When looking for a drink to quench your thirst, water is the first thing that comes to mind. It is a good choice and a healthy one too.

But did you know there's something you could add to the water to make your drink more healthy? Hibiscus tea, or dried calyces of Hibiscus sabdariffa, a herb with red flowers commonly known as roselle or krajiab daeng in Thai.

In addition to its aromatic taste and smell, research has shown it is a beverage that helps relieve a wide range of ailments and can provide protection against serious health conditions.

"Herbs have long been used as home remedy for treating minor illnesses but they are often overlooked," said Dr Supaporn Pitiporn, chief pharmacist at Chaophya Abhaibhubejhr Hospital. "Hibiscus tea is a good example. Drinking it regularly helps promote bowel movements as it also serves as a mild laxative."

According to the pharmacist, roselle is packed with anthocyanins, flavonoid compounds that have strong natural anti-oxidant properties, meaning they help provide protection against free radicals. These harmful substances damage cells in the body that bring on many diseases or set them in motion. As a result, roselle tea may help fight the advent of degenerative conditions including ageing and Alzheimer's disease.

"Herbs have disease-preventing nutrients. It's an important attribute that medicine doesn't have," Dr Supaporn said.

Importantly, if high blood pressure is cause of concern, making hibiscus tea a part of your daily drinking habit may help you keep it in check.

A study conducted by a nutrition scientist at American Heart Association in 2008 showed that people with pre-hypertensive symptom and mildly hypertensive adults responded favourably to hibiscus tea.

The study tested 65 patients aged 30 to 70 years old whose blood pressure was recorded and monitored from the start: their systole stood between 120-150mm Hg and diastole at 95mm Hg or less.

The patients were divided into two groups, with one group served three cups of hibiscus tea daily, while the other group was given a placebo drink containing artificial hibiscus flavouring and colour. And the subjects were allowed normal diet and physical activities and their blood pressure was measured on a weekly basis.

At the end of six weeks, those who drank the hibiscus tea had a 7.2-point drop in their systolic blood pressure, compared to 1.3 in the placebo group.

Those with high blood pressure (129 and above) saw it their systole drop 13.2 points and the diastole 6.4 points. In this sub group, the mean arterial pressure went down by 8.7 points.

The study concluded that daily consumption of hibiscus tea in an amount readily incorporated into the diet may play a role in controlling blood pressure. Despite the promising results, further studies are required.

"In addition to hibiscus tea, people should modify their lifestyle to help lower their blood pressure effectively," Dr Supaporn said. "Enjoy whole foods and nutrient-rich diets and have moderate physical activities. Most importantly, they have to learn to relax."

In fact, hibiscus tea can be good for the cardiovascular system. Anti-oxidants in the drink may ward off heart disease by relaxing blood vessels, inhibiting the formation of blood clots, and also help lower the level of cholesterol and triglyceride.

She cited a trial in mice with high cholesterol and triglyceride that were fed with food that contained extract of roselle calyces of 5% concentration.

It was found that the level of cholesterol and triglyceride in mice had decreased.

Acting as anti-oxidants, hibiscus tea can also help stimulate the immune system, thereby increasing the level of resistance of the body to diseases. It can be said that the tea may help guard people against flu and other infections.

Among other health benefits that people could take advantage of, affirmed Dr Supaporn, were the tea's ability to improve the rate of urination. It is also a mild diuretic and lowers chances of bladder infections, and relieves common respiratory symptoms including cough and sore throat.

"Make hibiscus tea your new drink of choice. Add other roselle-based products _ juice, salads or jam _ to your daily diet to help maintain good health." she advised.