Tea, it is said, is the cheapest beverage humans consume, next to the water. While drinking tea has been considered a health-promoting habit since ancient times, modern medicinal research is increasingly providing a scientific basis for this belief. Research has proved that green tea, along with many other teas, can speed up metabolism and boost fat loss. One study found that consumption of four cups of tea per day resulted in a significant decrease in body weight and waist circumference over 8 weeks. Research has also indicated that regular tea drinkers have less risk of developing neurological diseases such as Alzheimer's disease and Parkinson's disease in comparison to those who do not drink tea. One study has said that regular consumption of green tea boosts memory recall and retention as well as cognition. Researchers attribute these benefits to the presence of antioxidants including polyphenols, flavonoids, and catechins. Researchers have also said that one of the most potent health benefits of tea is its ability to prevent and even kill certain cancer cells. According to media reports, scientists at the National Cancer Institute of US have listed several clinical trials and epidemiologic studies that support tea's ability to prevent and fight cancer. Research is said to have demonstrated a direct link between tea and the prevention of oxidative damage, which leads to cancer. Antioxidants in tea are found to help eliminate free radicals and prevent oxidative stress that can lead to cancer of the liver and breast. Studies have also shown that regular drinking of tea can help to lower LDL cholesterol or bad cholesterol that can cause serious cardiovascular diseases. Some teas can also help to lower high blood pressure and improve blood circulation, lessening the chance of blood clots and heart attacks. Experts say three to six cups of tea every day can help regulate blood pressure and prevent heart problems.