Snap Beans Fingered as Calcium Source for Youths

Girls and boys absorb two important bone-building minerals--calcium and magnesium--from snap beans as easily as they absorb them from milk, according to an Agricultural Research Service study being reported today at the Experimental Biology 97 meeting in New Orleans.

That’s good news to researchers at the ARS Children’s Nutrition Research Center in Houston, Tex. They are looking for good sources of calcium to replace the 24-35 percent drop in milk consumption among children and teenagers since the late 1970's. Snap beans are a popular vegetable among this age group.

The researchers measured the rate of calcium absorption from milk and compared it with snap beans, broccoli and spinach in 12 girls and boys ages 9 to 14. They also looked at magnesium absorption from snap beans and spinach.

Although it takes about five cups of cooked snap beans to equal the calcium in one cup of milk, the rate of absorption was the same from both sources. The absorption rate was about 5 percent higher from broccoli, one cup of which provides about one quarter as much calcium as a cup of milk. But the calcium in spinach was poorly absorbed because of a high content of absorption-blocking compounds known as oxylates.

The youths absorbed magnesium from snap beans, spinach and milk at about the same rate. Snap beans provide nearly as much magnesium as milk, but spinach provides nearly five times more.

In a related tests, the researchers collaborated with University of Wisconsin plant breeders to assess 64 unique types of snap beans, looking for differences in calcium content. They found wide differences, indicating that calcium content has a strong genetic basis. This means breeders can develop snap bean varieties with extra calcium.

One discovery: The commercial snap bean variety Hystyle was among those with the highest calcium levels. In addition, the researchers found that younger, skinnier snap beans had significantly more calcium than older, fatter pods.

Scientific contact: Steven Abrams or Michael Grusak, Children’s Nutrition Research Center, Houston, Texas, (713) 798-7000, sabrams@bcm.tmc.edu and mgrusak@bcm.tmc.edu.