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United States Department of Agriculture

Agricultural Research Service

Food & Nutrition Research Briefs, January 2002

Table place setting with apple. Title: Food and Nutrition Research Briefs. Link to FNRB home page

January 2002

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Contents

Concentration, Memory Could Be Elemental

Colorful Potatoes Pack More Nutrients

Folate May Help Forestall Forgetfulness

Program Ups Breastfeeding Rates Among Hispanics

Protein May Telegraph Heart Attack,
Stroke Risk

Making Calcium More Available

Berry Bad News for Cancer Cells

Souped-Up Broccoli Deters Cancers in Rats

Viruses Instead of Antibiotics for Poultry Disease?

Concentration, Memory Could Be Elemental

If you've been having trouble concentrating, maybe you're not getting enough of certain essential elements. Studies are revealing new clues about the roles iron and zinc apparently play in keeping our mental capacities—or cognitive function—up to par. Much of the research that links inadequate nutrition to mental performance has been done with children. But these studies were done with adults and focused on marginal deficiencies.

Photo of physiologist Mary Kretsch and dietician Monique Derricot at computer In a 20-week study with eight healthy men, the researcher looked at the relationship between iron and the volunteers' ability to concentrate. She found that a low score for volunteers' attention span corresponded with a subsequent decline in iron levels in the body.

In an earlier study with 14 obese but otherwise healthy female volunteers, she and colleagues documented a similar change in ability to focus. The 21-week experiment showed that volunteers with borderline anemia, as measured by blood hemoglobin, were less able to concentrate than volunteers with higher hemoglobin. The studies are the first in healthy adults to link a decrease in iron with a decline in attention span and suggest that decreased ability to concentrate may be an early indicator that an individual's iron levels are declining.

The researchers also explored the interaction of brainpower and zinc, using the same eight men who were volunteers in the iron study. One of the tests evaluated the volunteers' ability to recall specific words. Preliminary results showed that, after only three weeks on a low-zinc regimen, the ability to recall the words slowed in many of the volunteers. Those who slowed the most also had the greatest decrease in blood levels of zinc.

For more information, contact Mary J. Kretsch, (530) 752-4171, Western Human Nutrition Research Center, Davis, CA

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Folate May Help Forestall Forgetfulness

Fortification of grain products with the B vitamin folate may help reduce memory loss in the over-60 set. That's the implication from a careful look at recent data from the third national health and nutrition examination survey, NHANES III.

The researchers had established that homocysteine levels were higher in elderly people with low intakes of B vitamins, especially folate. They had also validated reports that high homocysteine increases risk of stroke, which is a major player in the loss of cognitive function. But they wanted to see if high homocysteine levels or low B vitamin status had a more subtle influence in memory loss among people over age 60. That's because B vitamins are involved in the synthesis of chemicals crucial to brain function. Or, homocysteine itself might be toxic to nerve cells. Homocysteine is a byproduct of our own amino acid metabolism.

Fortuitously, the NHANES III included a sensitive test of recall after a short delay—one that can identify individuals with a milder loss of recall. It has been reported that homocysteine is related to Alzheimer's disease, as well as to poor cognitive function in elderly both with and without dementia. Perhaps 75 percent of dementia is due to stroke or Alzheimer's disease, which is now thought to develop from minor strokes.

So the researchers excluded data from people who had suffered a stroke. Their analysis showed elevated homocysteine levels were associated with memory loss. But the survey subjects whose blood folate levels were in the upper half appeared to be protected from memory loss even if their homocysteine levels were high. Reported in the American Journal of Clinical Nutrition, 2001 (vol. 73, pp. 927-933), the findings remind us to keep our folate levels up. And that's easy now; virtually all grain products have been fortified with the vitamin since 1998.

For more information, contact Martha Savaria Morris, (617) 556-3302, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA

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Protein May Telegraph Heart Attack, Stroke Risk

A protein that helps body cells store fat could help physicians assess whether patients whose blood vessels contain fatty deposits called plaque are at risk for a heart attack or stroke. Researchers found evidence that the protein—perilipin–was more actively synthesized in ruptured plaque than in stable plaque. When plaque ruptures, it triggers formation of a plug—an internal scab—that can stop blood flow in the artery or reduce it to a trickle. If the ruptured plaque is in the heart, it could cause a heart attack; if in the neck or head, a stroke could ensue.

A physician at the ARS-funded center in Boston collaborated on the study with a group of researchers at the University of Maastricht in The Netherlands. The researchers wanted to know if certain genes are more active—that is, expressed as proteins—in ruptured plaque. They cloned genes from ruptured and nonruptured plaque and looked for differences in expression among the genes.

There was good evidence that the perilipin gene was turned on and expressing the protein in the ruptured plaques, whereas it was difficult to detect any expression in stable plaques, according to the report in Circulation Research, 2001 (vol 89, pp. 547-554).

The team's findings could have several applications. First, a test for the presence and amount of perilipin could be developed to detect plaque in danger of rupture. For instance, a perilipin antibody, which would attach to the protein, could be tagged with a radioactive tracer and "seen" with imaging technology. Such a test could be used to monitor the effectiveness of nutritional interventions—such as folate or antioxidants—on risk for heart attack or stroke. Also, the discovery will help researchers better understand how plaques become unstable and could lead to preventative measures.

For more information, contact Andrew S. Greenberg, (617) 556-3144, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA

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Berry Bad News for Cancer Cells

Fruits and vegetables contain a wide array of compounds—or phytonutrients—reported to have anticancer activity in cell cultures. Now, ARS and Clemson University scientists are probing an assortment of berries, as well as muscadine grapes, for their ability to inhibit the growth of breast and cervical cancer cell lines. Among U.S. women, breast cancer is second only to lung cancer in cancer-related deaths.

The ARS scientists prepared extracts of the berries and muscadine grapes using various solvents and different parts of the fruit—such as juice, skin and seeds. A Clemson University colleague assayed the extracts on the cancer cell lines. Their findings, though very promising, are preliminary and will have to be validated in people through clinical trials.

Various extracts from muscadine grapes, raspberries and strawberries cut the growth of both breast and cervical cancer cell lines by more than half. Extracts from blueberries and blackberries were ineffective against the two cervical-cancer cell lines. But they suppressed breast cancer cell growth—each fruit suppressing a different cell line. Two breast cancer cell lines were used in these assays because their estrogen requirements are different.

Specific muscadine grape extracts suppressed a third breast cancer cell line much more than a line of healthy cells from the same donor. That means it's more selective for cancer cells.

Cancer develops in stages. First, a normal cell undergoes mutations. Then, mutated cells must be stimulated to keep dividing as they get cut off from blood-delivered oxygen. Finally, more mutations enable cells from a localized tumor to invade other tissues. The findings reported here deal with suppression of the second stage. The researchers are also assaying the berry and grape extracts for their ability to prevent mutations.

For more information, contact David E. Wedge, (662) 915-1137, ARS Natural Products Utilization Research Unit, Oxford, MS; or Lyndon L. Larcom, (864) 656-7939, Clemson University, Clemson, S.C.

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Colorful Potatoes Pack More Nutrients

Photo of brightly colored pototoesPotatoes are not only are tasty, they also provide a good source of complex carbohydrates, potassium, vitamin C, folic acid and iron. Now, studies are being conducted to examine additional health benefits of dark-pigmented varieties not often found in the United States. That's because brightly colored orange, red and purple potatoes might one day provide health-promoting properties beyond those found in ubiquitous white- and cream-colored spuds.

So far, the primary benefit likely to be derived from boldly colored potatoes seems to be heightened antioxidant activity. Indeed, orange-fleshed potatoes have been developed with up to four times the antioxidants zeaxanthin and lutein as white potatoes. In addition, the darker colored potatoes score well against other foods in a standard test for antioxidant capacity named ORAC, or oxygen radical absorbance capacity. The red- and purple-fleshed potatoes achieved ORAC scores comparable to brussels-sprouts, kale, or spinach.

And the bright colors occur naturally. The researcher identifies and selects test plants from mainstream potato breeding programs. Still, more research must be conducted to learn about traits such as composition and quantity of pigment, growing requirements, and yields before colorful spuds such a these can be commercialized.

For more information, contact Charles R. Brown, (509) 786-9252, Vegetable and Forage Crops Production Research Unit, Prosser, WA

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Program Ups Breastfeeding Rates Among Hispanics

Researchers are identifying effective ways to increase breastfeeding rates among low-income Hispanic mothers. The U.S. Surgeon General has made increasing breastfeeding rates a public health priority, but there has been little information about the best way to do so—until now.

Proyecto Leche de Vida (Project Milk of Life), a community-based pilot project, was designed to compare the effectiveness of home visits with telephone consultations by trained breastfeeding counselors in an area of Houston with a predominantly Hispanic immigrant population. Preliminary results from the study, which involved 105 new mothers, are striking. A full 38 percent of mothers in the trial breastfed exclusively for at least three months, compared to the typical five percent rate for new mothers in that area. Breastfeeding exclusively for three months helps reduce infant morbidity and health care costs during the first year of life.

Researchers found that 41 percent of new mothers who received home visits and 35 percent of those who received phone calls still breastfed their child exclusively at three months, compared to 11 percent in the control group. First-time mothers often lack breastfeeding knowledge and skills. Hispanic women also have limited access to Spanish-language breastfeeding information and assistance in hospitals. So bilingual, hands-on teaching during home visits was most effective.

After the study, the project was continued with financial support from Episcopal Health Charities and private philanthropists. Counselors have now provided over 2,700 breastfeeding consultations to more than 450 women. Another 1,000 women participated in prenatal breastfeeding classes.

For more information, contact Judy Hopkinson, (713) 798-7000, Children's Nutrition Research Center at the Baylor College of Medicine, Houston, TX

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Making Calcium More Available

Understanding why some plants like spinach store much of their calcium in a crystalline form could help scientists develop more nutritious varieties of vegetables. One cup of cooked spinach contains plenty of calcium—around 244 milligrams. But because most of the calcium is in calcium oxalate crystals that we can't digest, humans absorb a mere 12 milligrams—or five percent.

Turnip greens, on the other hand, are nearly crystal-free, making them an excellent source of calcium. One cup of cooked turnip greens provides us with about as much calcium as a cup of cow's milk.

To unlock the mystery of crystal formation and function, an ARS molecular biologist is studying a small, fast-growing plant called Medicago truncatula. His lab has inspected thousands of genetic variations of this simple plant, which normally stores much of its calcium in crystals. While the genetic variants look nearly identical to the naked eye, some have leaf cells packed with calcium oxalate crystals while others are nearly crystal-free, the researchers reported in Plant Physiology, 2000 (vol. 124, pp. 1097-1104).

They hope to determine whether calcium oxalate crystals play an important role in helping plants adapt to stressful growing conditions or fend off attacks by pathogens and insects. And they are looking for the genes that control crystal formation. Since the plants that don't make crystals appear to thrive as well as those that do, the researchers should be able to breed out or remove this characteristic from M. truncatula. If successful, this would be a first step toward making calcium oxalate-rich vegetables like spinach a better source of calcium for humans.

For more information, contact Paul A. Nakata, (713) 798-7013, Children's Nutrition Research Center at Baylor College of Medicine, Houston, TX

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Souped-Up Broccoli Deters Cancers in Rats

Specially grown broccoli--containing hundreds of times more selenium than grocery store varieties--protected laboratory rats against mammary tumors in a Buffalo, N.Y., laboratory. And high-selenium broccoli sprouts protected rats against precancerous colon lesions in a Grand Forks, N.D., laboratory.

Published in the Journal of Agricultural and Food Chemistry, 2001, (vol. 49, pp. 2679-2683), the findings are the combined work of researchers at ARS' Human Nutrition Research Center in Grand Forks, Roswell Park Cancer Institute in Buffalo, and Oregon State University in Corvallis. Whether the findings translate to humans will require further study.

The broccoli heads and sprouts used in these studies were produced for experimental purposes and are not available commercially. The rats were given only enough to approximate a human dose of about 200 micrograms daily—about three times the Reference Daily Intake. Several human studies have shown that taking a 200 mcg-selenium supplement can reduce the incidence of several types of cancer. But it will not reverse tumors once they develop.

The researchers enriched broccoli because it stores selenium in a unique form—called SeMSC for short—that is easy for people and animals to convert into the active anticancer agent. In earlier studies, when the Grand Forks researchers challenged rats with known carcinogens, the animals that had eaten the high-selenium broccoli had far fewer precancerous colon lesions than the groups given selenium salts--selenate or selenite.

In the latest studies, the Roswell Park researchers found a similar protective effect of high-selenium broccoli against mammary tumors, using a rat model for such tumors. The rats got about 30 times more selenium from the specially grown broccoli than they would in a standard diet.

Meanwhile, the Grand Forks lab tested high-selenium broccoli sprouts in a rat model for colon cancer and saw the same protective effect they had earlier gotten with high-selenium broccoli. Found in many health food stores, broccoli sprouts are known to be rich in other anticancer compounds, but they are not enriched in selenium.

For more information, contact John W. Finley, (701) 795-8416, ARS Grand Forks Human Nutrition Research Center, Grand Forks, ND; or Clement Ip, (716) 845-8875, Roswell Park Cancer Institute, Buffalo, NY;

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Viruses Instead of Antibiotics for Poultry Disease?

Early results with experiments using bacteriophages to reduce foodborne pathogens and treat various poultry diseases are encouraging. Bacteriophages—or phages for short—are viruses that infect and kill bacteria, and a particular phage can usually infect only one or a few related species of bacteria.

ARS researchers isolated a number of phages, that would target a particular strain of E. coli that causes an air sac infection, called air saculitis, in broiler chickens. The disease leads to death or condemnation of the carcasses during processing, and is very difficult to treat.

When the scientists mixed a bacteriophage with the E. coli strain—serotype 02—before they challenged broiler chickens with the bacteria, the animals were completely protected from respiratory infection. The researchers suspect other phage strains may be even better suited to prevent air saculitis. And they recently began to investigate the effectiveness of phages to treat the infection in poultry and perhaps become an alternative to antibiotic use.

The scientists are also investigating the efficacy of phages against other foodborne pathogens, such as Salmonella and Campylobacter. In cooperation with the University of Arkansas, they isolated phages effective against Salmonella. Phages were first discovered in 1915, but research on their therapeutic use was largely abandoned outside of Eastern Europe when antibiotic drugs became widely available in the 1940s.

For more information, contact William E. Huff, (501) 575-2104, Poultry Production and Product Safety Research Unit, Fayetteville, AR

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Last Modified: 2/14/2007