Showing posts with label better. Show all posts
Showing posts with label better. Show all posts

Monday, June 17, 2013

New dietary guidelines: Eat less, eat better and lose the salt

Americans need to make big changes in their eating habits to fight the obesity epidemic and a host of ailments caused by poor diets, including consuming less sugar, fat and salt and more fish, fruits and vegetables, the Obama administration recommended Monday.

In updating the federal dietary guidelines - required by law every five years - the departments of Agriculture and Health and Human Services outlined a long list of steps Americans should take to eat better to boost their chances of living longer, healthier lives.

While the new guidelines contain no dramatic changes from previous iterations, they are intended to simplify many messages and emphasize certain recommendations more starkly, officials said. For example, the first major message reads simply: "Enjoy your food, but eat less."

The guidelines also make a point of highlighting the importance of minimizing salt consumption. No one should consume more than 2,300 milligrams of sodium per day - about one teaspoon of salt - while African Americans and those who are ages 51 and older, have high blood pressure, diabetes or chronic kidney disease should take in no more than 1,500 milligrams, according to the guidelines. The second group accounts for about half the U.S. population. The recommended limits are essentially unchanged from the previous guidelines.

Currently, Americans consume about 3,400 milligrams of sodium each day, which many experts say increases their risk for high blood pressure, a major risk factor for a variety of illnesses, including heart attacks and strokes. Officials noted that much of the sodium people consume is hidden in processed foods. So the reduction would require major changes by the food industry.

"This is obviously a significant reduction that is being proposed and one that we hope the food processors in particularly will take into account," Agriculture Secretary Tom Vilsack said.

But industry groups immediately criticized the proposal. The Salt Institute questioned the link between sodium and high blood pressure, arguing the recommendation would have a variety of negative effects on health, including worsening the obesity epidemic by driving people to eat more overall to satisfy their desire for salt.

"The guidelines, if followed, may have negative substantial unintended health consequences," said Morton Satin, the institute's vice president for science and research.

Although most people have probably never read the guidelines, they have a broad impact on Americans' lives, dictating what many students eat for breakfast and lunch at school, what people getting food stamps are urged to buy and what information is highlighted on packages lining supermarket shelves.

Because they are potentially so influential, the guidelines are typically the focus of intense political lobbying.

With so many Americans overweight and obese, officials said they hoped the new guidelines might finally help get the message across about how to eat a more healthful diet.

"This is a crisis we can no longer ignore," Vilsack said. "The bottom line is that most Americans need to trim our waistlines to reduce the risk of developing diet-related chronic disease. Improving our eating habits is not only good for every individual and family, but also for our country."

The new guidelines include 23 specific recommendations for the general population and six recommendations for specific groups, such as pregnant women.

Among the recommendations are:

l In general, avoid "oversized" portions.

l Drink water instead of beverages containing sugar.

l Eat more fruits and vegetables. A good rule of thumb is that half the food on your plate should be fruits and vegetables.

l Consume less than 300 milligrams of cholesterol each day.

l Alcohol should be consumed only in moderation, which means up to one drink per day for women and two drinks per day for men.

l Consume more fat-free or low-fat dairy products, such as low-fat milk, yogurt and cheese.

l Consume more seafood; use it to replace some meat and poultry. Breast-feeding women should consume 8 to 12 ounces of seafood per week from a variety of sources. But they should limit intake of white tuna to 6 ounces per week because of its high mercury content and eat no tilefish, shark, swordfish and king mackerel for the same reason.

"Helping Americans incorporate these guidelines into their everyday lives is important to improving the overall health of the American people," said Health and Human Services Secretary Kathleen Sebelius. "The new dietary guidelines provide concrete action steps to help people live healthier, more physically active and longer lives."

The guidelines were prepared by a committee of experts that conducted an exhaustive review of the scientific literature about diet, exercise and health, as well as hundreds of public comments and testimony at a series of public meetings.

"I never would have believed they could pull this off," said Marion Nestle, a vocal food industry critic at New York University. "The new guidelines recognize that obesity is the number one public health nutrition problem in America and actually give good advice about what to do about it: eat less and eat better. For the first time, the guidelines make it clear that eating less is a priority."

But Nestle and others said they wished the guidelines went further in several areas.

"Without even more serious governmental efforts - such as banning artificial trans fat and limiting sodium in packaged foods - the dietary guidelines will not be sufficient to fend off the costly and debilitating diet-related illnesses that afflict millions of Americans," said Margo G. Wootan of the Center for Science in the Public Interest.

steinr@washpost.comsteinr@washpost.com


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Thursday, April 11, 2013

Podcast: A Better Sleep Drug, Spotting Cancer Cells, and the Impact of Flushed Pharmaceuticals

Have scientists developed a sleep drug without the side effects? How might a new device spot cancer cells before they metastasize? And what really happens to the drugs we flush down the toilet?

Science 's Online News Editor David Grimm chats about these stories and more with Science's Sarah Crespi.

Listen to the full Science podcast.

Read the transcript.

Hear more podcasts.


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Advancing secure communications: A better single-photon emitter for quantum cryptography


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Wednesday, April 10, 2013

Picking apart photosynthesis: New insights could lead to better catalysts for water splitting

This illustration depicts a metal cluster prepared in the agapie group on a background of photosystem ii, the protein complex that performs photosynthesis in leaves. Credit: Emily Tsui

(Phys.org) —Chemists at the California Institute of Technology (Caltech) and the Lawrence Berkeley National Laboratory believe they can now explain one of the remaining mysteries of photosynthesis, the chemical process by which plants convert sunlight into usable energy and generate the oxygen that we breathe. The finding suggests a new way of approaching the design of catalysts that drive the water-splitting reactions of artificial photosynthesis.

"If we want to make systems that can do artificial photosynthesis, it's important that we understand how the system found in nature functions," says Theodor Agapie, an assistant professor of chemistry at Caltech and principal investigator on a paper in the journal Nature Chemistry that describes the new results.

One of the key pieces of biological machinery that enables photosynthesis is a conglomeration of proteins and pigments known as photosystem II. Within that system lies a small cluster of atoms, called the oxygen-evolving complex, where water molecules are split and molecular oxygen is made. Although this oxygen-producing process has been studied extensively, the role that various parts of the cluster play has remained unclear.

The oxygen-evolving complex performs a reaction that requires the transfer of electrons, making it an example of what is known as a redox, or oxidation-reduction, reaction. The cluster can be described as a "mixed-metal cluster" because in addition to oxygen, it includes two types of metals—one that is redox active, or capable of participating in the transfer of electrons (in this case, manganese), and one that is redox inactive (calcium).

"Since calcium is redox inactive, people have long wondered what role it might play in this cluster," Agapie says.

It has been difficult to solve that mystery in large part because the oxygen-evolving complex is just a cog in the much larger machine that is photosystem II; it is hard to study the smaller piece because there is so much going on with the whole. To get around this, Agapie's graduate student Emily Tsui prepared a series of compounds that are structurally related to the oxygen-evolving complex. She built upon an organic scaffold in a stepwise fashion, first adding three manganese centers and then attaching a fourth metal. By varying that fourth metal to be calcium and then different redox-inactive metals, such as strontium, sodium, yttrium, and zinc, Tsui was able to compare the effects of the metals on the chemical properties of the compound.

"When making mixed-metal clusters, researchers usually mix simple chemical precursors and hope the metals will self-assemble in desired structures," Tsui says. "That makes it hard to control the product. By preparing these clusters in a much more methodical way, we've been able to get just the right structures."

It turns out that the redox-inactive metals affect the way electrons are transferred in such systems. To make molecular oxygen, the manganese atoms must activate the oxygen atoms connected to the metals in the complex. In order to do that, the manganese atoms must first transfer away several electrons. Redox-inactive metals that tug more strongly on the electrons of the oxygen atoms make it more difficult for manganese to do this. But calcium does not draw electrons strongly toward itself. Therefore, it allows the manganese atoms to transfer away electrons and activate the oxygen atoms that go on to make molecular oxygen.

A number of the catalysts that are currently being developed to drive artificial photosynthesis are mixed-metal oxide catalysts. It has again been unclear what role the redox-inactive metals in these mixed catalysts play. The new findings suggest that the redox-inactive metals affect the way the electrons are transferred. "If you pick the right redox-inactive metal, you can tune the reduction potential to bring the reaction to the range where it is favorable," Agapie says. "That means we now have a more rational way of thinking about how to design these sorts of catalysts because we know how much the redox-inactive metal affects the redox chemistry."

The paper in Nature Chemistry is titled "Redox-inactive metals modulate the reduction potential in heterometallic manganese-oxido clusters."

Journal reference: Nature Chemistry search and more info website

Provided by California Institute of Technology search and more info website


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