Drink first, before the onset of thirst
can be good preventive medicine.
In hot weather, the body loses more water than usual through perspiration. And being thirsty, the body's signal to replace that water, often isn't as good an indicator as is necessary, particularly in older people.
The thirst mechanism becomes less efficient with increasing age and also loses efficiency during and after vigorous activity. An older person who works out in the heat thus runs an increased risk of dehydration and the dizziness, nausea, chills and headaches it can cause.
It's easy to replace fluid lost by perspiration: just drink more. The recommended amount of fluid intake is six to eight cups a day.
Anything containing caffeine -- coffee, tea, some soft drinks -- increases fluid loss. So do alcoholic beverages. If you drink them, don't count them as part of the daily allowance.
Food as well as drink can contribute to the body's water supply. Fruits and vegetables can help, since most of them are about 80 percent water. And even meat is half water.
*** A cancer-causing chemical in bracken can get into cows' milk, and may cause cancer in people who drink it, researchers said this week.
Such contaminated milk may be responsible for high levels of stomach cancer in Central and South America.
Although cows do not normally eat the large, hardy ferns, found in temperate areas around the world, they will eat them if they have to, or if they get into a dense thicket.
Bracken is known to cause cancer if eaten, and milk from cows that eat it causes cancer in mice and rats.
Miguel Alonso-Amelot of the University of the Andes in Venezuela, working with New Zealand scientists, tested the milk of six cows they had forced to eat bracken. They zeroed in on a chemical called ptaquiloside.
They found ptaquiloside in the milk of the cows -- and the more bracken they ate, the more of the chemical there was in their milk.
"There is rather a high risk to humans of ingesting milk containing ptaquiloside in areas where bracken is dominant,'' Alonso-Amelot's group wrote in the science journal Nature.
