K-State, Texas A&M researchers boost lettuce calcium content
Led by 87 percent of the nation's teenage girls and 78 percent of U.S. women age 20 or older, today's average American eats far too little calcium--the most abundant mineral in the human body.
Calcium is best known for its role in deciding the lifelong, year-to-year strength or weakness of bones and teeth. The fact is, however, calcium intake is crucial to every bodily function, from nerves and muscles to glands and blood vessels.
That's why plant scientists at Kansas State and Texas A&M universities are working to make meeting daily calcium needs easier. Their plan is to expand people's range of calcium-rich food choices.
"Thus far, few vegetables are good sources of calcium. And, those few aren't a significant part of the average U.S. diet," said Sunghun Park, K-State horticulturist and the project's lead scientist.
The researchers' first results include a 25 to 32 percent hike in the in-bred calcium supplied by common leaf lettuce. The team now hopes to raise their lettuce lines' nutrient value even further.
Today, most of the calcium Americans eat comes from such dairy products as milk, yogurt and cheese, according to the Office of the Surgeon General. Some also comes from "fortified" products (orange juice, bread, cereals) and such dark, leafy greens as bok choy, collards and broccoli.
"To expand that list, we're using a strategy called biofortification. We're working to genetically improve what we know are popular vegetables, to make them more nutrient-dense," Park said.
The researchers' first report says their biofortified leaf lettuce lines are reproducing true to form and growing robustly under greenhouse conditions. Yet, the report emphasizes a different finding.
In an unusual move, the researchers submitted their "new" lettuce to the Sensory Analysis Center in K-State's Department of Human Nutrition. And, a panel of scientific evaluators there found the enhanced lettuce to be no different from "regular" leaf lettuce in flavor, bitterness or crispness.
"In other words, if you were to encounter both of them in a salad or hamburger, you wouldn't be able to tell which was which. That could make a big difference in public acceptance, if and when a product like ours enters the market," said team member Kendal Hirschi, who is a pediatrics and human genetics professor at the Baylor College of Medicine, as well as an associate research director at Texas A&M's Vegetables and Fruit Improvement Center.
Right now, however, marketability isn't the prime concern for the lettuce research team--which also includes two more K-State horticulturists, two K-State sensory analysts and the director of environment technologies at Edenspace Systems.
They don't think their research project is complete. They're looking into boosting their leaf lettuce's calcium content further by such methods as adding calcium to the plants' growing soil and/or immersing the harvested leaves in a calcium-rich solution.
Immersions of calcium have a long history as a post-harvest firming agent. Today, they're prolonging the shelf life of such fruits and vegetables as apples, cantaloupes, strawberries and carrots.
But, whether they also "up" fresh produce's calcium content is still an unknown, Park said.
"All we've established explicitly so far is that modifying a single plant-calcium transporter will increase calcium content without having a negative impact on lettuce quality. That's just one step toward getting biofortified lettuce on store shelves. Even so, our scientific approach should now be applicable to numerous other food crops, too," said Mark Elless of Edenspace, which is newly headquartered in Manhattan, Kan., with its newest research facilities in nearby Junction City, Kan.
An abstract and the research team's entire report, "Sensory analysis of calcium-biofortified lettuce," is available on the Plant Biotechnology Journal's Web site at http://www3.interscience.wiley.com/cgi-bin/fulltext/121451954/HTMLSTART.
A colorful outline of Americans' challenges with calcium--"The 2004 Surgeon General's Report on Bone Health and Osteoporosis: What It Means to You"--is at http://www.surgeongeneral.gov/library/bonehealth/docs/OsteoBrochure1mar05.pdf.