You’re probably tired of your parents saying, “Eat your beans.” Especially if you don’t like beans.

But what if they said, “DRINK your beans.” You’d probably think, boy, they’ve really lost it now.

Well, not really. Your parents would be looking out for your health. Beans have a lot of calcium, which helps your bones grow. Milk is a more common source of calcium, but not all kids can drink milk because they can’t digest a milk sugar called lactose.

While green beans are generally a good source of calcium, some beans have more than others.

This we know because of research by two plant physiologists [fizz-ee-ALL-o-jists], Michael Grusak and Kirk Pomper. They work at the Children's Nutrition Research Center at Houston, Texas.

Their mission: look at six different types of beans and see how much calcium they have. They found one variety, Hystyle, had about twice the calcium of another variety called Labrador.

Why? Because Hystyle is better at holding onto water. Water thins the calcium moving through a bean plant. Eventually, this diluted calcium reaches the bean pod (the part you eat), so there’s not as much calcium available in the pods.

Many ARS scientists study how nutrients feed plants so farmers can grow more and better plants. Grusak is figuring out how crops can feed people better.

Calcium is especially important for you as your bones grow. Research shows that if you have weak bones when you get older, it might be because you didn’t get enough calcium when you were a kid. So you really should drink your milk--and your beans!

How fast water gets in and out of a plant depends a lot on how quickly it leaves the plant’s surface. This process of water vapor leaving plants is called transpiration [trans-per-A-shun]. Plants control transpiration by opening and closing tiny pores called stomates.

The scientists found that the Labrador bean’s transpiration rate was about twice as high as Hystyle’s. That means Labrador plants had less calcium moving inside their xylem. Xylem transports liquid and nutrients throughout the plant, kind of like arteries carry our oxygen-rich blood.

So, now when your mom or dad says drink your beans, you’ll know what they mean.

You can read an Agricultural Research magazine story about the drink-your-beans research on the web at:

http://www.ars.usda.gov/is/AR/archive/nov99/beans1199.htm