Flavonoids in tea may cure heart disease

By Joko Pambudi and Nurfi Afriansyah

JAKARTA (JP): A piping hot cup of tea or coffee can be just right during the cool evenings of the rainy season.

It hits the right spot because of its warm temperature and the jolt of energizing caffeine. But coffee has traditionally got a bad rap for leaving an unsettling jittery buzz.

Unfortunately, research seems to be backing up the long-held view that coffee is bad for you, and tea is the best brew.

Norwegian researchers reported in American Journal of Clinical Nutrition recently that more than nine cups of coffee a day increased chances of heart attacks and stroke.

But the more tea consumed, the lower the chances of coronary heart disease, according to findings of a cross-cultural comparison study from Holland.

Daan Kromhout of the Public Health Research Division of the Netherlands' National Institute of Public Health and Environmental Protection made this conclusion from a prospective study of 16 cohorts over 25 years.

They findings showed that intake of flavonoids -- a non- nutritive antioxidant found in high concentrations in tea -- was inversely associated with the occurrence of coronary heart disease.

His study published last November in Journal of Medicine, a supplement to the Lancet, was classified as outstanding. This was because it revealed studies from seven countries -- the United States, the Netherlands, Finland, Italy, Japan, Serbia-Croatia and Greece -- involving 12,763 middle-aged men (40-59 years). In this study, the food composites representing the average food consumption of each cohort were chemically analyzed in one laboratory.

The results are consistent with those of a cohort study done 10 years ago by Michael G.L. Hertog et al. at the Department of Chronic Disease and Environmental Epidemiology, the Netherlands.

His study -- involving 804 elderly men aged 65-84 years and also part of the cross-cultural research done in the seven countries -- was reported in the Lancet's March edition this year.

He determined that flavonoid intake was inversely related to coronary heart disease mortality. Mean flavonoid intake was 26 mg per day, with major sources coming from tea at 61 percent and vegetables and fruits, particularly onions at 13 percent and apples at 10 percent.

Antioxidant

Flavonoids are a group of plant pigments that provide remarkable protection against damage by free radicals, the unstable molecules created by normal chemical processes in the body as well as by radiation and other environmental influences.

Flavonoids are a large group of poliphenolic antioxidants and they naturally exist in vegetables, fruits and beverages such as tea and wine. Subclasses include flavonols, flavones, flavanones, anthosianidins, catechins and biflavans.

In plants, flavonoids protect against environmental stress; ultraviolet rays, insects, molds, viruses and bacteria; as pollinator attractors; plant hormone controllers and enzyme inhibitors.

In recent years, antioxidant capacities of flavonoids and their potential role in inhibition of oxidation and platelet aggregation in low-density lipoprotein -- LDL which delivers cholesterol to tissues and has been implicated in the accumulation of plaque within arteries -- have been reported.

Catechins, flavonols, particularly quercetin and flavones, are predominantly found in tea.

Flavonoids are powerful antioxidants. Oxidant damage is thought to play an important role in atherogenesis, which is the initial process leading to atherosclerotic plaque formation, particularly in the artery wall.

Flavonoids inhibit LDL oxidation by macrophages (a kind of mononuclear scavenger's cell) in vitro, probably by protecting alpha-tocopherol in LDL from being oxidized by free radicals, by reducing the formation of free radicals in the macrophages or by regenerating oxidized alpha-tocopherol.

Milk tea

Hertog said high tea consumption partly explained the low rates of coronary heart disease in Japan and the Netherlands. He found that tea was the major source of flavonoid intake in Japan at more than 80 percent and in the Netherlands at 60 percent.

But Hertog's study merely showed that flavonoids consumption had a moderate impact on coronary heart disease in the cross- cultural study, as high saturated fat consumption was still a predominant factor.

According to Hertog, this may explain why in Britain the coronary heart disease remained a major cause of mortality, even though average tea consumption was high.

There is the possibility that British people's custom of adding milk to tea binds flavonoids milk proteins, and they are not absorbed in the gastrointestinal tract. The antioxidant properties of the tea would then be negated.

Many researchers are focusing on green tea -- a popular tea in Asia -- that has stronger antioxidant content than the black tea commonly drunk by Westerners and many Indonesian. And green tea contains more catechin than black tea.

But relatively new research, discussed by Jean Carper in her book Stop Aging Now published last year, showed that black tea contained substances other than antioxidants which hold similar potential properties as the antioxidants in green tea.

Black tea and green tea provide similar capacity to inhibit free radicals in the body. In the same way, instant tea and ice tea have the same active substances.

Tea bags

The content of flavonoids -- particularly quercetin flavonol -- of tea prepared with tea bags was higher than that prepared with loose leaves.

This was conformed by Hertog's finding that black tea infusions prepared with tea bags (four to five grams) contained 17-25 mg of quercetin. The quercetin content of black tea infusions prepared with loose leaves was considerably lower (10- 13 mg/liter). The size of tea leaves seems to be of far more importance.

Flavonoids yield in black tea was slightly higher when the brewing time was extended to 10 minutes, but the yield did not increase after 10 minutes. When the brewing time was 20 minutes -- as is usual for some British tea drinkers -- the flavonoids did not increase markedly.

The traditional way of preparing brewed tea -- by pouring 500 ml of boiling water onto five grams of tea leaves and steeping for five minutes -- will still yield 30-40 mg of combined flavonoids.

This amount contributes significantly to flavonoid intake in humans; a couple of cups daily may be the tonic for reducing the risk of heart disease.