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George Davey Smith challenges the findings of a new BMJ paper claiming that eating dark chocolate protects against Type 2 diabetes.

Xmas is supposed to be a time of goodwill, and medical journals like the BMJ print seasonal papers not intended to be taken too seriously. The topic of one of the latest papers – chocolate – has been the topic of Xmas BMJ papers in the past, but it appears this is intended to be a serious paper; it is certainly not entertaining. The paper suggests that dark chocolate can protect against type 2 diabetes. At the risk of being a Grinch at Christmas, it has to be said that this is, frankly, a meaningless paper. Indeed it is surprising to see such a paper published in 2024 in a supposedly reputable journal. (more…)

Amanda Hughes, University of Bristol; Neil Davies, University of Bristol, and Sean Harrison, University of Bristol

There’s a widespread belief that your testosterone can affect where you end up in life. At least for men, there is some evidence for this claim: several studies have linked higher testosterone to socioeconomic success. But a link is different to a cause and using DNA, our new research suggests it may be much less important for life chances than previously claimed.

In previous studies, male executives with higher testosterone have been found to have more subordinates, and financial traders with higher testosterone found to generate greater daily profits. Testosterone has been found to be higher among more highly educated men, and among self-employed men, suggesting a link with entrepreneurship. Much less is known about these relationships in women, but one study suggested that for women, disadvantaged socioeconomic position in childhood was linked to higher testosterone later in life.

The beneficial influence of testosterone is thought to work by affecting behaviour: experiments suggest that testosterone can make a person more aggressive and more risk tolerant, and these traits can be rewarded in the labour market, for instance in wage negotiations. But none of these studies show definitively that testosterone influences these outcomes because there are other plausible explanations.

Rather than testosterone influencing a person’s socioeconomic position, it could be that having a more advantaged socioeconomic position raises your testosterone. In both cases, we would see a link between testosterone and social factors such as income, education and social class.

There are plausible mechanisms for this too. First, we know that socioeconomic disadvantage is stressful, and chronic stress can lower testosterone. Second, how a person perceives their status relative to others in society might influence their testosterone: studies of sports matches, usually between men, have often found that testosterone rises in the winner compared to the loser.

It’s also possible that some third factor is responsible for the associations seen in previous studies. For instance, higher testosterone in men is linked to good health – and good health may also help people succeed in their careers. A link in men between testosterone and socioeconomic position could therefore simply reflect an impact of health on both. (For women, higher testosterone is linked to worse health, so we would expect an association of higher testosterone and lower socioeconomic position.)

Look at it this way

It is very difficult to pick apart these processes and study just the effects of testosterone on other things. With this goal in mind, we applied a causal inference approach called “Mendelian randomisation”. This uses genetic information relevant to a single factor (here, testosterone) to isolate just the effect of that factor on one or more outcomes of interest (here, socioeconomic outcomes such as income and educational qualifications).

A person’s circulating testosterone can be affected by environmental factors. Some, like the time of day, are straightforward to correct for. Others, like somebody’s health, are not. Crucially, socioeconomic circumstances could influence circulating testosterone. For this reason, even if we see an association between circulating testosterone and socioeconomic position, we cannot determine what is causing what.

This is why genetic information is powerful: your DNA is determined before birth and generally does not change during your lifetime (there are rare exceptions, such as changes which occur with cancer). Therefore, if we observe an association of socioeconomic position with genetic variants linked to testosterone, it strongly suggests that testosterone is causing the differences in socioeconomic outcomes. This is because influence on the variants of other factors is much less likely.

In more than 300,000 adult participants of the UK Biobank, we identified genetic variants linked to higher testosterone levels, separately for men and women. We then explored how these variants were related to socioeconomic outcomes, including income, educational qualifications, employment status, and area-level deprivation, as well as self-reported risk-taking and overall health.

Similar to previous studies, we found that men with higher testosterone had higher household income, lived in less deprived areas, and were more likely to have a university degree and a skilled job. In women, higher testosterone was linked to lower socioeconomic position, including lower household income, living in a more deprived area, and lower chance of having a university degree. Consistent with previous evidence, higher testosterone was associated with better health for men and poorer health for women, and more risk-taking for men.

However, there was little evidence that genetic variation related to testosterone affected socioeconomic position at all. In both men and women we detected no effects of genetic variants related to testosterone on any aspect of socioeconomic position, or health, or risk-taking.

Because we identified fewer testosterone-linked genetic variants in women, our estimates for women were less precise than for men. Consequently, we could not rule out relatively small effects of testosterone on socioeconomic position for women. Future studies could examine associations in women using larger, female-specific samples.

But for men, our genetic results clearly suggest that previous studies may have been biased by the influence of additional factors, potentially including the impact of socioeconomic position on testosterone. And our results indicate that – despite the social mythology surrounding testosterone – it may be much less important for success and life chances than earlier studies have suggested.

Amanda Hughes, Senior Research Associate in Epidemiology, University of Bristol; Neil Davies, Senior Research Fellow, University of Bristol, and Sean Harrison, Systematic Reviewer, University of Bristol

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Written by Marina Vabistsevits and Oliver Lloyd, researchers on PhD studentships linked to the  “Data Mining Epidemiological Relationships” programme at the MRC IEU. 

Follow us on twitter – @marina_vab,  @PlotThiggins 

Leaving the EU presents many unique challenges to Britain, among which is the crucial task of maintaining our high levels of food safety. As a submission to the Jean Golding Institute’s data visualisation competition, we briefly investigated the impacts that Brexit may have on British food supplies. The dataset used in this analysis was made available by the Food Standards Agency (FSA) as the focus of the competition, and all code used is freely available in our github repository. 

The Need for Information Recompense 

In the first part of the analysis, we explored cases where food imported to Britain led to an alert being raised. The two biggest sources for such alerts were Britain’s internal alert systems (largely the FSA), and the EU’s Rapid Alert System for Food and Feed (RASFF).  

Since Britain is on course to lose access to RASFF-supplied information once Brexit is finalised in early 2021, we created the visualisation below as a comparison of the FSA and the RASFF in terms of both the number of alerts raised and the corresponding food’s origin country for each alert.  

 

The arcs show the countries of origin of imports that raised alerts, and the yellow-red density map shows the recorded hazard alert frequency from those origins. Interactive versions of the two map instances can be found by following these links: RASFF, UK internal alerts. 

If the UK does indeed lose access to the RASFF, the loss of food hazards information about our own imports will be tremendous. The burden then falls on the FSA to develop and extend their alert system (which currently focuses very little on internationally supplied food) to bridge this information gap and ensure food safety for globally imported goods. As of the time of writing we are unsure what steps are being taken by the FSA, or the government at large, to address this issue. 

Post-Brexit Shifts in Food Hazard Threats  

As an extension of this work, we turned our attention to tariffs and the effect they might have on whom Britain chooses to import from. Upon leaving the EU the UK will have to negotiate new trade deals with both EU and non-EU countries. Since the cost for EU-produced food is expected to rise for Britain after Brexit, we may indeed see Britain importing more from outside of the union, which would naturally bring a shift to the make–up of food hazards that our alert systems will need to detect. Anticipating this shift will allow us to better mitigate the accompanying risk if it does begin to materialise.  

To this end, we explored the differences in food hazard threats posed by EU vs non-EU suppliers of Britain’s largest class of imported food: fruits and vegetables. The plot below shows the relative change in frequency for each category of food hazard in the case that Britain switched from 100% EU imports of fruit and vegetables to 100% non-EU. The hazard categories that are likely to increase in non-EU imports are highlighted in red.  Please note that this is the most extreme case possible and is unlikely to unfold to this extent in reality– this plot is therefore presented as a guide to the different food threats posed by EU vs non-EU imports. 

Our full submission ‘Too Much Tooty in the Fruity: Keeping Food Safe in a Post-Brexit Britain’ can be found here, and includes a further breakdown of some of the categories of hazards displayed in the chart above. This work was awarded one of two joint runner-up prizes of the competition, tied with Angharad Stell’s Shiny app: ‘From a data space to knowledge discovery’. The winner of the competition was Robert Eyre, who produced this impressive visualization dashboard using D3. The Jean Golding Institute are hosting a showcase event on the 18th November, where all competition entries will be presented.  

We would like to thank the JGI for hosting the competition, and our PhD supervisors, Prof. Tom Gaunt and Dr. Ben Elsworth, for encouraging us to enter.