crabsallover highlights, key points, comments / links.
Fri Jan 18, 2013 11:17
"One million people who have non-body odour gene still use deodorant," is the headline from The Daily Telegraph, with a similar Daily Mail report saying many people use deodorant needlessly because their sweat doesn’t smell.
The stories are based on research on a particular DNA sequence variation within the ABCC11 gene. This variation has previously been associated with both earwax production and armpit sweat production, with one variation (genotype) linked with both dry earwax and less smelly sweat, and another genotype linked with wet earwax and more odorous sweat.
In the current study, the researchers looked at a group of parents and children from a birth cohort and looked at which gene variant the mothers had and how often they used deodorant. They also looked at the partner’s (usually the father’s) deodorant use and whether it was linked to which form of gene their child had.
The researchers found a link between which variant mothers had and their deodorant usage. There was also a link between the partner’s use of deodorant and which variant their child had. However, around 80% of people with the dry earwax, “non-odorous” sweat variant still reported using deodorant.
After extrapolating these figures in order to take into account both the UK population and deodorant sales figures, the researchers estimated that around £9 million is wasted annually on deodorant by people who don’t need it. Ultimately, rather than judging by earwax type, whether people use deodorant or not will remain a personal choice.
Where did the story come from?
The study was carried out by researchers from the University of Bristol and Brunel University, London, and was funded by the UK Medical Research Council (MRC), the Wellcome Trust and the University of Bristol.
The study was published in the open access peer-reviewed medical journal Journal of Investigative Dermatology.
Both the Daily Mail and The Daily Telegraph reported the findings of this study accurately.
What kind of research was this?
This study examined the genetics and deodorant usage of around 17,000 individuals taking part in an ongoing cohort study known as the Avon Longitudinal Study of Parents and Children (ALSPAC).
The research focused on examining a single letter variation in the DNA (called a single-nucleotide polymorphism, or SNP) in the ABCC11 gene, which has previously been found to be associated with earwax type and armpit odour. Most SNPs have no noticeable effect on health and development, but a minority of them can have, in some cases, profound effects.
One variant of this SNP is reported to lead to a dry earwax type while another variant leads to a wet earwax type. The researchers say that there is a link between the glands that produce earwax and the glands that produce sweat, and people with the gene variant that produces dry earwax also produce less odorous sweat.
In this study the researchers wanted to see whether people with the dry earwax and less odorous variant may be using deodorant less, or using it when they may not need to.
What did the research involve?
The ALSPAC cohort recruited 14,541 pregnant women living in Avon and who were due to deliver their baby in 1991-92. There were 14,062 live-born children. This long-running study has collected a lot of data on health, genetics and environmental factors in these participants, which has been used in many research studies.
Eight months after the child’s birth the mother had been asked about deodorant use on a section of a questionnaire entitled “Chemicals in your environment”. The question asked was: “In the last few months, how often have you used the following (whether at home or at work)?” This was followed by a list of chemicals, including “deodorants”. The mother’s partner had been asked similar questions while the woman was pregnant about their deodorant use.
Of the mothers who answered questions on deodorant use, they were able to examine the DNA of 6,495 mothers and 7,132 of their children in the cohort to see which variant of the SNP (rs17822931) in the ABCC11 gene they had. They also had deodorant information available for 5,047 partners (most of whom were the father of the child).
The researchers used statistical models to look at weekly deodorant usage and variant type in the mother. They also looked at associations between deodorant usage by the partner and variant type of their child. As they did not have DNA information from the partner, they were using the child’s DNA as an indicator of which variant the partner may have. However, we don’t know for certain the father and child would share the same SNP variant within the ABCC11 gene. In fact, we are not even certain the partner is the child’s biological father in all cases. Therefore, information on deodorant use according to genotype will be less reliable for men than it will be for the women (where they looked at the woman’s own genotype).
What were the basic results?
The researchers found that which variant of the rs17822931 SNP people had was associated with how often they used deodorant. Women who had the variant associated with dry earwax and less odorous sweat were almost five times more likely to have reported never using deodorant or using it infrequently. However, 78% of women with this “non-odorous” variant, and 80% of fathers of children with the “non-odorous” variant, still used deodorants at least once a week.
Comparatively, only 5% of women with the gene variant associated with wet earwax (and more odorous sweat) did not use deodorant. A slightly higher percentage of fathers (13%) of children with this “odorous” gene type did not use deodorant.
These results were for people whose ethnicity was reported as white. The results were broadly similar for non-white people, although there were fewer non-white people in the study, which makes it harder to give reliable results for non-white people.
How did the researchers interpret the results?
The researchers conclude that they have shown that which variant of the rs17822931 SNP people have is a strong predictor of their deodorant usage. However, despite this, around 80% of genetically “non-odorous” white European mothers still use deodorant, and the findings may be true for men as well.
The researchers say that this is likely to be caused by sociocultural factors, but people with the dry earwax type could choose to abandon the chemical exposures and costs of deodorant use.
This is intriguing research following up on the previous finding that a particular DNA sequence variation in the ABCC11 gene is associated with both earwax and armpit sweat odour. One form of the variant is linked with dry earwax and less odorous sweat, while another is linked with wet earwax and more odorous sweat.
The researchers did find that there was a link between which variant mothers had and their deodorant usage. However, almost 80% of women with the dry earwax, “non-odorous” variant still reported using deodorant around once a week. The researchers’ results indicate the same may be true for men, but this would ideally need confirmation. This is because it is not certain whether the variant of the child was the same as the partner’s own or, indeed, whether in all cases he was the biological father.
The researchers suggest these people with the “non-odorous” variant could choose not to use deodorant. The study doesn’t appear to have asked people whether they find they experience body odour themselves, or why they do or don’t choose to use deodorant.
These results may prompt people to reassess whether they need a deodorant. However, it seems unlikely that you could persuade most people who usually use deodorant that they can abandon its use, simply by pointing out that they have dry earwax. Instead, it seems likely that whether people use deodorant (or not) will remain a personal choice depending on what they feel most comfortable with.
Links To The Headlines
One million people who have non-body odour gene still use deodorant: study. The Daily Telegraph, January 17 2013
A million Britons don’t need deodorant because their sweat doesn't smell. Daily Mail, January 17 2013
Links To Science
Rodriguez S, Steer CD, Farrow A, et al. Dependence of Deodorant Usage on ABCC11 Genotype: Scope for Personalized Genetics in Personal Hygiene. Journal of Investigative Dermatology. Published online January 17 2013