Watermelon juice may be novel amino acid source

Watermelon juice may provide a novel source of the essential amino acid arginine, says a new study that shows the juice is a rich source of its metabolic precursor.

Arginine is a precursor for nitric oxide, which has been shown to lower blood pressure, reduce blood clotting and protect against myocardial infarction and strokes. Researchers from the ARS, Texas A&M University, the University of Nevada, and Oklahoma State University, have reported that blood arginine levels increased by 22 per cent after three weeks of drinking watermelon juice with every meal.

"Some studies have reported that high oral doses of arginine were associated with nausea, gastrointestinal discomfort, and diarrhoea in humans. A solution to this potentially severe problem may be the alternative use of l-citrulline, an effective precursor for arginine synthesis," explained lead author Julie Collins in the journal Nutrition.

Indeed, L-citrulline is a neutral amine acid, meaning it does not compete with basic amino acids for transport by cells. Conversion of L-citrulline to arginine consumes ammonia, said Collins, meaning the amino acid could be useful for people with elevated ammonia levels, arginine transport problems, or enhanced intestinal arginine breakdown, as is found in people with stress and infection.

The researchers recruited healthy volunteers (between 12 and 23 per intervention group) and assigned them to receive 0, 780, or 1560 grams of watermelon juice per day, providing a daily L-citrulline dose of 0, 1 or 2 grams. The interventions lasted three weeks and subjects were later crossed over after washout periods of two to four weeks. After the three weeks of intervention, Collins and co-workers report that fasting blood levels of arginine had increased by 11 and 22 per cent for the low- and high-dose juice interventions, respectively.

Levels of ornithine, a product of arginine catabolism, also increased in the high-dose watermelon juice group by 18 per cent after three weeks. "Because the watermelon juice intervention was not continued longer than 3 wk, it is not known if arginine levels plateaued at 3 wk or if there would have been further increases with prolonged administration," stated the researchers.

Previous studies with animals have reported that citrulline administration may be detrimental to levels of other amino acids, but no such results were observed in this human study, they said. "In our study, we found that plasma concentrations of all other amino acids (essential and non-essential amino acids) were not affected by the low or high levels of watermelon juice consumption," wrote the researchers. "These results indicate that the doses of citrulline intake from watermelon juice have no deleterious effects on whole-body amino acid balance in humans."

"These results indicate that citrulline from watermelon was effectively converted into arginine and offers a potential role for exploring the dietary effects of watermelon in regulating whole-body metabolism of energy substrates, improving cardiovascular and immunologic functions, and preventing the aging-associated increase in tissue oxidative stress," they concluded. Watermelon is also a rich source of lycopene, a carotenoid that has been linked extensively to improvements in heart health and risk reductions for a range of certain cancers.

ARS scientists also reportedly found a way of extracting lycopene from the chromoplasts that encapsulate lycopene without damaging the carotenoid, that could see watermelon rival tomato as the optimal source of the nutrient for food and dietary supplements.

Infections explain why our blood groups differ

WHY people have different blood groups is something of a mystery. But a new analysis suggests that different groups evolved to give populations a balanced defence against viruses and bacteria. People have either blood group A, B, AB, or O, with each type occurring at different frequencies in populations around the world.

Now Robert Seymour and his colleagues at University College London have used a mathematical model to show that this diversity is caused by selection pressures imposed on human populations by viral and bacterial infections (Proceedings of the Royal Society B, DOI: 10.1098/rspb.2004.2674).

Their model reveals that if viral infections dominate a population, blood type O will be most common, whereas if bacterial infections are more common, then A and B blood types will be more frequent. These results closely resemble the balance of blood types seen in today's populations, Seymour says.

Viral infections increase the frequency of type ...

Not far from A to B

CHEMISTS have finally found the crucial difference between the enzymes that dictate which blood group we inherit. These enzymes, called glycosyltransferases, adorn the surfaces of blood cells with specific sugars that distinguish the blood groups A, B and O.

Now a Canadian team jointly led by Stephen Evans of the University of Ottawa has discovered that just one of the enzyme's chain of 354 amino acids decides whether we end up with group A or B blood (Nature Structural Biology, DOI: 10.1038/nsb832). People with group O inherit enzymes that make simpler surface sugars.

From issue 2357 of New Scientist magazine, 24 August 2002, page 24

Enzymes convert all donor blood to group O

You're rushed into hospital and need a blood transfusion – but what is your blood group? In future, it may not matter, thanks to enzymes that scrub antigens from red blood cells, turning all donated blood into group O – which can be given safely to anyone.

The A and B antigens, which give blood groups their name, are sugars carried on the surface of red blood cells. Human red blood cells can carry one of these antigens, both, or neither; giving four blood groups: A, B, AB and O, respectively. Receiving mismatched blood can cause a life-threatening reaction, and errors are made in 1 in every 15,000 transfusions, on average.

In the 1980s, a team in New York, US, showed that an enzyme from green coffee beans could remove the B antigen from red blood cells. It proved too inefficient for practical use, but Henrik Clausen at the University of Copenhagen in Denmark and colleagues have now screened bacteria and fungi for more powerful enzymes. "The diversity you get in the bacterial kingdom is much higher," Clausen explains.

The researchers homed in on two enzymes.

One, from a gut bacterium called Bacteroides fragilis, removes the B antigen.The other, from Elizabethkingia meningosepticum – which causes opportunistic infections in people – targets the A antigen.The purified enzymes are highly efficient. For example, the B. fragilis enzyme is used up at only one-thousandth the rate of the coffee bean enzyme.Clausen's team is working with a company called ZymeQuest in Beverly, Massachusetts, US, which plans clinical trials to test whether the treated blood is safe and effective. If so, the technology should be in hot demand, because group O blood – the only safe option if there is any doubt about the recipient's blood group – is a precious commodity. "We're always in a shortage," says Richard Benjamin, chief medical officer with the American Red Cross in Washington DC, US.

Journal reference: Nature Biotechnology (DOI: 10.1038/nbt1298)

Apples and fish protect unborn children

Apples and fish sound an unlikely food combination, even for a pregnant woman, but new evidence suggests they can protect unborn children against allergic diseases.

Researchers found that children whose mothers enjoyed munching apples while pregnant were less likely to have suffered from wheeze or been diagnosed with asthma by the age of five. Similarly, the sons and daughters of mothers who ate fish once or more a week during pregnancy appeared to be protected against the skin allergy eczema. Scientists believe the effects may be due to powerful antioxidants in apples called flavonoids, and omega-3 fatty acids in fish. A range of other foods studied, including vegetables, fruit juice, citrus and kiwi fruit, whole grains, dairy fat and margarine, did not produce the same protective effects. The investigation was conducted at the University of Aberdeen in Scotland. Researchers studied 1,212 children born to women who had filled out food questionnaires during their pregnancy. When the children reached the age of five, the team questioned the mothers about their offspring's respiratory symptoms, allergies, and diet. The children were also given lung function and allergy tests.

Children whose mothers ate the most apples were less likely to have experienced wheeze or asthma than those whose mothers had the lowest apple consumption. Mothers who ate fish once or more a week while pregnant had children who were less likely to have had eczema than children of mothers who never ate fish. Previous studies involving the same group showed that taking vitamins E and D and zinc during pregnancy helped reduce a child's risk of wheeze and asthma.

Researcher Saskia Willers, from Utrecht University in the Netherlands, said a mother's pregnancy diet may have more influence on a child's respiratory health than the child's own food consumption - at least until the age of five. She said: "Other studies have looked at individual nutrients' effect on asthma in pregnancy, but our study looked at specific foods during pregnancy and the subsequent development of childhood asthma and allergies, which is quite new.

Researchers find big batch of breast cancer genes

WASHINGTON (Reuters) -- A genetic mutation that raises the risk of breast cancer is found in up to 60 percent of U.S. women, making it the first truly common breast cancer susceptibility gene, researchers report.

Reports from several teams around the world identified changes in four other genes that raise the risk of breast cancer significantly. Several are found in many men and women.

More than 60 percent of the women in the United States probably carry at least one of the mutations in one of the genes, called FGFR2, the researchers said.

"This is a truly landmark breakthrough for breast cancer research, because these genes are the first confirmed common genetic risk factors for breast cancer," said Jianjun Liu of the Genome Institute of Singapore, who took part in one of the studies.

The researchers, reporting in the journals Nature and Nature Genetics, said the discoveries are the most important genes associated with breast cancer since BRCA1 and BRCA2 were identified.

Women with faulty copies of BRCA1 or BRCA2 have a 50 percent to 85 percent chance of getting breast cancer in their lifetimes. But they are rare genes, and account for only 5 percent to possibly 10 percent of breast cancer cases.

Researchers have been testing women for other genes associated with breast cancer, to find its causes, to understand how and why it develops, and to make more effective treatments.

Better techniques to analyze DNA, and the publication of the human genome, the map of all DNA in the body, have made this a much faster and easier process.

David Hunter of Harvard University and a team at the U.S. National Cancer Institute looked at more than 2,200 women of European ancestry.

Common gene, big risk

They found four common mutations in FGFR2 associated with the breast cancer in women after menopause who do not have known relatives with breast cancer.

The mutations raise the risk of breast cancer risk by 20 percent if they carry one copy of the gene and by 60 percent if they carry two copies. And close to 60 percent of the women they studied carried at least one copy.

The findings do not yet have any real relevance for women, Hunter stressed.

"It is premature to recommend screening women for these gene variants, at least until the scientific community has further combed through the genome-wide findings and found all the variants that are associated with increased risk," Hunter said in a statement.

Douglas Easton of Britain's University of Cambridge led a team of researchers around the world to look at tiny changes in the DNA code called single nucleotide polymorphisms or SNPs -- pronounced "snips" -- in the DNA of 21,860 people with breast cancer and 22,578 people without it.

They found mutations in four genes that were more common in the people with breast cancer -- FGFR2, TNRC9, MAP3K1 and LSP1.

FGFR2 may be a logical candidate for a breast cancer gene -- it is a receptor, a kind of molecular doorway, for compound called tyrosine kinase which is involved in several cancers.

In a third study, a team at deCODE genetics, the University of Nijmegen in the Netherlands and elsewhere studied 22,000 people to find two other gene mutations associated with breast cancer. One is also near TNRC9.

"DeCODE estimates that these two variants are contributing factors in one quarter of breast cancer cases in women of European origin," the company wrote in a statement.

Breast cancer kills 500,000 people a year globally according to the World Health Organization, and 1.2 million men and women are diagnosed with it every year.

Understanding Diarrhea - the Basics

What Is Diarrhea?

Doctors usually define diarrhea as a significant increase in the total weight of stool passed in a single day. Most people, however, think of diarrhea as an illness during which they have more frequent, loose, watery stools.

Almost everyone has diarrhea at some point in his or her life. In developing countries, where illnesses that cause diarrhea are more common and where health care is less readily available, diarrhea is a major health concern because of its potential to cause severe, life-threatening dehydration. Infants and the elderly are more prone to dehydration from diarrhea.

Diarrhea that comes on suddenly and goes away over a period of a couple of weeks is usually referred to as "acute diarrhea." Most people with acute diarrhea recover on their own. Diarrhea that lasts more than four weeks is thought of as "chronic diarrhea." Typically, chronic diarrhea requires medical care to find the underlying cause and treat complications, such as dehydration.

What Causes Diarrhea?

Many different things can cause diarrhea. Here are the major causes:

Infections

You are most likely to come down with diarrhea after coming into contact with these infectious organisms and agents:

• A virus, such as rotavirus, Norwalk agent, enterovirus, or a hepatitis virus.
• A bacterium, such as E. coli, salmonella, shigella, clostridium, or Vibrio cholerae.
• A parasite, such as those that cause giardiasis and amebiasis.

You may pick up an infectious agent from contact with another individual who has it, or you may get it after eating contaminated food or drinking contaminated water. If you eat food that was improperly cooked or was contaminated after cooking, you may get food poisoning, which can lead to diarrhea. Children who attend day care and their families are more likely to be exposed to certain infectious agents.

Many people who travel to foreign countries develop what is termed "traveler's diarrhea," usually after drinking contaminated water. Infectious diarrhea is a particular hazard in developing countries where it may be difficult to keep waste water and sewage separate from water used for cooking, drinking, and bathing and where inadequate facilities make it difficult to practice good personal hygiene.

Other Medical Conditions

A number of noninfectious medical conditions may cause diarrhea, too. These include:

• Inability to digest certain foods, including a lactose intolerance (difficulty digesting sugar found in dairy products); celiac disease (inability to digest wheat and sometimes other grains); and pancreatic problems, such as those caused by cystic fibrosis, which interfere with production of important digestive substances.
• Surgery to remove part of your intestine. A shortened intestine may be unable to absorb all the substances you eat. This is referred to as short-bowel syndrome.
• Surgery after removal of the gallbladder. An increase in bile in the colon may result in watery stools.
• Certain diseases of the endocrine (hormonal) system, including thyroid disease, diabetes, adrenal disease, and Zollinger-Ellison syndrome.
• Certain rare tumors (including carcinoid tumor and pheochromocytoma) that produce diarrhea-causing substances.
• Inflammation in the intestinal tract, which can result in chronic diarrhea. If you have inflammatory bowel disease (such as ulcerative colitis or Crohn's disease), you will have regular bouts of diarrhea during a flare-up of your disease. Sometimes, people who develop bumps in their intestine from diverticulitis also get diarrhea.
• Irritable bowel syndrome, which may cause alternating bouts of diarrhea and constipation.

Medications and Other Substances

Many medications can cause diarrhea. Some of the most common include antacids containing magnesium, laxatives, digitalis, diuretics, a number of antibiotics, chemotherapy drugs, cholesterol-lowering agents, lithium, theophylline, thyroid hormone and colchicine.

Radiation therapy for prostate cancer or cancers in the abdomen can damage the intestine and cause diarrhea.

Toxins such as insecticides, psychedelic mushrooms, and arsenic can cause diarrhea, and overuse of caffeine or alcohol may contribute to diarrhea.

Understanding Food Poisoning - the Basics

What Is Food Poisoning?

You can get food poisoning after eating food contaminated by viral, bacterial, or chemical agents. Food poisoning causes mild to severe, acute discomfort and may leave you temporarily dehydrated. Mild cases last only a few hours and at worst a day or two, but some types, such as botulism or certain forms of chemical poisoning, are severe and possibly life-threatening unless you get medical treatment.

What Causes It?

Many bacteria can cause food poisoning. People who are ill or infected can transmit staphylococcus bacteria to food they are preparing. People who eat or drink contaminated food or water can get travelers' diarrhea, usually caused by the bacterium E. coli. Salmonella poisoning can occur from eating contaminated poultry, eggs, and meat; though potentially fatal, most cases cause only mild discomfort. Harmful bacteria grow in cooked and raw meat and fish, dairy products, and prepared foods left at room temperature too long; dishes made with mayonnaise are notorious culprits.

Canned goods, especially home-canned produce, can harbor a bacterium that needs no oxygen to multiply and is not destroyed by cooking. This bacterium causes botulism, a rare but potentially fatal food poisoning. Infants may develop botulism from eating honey because their immature digestive systems, unlike those of adults, cannot neutralize its naturally occurring bacteria.

Raw seafood, especially contaminated shellfish, may bring on viral food poisoning. Certain mushrooms, berries, and other plants are naturally poisonous to humans and should never be eaten; potato sprouts and eyes also contain natural toxins. Toxic mold can form on improperly stored fruit, vegetables, grains, and nuts. Chemical food poisoning can be caused by pesticides or by keeping food in unsanitary containers.

Can Soft Drinks Be Healthy?

New sodas are aimed at health-conscious consumers but fall short experts say.

The idea of a healthy soft drink may sound like an oxymoron. But to soda manufacturers, it's the hottest trend in the better-for-you category of food and beverages. With all the attention on obesity and health, consumers are looking for healthier, more natural beverages. And manufacturers are hoping to perk up sagging soda sales with new "healthy" soft drinks spiked with vitamins and minerals and marketed with natural-sounding terms.

Soda Sales Sagging

Sales of carbonated drinks have been sagging due to the popularity of bottled water and noncarbonated drinks like teas, juices, sports drinks, and "functional" drinks with added ingredients purported to reduce stress or increase energy. Soda companies have responded by launching new products and marketing efforts.

Some carbonated beverages are now being marketed as "sparkling," implying a healthier, more natural beverage. There are caffeine- free, no-calorie beverages laced with vitamins and minerals, like Diet Coke Plus and Tava from Pepsi. "Zero-calorie" sodas are aimed at consumers who don't like the idea of a "diet" drink. Jazzed-up flavors like pomegranate, cherry, vanilla, lemon, lime, and caramel are also making their way into soft drinks. "The beverage industry believes that all beverages, including carbonated soft drinks, can be part of a healthy and balanced lifestyle," says Tracey Halliday, spokeswoman for the American Beverage Association. She points out that many of the beverage industry's products, including bottled waters, juices, sports drinks, and diet soft drinks, can be catalysts to health and fitness.

How Healthy Are the New Soft Drinks?

The truth is that artificially sweetened soft drinks – even those fortified with vitamins and minerals -- are anything but natural and healthy, says Marion Nestle, New York University nutrition professor and author of What to Eat. "It is ridiculous to market soft drinks as healthy, but in today's marketplace consumers are demanding more healthylooking food, and beverages and soft drink manufacturers need to boost sales," she says. Most consumers do not need the extra vitamins found in fortified soft drinks, she adds. "We are not vitamin deficient, and these beverages do not address the real health issues of our country of obesity, heart disease, or cancer," says Nestle. University of Vermont researcher Rachel Johnson, PhD, RD, agrees.

"It concerns me that we have so many ultra-fortified products where we virtually put a vitamin pill into a soft drink," she says. "The nutrients put into these soft drinks are not the shortfall nutrients that are lacking in our diets such as calcium, potassium, folate, or vitamin D."

Johnson advises consumers to choose beverages that not only quench thirst but also deliver needed nutrients, such as 100% fruit juice and skim or low-fat milk. "These beverages will help you meet your nutritional needs and satisfy the recommendations of the [U.S. government's] 2005 Dietary Guidelines," she says.

Diet Soft Drinks vs. Regular

Consumers are turning away from sugary sodas because of the potential link to obesity. Yet "there is very little evidence that diet sodas help people lose weight," says Nestle. "In fact, one
study suggested that people use diet drinks to help justify eating more calories." Experts do agree that low- or no-calorie soft drinks are better than sugary regular sodas.

"It is fine to enjoy a diet soda as long as you don't use them as a license to add more calories from other foods. Because some people drink a diet drink so they can eat a big piece of cake," says Nestle. Diet soft drinks are also helpful for consumers who are hooked on regular sodas and trying to wean themselves off the sugary beverages. Liquid Calories Add Up Quickly Liquid calories can lead to weight gain because beverages go down so easily. They may satisfy thirst, but they don't affect hunger. So people who drink sugary sodas don't generally take in fewer calories from food to compensate.

"Lots of people don't think about what they are drinking and how it impacts the overall diet," says Johnson. "The average American gets 22% of their calories from beverages." Indeed, a recent study from Yale University analyzed 88 soda studies and found a clear link between soft drink intake and consumption of extra calories.

"The most compelling studies showed that, on days when people drink soft drinks, they consumed more calories than on the days when they did not have soft drinks," study co-author Marlene Schwartz tells WebMD.

When you do want a regular soda, Nestle suggests that you think of it as dessert.

"If we treated a can of regular soda like a dessert, it would help keep extra calories under control," she says. The Bottom Line The experts agree that there is no harm in enjoying a low- or no- calorie soft drink. But they point out that the additives in some of the new sodas -- no matter how healthy sounding -- are either unnecessary or are added in such small quantities that they don't do anything for your health.

Nestle would rather see people choose beverages with nothing artificial added, such as a glass of sparkling water sweetened with real fruit juice. Her advice: Consume the most natural foods and beverages, and always read the label. Check calories first, followed by sugar calories. Equipped with the facts, you can select the drink that's right for you. And keep in mind, Johnson says, that soft drinks have no place in the diets of children 11 and under.

"Soft drinks do not belong in young children's diets," says Johnson. "Because they need so many nutrients for growth and development, there is little room for soft drinks unless they are extremely active -- and even then it should only be an occasional treat."