Tea with milk safer than tea without says study

By SIMON COLLINS science reporter

Milk in your tea can be good for you, a study has found.

Lincoln University scientists have discovered that people who drink tea without milk have relatively high levels of oxalates, waste products that have to be passed out of the body in urine.

In a small number of people the oxalates accumulate to form kidney stones, which are intensely painful when they pass out of the body.

But putting milk in your tea reduces this risk, because the calcium in the milk combines with the oxalate and allows it to be excreted normally.

"So it's safer to drink tea with milk, or green tea," says Lincoln food scientist Dr Geoffrey Savage.

"I wouldn't ever say that tea is bad for you, but this is something in tea that needs some consideration."

Other foods with high oxalate content include spinach, rhubarb, beets, nuts, chocolate, wheat bran and strawberries.

"Oxalates are made by plants as a protectant," Dr Savage said. "They are designed to be toxic so that anything eating it will die. That's why animals do not eat spinach."

To test the effect of having milk in tea, he asked 10 Lincoln staff and students to drink six cups of tea a day, at 9am, 10.30am, noon, 2.30pm, 4pm and 6pm. First they drank six cups without milk, and in a later experiment they drank six cups with milk.

The experiments were repeated for two brands of tea, Edglets and Bell. As a control experiment on another day, the volunteers drank the same quantities of water.

The results, published in the European Journal of Clinical Nutrition, showed roughly the same level of oxalates in their urine after drinking either water or black tea. But when they put milk in their tea, their oxalate levels dropped by a fifth.

"The consumption of tea with milk would mean that very little oxalate would be absorbed from tea on a daily basis and would place tea in the low-risk group of foods," the study concluded.

Another Lincoln study found much lower oxalate levels in green tea.

Auckland University nutritionist Professor Lynn Ferguson said tea drinkers needed to balance the dangers of oxalates against the beneficial antioxidants in both green and black tea.

"Yes, it [milk in tea] may well remove the oxalates, but there has been a little evidence that it also reduces the antioxidant effect of it," she said.

But the scientific director of the NZ Nutrition Foundation, Dr Cliff Tasman-Jones, said there was no strong reason for most people to stop having milk in their tea, even if they were concerned about heart problems.

"My reaction is that, yes, those who are prone to stones, who will know it from their family history, would be well advised to have milk in their tea.

"For everyone else, it is really of little importance to them."

What are oxalates?

* Oxalates are solids produced by oxalic acid, a compound of oxygen, carbon and hydrogen which is produced by plants to deter predators.

* High oxalate levels can cause painful kidney stones in a small proportion of people.

* Plants high in oxalates include tea, spinach, rhubarb, beets, nuts, cocoa and strawberries.

Food science