Side effects of tea
Though tea intake has several positive health effects as I wrote in my last post, it has some negative effects too.
Consumption of high concentrations of tea polyphenols results in adverse effects such as nausea, stomach ache, heartburn, muscle pain, dizziness etc. Moderate amounts of caffeine consumption from tea (more than 300 mg to 400 mg) may have adverse effects on health. Black and green tea may also inhibit iron bioavailability/iron absorption - so have negative effects on anemic patients. Some tea contains higher amounts of caffeine such as black tea, oolong tea which should be taken under certain limit. Also some types of black, green, oolong, white, pu-erh and matcha tea, that grow in China, may contain heavy metals such as lead (Pb), aluminium (Al), arsenic (As), cadmium (Cd), mercury (Hg) and fluoride (F-) that have negative impact on health such as birth defects, osteomalacia and neurodegenerative disorders as all heavy metals are neurotoxic material. China grown tea have alarming level of heavy metals due to use of coal fired power plant (which provides about 70% of China’s energy) and the pollutants derived from these coal plants contaminate the tea plants [1]. A recent joint research study by University of Alberta and Lulea University of Technology in Sweden found that tea contains toxic elements that might be risky for pregnant and nursing women [2]. Heavy metals and other toxic components from tea can result in various types of birth defects, dampen brain development and cause chromosomal anomalies in the unborn child of pregnant women. A recent Canadian study found that Chinese oolong tea had highest level of arsenic, lead and cadmium than other types of regular or organic green tea, white tea and black tea. Tea can be contaminated with heavy metals even if it is USDA organic because organic tea may not be coated with pesticides but they could be tainted by the heavy metals from the water and soil. Also the high fluoride concentration of tea can result in dental and skeletal fluorosis [3] because mature tea leaves are fluoride accumulator.
Teas that grow in Japan such as organic green tea or matcha green tea have a risk of contamination with radioactive elements due to nuclear disaster after the 2011 tsunami [6]. Surprisingly organic green tea/organic matcha tea have higher level (30 %) of toxic components or heavy metal concentrations than the regular one. ConsumerLab.com study estimates that a cup of matcha green tea contain 30 times more lead than a cup of regular green tea [4]. As per research Camelia sinensis (tea tree) is a “hyperaccumulator” type tree that has a built in molecular mechanism to extract metals from the soil and accumulates them in its leaves [5]. Older leaves have highest metal concentration (20 times higher) than the younger leaves. Also higher steeping time (more than 4 minutes) leads to increased level of lead and aluminium (potential neurotoxin linked to Alzheimers) concentration.
Due to the contamination of tea with toxic material/heavy metal it is recommended that children and pregnant women should be very careful about the type of the tea they are drinking. The African red rooibos tea is generally safe for pregnant women and they are full of antioxidants. Though tea consumption is a healthy alternative of water it should be taken under certain limit as it has some negative impact on health that you cannot ignore.
References:
