DEAR DOCTORS: I love decaffeinated black tea and drink a lot of it. Since I don't add sugar or milk, I have always felt it was healthy. Now I'm questioning that assumption because I've heard that the decaffeination process can make the tea unhealthy. Should I be cutting back?
DEAR READER: Caffeine is an organic compound that occurs naturally in more than 60 plants. It is highly soluble in warm water, which makes it easy to extract for use in beverages.
Here in the United States, the most common natural sources of caffeine are coffee beans, tea leaves, kola nuts and cacao pods. The first two are self-explanatory. Kola nuts are used to flavour soft drinks, and cacao pods are the basis for chocolate products. Growing in popularity are yerba mate and guarana, plants that hail from South America. Caffeine also exists in synthetic form. It is widely used in energy drinks and is added to some foods and over-the-counter medications.
Because caffeine acts as a stimulant on the central nervous system, it meets the criteria of being considered a drug. It gives a boost to energy and mood and helps with wakefulness. However, the physical effects of caffeine don't end there. It can also increase stomach acid, affect how the body uses glucose, raise blood pressure, stimulate the bowels, act as a diuretic, adversely affect heart rhythms and interfere with sleep.
The way the body processes caffeine changes as we age. Older adults metabolise it more slowly, and some find that even small amounts can cause disturbed sleep. Whether due to health issues or as a personal choice, some people steer clear of caffeine.
But thanks to the process of decaffeination, they can continue to enjoy beverages that would otherwise be off-limits. The most common method uses chemical solvents -- typically ethyl acetate or methylene chloride -- to remove caffeine. The process includes a step in which the solvents are rinsed, evaporated or vaporised away. However, the final product does contain trace amounts of the solvent that was used. A small amount of caffeine remains as well.
Both tea and coffee can also be decaffeinated via a process that uses carbon dioxide and activated carbon filters. It's a bit more costly to produce decaf teas and coffee this way, and they may not be as widely available.
When it comes to choosing decaffeinated products, beverage drinkers need to consider both the presence of residual solvents, as well as the small amount of caffeine that remains in the product. The solvents are highly volatile chemicals that vaporise at under 52C. Coffee roasts at 205C, and black tea is fermented at about 71C, each well above the temperature at which the solvents are destroyed. The amount of caffeine that remains varies depending on the product. Tests show it ranges from about 2% to about 10%.
Since your concern about decaf tea arises from the potential presence of solvents, consider seeking out products that use the carbon dioxide method. You might also give the fascinating, flavourful and naturally caffeine-free world of herbal teas a try. Universal Features Syndicate
Dr Eve Glazier is an internist and associate professor of medicine at UCLA Health. Dr Elizabeth Ko is an internist and assistant professor of medicine at UCLA Health.
