Monday 28 January 2013

Potassium and Health


Potassium and Health

by J. Anderson, L. Young and E. Long1 (Revised 8/08)

Quick Facts...

  • A diet low in potassium and high in sodium may be one of the factors that leads to high blood pressure.
  • Eating equal amounts of sodium and potassium is recommended.
  • Athletes involved in hard exercise may require larger quantities of potassium-rich foods.
  • Potassium is found in meats, milk, fruits and vegetables.

Role in Health

Many people know that high sodium intake may lead to hypertension. Approximately 10 percent of people with high blood pressure are sensitive to dietary salt (or sodium). A reduction in sodium helps lower blood pressure in all people with hypertension.
Newer evidence suggests that dietary potassium may play a role in decreasing blood pressure. Potassium is involved in nerve function, muscle control and blood pressure. A diet low in potassium and high in sodium may be a factor in high blood pressure. Increasing potassium in the diet may protect against hypertension in people who are sensitive to high levels of sodium.
For people who have hypertension, following an overall eating plan called DASH (Dietary Approaches to Stop Hypertension) may be useful for lowering blood pressure. The DASH diet is higher in potassium, magnesium, and calcium, and lower in total fat, saturated fat, and sodium than the typical American diet. For more information about the DASH eating plan or diet and hypertension in general refer to fact sheet 9.318, Diet and Hypertension.
However, taking potassium supplements is generally not recommended for people with high blood pressure. Instead, a variety of potassium-rich foods should be eaten daily.
Athletes also may need more potassium to replace that lost from muscle during exercise and the smaller amount lost in sweat. Low potassium can cause muscle cramping and cardiovascular irregularities. Eating foods high in potassium can prevent these symptoms. One cup of orange juice, a banana or a potato is sufficient to replace the potassium lost during one to two hours of hard exercise. Sport drinks are poor sources of potassium.

What Does it Do?

Potassium works with sodium to maintain the body's water balance. One possible explanation for potassium's protective effect against hypertension is that increased potassium may increase the amount of sodium excreted from the body.
The kidneys regulate the level of potassium in the body. Potassium deficiency is not common but may result from excessive losses due to severe diarrhea, poor diabetic control, low-calorie diets (less than 800 calories per day), chronic alcoholism, hard exercise, or some diuretics and laxatives.
Although their purpose is to eliminate excess sodium from the body, certain diuretics may increase potassium losses, while others retain potassium. If you take certain diuretics, you may need more or less potassium. Ask your physician about the type of diuretic drug you take and whether you require additional potassium. Some people who take diuretics may be prescribed a potassium supplement to help replace potassium loss.

How Much Potassium?

Most Americans do not get enough potassium in their diets. The recommended daily potassium intake is 4.7 grams a day. Athletes involved in prolonged, hard exercise may require more potassium a day.

Food Sources

Potassium is found in many foods, especially meat, milk, fruits and vegetables (see Table 1). Eat a variety of foods to get the recommended amount.
While sodium is added to most highly processed foods, potassium is not. Eating more fresh and frozen foods, which are usually lower in sodium, may be helpful. (See fact sheet 9.354,Sodium in the Diet.)
Potassium is essential for good nutrition and health. Meeting the minimum requirement is not difficult if you eat a variety of foods. Maintaining the recommended sodium-to-potassium ratio, however, may be more difficult. Eat more fruits and vegetables and fewer processed foods. A moderate increase in dietary potassium, in addition to a reduction of excess sodium, may be beneficial, especially for people at risk for hypertension.

References

  • Altschul, Aaron. 1981. Sodium Sensitivity, Processed Foods and Hypertension. Lillian Fountain Smith 1981 Conference for Nutrition Educators Proceedings. pp. 135-141.
  • Clark, Nancy. 1990. Sports Nutrition Guidebook: Eating to Fuel Your Active Lifestyle. Leisure Press, Illinois.
  • Darling, Mary. 1982. Potassium: Its functions and Sources. Agricultural Extension Service, University of Minnesota, Extension Folder 652.
  • National Research Council, 1990. Recommended Dietary Allowances. pp.173-178.
  • U.S. Department of Agriculture. Agricultural Research Service. Agricultural Handbook No. 8.
  • Institute of Medicine of the National Academies. www.iom.edu.
Table 1: Where's the potassium?
Very good sources (300 mg or more)Fair sources (200-300 mg)Poor sources (less than 100 mg)
SourceServing sizeSourceServing sizeSourceServing size
Breads and Cereals
NoneNoneBread1 slice
Breakfast cereal1/2 cup
Pasta3/4 cup
Dairy
*Buttermilk1 cupIce cream1 cup*American cheese1 ounce
Milk1 cupNatural cheese1 ounce
Yogurt1 cupEggs1
Fruit
Apricots3Apples1 largeApplesauce1/2 cup
Avocado1/4Grapefruit juice1/2 cupBlueberries1/2 cup
Banana1 mediumOrange1 mediumGrapes10 medium
Cantaloupe1 cupOrange juice1/2 cup
Dates10 mediumPeaches1 medium
Honeydew melon1 cupStrawberries1 cup
Nectarines1 large
Prunes10 medium
Raisins1/4 cup
Meat
Chicken3 ouncesBeef3 ounces*Bacon3 slices
Fish3 ounces*Ham3 ounces*Bologna1 slice
*Canned salmon, tuna3 ouncesLamb3 ounces*Corned beef3 ounces
Turkey3 ouncesPork, fresh3 ounces*Frankfurter1
Vegetables**
Carrot1 largeBroccoli1/2 cupCorn1/2 cup
Celery1 stalkBeets1/2 cup*Olives10
Dry beans, cooked1/2 cupPeas1/2 cup
Greens, cooked1/2 cup
Potato, baked1 medium
Spinach1/2 cup
Squash, winter1/2 cup
Sweet potato1 large
Tomato1 large
*Tomato juice1 cup
Other
Molasses2 tablespoons*Dill pickle1Butter1 tablespoon
Nuts, unsalted1/2 cupPeanut butter2 tablespoonsSalad dressing1 tablespoon
* These foods have a high sodium content (greater than 300 mg per serving).
** Canned vegetables have a much higher sodium content than fresh or frozen vegetables.
1J. Anderson, Colorado State University Cooperative Extension foods and nutrition specialist and professor; L. Young, M.S., former graduate student; and E. Long, graduate student, food science and human nutrition.12/92. Revised 8/08. Go to top of this page.
Updated Friday, August 03, 2012
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Researchers claim NHS drug decisions 'are flawed


Researchers claim NHS drug decisions 'are flawed'

By Jane DreaperHealth correspondent, BBC News
Pills in a handNICE decides which drugs are cost effective on the NHS

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The formula used by the NHS to recommend which drugs should be funded is "flawed" and should be scrapped, researchers say.
The European Commission-funded study tested the assumptions of the system used by NICE (the National Institute for Health and Clinical Excellence).
Researchers concluded the watchdog's system failed
to reflect variations in views on illness and disability.
NICE called the study "limited" and said the measure it used was the best.
NICE uses a method called quality-adjusted life years (QALY) for assessing the value of new drug treatments in England and Wales. A similar system is used by the Scottish Medicines Consortium (SMC).
The formula looks at the cost of using a drug for a year and weighs it against how much someone's life can be extended and improved. Generally if a treatment costs more than £20,000-30,000 per QALY, it would not be recommended as cost-effective by NICE.

“Start Quote

"This isn't a scientific way to classify and prioritise the drugs - mathematically, it's totally flawed.”
Ariel BeresniakResearch leader
The European Consortium in Healthcare Outcomes (ECHOUTCOME) researchers will present their findings at a conference in Brussels on Friday.
Their work has already prompted a backlash by UK-based experts, who defended the current system for making decisions.
The researchers analysed a detailed questionnaire with more than 1,300 respondents - including 301 in the UK.
Their findings criticised the QALY system for grading different states of health. The researchers said people varied in their views about the impact of different levels of illness or disability, and in their approach to risk.
They also found that people's willingness to sacrifice remaining years of life in order to have better health varied enormously over different periods of time.
The researchers said 71% of the respondents would prefer to live 15 years in a wheelchair than die after 10 or five years in a wheelchair - but the remaining 29% said they would prefer to die earlier rather than spend 15 years in a wheelchair.
The project leader, Ariel Beresniak, a French doctor and economist who used to work in the drug industry, said: "Important decisions are being made on the basis of QALY, but it produces the wrong results.
"This isn't a scientific way to classify and prioritise the drugs - mathematically, it's flawed.
"We think it is time to open this debate, particularly as some of the newer European countries are trying to organise their health assessment systems and might be considering QALY.
"NICE has made negative recommendations about many major innovative drugs, based only on arbitrary incremental cost per QALY.
"Agencies such as NICE should abandon QALY in favour of other approaches."
Cost-benefit approach
A similar method is used by Canada and Australia for assessing new treatments.
The researchers suggest instead using a cost-benefit approach - such as how many cases of remission a drug can provide, or how many relapses it might prevent.
A NICE representative said: "We need to use a measure that can be applied fairly across all diseases and conditions. The QALY is the best measure anyone has yet devised to enable us to do this.
"It's developing and improving all the time and the criticisms in this rather limited study haven't shaken our confidence in its value to NICE in helping make decisions on the best way to use new and sometimes very expensive drugs and other health technologies."
John Cairns, professor of health economics at the London School of Hygiene and Tropical Medicine and a member of the NICE's appraisal committee for 10 years, said: "QALYs are certainly not perfect and we should be looking for better ways of informing decision making.
"But getting rid of an imperfect system without replacing it with a better one is not the way forward."
Dr Andrew Walker, an economist at the University of Glasgow, with 10 years' experience of reviewing new medicines at the SMC, said: "I am amazed it has taken these authors three years and one million euros to establish what we already know, that QALYs are not perfect.
"Anyone who makes decisions using QALYs and who cannot think of at least three issues with them is not thinking hard enough.
"As an alternative they propose cost per remission in arthritis, but I ask them to tell me how they define remission, how long remission lasts and how much we are willing to pay for one remission.
"If we want to spend more on cancer medicines, it has to come from somewhere. The researchers speak as though there were no budget limits."

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Friday 25 January 2013

Quadruple helix' DNA seen in human cells


'Quadruple helix' DNA seen in human cells

Jonathan Amos By Jonathan Amos Science correspondent, BBC News
A representation of the four-stranded structure (L) and fluorescent markers reveal its presence inside cells (R) A representation of the four-stranded structure (L) with fluorescent markers revealing its presence inside cells (R)

Cambridge University scientists say they have seen four-stranded DNA at work in human cells for the first time.
The famous "molecule of life", which carries our genetic code, is more familiar to us as a double helix.
But researchers tell the journal Nature Chemistry that the "quadruple helix" is also present in our cells, and in ways that might possibly relate to cancer.
They suggest that control of the structures could provide novel ways to fight the disease.
"The existence of these structures may be loaded when the cell has a certain genotype or a certain dysfunctional state," said Prof Shankar Balasubramanian from Cambridge's department of chemistry.
"We need to prove that; but if that is the case, targeting them with synthetic molecules could be an interesting way of selectively targeting those cells that have this dysfunction," he told BBC News.
Tag and track It will be exactly 60 years ago in February that James Watson and Francis Crick famously burst into the pub next to their Cambridge laboratory to announce the discovery of the "secret of life".
What they had actually done was describe the way in which two long chemical chains wound up around each other to encode the information cells need to build and maintain our bodies.
Today, the pair's modern counterparts in the university city continue to work on DNA's complexities.
Balasubramanian's group has been pursuing a four-stranded version of the molecule that scientists have produced in the test tube now for a number of years.
It is called the G-quadruplex. The "G" refers to guanine, one of the four chemical groups, or "bases", that hold DNA together and which encode our genetic information (the others being adenine, cytosine, and thymine).
The G-quadruplex seems to form in DNA where guanine exists in substantial quantities.
And although ciliates, relatively simple microscopic organisms, have displayed evidence for the incidence of such DNA, the new research is said to be the first to firmly pinpoint the quadruple helix in human cells.
'Funny target' The team, led by Giulia Biffi, a researcher in Balasubramaninan's lab, produced antibody proteins that were designed specifically to track down and bind to regions of human DNA that were rich in the quadruplex structure. The antibodies were tagged with a fluorescence marker so that the time and place of the structures' emergence in the cell cycle could be noted and imaged.
This revealed the four-stranded DNA arose most frequently during the so-called "s-phase" when a cell copies its DNA just prior to dividing.
Prof Balasubramaninan said that was of key interest in the study of cancers, which were usually driven by genes, or oncogenes, that had mutated to increase DNA replication.
If the G-quadruplex could be implicated in the development of some cancers, it might be possible, he said, to make synthetic molecules that contained the structure and blocked the runaway cell proliferation at the root of tumours.
"We've come a long way in 10 years, from simple ideas to really seeing some substance in the existence and tractability of targeting these funny structures," he told the BBC.
"I'm hoping now that the pharmaceutical companies will bring this on to their radar and we can perhaps take a more serious look at whether quadruplexes are indeed therapeutically viable targets."
Prof Shankar Balasubramanian Prof Shankar Balasubramanian in front of a painting by artist Annie Newman that represents quadruplex DNA

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Why are the British revolted by the idea of horsemeat?


Why are the British revolted by the idea of horsemeat?

Burgers and sausages on BBQ

In today's Magazine

Horsemeat has been found in beefburgers on sale in UK and Irish Republic supermarkets. But why do the British have such a revulsion over the idea of eating horsemeat?
The discovery of horse DNA in burgers in major supermarkets such as Tesco and Iceland has been met with alarm among consumers.
Horse-eating, or hippophagy, spread in Europe in the 19th Century, after famines caused several governments to license horse butcheries.
The meat is still commonly consumed in France and Belgium, as well as parts of Central Asia and South America.
So why are the British so squeamish about eating horse?

The answer

Horse eating carrots and apple
  • Horses are seen as pets
  • Historically, they were useful for transport and war
  • There are emotional connotations
There is no real logic as to why plenty of Britons are perfectly willing to eat cows, pigs, and chickens, but see horses as taboo, according to Dr Roger Mugford, an animal psychologist who runs the Animal Behaviour Centre.
"I'm a farmer and there is an irony. Why are horses different from pigs and lambs?" he says.
Part of the reason is people frequently see horses as pets, and humans tend to put "extra qualities and values" on animals they call pets, he says.
"As soon as you give an animal a name, how can you eat it? I've got lambs, sheep, with names - they live forever. I don't name the commercial flock, which won't," he says.

Quite the fashion

Horse-meat butcher in Paris
From Curiosities of Food by Peter Lund Simmonds, published 1859
At Paris, where all eccentricities are found and even encouraged, one of the latest gastronomic innovations is the use of horse-flesh.
This social phenomenon of making the horse contribute to the nourishment of the human race is not altogether new. The ancient Germans and Scandinavians had a marked liking for horse-flesh. The nomad tribes of Northern Asia make horse-flesh their favourite food.
With the high ruling prices of butcher's meat, what think you, gentlemen and housekeepers, of horse flesh as a substitute for beef and mutton?
Banquets of horse-flesh are at present the rage in Paris, Toulouse and Berlin. The veterinary schools there pronounce horse-bone soup preferable beyond measure to the old-fashioned beef-bone liquid, and much more economical.
History is also responsible for attitudes towards horses, according to Mugford.
"Horses helped out in warfare. There have been huge sacrifices alongside riders in historic battles. And there are sentimental depictions like War Horse," he says.
Their widespread use as working animals has had a lasting effect, argues food historian Ivan Day.
"We have to remember at one point, before railways, horses were the main means of transport. You don't eat your Aston Martin," he says.
Food historian Dr Annie Gray agrees the primary reasons for not eating horses were "their usefulness as beast of burden, and their association with poor or horrid conditions of living".
She suspects the practical considerations have become so embedded in culinary norms that horseflesh has garnered emotional connotations.
But all of the above reasons apply as much to France as they do to the UK. There must be more to it.
"It enables us to have yet another point of difference with the French," says Gray.
"Beef has long been symbolic of Englishness and therefore anything we can do or say to put British beef on a pedestal is usually done - ergo the thought that the French eat horse while we eat good beef becomes a chauvinistic way of asserting national identity," she says.

Horsemeat production levels in 2009

  • China - 168,000 tonnes
  • Mexico - 81,749 tonnes
  • Kazakhstan - 71,387 tonnes
  • Russia - 48,936 tonnes
  • Argentina - 37,712 tonnes
  • Mongolia - 35,582 tonnes
Source: United Nations' Food and Agriculture Organisation
Gray, who lived in France for three years, says for her, it is completely natural to eat horsemeat as it was sold at her local butcher.
"I am far more concerned with where the food is from. I would far rather eat ethically sourced, well-cared for horse, than battery chicken, for example," she says.
So are attitudes changing at all?
Peta says the thought of unexpectedly tucking into a horse burger has "rightly shocked the nation". But it says Britons who say "neigh" to horsemeat do so only because they find ponies "cute".

Who, what, why?

Question mark
A part of BBC News Magazine, Who, What, Why? aims to answer questions behind the headlines
"Why is one species cherished while another is spurned? If this story has shocked people, they should consider leaving all flesh off their plates and going vegan," it says.
Rather than seeing them as "cute", others may be more inclined to think of horses as majestic, or associate them with nobility.
The killing of horses for meat is still an emotive subject as many people see them as companion animals rather than a food source, according to the RSPCA.
But the proliferation of horsemeat jokes on Twitter suggests other people are seeing the lighter side of the story.
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Contaminated horsemeat sold for food, FSA admits


Contaminated horsemeat sold for food, FSA admits

Mary CreaghMary Creagh has called for action to stop any more horses with bute entering the food chain

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The Food Standards Agency has admitted five horses which tested positive for a drug harmful to humans were exported to France for food.
Earlier, shadow environment secretary Mary Creagh said "several" UK-slaughtered horses with phenylbutazone, or bute, may have been sold for food.
The FSA said it identified eight cases of bute-positive horsemeat in 2012, none of which was for the UK market.
The drug is banned from being consumed by humans within the EU.
The FSA added that the other three horses which tested positive did not enter the food chain.
"Where the meat had been exported to other countries, the relevant food safety authorities were informed," it said. "None of the meat had been placed for sale on the UK market."
The news comes after traces of horse and pig DNA was recently found in some burgers.
Some of these were sold in Tesco, Iceland, Lidl, Aldi and Dunnes stores in the UK and Irish Republic. Tesco took out adverts in British newspapers apologising for selling some of the burgers.
There is no suggestion that these burgers contained phenylbutazone.
'Right to know'
Phenylbutazone is an anti-inflammatory drug which is given to horses for the treatment of lameness, pain and fever.
It is thought to cause bone marrow disorders in rare cases - and horses that have been administered the drug should have the information recorded on their passport.
image of David ShukmanAnalysisDavid ShukmanScience editor, BBC News
For horsemeat containing bute to get into the food chain, several safety processes have to fail.
First the horse's passport tracking its drug history has to be misleading - an illegal act in itself.
Then the horse has to get past the spot checks - relatively easy because not many are carried out.
Finally, the meat has to end up being processed and sold for human use - almost always on the Continent, very little being eaten here.
The numbers involved in this scenario cannot be large since only around 8,000 horses are slaughtered each year.
But checks since 2007 do show bute turning up in small but consistent quantities. And the stuff is best avoided.
A specialist Defra committee says it has "serious adverse effects". Real harm is very unlikely, but the episode once again raises awkward questions about the international meat trade.
But Labour claims the issuing of horse passports in the UK is fragmented, as there are 75 approved issuing organisations in the UK, with no national database to track the information.
Speaking prior to the FSA's statement, Ms Creagh told agriculture minister David Heath in the Commons: "I am in receipt of evidence showing that several horses slaughtered in UK abattoirs last year tested positive for phenylbutazone, or bute, a drug which causes cancer in humans and is banned from the human food chain.
"It is possible that those animals entered the human food chain."
When Ms Creagh asked if Mr Heath was aware of the phenylbutazone cases to which she referred, the minister replied: "The Food Standards Agency carry out checks in slaughterhouses to ensure that equine animals presented for slaughter are fit for human consumption in the same way as they do for cattle, sheep and other animals.
"In addition, the FSA carry out subsequent testing for phenylbutazone and other veterinary medicines in meat from horses slaughtered in this country.
"Where positive results for phenylbutazone are found, the FSA investigates and takes follow-up action to trace the meat."
Ms Creagh then asked if that meant Mr Heath was aware of the issue.
"I'm astonished that you have not raised this and I think the public have a right to know," she said.
'No evidence'
She also said the news was a "very serious development" and demanded action to ensure that "illegal and carcinogenic horsemeat stops entering the human food chain".
And she called on the government to reverse a "reckless" decision to end the National Equine Database.
But Mr Heath replied: "There is no difficulty in tracing the use of a horse passport. To suggest the National Equine Database was required to do that is simply erroneous."
Alastair Hay, professor of environmental toxicology at the University of Leeds, disputed Ms Creagh's claims about the drug causing cancer in humans.
He said there was "no convincing evidence" of phenylbutazone's carcinogenicity in humans "because in the individuals studied many other drugs had also been taken and any one of these might have caused the cancers seen".
And there is no animal evidence either that it is a carcinogen, he added, saying that "phenylbutazone is not classifiable as to its carcinogenicity" according to the International Agency for Research on Cancer.
"The reason the chemical is not for human consumption appears to be rare and idiosyncratic responses in humans to the chemical. These include aplastic anaemia and some other disorders of the bone marrow. But these are not cancer events."

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