ARS scientists are part of an international team pinpointing rice, wheat, corn, bean and cassava varieties high in micronutrients the human digestive system can readily use. Billions of people have diets low in bioavailable micronutrients, including zinc, iodine, essential trace elements, vitamins and--especially--iron. Once scientists identify varieties high in bioavailable micronutrients, plant breeders can produce new varieties that have critical agronomic and commercial traits. To tackle the iron problem, the international team screened 24 selected genotypes from thousands of common beans from the seed bank at the International Center for Tropical Agriculture, Cali, Columbia. Iron levels in the beans ranging from 51 to 157 micrograms per gram of dry weight and zinc levels from 30 to 65 mg/g. Rat feeding studies showed the beans' bioavailable iron varied from 53 to 76 percent. Recent tests of hundreds of rice varieties also uncovered wide diversity in iron and zinc levels that could be exploited. Future rat and cultured human caco-2 cell studies will determine iron and zinc bioavailability in other micronutrient-enriched staple food crops, including corn, wheat and cassava.

U.S. Plant, Soil and Nutrition Research, Ithaca, NY
Ross W. Welch, (607) 255-5434, rmwl@cornell.edu

To guard against osteoporosis, people may be wise to eat more fruits and vegetables as well as dairy products. Recent research found a significant association between intakes of potassium, magnesium and fruits and vegetables--which are good sources of the minerals--and bone mineral density measurements at the hip and wrist in elderly men and women. Researchers at the ARS/Tufts center in Boston and at Harvard Medical School analyzed data from 907 members of the original Framingham Heart Study--345 men and 562 women. They found correlations across the board--with potassium alone, magnesium alone, potassium and magnesium together, and fruits and vegetables together. Men and women with high intakes had stronger bones. The researchers also analyzed data from a smaller group--229 men and 399 women--looking for changes in bone mineral density over time. In measurements 4 years apart, they found a slowing of bone loss in men--but not women--linked to potassium and magnesium levels, separately and together, as well as to fruits and vegetables. Fruits and vegetables may help prevent the loss of bone minerals by counteracting the acid environment generated during normal digestion, the researchers conjecture. When the body's environment is acidic, minerals are believed to be drawn out of the bone to neutralize the acid, thereby reducing bone strength. It is also possible that potassium and magnesium have direct effects on bone cells. Good sources of potassium include bananas, oranges, tomatoes, potatoes, broccoli and melon. Good sources of magnesium include fruits and vegetables, milk, fish and whole grains.

Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
Katherine Tucker, (617) 556-3351, tucker@hnrc.tufts.edu.

Chlorine levels recommended for swimming pools and water parks may not be high enough to kill Cryptosporidium parvum, a parasite that causes diarrhea, according to ARS experts. This single-celled organism is transmitted in the feces of infected people and animals. Infection occurs by swallowing oocysts. Cryptosporidium has caused numerous recent outbreaks in recreational water, such as swimming pools and water parks, often visited by diapered children. In collaboration with the Centers for Disease Control and Prevention (CDC), ARS researchers tested water that had fecal matter added to simulate conditions in a contaminated swimming pool. When the water contained this organic matter, currently recommended levels of chlorine did not kill the parasite. That's because organic material deactivates some of the chlorine. Swimming pools are likely to contain hair, skin cells, suntan lotion, algae or leaves, and sometimes urine and feces--all of which can decrease the effectiveness of chlorine. Previous tests showing that recommended chlorine levels are adequate had been conducted in clean water. Based on the ARS findings, the CDC suggests changes in engineering of public pools and water parks, such as improved filtering and more frequent turnover of the water. It also suggests changes in pool policies, such as requiring diapered children to wear rubber pants or “swim diapers.” And it recommends educating staff and visitors about simple measures for preventing waterborne disease transmission: staying out of the pool while ill with diarrhea and for several days afterward; trying not to swallow pool water; using safe diaper-changing and hand-washing practices; giving young children frequent bathroom breaks; and encouraging swimmers to shower before entering a pool.

Immunology and Disease Resistance Laboratory, Beltsville, MD
Ronald Fayer/James Trout, (301) 504-8750/(301) 504-8496, rfayer@lpsi.barc.usda.gov/ jtrout@lpsi.barc.usda.gov

Is depression in women of childbearing age linked to low iron reserves? Not according to a recent study that found no relationship between mood and marginal iron status. That's different from severe iron deficiency, which can cause depression. About 1 in 5 women of childbearing age has low iron stores compared to 1 in 60 men. And twice as many women as men are clinically depressed--a gender difference that begins in adolescence. Depression is more pronounced among married women age 25 to 45 with children. But earlier studies on the subject produced conflicting findings. So a nutritionist and a psychologist checked 384 women, ages 20 to 45, who were not diagnosed as depressed. They used a standardized psychological profile and mood checklist to test the volunteers. They also analyzed the volunteers' blood samples by the most sensitive tests of iron stores. There were no relationships between mood scores and three signs of iron status--serum ferritin, serum iron and hemoglobin. Serum ferritin is the first indicator of iron status to drop, while hemoglobin is the last and most resistant indicator to change. Iron deficiency severe enough to cause depression and fatigue would show up in a simple hemoglobin or hematocrit test.

Grand Forks Human Nutrition Research Center, Grand Forks, ND
Janet R. Hunt, (701) 795-8328, jhunt@gfhnrc.ars.usda.gov