The good news for coffee and tea drinkers

At some time late last century, coffee preferences split into a score of variants. The sound of baristas drumming out their used beans now reverberates through our CBDs.

More recently, ‘‘old gumboot’’ tea evolved into the new urban sophisticate – a wide variety of exotic and herbal teas have become de rigueur in educated health-conscious circles.

We are increasingly fussy about our beverages, but what do we actually know about the benefits or harm caused by tea and coffee drinking?

In 1960s grandmotherly circles, it was well known that you should not drink tea with your meals because compounds in the tea would bind with the iron in food, preventing their absorption.

Dr Ali Rashidinejad, a food scientist at the Riddet Institute (Massey University), who has spent years researching the ‘‘bioactive’’ compounds in food and drink, especially teas and coffees, confirms this.

However, all coffees and teas, notably green tea, contain valuable antioxidants that counteract the destructive effects of the free radicals responsible for many chronic diseases, and have a protective effect against various diseases such as Alzheimer’s.

Take that as a licence to continue your habit, in moderation.

Rashidinejad suggests an athome experiment to show the existence of these antioxidants. Make a cup of black or green tea, pour it into a glass and leave it. Note the change of colour. Green tea goes red or even black, given enough time.

This is due to the action of an enzyme that progressively breaks down some polyphenolic antioxidants, reducing their potency. Don’t let your tea steep for longer than eight minutes if you want to get the most out of your brew.

Temperature is another factor affecting the degree of bioactive benefit. Rashidinejad advises that you are better to make tea and coffee with water below boiling point. A lot of bioactives are not stable under very hot conditions.

And the quality of tea counts, not just with taste. The bioactive content depends on several factors – age of the leaf, the season when it is harvested, and the way the tea is dried, fermented and stored.

Rashidinejad is a big consumer of green tea, which is rich in antioxidants, and has a lot less caffeine than coffee or black tea.

One question that has consumed him for the past decade is the effect of adding milk to tea and coffee. Does the milk change or reduce the uptake of bioactives? Of course milk has its own nutritional benefits, but is it better to consume your dairy separately, and drink your tea and coffee black?

The results of research by Rashidinejad and others shows a mostly negative effect of milk addition on the bioactivity of tea and coffee, but it is not black and white and is unlikely to influence drinking habits.

What is becoming increasingly clear, too, is that digestion and the uptake of nutrients from food and drink vary a lot among individuals.

But it is safe to generalise about the immeasurable social benefits of getting together over a cup of coffee or tea.