By Wong Mei Ling

If you have a weak stomach and poor digestion, do not drink green tea or jasmine tea, advised Professor Hong Hai, a registered TCM practitioner.

'You could feel slight pain in the stomach after drinking the tea even in moderate quantities,' said the Nanyang Business School professor from the Nanyang Technological University.

He recommended oolong and pu er tea instead for such people. According to the Journal Of Chinese Medicine, these invigorate the spleen, where redundant red blood cells are destroyed, clears stomach heat and counteracts alcohol toxins.

Drinking green tea on an empty stomach is also not recommended by Chinese tea specialists, especially for those with gastric problems. This is because the acid in the tea can harm the stomach, causing stomach aches and, in severe cases, stomach flu.

Tea is also not recommended for pregnant women and toddlers said Ms Karen Wright, head dietitian at the Food Clinic. This is because polyphenols in tea bind with iron, making it harder for the body to absorb it.

Cutting down on tea and coffee could help to improve iron levels in the body. This is important particularly for young or pregnant women and toddlers who are most at risk of iron deficiency anaemia, she said.

Drinking too much tea can also be counter-productive.

'Supposedly one has to drink more than five cups of green tea to obtain a good level of the antioxidant...[but] I wouldn't tell people to drink that much. Probably two to three cups should be the max,' holistic nutritionist Yondi Lee of Ascension Healing said, adding that it also depends on what type of tea one is drinking.

This is because teas are diuretic, which increases the rate of urination. This in turn causes the body to lose minerals if a person passes urine too often. The tannin, a polyphenol in tea, can also reduce absorption of minerals, she said.

According to Prof Hong, too much tea can have negative effects on the body.

'You have drunk more than you need when you feel uncomfortable in the stomach, or your sleep is disturbed. You could also have loose stools the day after drinking a lot of tea,' he said.

This article was first published in Mind Your Body, The Straits Times on Jan 22, 2009.