Antioxidants, Free Radicals and Oxidative Stress
We hear quite a bit about the importance of antioxidants, which are natural substances in foods that prevent or delay some types of cell damage. According to the National Center for Complementary and Integrative Health, our body is under assault from a variety of free radicals. Free radicals are unstable molecules that can cause oxidative stress. This stress damages our cells and is thought to play a role in a variety of diseases such as cancer, cardiovascular disease, diabetes, Alzheimer’s, Parkinson’s, cataracts, and age-related macular degeneration. Free radicals are formed in our bodies from environmental sources such as air pollution and cigarette smoke, and they are also part of our bodies’ natural processes, formed when we exercise or when our bodies digest food.
Antioxidants have been shown to decrease oxidative stress from free radicals in laboratory experiments as well as in animals, and there is ongoing research and debate about the potential beneficial role of antioxidants for humans.
Antioxidants and Green Tea
Drinking green tea is associated with a lower incidence of cardiovascular disease and cancer where oxidative stress plays an important role. The strongest antioxidants identified in green tea are the flavanols epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), and epigallocatechin gallate (EGCG). While several research studies show the helpful antioxidant effect of these flavanols in animal studies, the results from human studies are inconsistent.
Some epidemiological studies of the association between tea consumption and cancer risk show reduced risk of cancer of the colon, breast, ovaries, prostate, and lungs. Limited scientific research suggests the possibility of green tea reducing blood pressure and cholesterol levels, although more research is needed.
The inconsistent results could be dependent on the amount of tea consumed, how oxidative stress is measured, and the amount of oxidative stress in the research subjects. Other variables include genetic variations in how people respond to the antioxidants in tea.
There are also lifestyle factors that may influence the risk of cancer or cardiovascular disease such as body weight, physical activity, and tobacco and alcohol use. How the green tea is prepared also makes a difference in antioxidant content. For the highest number of antioxidants, brew green tea in boiling water for 5 minutes. Instant tea, iced tea, and ready-to-drink teas contain far fewer antioxidants.
Cautions with Green Tea
Tea is generally recognized as safe by the U.S. Food and Drug Administration. While drinking green tea as a beverage is considered safe, green tea extracts may lead to liver problems in some people.
Tea naturally contains caffeine, and negative effects associated with caffeine include erratic heart rate, insomnia, restlessness, nervousness, headache, and nausea. The current recommendation is that adults consume no more than 400mg of caffeine per day. The amount of caffeine present in tea varies by the type of tea.
• Black teas contain the highest amount of caffeine, ranging from 64 to 112 mg per 8 fl oz serving
• Oolong tea, which contains about 29 to 53 mg per 8 fl oz serving, is next in line.
• Green and white teas contain slightly less caffeine, ranging from 24 to 39 mg per 8 fl oz serving and 32 to 37 mg per 8 fl oz serving, respectively.
• Decaffeinated teas contain less than 12 mg caffeine per 8 fl oz serving.
Both black and green tea inhibit the absorption of iron from foods consumed at the same time as the tea. Drinking tea between meals or including a source of vitamin C such as oranges or grapefruit improves iron absorption.
Green tea has also been shown to reduce the effectiveness of nadolol, a beta-blocker used in people with high blood pressure and heart problems. Green tea may also interact with other medications. Check with your doctor if you have any concerns.
Tea Bags vs Whole-leaf-tea
Why would leaf teas (such as “loose-leaf tea” and “whole-leaf tea”) be better than teabags? Whole-leaf tea is tea that’s made up mainly of whole, unbroken leaves. Teabags are usually made from lower grade teas and smaller pieces of tea. They have a larger surface area than whole leaves. A larger surface area means that the essential oils, which make tea flavorful and aromatic, evaporate and the tea ends up dull and stale.
Freshness can be a major issue with teabags due to the packaging. Some tea bags are made with whole-leaf tea, but these are the exception rather than the rule. Loose-leaf tea is a tea that is not brewed in a teabag. There is typically room made for the tea leaves to absorb water and expand. Water flows through the leaves and a wide range of vitamins, minerals, flavors, and aromas are extracted from the leaves.
Teabag Size
Teabags limit the infusion of the tea because of the size of the teabag. Even if you pack loose-leaf tea into a small tea bag, it won’t be very flavorful. Tea was adapted to the teabag. Tea companies are now adjusting the size of the teabag to the tea. Instead of the tiny, broken leaves, higher grades of tea are being used that have better flavor and aromas. They are using larger-size teabags, also called tea pouches, tea socks, or pyramid bags. These teabag variations allow the leaves to expand more than traditional tea bags, thus creating a better brew.
Caffeine and Tea
For the most part, tea bags will have more caffeine than their loose-leaf tea. It can depend on the tea variety. Teas such as black tea, green tea, and other tea blends naturally have caffeine. Check the label to find out how much caffeine is in the tea. Hotter water and a longer steeping time draw more caffeine out of the brewed tea. Cooler water and a shorter steeping time will extract less caffeine.
*These statements have not been evaluated by the Food and Drug Administration. This information is for educational purposes only. The statements have not been evaluated by the Food and Drug Administration and are not intended to diagnose, treat, cure, or prevent any disease. Consult your physician if you have any question regarding a medical condition
