While a sizzling cup of tea is refreshing and can help to relax, experts are warning that excessive tea is harmful to health, affects the body systems can even cause unusual bone disease, and should be avoided.Tea contains toxic elements like tanine and caffeine which are detrimental to health. Tanine adversely affects the digestive process because it affects the secretion of juices. It also affects the water content in the body, resulting in a brittle and rough skin.Caffeine on the other hand, affects the nervous system and keeps a person awake at night. It can raise blood pressure and cause poor concentration, irritability and nervousness.Excessive tea drinking is also said to lead to excessive passing of urine, but the toxic element are not gotten rid of. Urine gets solidified, forming uric acid which gets deposited in joints resulting in gout and arthritis. It can also result in high levels of fluoride which is bad for the teeth and bones.Such was the case of a 47-year-old Michigan woman who developed a bone disease rarely seen in the U.S. after she drank a pitcher of tea made from at least 100 tea bags daily, for 17 years, researchers report.The Detroit woman visited the doctor after experiencing pain in her lower back, arms, legs and hips for five years. X-rays revealed areas of very dense bone on the spinal vertebrae and calcifications of ligaments in her arm, said study researcher Dr. Sudhaker D. Rao, a physician at Henry Ford Hospital who specializes in endocrinology and bone and mineral metabolism.The researchers suspected the woman had skeletal fluorosis, a bone disease caused by consuming too much fluoride, a mineral found in tea as well as drinking water.According to researchers, the patient's blood levels of fluoride were four times higher than what would be considered normal. Skelectal fluorosis is endemic in regions of the world with naturally high levels of fluoride in drinking water, including some parts of India and China, but is rare in Europe and North America.This is because low levels of fluoride are added to drinking water in the United States to prevent cavities but are not enough to cause fluorosis.Dr. Rao said the patient was originally referred to him because her doctors suspected she had cancer, which can also show up on an X-ray as areas of dense bone. But because he had seen cases of skeletal fluorosis in his native India, "I was able to recognize it immediately," he said.Excess fluoride is typically eliminated from the body by the kidneys, Rao said. "But if one consumes a lot of it, as this patient did through tea drinking, over time, the fluoride forms crystal deposits on bone", Rao said. A few other cases of skeletal fluorosis caused by tea drinking have been reported in the United States. In these cases, patients typically drank a gallon of tea a day, Rao said. Dr. Rao and colleagues have instructed their patient to stop drinking tea, after which she experienced an improvement in symptoms. The fluoride deposits will gradually go away as the bone remodels itself, a process that occurs frequently in the body, Rao said.