Each week a nutritionist from the University of Maryland Medical Center provides a guest post to The Baltimore Sun's health blog Picture of Health (baltimoresun.com/pictureofhealth), which is reprinted here. This week, Elaine Pelc weighs in on teas.
There are many health claims surrounding tea. Some have stronger supporting evidence than others.
Tea can be broken down into five types: white, green, black, oolong and herbal. The first four are all created from the leaves of the Camellia sinensis bush and are categorized based on their levels of oxidation, which means a change in chemical structure when exposed to oxygen. White and green teas are not oxidized, oolong is partially oxidized and black tea is fully oxidized.
Herbal teas, on the other hand, typically contain herbs, fruits, seeds or roots and might not contain any tea leaves. Herbal teas typically have lower concentrations of antioxidants than the other teas, and little research has been done to explore their benefits.
It is important to keep in mind that bottled teas are typically not equivalent to brewed teas because of processing and additives. And adding cream and sweetener can affect tea's nutritional profile by increasing calorie and fat content. For example, an 8-ounce serving of sweet tea can contain 70 to 100 calories, and most bottles contain more than 8 ounces.
Most of tea's benefits come from a type of polyphenol or antioxidant known as flavonoids. The most potent is epigallocatechin gallate, also known as ECGC, which may help fight cancer, heart disease and clogged arteries.
The potential benefits of consuming tea depend not only on the quantity consumed but also on the availability of the polyphenols. Oolong and black tea have fewer flavonoids than green tea because of the oxidation and processing they go through, however, they are still high in antioxidants. Green tea tends to have the highest percentage of polyphenols, specifically ECGC.
There is a large body of research on the benefits of tea. Most of the studies have been in animals where very large quantities of tea were consumed. Therefore, the effect may not be the same in humans. However, there has been some evidence that tea helps inhibit the growth of some cancers and improves levels of low-density lipoprotein (bad) cholesterol, triglycerides and high-density protein (good) cholesterol. There has been some evidence that tea helps with diabetes and weight loss, but the results have been inconsistent.
Why choose tea?
•Although the research isn't always strong, it's hard to say that tea doesn't provide any benefit because of its concentration of antioxidants.
•Tea is typically lower in caffeine (40-120 milligrams per serving) than coffee (102-200 milligrams per serving).
•Tea is naturally calorie-free, while many other beverages contain sugar, additives and/or fat.
Consumers should be wary of tea brands that make unsubstantiated health claims such as fighting cancer. Consult with a health professional and read all labels of teas containing supplements. Some experts also urge caution when consuming laxatives, which includes some teas that contain senna, aloe and buckthorn.