LONDON (Reuters) - Prince Philip, the 91-year-old husband of the Queen, is making satisfactory progress in hospital after an operation on Friday, a royal spokesman said.

His wife of 65 years carried on with her official engagements, visiting state broadcaster, the BBC, just half a mile from the central London hospital where the operation took place.

Philip, who turns 92 next week, was admitted to the London Clinic on Thursday and is expected to remain for two weeks after what Buckingham Palace described as "an exploratory operation following abdominal investigations".

"The results will now be analysed," the palace said in a statement. "At this early stage he is progressing satisfactorily."

It was the fourth time Prince Philip, also known as the Duke of Edinburgh, has undergone hospital treatment since Christmas 2011.

Philip was admitted to hospital during the queen's Diamond Jubilee last year with a bladder infection.

The 87-year-old queen visited the BBC's newly opened headquarters alone on Friday. She left without making public reference to Philip's hospital stay.

Philip was taken to the London Clinic by appointment after attending a garden party at Buckingham Palace with the queen. Television footage showed him in a grey top hat and tails, smiling and chatting with guests.

Prime Minister David Cameron described Philip as an "extraordinarily dedicated public servant and such an enormous support for our sovereign".

"The whole country will be thinking about him, thinking about the family and wishing him well," Cameron told reporters.

Married in 1947, Philip - the son of the exiled Prince Andrew of Greece - is renowned in Britain for his outspoken comments and off-the-cuff remarks.

Against a backdrop of trumpets and cheering crowds, the queen and Philip were joined by 2,000 guests at Westminster Abbey on Tuesday to celebrate 60 years since her coronation.

(Additional reporting by Mark Anderson and Peter Griffiths; Editing by Stephen Addison and Robin Pomeroy)

FRANKFURT (Reuters) - In a leafy suburb of Frankfurt, a state-of-the-art plant churns out up to 1 million insulin pens every day in French drugmaker Sanofi's drive to keep its no. 2 spot in the $43 billion-a-year diabetes market.

The facility is part of a hub - nicknamed Insulin City - dedicated to research and development, production, and smart technology for diabetes treatments that Sanofi says will help drive its growth as older blockbusters lose patent protection.

"This site represents an investment of more than 1 billion euros ($1.3 billion) and clearly shows our dedication to diabetes," Christian Lerche, head of R&D project direction at Sanofi's diabetes unit, told Reuters.

It is a critical moment for Lerche and his colleagues: while arch-rival and market leader Novo Nordisk has suffered a recent product setback in the United States, competition is mounting from the likes of Eli Lilly, Bristol-Myers Squibb and AstraZeneca.

All are eyeing a fast-growing global market in which the total number of diabetes sufferers is projected to leap to well over half a billion by 2030.

Lantus, a synthetic insulin developed at the Frankfurt centre in the 1990s, is currently Sanofi's top-selling drug. Last year it grew almost 20 percent to generate 5 billion euros in sales - but is set to lose patent protection in 2015.

To fend off its rivals, Sanofi is testing an improved version of Lantus in late-stage trials as well as a combination of the product with Lyxumia, a once-daily injection that controls blood sugar levels in a different way.

Investors and medics will get an insight into whether Sanofi has a new winner when data on these studies are made public at the June 21-25 American Diabetes Association annual meeting in Chicago. If positive, the results could prove Sanofi is in good shape to protect its market position.

As part of its plan to broaden its diabetes portfolio beyond drugs and injection pens, Sanofi has also rolled out new devices, like a blood glucose meter plug-in for Apple's iPhone in the United States, which allows diabetics to check their levels on a smartphone. It is currently testing more advanced versions that would e-mail readings to the doctor.

FIERCE COMPETITION

Drugmakers are competing fiercely in the type 2 diabetes market as the number of people with the disease, which is linked to obesity, continues to grow rapidly - including in emerging markets where middle classes are switching to a Western diet.

An estimated 371 million people worldwide are living with diabetes, with China now topping the list, according to the International Diabetes Federation. It predicts as many as 552 million may have the disease by 2030.

Diabetics typically start out on oral medicine but often need to move on to insulin injections to regulate their blood-sugar levels.

One side-effect of taking insulin can be hypoglycaemia, when sugar levels become dangerously low.

The new formulation of Lantus promises to last longer and reduce the incidence of hypoglycaemia seen with the old version - a drawback that Novo Nordisk has highlighted when touting its big new product hope, a novel insulin called Tresiba.

Although Tresiba is approved in Europe, Novo Nordisk suffered a setback in the United States where concerns over potential heart side effects mean new tests are needed, delaying a U.S. launch by several years.

That delay could play straight into Sanofi's hands, provided the improved version of Lantus avoids similar safety issues.

Deutsche Bank analysts expect the latest clinical trials to confirm a good profile for the Sanofi product, increasing investors' confidence that the French group can not only protect but also grow its diabetes business beyond 2016.

Sanofi shares have outperformed the European drugs sector by 16 percent over the past 12 months on growing optimism that the company will find new growth drivers, in diabetes and elsewhere, to offset loss of patent protection on older medicines.

BIOSIMILAR THREAT

Still, the pressure is on. Sanofi needs to make its new Lantus a success because it is likely to face competition from a so-called biosimilar version of the original Lantus made by Eli Lilly, the world's no. 3 insulin maker.

Because Lantus is a complex biological drug, it is difficult to make chemically identical generic versions but rivals can develop a product that is very similar.

"Since Eli Lilly is an established diabetes player, that's quite a threat," said Valentina Gburcik, a healthcare analyst at consulting firm GlobalData.

At the same time, Sanofi faces indirect competition from the growing class of injectable GLP-1 medicines that stimulate insulin production when blood sugar levels become too high.

Sanofi's own Lyxumia is just such a product but the GLP-1 landscape is becoming increasingly crowded. Novo Nordisk is pushing its top-seller Victoza hard in the face of competition from Byetta and Bydureon, which are now sold jointly by Bristol-Myers and AstraZeneca, after they bought out Amylin Pharmaceuticals. Several others are waiting in the wings.

Having launched Lyxumia in Europe, Sanofi is working to develop a pen that would deliver a combination of the treatment with Lantus.

"Lyxumia will take a small market share by itself, but it may grab considerable market share from Lantus biosimilars because the combination shows a much better profile than Lantus alone," Gburcik said.

There is plenty of work to keep the diabetes team in Frankfurt busy. ($1 = 0.7579 euros)

(Editing by Ben Hirschler and Mark Trevelyan)

"If there is no basis to the , then how do you explain the suns alignment with the center of our galaxy that is predicted to occur on Dec. 21?"

Putting as earnest a look on my face as possible, I replied, "Youre absolutely correct the sun will indeed be aligned with the center of our galaxy on Dec. 21." I then quickly added, "But of course that happens every year on Dec. 21." []

The look on my inquisitors face was priceless. "Really? But how can that be?"

The sun's annual path

As the Earth moves around the sun, we see the sun change its position against the background stars a full 360-degree circle around the sky during the course of a year. That apparent path is known to astronomers asout toward the sky.

As it turns out, the moon and the seven other planets that comprise thealso move in orbits whose planes dont vary too greatly from that of Earths orbit. As a result, the moon and the other planets also appear to stay relatively close to the ecliptic.

The sun never deviates from the ecliptic and so as Earth travels around it, from our perspective, it will always take the exact same path against the same background stars every year.

Since when were looking towardwere also looking toward the center of the Milky Way, when the sun reaches that same point on the ecliptic in Sagittarius on Dec. 21 every year, the sun and the galaxys center are indeed aligned.

The ecliptic is a very important feature because it marks "the pathway," so to speak, for the sun, moon and planets as they move across the sky. Most sky charts plot the position of the ecliptic for this reason, for it provides sky watchers with a clue as to where one or more of these objects will appear.

Because theyre not located exactly in the same orbital plane as Earth, the moon and planets usually are not found exactly on the ecliptic line, but rather within several degrees of it. Thus, instead of a line, we find the moon and planets wandering along the sky within a band that encompasses the entire sky, which we call the zodiac.

The ecliptic runs exactly along the middle of that zodiacal band.

The 'classic 12'

The word "zodiac" is derived from the Greek, meaning "animal circle." A sort of "celestial zoo."

And with the sole exception of one of the "classic 12"that belong to the zodiac, all of the zodiac members refer to living things. Many of these constellations are named for animals, such as Leo, the Lion, Taurus, the Bull and Cancer, the Crab, just to name a few.

The sole inanimate member is Libra, the Scales.

All of these names can be readily identified on sky charts and are familiar to millions of horoscope users (who ironically would be hard pressed to find them in the actual sky.) []

If we could see the stars in the daytime, we would see the sun slowly wander from one constellation of the zodiac to the next, making one complete circle around the sky in one year.

Ancient astrologers were able to figure out where the sun was on the zodiac by noting the last zodiacal constellation to rise ahead of the sun, or the first to set after it. Obviously, the sun had to be somewhere in between.

Each month a specific constellation was conferred the title, "house of the sun," and in this manner each month-long period of the year was given its "sign of the zodiac."

Some discrepancies

A couple of years ago, a board member of the Minnesota Planetarium Society caused quite a stir when he pointed out that the zodiacal sign that had been assigned for a given month in the newspaper horoscope is not where the sun actually is for that month.

He pointed out that, in reality, todays astrologers continue to adhere toby at least a millennium. For instance, according to astrology, youre a Leo if you were born between July 23 and Aug. 22 because thats the time of year where the sun supposedly is in the zodiac.

That might have been true 1,000 years ago, but no longer. In fact, on July 23, the sun is not in Leo, but in Cancer. This discrepancy is due to the "wobble" of the Earths axis (known as precession).

As a consequence, there then came the revelation (even though it has been known by astronomers for a long time) that astrologers continue to adhere to star positions that for all intents and purposes are out of date by 10 centuries or more.

Outcasts of the zodiac

One thing that I have never been able to understand is why astrologers fail to recognize Ophiuchus, the serpent holder. He certainly should be considered as a card-carrying member of the zodiacal fraternity since the sun spends more time traversing through Ophiuchus than .

It officially resides in Scorpius for less than a week: from Nov. 23 to 29. It then moves into Ophiuchus on Nov. 30 and remains within its boundaries for more than two weeks until Dec. 17. And yet, the serpent holder is not considered a member of the Zodiac.

In addition, because theand planets are often positioned either just to the north or south of the ecliptic, they sometimes appear within the boundaries of several other non-zodiacal star patterns.

The revered Belgian astronomical calculator Jean Meeus has pointed out that there are actually 22 zodiacal constellations in which the moon and some of the planets from Mercury to Neptune can occasionally enter.

In addition to the 12 classical zodiacal signs and , we can also add: Auriga, the charioteer; Cetus, the whale; Corvus, the crow; Crater, the cup; Hydra, the water snake; Orion, the hunter; Pegasus, the flying horse; Scutum, the shield; and Sextans, the sextant.

And in case youre interested, in the upcoming month, the moon will be in Orion on May 13, Sextans on May 19 and Ophiuchus on May 26.

I guess you can say that so far as the celestial zoo is concerned, these three constellations are on the outside of the cage looking in.

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for the New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York. Follow us on , and . Original article on .

In one of the most electric moments since the IRS controversy erupted nearly two weeks ago, Lois Lerner unwaveringly but briefly defended herself before the House Oversight and Government Reform Committee. But she would say no more, citing legal advice in the face of a federal investigation.

Members of Congress have angrily complained that Lerner and other high-ranking IRS officials did not inform them that conservative groups were singled out, even though lawmakers repeatedly asked the IRS about it after hearing complaints from local tea party groups.

The Justice Department has launched a criminal probe of the murky events over the 2010 and 2012 election campaigns, saying it is looking into potential civil rights violations. Top IRS officials say Lerner didn't tell them for nearly a year after she learned that agents working under her had improperly singled out conservative groups for additional scrutiny when they applied for tax-exempt status.

Under unrelenting criticism most forcefully from Republicans but also from Democrats and people outside politics administration officials from President Barack Obama on down have denounced the targeting as inappropriate and inexcusable.

Lerner, who heads the IRS division that handles applications for tax-exempt status and first disclosed the targeting at a legal conference, has said the same. But she also spoke up for herself Wednesday, sitting stern-faced at the committee witness table.

"I have not done anything wrong," she said. "I have not broken any laws, I have not violated any IRS rules or regulations, and I have not provided false information to this or any other congressional committee."

By one lawmaker's count, Lerner was asked 14 times by members of Congress or their staffs without revealing that the groups had been targeted. On Wednesday, lawmakers didn't get a chance to ask Lerner again.

Nine minutes after she began speaking, Lerner was excused, though committee Chairman Darrell Issa, R-Calif., said he might recall her. He and other Republicans say they believe she forfeited her Fifth Amendment privilege not to testify by giving an opening statement in which she proclaimed her innocence, but several law professors were skeptical they could make that stick.

Issa later said he would consult with others including her lawyer and House attorneys before determining whether to summon her again, hopefully deciding by the time Congress returns from an upcoming recess early next month.

"She's a fact witness with a tremendous amount that she could tell us," Issa said.

By leaving early, Lerner missed out on a six-hour grilling that three other witnesses endured.

The hearing was Congress' third on the IRS controversy in the past week. Taken together, testimony by current and former officials indicates that Lerner's actions were consistent with theirs: Once officials learned that conservative groups were being targeted, they say they made sure the practice was stopped, but they were slow to tell superiors, if they did so at all.

They also didn't tell Congress, until Lerner herself made it public at a May 10 legal conference.

"Think about it. For more than a year, the IRS knew that it had inappropriately targeted groups of Americans based on their political beliefs without mentioning it," Issa said. "There seemed to be a culture of insulation that puts higher priority on deniability than addressing blatant wrongdoing."

The hearings have been notable for what they have not shown as well as what they have. No evidence has emerged that anyone outside the IRS, including the White House, directed agents to go after conservative groups. And there has been no evidence that anyone outside the IRS was made aware that the groups were being targeted until a few weeks before the inspector general released his report on the situation last week.

Still, Obama's top spokesman said Wednesday the White House is facing "legitimate criticisms" for its shifting accounts about who knew what, and when they knew it.

Press secretary Jay Carney first said only Obama's top lawyer knew the IRS was being investigated in the weeks before the inspector general's report was released. Later, he said the chief of staff and other top officials also knew.

"There have been some legitimate criticisms about how we're handling this," Carney said. "And I say 'legitimate' because I mean it."

The report said IRS agents in a Cincinnati office started targeting tea party and other conservative groups for additional scrutiny in March or April of 2010. By August 2010, "tea party" became part of a "be on the lookout," or "BOLO" list of terms to flag for additional screening.

Lerner learned in June 2011 that agents in her division were singling out groups with "Tea Party" and "Patriots" in their applications for tax-exempt status, the report said. She ordered agents to scrap the criteria immediately, but later it evolved to include groups that promoted the Constitution and the Bill of Rights.

"After that date, Ms. Lerner had 14 opportunities in direct and distinct interactions with the Ways & Means Committee and with this committee 14 different occasions where she could have set the record straight, and she chose not to do it," said Rep. Jim Jordan, R-Ohio.

Lerner, 62, is an attorney who joined the IRS in 2001. She expressed pride in her 34-year career in federal government, which has included work at the Justice Department and Federal Election Commission, and she said she currently oversees 900 workers and a budget approaching $100 million.

She has faced no discipline for her actions, IRS officials said. A new acting commissioner is conducting a 30-day review of the division.

J. Russell George, the Treasury Department inspector general for tax administration, has blamed ineffective management for allowing agents to improperly target conservative groups for more than 18 months.

On Wednesday, he hinted that there may be more revelations to come. He told the oversight committee that his office has since uncovered other questionable criteria used by agents to screen applications for tax-exempt status. But he refused to elaborate.

"As we continue our review of this matter, we have recently identified some other BOLOs that raised concerns about political factors," George said. "I can't get into more detail at this time as to the information that is there because it's still incomplete.

Lerner's supervisors said they, too, were kept in the dark for nearly a year. One of those supervisors was Deputy IRS Commissioner Steven Miller, who later became acting head of the agency. He was forced last week to resign.

Miller said he first learned in May 2012 that conservative groups had been singled out. He promptly told his boss, IRS Commissioner Douglas Shulman.

But for the second straight day, Shulman testified that he didn't tell anyone in the Treasury Department or the White House because he was awaiting the results of an audit by the agency's inspector general. The IRS is part of the Treasury Department.

Shulman stood by that Wednesday, and was pressed once again by lawmakers about why he didn't say anything.

"At the time I learned about this list, I felt I was taking the appropriate actions and that my course was the proper one, and I still feel that way today," Shulman said.

Shulman, who was appointed by President George W. Bush, left in November when his five-year term expired. Miller became acting commissioner when Shulman left.

In the spring of 2012, George told a top Treasury official that the inspector general's office was investigating complaints by conservative groups. George, however, did not reveal any details about what he had uncovered, said Deputy Treasury Secretary Neal Wolin, who also testified Wednesday.

"He told me only of the fact that he had undertaken such an audit, and he did not provide any findings," Wolin testified. "I told him that he should follow the facts wherever they lead. I told him that our job is to stay out of the way and let him do his work."

Wolin said he didn't tell any of his superiors at Treasury or the White House about the investigation.

___

AP White House Correspondent Julie Pace contributed to this report.

___

Follow Stephen Ohlemacher on Twitter: http://twitter.com/stephenatap

Nontraditional military activities such as peacekeeping, disaster relief and anti-piracy operations offer opportunities to boost cooperation and "contribute to greater mutual confidence and understanding," Donilon told Gen. Fan Changlong, a vice chairman of the commission overseeing China's armed forces.

A "healthy, stable, and reliable military-to-military relationship" is an essential part of overall China-U.S. ties, Donilon said at the start of the meeting at China's hulking Defense Ministry building in central Beijing.

Donilon met with a range of Chinese officials over two days to hammer out plans for the June 7-8 summit, the first face-to-face meeting between the presidents since Obama's re-election and Xi's promotion to Communist Party chief last November.

Their informal summit at the private Sunnylands estate of the late publishing tycoon Walter Annenberg in southern California will come months before the two leaders had been originally scheduled to meet, underscoring concerns that the U.S-China relationship was drifting.

Xi told Donilon on Monday that relations were at a critical juncture, and that the sides must now "build on past successes and open up new dimensions for the future."

Building trust between their militaries is one of the main challenges the sides face in seeking to stop a drift in relations, troubled by issues from trade disputes to allegations of Chinese cyberspying.

Although Washington and Beijing have talked about boosting military cooperation for more than a decade, distrust runs high and disagreements over Taiwan, North Korea and China's assertive claims to disputed territories in the East and South China seas remain potential flashpoints.

The U.S. has repeatedly questioned the purpose of China's heavy military buildup over the past two decades, while Beijing is deeply suspicious of Washington's new focus on military alliances in Asia and plans to redeploy more weaponry and troops to the Asia-Pacific region.

Steps to increase benign interactions between their militaries have been modest so far, including joint anti-piracy drills in the Gulf of Aden and a classroom natural disaster response simulation. The U.S. has also invited China to take part in large U.S.-led multinational naval exercises, though China has not said if it would participate.

Apart from purely military issues, distrust has deepened as the U.S. feels its world leadership challenged and China, its power growing, demands greater deference to its interests and a larger say over global rule-setting. Chinese officials and state media regularly say Washington is thwarting China's rise by hemming Beijing in through its Asian alliances and discouraging Chinese investment in the U.S. on grounds of national security.

LEEDS, England, May 27 (Reuters) - England captain Alastair Cook completed his 25th test century before tamely falling for 130 as the hosts continued to bat New Zealand out of the second and final test with a lead of over 400 on Monday.

Cook, who declined to make New Zealand follow-on on Sunday after they were dismissed for 174, was again untroubled until he danced down the wicket and miscued spinner Kane Williamson to Tim Southee at mid-off.

Williamson then took his third wicket of the innings when Ian Bell, looking to push the scoring along, top-edged a slog-sweep.

At lunch on the fourth day at Headingley, England were 249 for three, a lead of 429, and set to secure a series victory after winning the first test at Lord's by 170 runs.

Jonathan Trott was unbeaten on 76 after sharing a second-wicket stand of 134 with Cook.

In contrast to his stubborn and defensive occupation of the crease on Sunday, Trott was in a more attacking mood and produced some deft flicks on both sides of the wicket.

New Zealand captain Brendon McCullum was forced into a policy of containment after his bowling attack, already depleted by the absence of a frontline spinner with Bruce Martin, suffered another setback with left-arm seamer Trent Boult unable to bowl on Monday.

Boult, who took five wickets in the first innings and swung the ball, suffered a right side strain on Sunday. (Editing by Ed Osmond)

The , a daily record of atmospheric carbon dioxide, has been running continuously since March 1958, when a carbon dioxide monitor was installed atin Hawaii. On its first day, the observatory measured a carbon dioxide concentration of 313 parts per million (ppm). That number means there were 313 molecules of carbon dioxide in the air for every 1 million air molecules.

The number continued to climb through May 1958 and then slowly started to drop, reaching a minimum in October that year. This maximum-minimum pattern, repeated seasonally, reveals how trees withdraw carbon dioxide from the air in summer to grow and then release it through dead, decaying leaves and wood in the winter.

Upward creep

But humans release carbon dioxide into the air, too, by burning fossil fuels. This activity has caused the Keeling Curve to creep ever upward since 1958: The lows get a little higher each year, as do the highs. []

Because carbon dioxide typically peaks in May, researchers are expecting the Keeling Curve to break a milestone of 400 ppm this year. (If not, the number will almost certainly be reached in May 2014.) As of May 1 of this year, the last day data was available, the Mauna Loa observatory recorded 399.39 ppm of carbon dioxide in the air.

There will be no huge atmospheric or climatic shift once carbon dioxide hits 400 ppm, but the milestone has symbolic significance, said Michael Mann, a climate scientist at Pennsylvania State University.

"It is a reminder of just how uncontrolled this dangerous experiment we're playing with the planet really is," Mann told LiveScience.

What 400 ppm means

In the 1,000 years that occurred before the Industrial Revolution of the 18th century, atmospheric carbon dioxide held steady at around 270 to 280 parts per million.

Scientists believe that the most recent period to reach 400 ppm was the Pliocene Epoch, between 5 million and 3 million years ago, according to the Scripps Institution of Oceanography, which keeps track of the Keeling Curve.

Back then, it was a different world. Global average temperatures during the period were between 5.4 and 7.2 degrees Fahrenheit (3 to 4 degrees Celsius) higher than today, and sea level was as much as 131 feet (40 meters) higher in some places. Even the least-affected regions saw16 feet (5 meters) higher than today's.

A major difference between then and now, though, is the speed at which carbon dioxide is rising today. Typically, in the last 40 to 50 years, the Keeling Curve shows increases of 2 to 2.5 ppm a year, Mann said. In the 1950s and 1960s, carbon dioxide increased by less than 1 ppm each year, according to Scripps.

"We're on course for more than 450 ppm in a matter of decades if we don't get ourunder control quite soon," Mann said.

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NEW YORK (Reuters Health) - Herbal supplements aimed at improving men's sexual abilities often contain the active ingredients in erectile dysfunction pills such as Viagra, according to a new study.

Additionally, researchers found that some of these over-the-counter herbal remedies contained more of the ingredient than is allowed in prescription-only pharmaceuticals.

"It's pretty scary stuff," said Neil Campbell, the lead author of the study and a researcher at Pfizer, which sells Viagra. "These products are not herbal at all, they're adulterated."

The U.S. Food and Drug Administration, which is in charge of regulating herbal supplements, posted 11 warnings to consumers in 2013 alerting them of unlabeled pharmaceuticals being found in these products.

Campbell and his colleagues analyzed 91 samples from 58 products.

They sent undercover consumers into convenience stores and gas stations in the Atlanta and Baltimore areas, and bought products such as Rize 2 The Occasion, Stiff 4 Hours, and Man King.

Although 57 of the products claimed to be "all natural," 81 percent of them contained the tadalafil or sildenafil (marketed as Cialis and Viagra, respectively) or similar ingredients that are not approved by the FDA.

The products also had labeling problems, indicating poor quality production, according to the authors. In some cases, expiration dates or lot numbers were missing, manufacturers could not be identified, or samples of the same product had different appearances.

"There's so little effort to do something the right way to produce a legitimate product," Campbell told Reuters Health. "This is an all time low."

None of 10 supplement companies contacted by Reuters Health responded to a request for comment, nor did the FDA.

Campbell said given the potential side effects and health risks associated with prescription erectile dysfunction drugs, men are "risking their lives" taking herbal sex enhancement drugs.

"Almost one patient a day says they've tried Mojo or one of these over-the-counter products," said Dr. Gregory Lowe, an assistant professor of urology at Ohio State University who was not part of this study.

"One of the big concerns is that we don't know what the patient's getting," he added.

Seven samples that Campbell's group analyzed contained only unknown substances.

"Commonly, I hear patients say, 'it worked one time and it didn't work other times.' And that fits in well with what they found here" that quality control is lacking, he added.

It's unclear where the ingredients are coming from.

Lowe advises men who are interested in taking these pills to talk to their doctors first.

He says patients often turn to these products because they are cheap - costing between $2.99 and $17.99, according to Campbell's study, published in the Journal of Sexual Medicine.

But they are taking a health risk in doing so.

Erectile dysfunction medicines can be unsafe for men taking nitrates for chest pain, but only 14 of the samples in the study included a warning against combining the drugs.

"Unfortunately, to an unwitting patient they think they're taking an herbal product," said Campbell. "It really poses a really scary threat for patient health and safety."

SOURCE: http://bit.ly/17KGjiu Journal of Sexual Medicine, online May 1, 2013.