Researchers work to enhance nutritional value of foods

 People say that "an apple a day keeps the doctor away" - but that’s only part of the story.

  The Dietary Guidelines for Americans, published jointly by the U.S. Departments of Agriculture and of Health and Human Services, recommend consuming a variety of fruits, as well as vegetables, whole-grains, low-fat or fat-free milk products, and lean meat and beans.

  Here are a few of the many efforts by the Agriculture Research Service to improve the nutritional value of these foods.

VALUABLE VEGETABLES

  Today’s carrots are more nutritious than the carrots we ate 30 years ago. That’s because ARS scientists discovered a way to breed carrots with high amounts of beta-carotene, an orange pigment that helps humans make vitamin A. In fact, modern carrots have 75 percent more beta-carotene than their predecessors.

  The Vegetable Crops Research Unit at Madison, Wis., is now working to produce the same results in cucumbers and melons. They’re also breeding red carrots, which contain more lycopene; yellow carrots, containing more lutein; and purple carrots, full of anthocyanins.

  The same researchers are also using classical breeding methods to raise levels of thiosulfinate compounds - in onions and garlic - that are thought to have heart-healthy benefits.

  Colleagues at the Western Regional Research Center at Albany, Calif., are seeking genes that cue tomatoes to produce another carotenoid: lycopene. The California research may lead to fresh-market and processing tomatoes with more lycopene than ever.

  Researchers in the Vegetable and Forage Crops Production Research Unit at Prosser, Wash., have developed flavorful orange-fleshed potatoes with up to 52 times the antioxidants zeaxanthin and lutein as are found in white potatoes.

  They’ve also developed red- and purple-fleshed varieties with more than four times the antioxidants of existing commercial dark-fleshed potatoes. In addition, they’ve identified potatoes with elevated levels of folate, an important B vitamin, and are breeding folate-rich potatoes.

TIP OF THE ICEBERG

  Plant breeders in the ARS Crop Improvement and Protection Research Unit at Salinas, Calif., want to boost the vitamin and mineral content of iceberg lettuce. In one experiment, researchers periodically pried open the leaves of iceberg lettuces as they grew so that the familiar, tightly closed heads couldn’t form.

  With more leaf surface exposed to sunlight, the lettuces made twice as much iron and calcium, five times as much vitamin C and eight times as much beta-carotene as a typical iceberg lettuce.
Goodness of grains

  Researchers in the Small Grains and Potato Germplasm Research Unit at Aberdeen, Idaho, are helping our bodies get more of the minerals packed into oats, rice, barley and corn. Their patented work has led to new varieties that have lower amounts of phytic acid, thereby enhancing our absorption of minerals like calcium, zinc, iron and magnesium, and stepping up the grains’ nutritional value.

  ARS-funded tests showed that avenanthramide, a compound found in oats, helped prevent unwanted buildup of blood cells in laboratory cultures of artery-wall cells. Preventing blood cells from sticking helps reduce the risk of heart attack and stroke.

  At Ithaca, N.Y., ARS scientists are working with the Gates Foundation and the U.S. Agency for International Development to improve the iron content and bioavailability of maize, a staple crop for many African nations.

GO FISH

  Freshwater fish, such as catfish, have lower levels of nutritious omega-3 highly unsaturated fatty acids than marine fish. Researchers in the ARS Aquatic Animal Health Research Unit at Auburn, Ala., increased these levels in catfish by feeding them diets supplemented with marine fish oil and determined the optimal feeding conditions for increasing fatty acid levels.

  ARS experts in Idaho have developed an easy-to-use test that breeders of rainbow trout should be able to use to identify those fish that excel in converting feed into tender, delicately flavored meat instead of unwanted fat. The test can help single out those trout best suited to serve as parents of new generations of farm-raised fish.

GOING 'PRO'

  Many yogurt varieties contain beneficial microorganisms called "probiotics." Researchers in the ARS Dairy Processing and Products Research Unit at Wyndmoor, Pa., are developing probiotic bacteria that produce bioactive compounds that may lower blood pressure and protect dairy foods from harmful microbes.

  By modifying manufacturing procedures, researchers in the same unit created a flavorful mozzarella that melts and tastes like regular mozzarella but has only half the fat.

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This article was produced by Laura McGinnis and Marcia Wood, Agricultural Research Service information staff, and was published in the March 2008 issue of Agricultural Research magazine.