Evidence continues to pile up about green tea’s healthy properties.

For coffee drinkers, that first sip of piping hot java is a crucial part of the morning routine. It jolts us awake, fires up our neurons and gives us the stamina to tackle the day. But is it healthier to free ourselves from the delicious shackles of America's most widely used psychoactive substance?

In short, it's a highly personal decision; every human body processes coffee differently, and it changes as we age. But while coffee's benefits are vast—from improved mental processing and athletic enhancement, to its myriad of antioxidants and nutrients—evidence suggests that it may be worth slogging through the withdrawal headaches and brain fog to replace coffee with an alternative psychoactive substance: green tea.

Green tea's most powerful edge on coffee is the potent antioxidant epigallocatechin gallate, or EGCG. “There's a subgroup of women where this is an actual anti-breast-cancer agent,” says Dr. Dawn Motyka. “So if you get your DNA checked, and you have the enzyme, drinking green tea on a regular basis will actually lower your breast cancer risk.”

The anti-cancer agent EGCG has also been found to protect neurons against dementia, Alzheimer's and Parkinson's disease. Due to the roasting and fermentation process, EGCG is only found in trace amounts in black tea.

Further anti-cancer evidence turned up in a 2007 study of 69,710 Chinese women, where green tea drinkers had a 57 percent lower risk of colorectal cancer, and in a 2007 study in Japan which found that men who drank green tea had a 48 percent lower risk of developing prostate cancer. To be fair, coffee also has its fair share of antioxidant polyphenols, and is linked to a lowered risk of liver and colorectal cancers.

But drinking the safe one or two cups of coffee a day may not be sustainable for life. The methylxanthines, or “plant speed” in coffee, fit into the brain's adrenaline receptors, acting as a diuretic, and cardiac and mental stimulant. “Those alertness receptors eventually stop responding,” says Dr. Motyka, which is why we often need to up our coffee intake to produce the same effect. “We're not built, or intended by nature to be in a constant state of alertness and arousal. That's not good for us.”

Interestingly, as we age, the body's ability to process caffeine deteriorates—especially for women. “And it's an abrupt change. In men the decline is more gradual,” says Dr. Motyka, who finds that women suffering from menopausal symptoms like hot flashes and night sweats almost always experience relief after stopping coffee.

That's not to say that green tea does not contain caffeine—a cup of the green stuff contains anywhere from 15mg to 75mg of caffeine, whereas coffee contains 95mg to 200mg. Remaining in the body for up to 12 hours, caffeine in both substances has been found to temporarily raise the metabolic rate and help burn fat.

The difference is that green tea comes with a built in buffer: tannins, and the amino acid L-theanine. Acting on the neurotransmitter GABA, these compounds are calming agents, increasing dopamine and the production of alpha brain waves.

“The presence of these chemical compounds together in tea allows you to control its effect,” says James Heffley, Ph.D. “When boiling water is poured onto the tea leaves, in the first two minutes all the caffeine is drawn out. At this point, tea is most stimulating. During the next few minutes, tannin and theanine are gradually brought out of the tea leaves. After about five minutes, this will tend to cancel out the effects of the caffeine and will make a more relaxing, calming tea.” For those who are caffeine-sensitive, pouring out the initial steep effectively reduces caffeine jitters.

The catechins in green tea have also been show to have anti-viral and anti-bacterial properties, lowering the risk of infections and improving dental health, while coffee stains on teeth are sticky, and are said to attract food particles and bacteria.

If your coffee dependence is at an all-time high, think of it this way: In Chinese medicine terms, coffee is pure yang, while green tea is yang with a shot of yin to balance it, says Dr. Motyka. Altogether, the green tea buzz is a much mellower one, but the synergy of caffeine with L-theanine's anti-anxiety effect gives some people a greater ability to focus than coffee does. Give it a try, and decide for yourself.