& Joannie Dobbs Tuesday, June 24, 2014
Consuming coffee and tea comes with downsides, too
People love to rank things. The 10 best, the 20 worst — you name it. We like to express our opinions, vote for our favorites on reality TV, and feel like we know what is best and what is worst. Perhaps it just comes along with an inherent competitive human nature.
But when it comes to health, opinion is not worth much unless it is based on a body of reliable (ideally science-based) information. Even opinions founded in evidence-based information have their limits. This often is the case when it comes to food and health. Both too little and too much of a "healthy" food can be bad for you.
Some foods have gone from having a reputation of being bad foods to good foods and then to "superfood" status. As our regular readers will guess, we are not fond of the superfood concept. It tends to draw people into overdoing the superfoods, often at the expense of missing out on a variety of other valuable food components that, of course, come only from consuming a wide variety of foods.
Tea and coffee are good examples of this bad-to-good-to-super phenomenon. Tea has been ahead of coffee, but coffee is rapidly catching up.
QUESTION: What are the benefits of tea?
ANSWER: Strictly speaking, tea refers only to leaves from the Camellia sinensis plant. There are many "herbal teas" that come from very different plants and have their own mix of potential benefits and risks. Here, we are only talking about "proper" tea.
The various types of tea (green, white, black, etc.) result from variations in the maturity of harvesting the leaves and the way the tea leaves are processed. These teas have been studied extensively and linked with reduced risks of cardiovascular disease, cancer, osteoporosis and dental cavities. However, some well-designed studies do not support all of these potential benefits of tea.
There also have been claims that tea and tea extracts promote weight loss. Not all studies support this claim, and those that do primarily indicate any effect is likely small.
Q: Why is tea not a superfood?
A: There are potential downsides from consuming too much tea or its extracts. Excess caffeine intake affects some people more than others. Tea components have complex interactions with a wide variety of drugs. Additionally, when tea is consumed with a meal, it substantially reduces the absorption of iron from the meal.
Q: What are the benefits of coffee?
A: Studies have linked coffee to a reduced risk of developing type 2 diabetes, colorectal cancer, some liver diseases and, possibly, Parkinson's disease. Of course, the caffeine in coffee is known to enhance alertness and give the body's metabolic rate a small boost.
Q: Why is coffee not a superfood?
A: Some people are more sensitive to caffeine than others. Adverse effects include rapid heart rate, nervousness and insomnia. Coffee's components can affect the function of many prescription drugs, and some drugs can even increase the effects of the caffeine in coffee. Like tea, coffee reduces iron absorption from foods when they are consumed together.
So, the bottom line on tea and coffee is that they both seem to provide more health benefits than problems. However, more is not always better, so remember to apply the Goldilocks principle and work out what is "just right" for you.
Alan Titchenal, PhD, CNS and Joannie Dobbs, PhD, CNS
are nutritionists in the Department of Human Nutrition, Food and Animal Sciences,
College of Tropical Agriculture and Human Resources, UH-Manoa. Dr. Dobbs also works with the University Health Services.
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