hints that long-term use of black tea may also help protect against: Osteoporosis But larger-scale studies are needed to confirm these uses. Black tea extract is sold as a supplement. Sometimes, the supplement includes other types of herbs, vitamins, or minerals. Drinking a moderate amount of black tea (one to four cups a day) may boost blood pressure slightly, but the effect does not last long. And drinking this amount of black tea is not associated with long-term high blood pressure. Preliminary studies in people show that a black tea supplement can boost metabolism and increase blood pressure. Changes in blood pressure can be a concern. Optimal doses of black tea have not been established. Supplement ingredients and quality may vary widely. This makes it hard to set a standard dose. Black tea can be found in most stores. You can drink it hot or cold to get its benefits, but it should be steeped in hot water before it is cooled. Drinking black tea in moderate amounts is generally safe for most people. Drinking large amounts of black tea, or more than four or five cups a day, may cause health problems. That's mostly because of caffeine-related side effects. Side effects of black tea (most often in high amounts) may include: Anxiety and difficulty sleeping Faster breathing Headache Increased urination Irregular heartbeat Nausea and vomiting Nervousness and restlessness Ringing in the ears Tremors Combining black tea with other types of caffeine or a product called ephedra can be very dangerous. Some of the problems it can cause include jitteriness, increased blood pressure, heart rate changes, seizures, and passing out. Black tea or black tea supplements may interfere with other medicines and supplements you are taking. Some medicines can cause caffeine to stay in your body longer than usual. Talk to your doctor to see if medicines you are taking may have this effect. Always tell your doctor about any supplements you are taking, including natural ones and those bought without a prescription. That way, your doctor can check on any potential side effects or interactions with any medications and your health conditions. The caffeine in black tea may also interfere with certain blood tests. Tell your doctor if you drink a lot of black tea. The U. S. Food and Drug Administration ( FDA) does regulate dietary supplements; however, it treats them like foods rather than medications. Unlike drug manufacturers, the makers of supplements don't have to show their products are safe or effective before selling them on the market.