While both black and green teas are made from the same plant, green tea leaves undergo minimal processing, while black tea has gone through an oxidation process, called fermentation. Both types of tea make a healthful addition to your diet, but, because of the variation in their nutrient content, they offer slightly different health benefits.
Black and green teas both support healthy bones and teeth, due to their fluoride content, but black tea can provide more fluoride per serving. Your body can incorporate the fluoride in your diet into hydroxyapatite, the mineralized tissue that makes up your teeth and bones. Consuming fluoride helps harden your teeth and prevents cavities. Black tea contains between 0.2 and 0.5 milligrams of fluoride per cup, while green tea provides 0.3 to 0.4 milligrams. Making your tea with tap water further increases your fluoride intake. For example, an 8-ounce serving of black tea made from fluoridated tap water contains 0.9 milligrams of fluoride.
Green tea comes out ahead of black tea when it comes to cancer-fighting benefits. It serves as a rich source of four catechins -- a family of flavanols partially responsible for the tea's health benefits. One type of catechin, called epigallocatechin gallate, or EGCG, regulates gene activity in cancer cells, and might fight cancer growth. One study, published in the journal "Toxicology and Applied Pharmacology" in 2013, found that EGCG promotes skin cancer cell death. Another study, from the November 2013 issue of "Oncology Letters" found that EGCG had a similar effect on colon cancer cells. The study also found that EGCG inactivate genes needed for colon cancer metastasis, which means that the EGCG in green tea might fight cancer spread.
Both black and green tea offer cardiovascular benefits. The EGCG abundant in green tea interacts with the cells that line your blood vessels and promotes autophagy -- a physiological process shields your cells from stress -- according to a study published in the "Journal of Biological Chemistry" in 2013. Green tea also helps control your blood cholesterol levels, boosting the amount of beneficial cholesterol in your bloodstream while reducing the amount of harmful cholesterol. However, black tea also offers some benefits, and drinking it improves blood vessel function if you have coronary artery disease, explains the Linus Pauling Institute.
Black and green teas differ in their caffeine content. Green tea contains between 9 and 50 milligrams of caffeine per cup, while black tea offers 42 to 72 milligrams, according to the Linus Pauling Institute. This caffeine can temporarily increase your mental alertness, promote productivity and perhaps even aid in weight loss, but it can also keep you up at night, especially if you consume too much -- for example, drinking several cups of tea per day. Limit your tea intake to 5 servings daily, recommends the University of Maryland Medical Center, and opt for green tea over black tea, to reduce your caffeine consumption.