by Lindsey Goodwin 

Tea has ancient associations with wellness, and it’s only beginning to receive the medical research necessary to prove (or disprove) the many health claims surrounding it.

World Tea News Contributing Editor Lindsey Goodwin spoke with Iman Hakim, a physician with multiple advanced degrees, including an MD, in the field of public health. Hakim is currently the endowed chair at the Mel & Enid Zuckerman College of Public Health. about her research on tea.

Goodwin: What are your findings on tea and heart health?

Hakim: Tea is shown to improve the fluidity of the blood, which makes circulation easier, so it can lower your blood pressure and lower incidence of stroke. We have also seen a very beneficial effect on lipids in general. One study was on patients in the Middle East who drank two to three cups of tea a day. It showed a decrease in LDL (bad cholesterol) and an increase in HDL (good cholesterol) that was particularly strong amongst women who smoke.

Goodwin: Does tea impact diabetes?

Hakim: As long as it doesn’t have any sugar in it, of course, tea can control blood sugar. It can also prevent complications, like the cardiovascular effects that accompany Type 2 diabetes. The research was first done on black tea, but now they are studying green tea. Both black and green come from the same plant, so if it works with one, more than likely, it works with the other.

Goodwin: Why do most people associate particular benefits with particular tea types?

Hakim: Most of the studies that were done early (around 2000 and prior) on tea and heart health were on black tea. In the same era, most of the cancer studies were with green tea. Now we are trying to see if black tea has any preventative cancer effect, and if green tea impacts heart health.

Goodwin: Are people studying tea types besides green and black more often now?

Hakim: People haven’t studied oolong a lot. It’s mainly been based around obesity. White tea has been studied in preclinical trials with animals, but not with humans. The assumption is that it’s as effective as green tea, but not enough human studies have been done. Many universities are studying different aspects of tea and cancer. Everybody is either studying tea and health or asking (about tea and health) on questionnaires.

Goodwin: What are your findings on tea and cancer?

Hakim: We studied squamous cell skin cancer. Subjects drank two cups of strong tea a day and had 30 to 40 percent reduction. We then studied the effect of green tea on decreased DNA damage in lung tissue amongst high-risk groups, like people with chronic obstructive pulmonary disease. We found a 30 percent decrease in DNA damage in high-risk populations when they drank four cups of green tea a day for four months in one study and six months in the other, with 158 to 168 people per group. It’s a good reliability. It’s seen with both genders, but it’s more significant amongst women.

Goodwin: There was a recent study linking tea and an increased incidence of throat cancer.

Hakim: Yes, there is a thermal effect on the throat (from very hot beverages). A reasonable temperature will prevent any thermal injury.

Goodwin: What is the ideal quantity of tea to consume daily?

Hakim: Two to four cups for a healthy person. You can go up to eight, but it’s not necessary unless there’s a motivation to do so.

Goodwin: A recent study concluded that catechin levels in bagged green tea decreased by 28 percent after six months of storage.

Hakim: This is inconsistent with what we’ve found. We study the catechin content in green tea every six months, and we have studied millions of teas. It always has a shelf life of about three years, and the variability is about 10 percent. We have not seen a variance of 28 percent in all the studies we have done. However, the decaffeination process decreases catechins around 20 to 25 percent.

Goodwin: Are there benefits to loose-leaf tea over other types?

Hakim: Most of the time, loose-leaf tea has a higher catechin level than bagged tea. There’s a usual variability of around 10 percent, but some of the bag teas have very low catechin levels and some bottled teas have a negligible amount.

You can read more about tea and health in recent World Tea News articles Tea & Health, Questions & Answers and Tea & Weight Loss.