Search results for pomegranate (6)

While distracted by a conference in late January, I missed the next exciting installment of the Edinburgh pomegranate saga.

As you will recall, a research group in Edinburgh have put out press releases in recent years about the impact of pomegranate juice on blood pressure, cortisol (a stress hormone), and testosterone.  They haven’t published any scientific papers about these findings, though they have produced a presentation at a scientific conference.

The most recent installment claims that pomegranate extract reduces hunger and food consumption. This study seems to be better designed than the previous ones: participants were randomised to pomegranate extract tablets or placebo for three weeks.  They were then given a glass of pomegranate juice and a meal.  Those who had been taking the pomegranate extract reported feeling less hungry and ate less — 22% less. It’s a pity the study didn’t measure weight, because if the 22% reduction in food consumption generalised beyond the one experimental meal it would have led to measurable weight loss over three weeks.

Again, this was a premature and unsubstantiated press release, and the experiment has not been published in a peer-reviewed journal, although the researchers do at least say they will be presenting it at a conference later in the year.

Back in May, there was a really bad Herald story on pomegranates.  At the time, I said,

Well, what we have is a story based on a press release about a small, unpublished, uncontrolled, open-label study. The most positive one could possibly be about this is “It will be worth waiting for the real publication” or,  perhaps, “I hope it’s not true, because messing with steroid hormones like that is scary”. 

Since bloggers always complain about the lack of follow-up in mainstream media, I should report back on what has happened since.  There still isn’t a publication, but there is an abstract of a conference presentation.

It’s still a small non-randomized open-label study, and one that I would call uncontrolled (in the sense that there aren’t any control participants). The researchers call it ‘controlled’, presumably because there are control measurements before the pomegranate juice was started.  There was a decrease in blood pressure and an increase in salivary testosterone. The blood pressure decrease (4/2.5 mmHg) isn’t very impressive, especially for an open-label study.  I don’t know how impressive the testosterone difference is.

The abstract, amazingly, doesn’t actually give the dose of pomegranate juice that was used. The abstract for a previous study of the same size and duration by the same researchers used 500ml/day.  According to a newspaper story this was PomeGreat brand juice, meaning that 500ml is 5 times the serving size on the package. I found a price of GBP3.39 (about NZ$ 6.60) for this daily dose (that’s the pure juice as used in the research; there are cheaper blends).

The abstract specifically says there were no conflicts of interest and no direct external funding. In previous studies the pomegranate juice has been supplied by a manufacturer, which I would have considered worth reporting as a conflict and as a source of funding.  However, the research idea did come from the researchers, not the company.

So, what other research is there that might be relevant? A PubMed search for “pomegranate testosterone” gives just four papers. Only one is in live people, a study looking at pomegranate extract in prostate cancer. This didn’t find any differences in testosterone between the two doses they examined. Interestingly, this study was motivated by the idea that pomegranate would help by reducing the production of male sex hormones.

The problem with the pomegranate research is that it’s extremely widely publicised, without having been published in peer-reviewed journals.  This gives the impression of more scientific scrutiny of the results than has actually occured. And it’s not that this publicity just happened. Since the results weren’t published, no-one would know about them without the help of some professional publicity machine.  This phenomenon is clearly to the benefit of people selling pomegranates, but not to science or nutrition. An Ireland Advertising Standard Authority decision does illustrate one way that individuals can fight back.

The conclusion is still the same as last time:

The findings about pomegranate juice could be true, but it’s clear that the target isn’t people who actually care whether they are true.

Morning Consult and Politico run a survey where they asked registered US voters to point Iran out on a map.  About a quarter could. Here are the complete results

As you will notice, there are dots everywhere. Morning Consult didn’t go in for any grandiose interpretations; they just presented the proportion of respondents getting the answer correct. Other people were less restrained. There was much wailing and gnashing of teeth over this map, on Twitter, but also at other media outlets.  For example, Rashaan Ayesh wrote at Axios

While the Middle East saw definite clustering, some respondents believed — among dozens of wild responses — that Iran was located in:

• The U.S.
• Canada
• Spain
• Russia
• Brazil
• Australia
• The middle of the Atlantic Ocean

The claim that some respondents believed Iran to be in the US or the middle of the Atlantic ocean is worrying to me.   I can’t see how a sensible journalist could possibly state as a fact that someone had a belief like that based just on the incredibly flimsy evidence that there’s a dot there on the map.  I’d want to at least have someone explicit claim that they thought Iran was in the middle of the ocean, and ideally have follow-up questions asked about where they think Iranians keep their mosques and carpets and where they grow their rice and barberries and pomegranates and walnuts and so on.

It’s a well-known phenomenon that people don’t always give the answers you want on surveys. Scott Alexander has written about the ‘Lizard-man constant’, and that’s even before you give people a clicky interactive map to play with.   It’s barely conceivable — no, actually it isn’t, but let’s pretend it is — that some people think that large continent on the upper left of the map is the Middle East, or recognise it as North America but believe Iran is in the US.

It seems much more likely to me, though, that

• they don’t know where Iran is and would rather give an obviously wrong answer than look as if they’re trying
• they clicked wrong on the map, because interactive maps are actually kind of a pain to use, especially on a phone.
• they think having heard of Iraan, Texas (pronounced Ira-an), or Persia, Iowa, will make them look clever.
• they want to mess up the survey because they hate polling or for political reasons or because they’re having a bad day

The next question, of course, is how much it matters that the majority of US voters couldn’t find Iran on a map.  Iran is relatively easy, as countries go — I knew that it had a coastline on the Persian Gulf and that it wasn’t on the Arabian Peninsula, and Iran is big enough that this is sufficient.  But suppose I thought it was where Iraq is, or Syria, as many people did. Should have an impact on my political views (assuming I’m in the US)?  It’s not clear that it should.  The potential ability of Iran to close the Straits of Hormuz (and the Doha and Dubai airports) does depend on its location, but the question of whether the US was justified in killing Qasem Soleimani or threatening to bomb Iranian cultural sites doesn’t seem affected.

The Herald has a Daily Mail story about vitamin D for making you generally feel better. It’s not so long ago that the NZ media had a lot of less supportive coverage on vitamin D — Ian Reid, Mark Bolland, and Andrew Grey won the Prime Minister’s Science Prize last year for their work showing that calcium and vitamin D aren’t all they’re cracked up to be.

The story does have some new evidence.

In the study, by a medical team in Edinburgh, volunteers were asked to cycle for 20 minutes. They were then given either a placebo or vitamin D and, two weeks later, were asked to cycle for 20 minutes again.

I linked earlier to Jeff Leek’s post on fivethirtyeight.com, because I thought it talked sensibly about assessing health news stories, and how to find and read the actual research sources.

While on the bus, I had a Twitter conversation with Hilda Bastian, who had read the piece (not through StatsChat) and was Not Happy. On rereading, I think her points were good ones, so I’m going to try to explain what I like and don’t like about the piece. In the end, I think she and I had opposite initial reactions to the piece from on the same starting point, the importance of separating what you believe in advance from what the data tell you. (more…)

The Herald has a story claiming that a set of chemicals that have been proposed as an antibacterial additive for meat actually have large effects on sex-hormone levels.  Usually this would be a story about the need to ban the chemicals immediately, but this time the headline is “‘Viagra effect’ from pomegranate juice”, and they’re in favour of it.

Of course, the ‘Viagra effect’ label is completely bogus (the quote marks suggest that it comes from the researchers’ press release, which would be very dodgy if true).  The researchers claim to have found an increase in testosterone levels in men and women who drank a daily glass of pomegranate juice.  Viagra is involved in blood vessel dilation; it has nothing to do with testosterone, and a previous suggestion that pomegranate juice might really have Viagra-like effects has been tested and rejected.

So, what about the testosterone effects?  Well, what we have is a story based on a press release about a small, unpublished, uncontrolled, open-label study. The most positive one could possibly be about this is “It will be worth waiting for the real publication” or,  perhaps, “I hope it’s not true, because messing with steroid hormones like that is scary”.  It’s reassuring to note that last year the same group said pomegranate juice reduced office stress.  In 2009, they said it reduced blood pressure and cortisol levels.   You will notice that the last link is a press release from a manufacture of pomegranate juice, who sponsored all these studies.  I haven’t linked to actual publications, because according to the PubMed database neither of these results has yet been published either.

There’s a lot of this around: a different pomegranate manufacturer has been sued by the US Federal Trade Commission (in 2010).  The Wall Street Journal wrote

The FTC’s target is not POM’s generally worded, eye-catching ads with lines such as “Cheat Death,” said an agency official. That ad showed a bottle of pomegranate juice with a rope around its neck.

Instead, the government complaint is directed at more specific health claims.In addition to talking about arterial plaque and blood flow, some POM ads describe company-funded clinical trials that, according to the company, show POM juice products can slow the progression of prostate cancer by lowering the level of antigens in the body called PSAs.

The agency’s complaint says that some of POM’s studies did not show heart disease benefits and that the prostate cancer study wasn’t conducted in a standard, scientifically rigorous manner.

The findings about pomegranate juice could be true, but it’s clear that the target isn’t people who actually care whether they are true.