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For years the husband has insisted that chocolate is a health food. He's also spun me the line that eating it is good for the rainforest, as the mature cacao trees apparently grow in mature forest. So he'll be happy with the Herald's story on his sweet treat, which has the enticing title of "Sweet news: chocolate is good for you", and comes direct from the Daily Mail, that fount of all things good in science reporting. (Not.)

Me? Not so much. Like cautious investors, I tend to subscribe to the view that if something sounds too good to be true, it probably is. 

The item begins:

Just in time for Easter, it's the news chocolate lovers have dreamt of - official confirmation that their favourite guilty pleasure can be good for you.

New research shows that eating just a single chocolate bar has a direct effect on the brain and may cut the risk of stroke.

The research on which the Daily Mail's story is based was published last week in the journal Neurology, to which - alas! - we don't have a subscription. The brief excerpt I can see indicates that the researchers were building on an earlier publication:

Larsson et al. investigated the association between chocolate consumption and risk of stroke in men, concluding that moderate chocolate consumption may lower the risk of stroke. We performed a prospective mechanistic study that may suggest a potential mechanism for this observation.

A prospective study is one that takes a group of individuals & follows them for some period of time, studying the impact of various factors on that group; 'mechanistic' means that the researchers would be looking to explain their findings in terms of physical or biological causes. In this case they were interested in the impact of eating chocolate, & apparently found that this had an impact on blood vessels; specifically, on the stiffness of the vessel walls. It would be interesting to read the actual paper because I'd like to know, for example, which blood vessels were studied, & how they determined the 'impact' of chocolate on brain cells. It's notable that there's no indication of what constituent of chocolate might be involved in any possible outcomes, so it's a very broad-brush, preliminary outcome.

In its timing this mirrors an earlier story, published just before Easter 2010. However, the 2010 story is much more balanced in scientific terms, pointing out the shortcomings of the earlier research (and that most newspapers Got It Wrong) & noting that while it was possible that eating a small quantity of chocolate might confer some benefit, the association between choccy consumption & health wasn't particularly strong. (And in fact, reported chocolate consumption appeared awfully low - the 'high intake' group reported eating a mere 7.5g/day!) 

In this week's Daily Mail story, the lead researcher is quoted as saying that

We think a reduction in stroke risk may be caused by chocolate changing how brain blood vessels behave.

It's a real pity that the DM left this next part of the message until the very end of the tale, but at least the paper does note that

chocolate also has a high sugar and fat content which can cause obesity - a definite risk factor for strokes.

I hate to dash the husband's hopes, but it would be a leetle premature to add this putative benefit to his list of reasons to eat his favourite Whitaker's bar :( 


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What follows is a piece I wrote (quite a while ago now) for students planning on sitting Scholarship Biology. It was intended to start them thinking :) I've just been asked to contribute to a panel discussion on RNZ around this subject, so thought it might be timely to re-post this article (I think time has been kind to it!).

Here's a question to consider: are humans still evolving? What sort of evidence could we use to answer this question?

We do tend to view evolution as something that happened in the past, and see the study of evolution as a 'historical' science. But nothing could be further from the truth. Evolution is an ongoing process, and we can detect its influence on the present-day human gene pool just as easily as we can view the development of our species' family tree.

Remember that evolution is essentially a change in a population's gene pool, as the result of 'drivers' such as natural selection and genetic drift. And studies of present-day human evolution look just there, at our genes. Some of these studies are summarised in a [relatively] recent paper in Science (Michael Balter (2005) "Are humans still evolving?" Science 309: 234-237), which is the basis for this posting.

To some degree the answer to this question depends on whether we are talking about ‘western’ populations. In the developed world, the combination of modern medicine, new agricultural and technological techniques, and cultural changes have significantly reduced the effects of natural selection: individuals who in the ‘old days’ would have been removed from the population (by famine, warfare, or disease) without contributing to the gene pool, now survive and have children. But in the developing countries, people are still subject to these selection pressures, so it’s probably here that we should be looking for evidence of evolutionary change: the spread of alleles that give resistance to diseases such as malaria, for example.

In those parts of the world where malaria is endemic, anyone with a genotype giving resistance to malaria would be at a selective advantage: they’d be more likely to survive and reproduce, passing their advantageous combination of genes on to at least some of their children. The overlap between the geographic spread of malaria in Africa with the presence of the sickle-cell allele is an example: individuals heterozygous for this allele are at a selective advantage over unaffected individuals (and those homozygous for the allele) where malaria is present. And other gene loci also seem to be involved in resistance to malaria. Variants of the glucose-6-phosphate dehydrogenase gene (which is involved in cellular respiration), one of the Duffy blood group alleles, and one haemoglobin C allele are all more common where malaria is endemic.

Another example is that of the “CCR5” gene. This gene codes for CCR5, a surface protein on white blood cells that is also the docking site for the HIV virus. People homozygous for a mutation (‘delta 32’) in this gene are resistant to attack by HIV, and are thus at a selective advantage in areas where HIV, and AIDS, are common. Yet the mutation is most common in white Europeans, and very rare in other ethnic groups – including Africans. AIDS is far more common in Africa than in Europe, so these differences in allele frequency are difficult to explain – unless they are the result of some other selective pressure that predates the AIDS epidemic. Scientists have dated the origins of the delta 32 mutation to around 700 years ago, and the current hypothesis is that it provided protection against an epidemic disease of that time, perhaps plague or smallpox. Can you make a prediction about the future prevalence of this particular allele, given the relative frequency of AIDS in different parts of the world, and the availability of medical care for patients?

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Here's another of those catchy science-based ditties - & definitely one I'll be adding to my collection for showing in class :) (I would have embedded it, but MT is not doing what it should today...later edit: thank goodness for IT wizards!)


And a happy St Patrick's day!

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A while back, I wrote about the so-called hCG 'diet' drops: homeopathic drops that might just possibly (depending on dilution) contain a molecule of human chorionic gonadotropin (or maybe not), and which supposedly help one to lose weight. 

Ooops, nearly forgot to mention that you need to accompany your daily dose of magic water with the greatly reduced food intake that is all you get on a 500 calories/day diet...

My attention was originally drawn to this... um... creative bit of marketing by spam emails, but these days you can buy the drops in New Zealand, as noted in the NZ Herald:

Government agencies are assessing the legality of a diet that promises people they will lose up to half a kilogram a day by using a homeopathic fertility hormone banned in the United States.

The diet, which is gaining popularity in New Zealand, involves taking a substance known as hCG and restricting food to 500 calories a day for up to 40 days.

The Herald article is reasonably sceptical - apart from the comment about taking "a substance known as hCG": if this is truly a homeopathic preparation then all the purchaser is swallowing is water**. They would not be taking biologically-active quantities of the actual hormone (which is licensed in the US only as an injectable prescription drug). 

And that amazing weight loss is pretty much what you'd expect on a diet that provides well below the calorie intake recommended for the average person.

** and remarkably expensive water, at that. According to the Herald, the NZ purveyor 

sells a 23-day suppoly of hCG - human chorionic gonadotropin - for $135 and a 40-day supply for $180. Her cheapest option is an eight- to 10-day supply for $55.

You get 60ml for that $180...

But wait, there's more: I notice they're into 'alkalising' the body as well (another idea with no biological plausibility).

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