The Health Dangers of Tea

As a calorie-free beverage with healthy antioxidants, tea is generally a smart sipping choice. No food or drink is perfect, however, and drinking large quantities of white, green or black tea -- as well as any other beverage made with tea leaves -- may cause side effects. Drinking three to four cups of tea per day is a safe amount, according to Harvard School of Public Health.

Caffeine Content

Tea naturally contains caffeine, which may cause a rapid heart rate, anxiety, insomnia, upset stomach and tremors. Over time, your body can also grow dependent on caffeine so you may experience tiredness, headaches and irritability if you stop consuming it after regular use. Caffeine content in tea can range from 14 to 60 milligrams per cup, with black tea containing the highest levels, oolong tea containing moderate levels, and green and white teas containing relatively low levels. Consuming 200 to 300 milligrams of caffeine per day is considered moderate intake, according to MedlinePlus.

Iron-Absorption Issues

Tea contains antioxidants called flavonoids, which are being studied for their role in disease prevention. Healthy as they may be, however, flavonoids interfere with the absorption of nonheme iron, found in plant foods such as beans and vegetables. If you're concerned about iron deficiency, it may be wise to avoid tea at mealtime. You can also reduce the iron-blocking effect of tea by adding lemon juice or milk, according to Harvard Health Publications.

Additive Alert

Beware of tea beverages from your local coffee shop or restaurant, such as chai lattes, Thai iced teas or fruit-flavored tea drinks. These may be loaded with sugar, fatty whole milk or cream, potentially containing hundreds of calories per serving. Bottled iced teas are also often loaded with sugar, so read labels to learn what you're drinking. For a waistline-friendly beverage, choose unsweetened hot or iced tea with a squeeze of citrus for flavor. If you can't live without some sweetness, add a half-tablespoon of honey, which will only cost you about 30 calories.

Extract Effects

Brewed tea has been around for centuries, but concentrated tea supplements have not -- and they may come with additional side effects. The Linus Pauling Institute cites studies of both caffeinated and decaffeinated green-tea extracts in which some subjects experienced nausea and dizziness. Some of those who took caffeinated extracts also experienced abdominal pain, diarrhea, agitation, restlessness, confusion and trouble sleeping.