Note to Reporters: The following column is written by Shirley Perryman, an Extension specialist in the Department of Food Science and Human Nutrition. The department is part of the College of Applied Human Sciences at Colorado State University.
The health benefits of tea, the second most commonly consumed beverage in the world after water, are often discussed. All tea comes from the warm weather Camellia sinensis plant, an evergreen shrub that is grown world-wide.
Where tea is grown and how it is processed determines its flavor, color and health effects. There are many steps to tea processing and how the tea leaves are processed determines how the tea is classified.
• White tea is harvested early in the spring before the buds contain chlorophyll, which means that the leaves are harvested while still white. It is uncured, unfermented and usually more expensive than green, oolong or black tea.
• Green tea is made from leaves that are dried and steamed after they are harvested. This process accounts for the lighter color, taste and higher concentration of catechins, or antioxidants. Currently, green tea is the most widely promoted tea for health benefits.
• Oolong tea is partially oxidized and falls between green and black tea in its antioxidant and caffeine levels.
• Black tea is made from fully oxidized and crushed tea leaves, which explains the darker color and stronger flavor. It has the highest caffeine content but still only about half that of coffee.
• Dark specialty teas such as Pu-erh and Fuzhuan tea are made from microbially fermented green tea leaves. They have an earthier taste and unique chemicals that impart health benefits. The costs can vary widely depending on whether the fermentation occurs through aging or through a manufacturing process.
• Kombucha is produced when any of the previously described teas is brewed and then sugar is added and the tea is fermented by a group of bacteria and yeasts, giving it a low content of alcohol.
• Herbal teas are not true teas; they are made from other plants.
All of types of true tea contain antioxidant polyphenols which protect against free radical damage. These polyphenols are extracted from leaves brewed in hot water and offer protection for heart health, improve bone density, decrease cognitive decline, help fight cancer and boost immunity. The longer tea is brewed, the stronger the tea and the greater the health benefits.
Tea ranks as high or higher than many fruits and vegetables for the antioxidant potential of plant-based foods. Most tea consumed in the United States is iced, black tea. Iced tea drinkers may be interested to know that polyphenols in steeped tea break down over time, so iced and bottled teas that are stored for several days may not carry the same benefits.
Although processing diminishes the antioxidant content – tea’s health benefit– in unsweetened bottled and instant teas, tea is still typically a better choice than sugary beverages. Check the label of bottled tea to be sure it contains more tea than sugar. Sweetened teas may have a higher sugar content, which can quickly cancel out the beneficial health effects. You also may want to experiment with various herbs and fruits to add flavor to hot or iced tea without extra calories.
Caffeine content of teas vary according to the type, quantity used, length of time it is steeped, and whether it is loose or in a bag. Caffeine is generally highest in black tea followed by green, oolong and lastly white tea. An 8-ounce cup of brewed black tea contains about 40 milligrams of caffeine compared, to 80 to 120 milligrams in a cup of brewed coffee.
Teas also contain a compound called L-theanine that is more abundant in dark teas. It promotes relaxation and can counteract the effects of caffeine.
Decaffeinated teas are another option, but whether decaf teas contain the same amount of antioxidants or polyphenols — the health benefits of caffeinated tea — is unknown. It is speculated that the decaffeinating processing to remove caffeine from tea may also remove polyphenols.
Herbal teas do not always contain C. sinensis leaves but are made of combinations of herbs, flowers, fruits, roots, spices or other parts of some plants. Herbal teas are typically caffeine-free but check the label to be sure since they are usually a blend. Research on the health benefits of herbal teas is limited and inconclusive. Be cautious about herbal teas that are promoted to cure health problems or promote weight loss. Check the FDA web site for current updates or warnings on herbal teas associated with unproven scientific findings, and check with your physician to steer clear of any herb-drug interactions.